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In this study conducted along the coast of Odisha, India, reproductive trade-offs in isopods of the family Cymothoidae were investigated, focusing on the relationship between the number vs. volume of eggs and the percentage of brood to body volume. Ovigerous females from species with substantial sample sizes (n > 30) were analyzed to understand their survival strategies. The findings highlight distinct strategies among different parasite types within Cymothoidae. Buccal parasites such as Cymothoa frontalis and Cymothoa indica, along with branchial parasites like Joryma sawayah and Agarna malayi, generally produced a higher number of smaller eggs, except for A. malayi, which produced fewer but larger eggs. In contrast, the external body surface-attaching parasite, Nerocila orbignyi, was observed to produce fewer eggs of larger size. Across all parasite types (intraspecific), there was a statistically significant negative correlation between egg number and egg volume (p < 0.05). Buccal parasites were observed to have the highest percentage of marsupium volume relative to body volume, indicating a strategy to maximize egg storage. Conversely, external body surface-attaching parasites had the lowest percentage, possibly reflecting adaptation to a different reproductive environment. Additional observations revealed anatomical adaptations in all the studied isopod species which include the shift of the alimentary canal to the dorsal side to accommodate the development of the marsupial sac for egg incubation. In summary, these findings illustrate how parasitic isopods of the family Cymothoidae manage trade-offs between reproductive potential and success, crucial for their species' continuity and survival strategies in coastal ecosystems., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Artificial Light at Night (ALAN) threatens to disrupt most natural habitats and species, including those in coastal settings, where a growing number of studies have identified ALAN impacts. A careful examination of the light properties behind those impacts is important to better understand and manage the effects of this stressor. This study focused on ALAN monochromatic wavelengths and examined which types of light spectra altered the natural activity of two prominent coastal species from the Pacific southeast: the talitroid amphipod Orchestoidea tuberculata and the oniscoid isopod Tylos spinulosus. We compared the natural daylight/night activity of these organisms with the one they exhibit when exposed to five different ALAN wavelengths: lights in the violet, blue, green, amber, and red spectra. Our working hypothesis was that ALAN alters these species' activity at night, but the magnitude of such impact differs depending on light wavelengths. Measurements of activity over 24 h cycles for five consecutive days and in three separate experiments confirmed a natural circadian activity pattern in both species, with strong activity at night (∼90% of probability) and barely any activity during daylight. However, when exposed to ALAN, activity declined significantly in both species under all light wavelengths. Interestingly, amphipods exhibited moderate activity (∼40% of probability) when exposed to red lights at night, whereas isopods shifted some of their activity to daylight hours in two of the experiments when exposed to blue or amber lights, suggesting a possible alteration in this species circadian rhythm. Altogether, our results were consistent with our working hypothesis, and suggest that ALAN reduces night activity, and some wavelengths have differential effects on each species. Differences between amphipods and isopods are likely related to their distinct adaptations to natural low-light habitat conditions, and therefore distinct sensitivity to ALAN., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

All species of the isopod family Cymothoidae are obligate fish parasites, extracting nourishment through hematophagy and tissue consumption. To elucidate the detrimental effects of this parasitic relationship upon the host fish, we examined body length, weight of body, gonad, liver and stomach contents, and condition factor of Japanese scad Decapterus maruadsi infected with the buccal cavity parasite Ceratothoa carinata in different seasons. During the host fish's breeding season in July, the wet weight and condition factor of male and female host fish ages 1 and 2 were conspicuously diminished. No impacts were detected in September, after the breeding season. We found no impact of the parasite on the stomach content weight or signs of prey fish in the stomachs. Thus, parasite infection with C. carinata potentially diminishes the reproductive success of the host fish by negatively impacting the host's physiological condition, particularly during the breeding season.

Background: Lithognathus mormyrus fish is one of the fish of high economic importance in the countries of the world in general and the Mediterranean countries in specific, including the Libyan Sea waters, for this it is necessary to know everything related to this type of fish, including its infection with parasites. Parasites are considered one of the factors threatening the life of fish, being one of the food chains and the ecological composition of life., Aim: The current study aims to isolate and identify the parasites that infect the L. mormyrus ., Methods: A total of 368 specimens of L. mormyrus were collected by fishermen, from the western coast of Libya. The study was focused on metazoan parasites. When fish were fully examined for the presence of ectoparasites under a dissecting microscope with incident light, the software camera connected with a microscope and semichon' acetocarmine technique for identification of parasites., Results: Two species of Monogenea ( Encotyllabe valley, Pagellicotyle mormyri, and Lamellodiscus spp . ), Isopoda (Gnathia), Copepoda ( Lernaeolophus sultanus ), and Annelidae ( Trachelobdella lubrica ) has been isolated from this species of fish. The highest prevalence of infection was Gnathia parasites (8.47%)., Conclusion: There were differences in the parasite species that infect L. mormyrus from one country to another, and also from city to other cities in the same country, as in the Tunisian waters., Competing Interests: The authors declare that there is no conflict of interest.

In cave environments, stable conditions devoid of light-dark cycles and temperature fluctuations sustain circadian clock mechanisms across various species. However, species adapted to these conditions may exhibit disruption of circadian rhythm in locomotor activity. This study examines potential rhythm loss due to convergent evolution in five semi-aquatic troglobitic isopod species (Crustacea: Styloniscidae), focusing on its impact on locomotor activity. The hypothesis posits that these species display aperiodic locomotor activity patterns. Isopods were subjected to three treatments: constant red light (DD), constant light (LL), and light-dark cycles (LD 12:12), totaling 1656 h. Circadian rhythm analysis employed the Sokolove and Bushell periodogram chi-square test, Hurst coefficient calculation, intermediate stability (IS), and activity differences for each species. Predominantly, all species exhibited an infradian rhythm under DD and LL. There was synchronization of the locomotor rhythm in LD, likely as a result of masking. Three species displayed diurnal activity, while two exhibited nocturnal activity. The Hurst coefficient indicated rhythmic persistence, with LD showing higher variability. LD conditions demonstrated higher IS values, suggesting synchronized rhythms across species. Significant individual variations were observed within species across the three conditions. Contrary to the hypothesis, all species exhibited synchronization under light-dark conditions. Analyzing circadian activity provides insights into organism adaptation to non-cyclical environments, emphasizing the importance of exploring underlying mechanisms.

The "paradox of sex" refers to the question of why sexual reproduction is maintained in the wild, despite how costly it is compared to asexual reproduction. Because of these costs, one might expect nature to select for asexual reproduction, yet sex seems to be continually selected for. Multiple hypotheses have been proposed to explain this incongruence, including the niche differentiation hypothesis, the Red Queen hypothesis, and accumulation of harmful mutations in asexual species due to inefficient purifying selection. This study focuses on the accumulation of mutations in two terrestrial isopods, Trichoniscus pusillus , which has sexual diploid and parthenogenic triploid forms, and Hyloniscus riparius , an obligately sexual relative. We surveyed sex ratios of both species in an upstate New York population and obtained RNA-seq data from wild-caught individuals of both species to examine within- and between-species patterns of molecular evolution in protein-coding genes. The sex ratio and RNA-seq data together provide strong evidence that this T. pusillus population is entirely asexual and triploid, while the H. riparius population is sexual and diploid. Although all the wild T. pusillus individuals used for sequencing shared identical genotypes at nearly all SNPs, supporting a clonal origin, heterozygosity and SNP density were much higher in T. pusillus than in the sexually reproducing H. riparius . This observation suggests this parthenogenic lineage may have arisen via mating between two divergent diploid lineages. Between-species sequence comparisons showed no evidence of ineffective purifying selection in the asexual T. pusillus lineage, as measured by the ratio of nonsynonymous to synonymous substitutions (dN/dS ratios). Likewise, there was no difference between T. pusillus and H. riparius in the ratios of nonsynonymous to synonymous SNPs overall (pN/pS). However, pN/pS ratios in T. pusillus were significantly higher when considering only SNPs that may have arisen via recent mutation after the transition to parthenogenesis. Thus, these recent SNPs are consistent with the hypothesis that purifying selection is less effective against new mutations in asexual lineages, but only over long time scales. This system provides a useful model for future studies on the evolutionary tradeoffs between sexual and asexual reproduction in nature., Competing Interests: The authors declare that they have no competing interests., (©2024 Yarbrough and Chandler.)

A total of 366 individuals of Lutjanus argentiventris (Peters, 1869) were collected over a 5-yr period (October 2018 to June 2022) from Acapulco Bay, Mexico. Parasite communities in Lutjanus argentiventris were quantified and analyzed to determine the main factors that generate changes in species richness and/or species composition over time. The digeneans and copepods were the best-represented parasite groups. The parasite communities were characterized by a high numerical dominance of ectoparasites, mainly isopod larvae. Species richness at the component community level (9-23 species) was similar to the reported richness in other Lutjanus spp. The parasite communities of Lutjanus argentiventris exhibited high variability in species composition, suggesting that each parasite species may respond differently to environmental changes. However, the species richness and diversity were fairly stable over time; therefore, a clear pattern of interannual variation was not observed. Variations in the community structure probably were due to factors such as host traits (e.g., feeding behavior and body size), and possible interannual differences in environmental factors amplified by the occurrence of the anomalous event of La Niña., (© American Society of Parasitologists 2024.)

The southern king crab (SKC) Lithodes santolla is a crustacean parasitised by the bopyrid Eremitione tuberculata. This study aimed to analyse spatial and temporal variations in E. tuberculata prevalence in the juvenile SKC population of San Jorge Gulf (SJG) and adjacent waters (Argentine Patagonia), and evaluate the effects of the parasite on SKC juveniles to improve our understanding of its impact as a disease on SKC health condition. Moult increment and body weight were compared between parasitised and unparasitised individuals. The prevalence of E. tuberculata in SKC juveniles varied both spatially and temporally. In the south of SJG, the prevalence was 54.5% (n = 11). Temporal prevalence analysis revealed values lower than 17.4% in mid SJG during May and September 2015. No significant differences were observed in E. tuberculata prevalence between sexes or among seasons. Eremitione tuberculata had a negative effect on SKC growth (lower body dry mass, moult increment and relative increment rate) in parasitised individuals. We hypothesised that the higher prevalence of E. tuberculata in the south SJG could be attributed to the retention of parasite larvae and the presence of the frontal system in this part of the gulf. The temporal variations could reflect host mortality. Our results suggest that bopyrid infestation may have a more important role than previously believed in the dynamics of the SKC population in mid-Patagonia.

Species in the anthurid isopod genus Mesanthura have specific, dorsal dark pigmentation patterning on the body. Though Mesanthura species have traditionally been distinguished mainly by differences in the dorsal pigmentation pattern in females, the stability of the pigmentation pattern within species had not been investigated, and information was lacking on ontogenetic variation in the pattern. Our study showed the following for M. miyakoensis . (1) Mancae begin to show dorsal pigmentation in the marsupium roughly 9 days before their release. (2) The pigmentation pattern in the first-instar mancae (first free-living stage) differs from that in later instars. (3) The pigmentation pattern in females is discrete and stable from putative second-instar mancae through females lacking oostegites, and distorted but recognizable in ovigerious females. (4) The pattern in males is different from and less discrete than that in females; it remains similar through the molt from subadult to adult male but changes markedly with age, leading to heavy pigmentation of the body. (5) The pigmentation pattern in mancae and females remains stable and observable after storage in ethanol for at least 13.7 months. Our results suggest that comparisons of pigmentation pattern across species in Mesanthura taxonomy should be restricted to females in the post-manca or later stages.

Most deep-ocean life relies on organic carbon from the surface ocean. While settling primary production rapidly attenuates in the water column, pulses of organic material can be quickly transported to depth in the form of food falls. One example of fresh material that can reach great depths across the tropical Atlantic Ocean and Caribbean Sea is the pelagic macroalgae Sargassum . However, little is known about the deep-ocean organisms able to use this food source. Here, we encountered the isopod Bathyopsurus nybelini at depths 5002-6288 m in the Puerto Rico Trench and Mid-Cayman Spreading Center using the Deep Submergence Vehicle Alvin . In most of the 32 observations, the isopods carried fronds of Sargassum . Through an integrative suite of morphological, DNA sequencing, and microbiological approaches, we show that this species is adapted to feed on Sargassum by using a specialized swimming stroke, having serrated and grinding mouthparts, and containing a gut microbiome that provides a dietary contribution through the degradation of macroalgal polysaccharides and fixing nitrogen. The isopod's physiological, morphological, and ecological adaptations demonstrate that vertical deposition of Sargassum is a direct trophic link between the surface and deep ocean and that some deep-sea organisms are poised to use this material.

Microplastic (MP) is an environmental burden and enters food webs via ingestion by macrofauna, including isopods (Porcellio scaber) in terrestrial ecosystems. Isopods represent ubiquitously abundant, ecologically important detritivores. However, MP-polymer specific effects on the host and its gut microbiota are unknown. We tested the hypothesis that biodegradable (polylactic acid [PLA]) and non-biodegradable (polyethylene terephthalate [PET]; polystyrene [PS]) MPs have contrasting effects on P. scaber mediated by changes of the gut microbiota. The isopod fitness after an 8-week MP-exposure was generally unaffected, although the isopods showed avoidance behaviour to PS-food. MP-polymer specific effects on gut microbes were detected, including a stimulation of microbial activity by PLA compared with MP-free controls. PLA stimulated hydrogen emission from isopod guts, while PET and PS were inhibitory. We roughly estimated 10 7  kg year -1 hydrogen emitted from the isopods globally and identified their guts as anoxic, significant mobile sources of reductant for soil microbes despite the absence of classical obligate anaerobes, likely due to Enterobacteriaceae-related fermentation activities that were stimulated by lactate generated during PLA-degradation. The findings suggest negative effects of PET and PS on gut fermentation, modulation of important isopod hydrogen emissions by MP pollution and the potential of MP to affect terrestrial food webs., (© 2023 The Authors. Environmental Microbiology published by Applied Microbiology International and John Wiley & Sons Ltd.)

Prey should select safer breeding sites over riskier sites of otherwise similar habitats. This preference, however, may differ between conspecifics of different competitive abilities if the costs of intraspecific competition overpower the benefits of breeding in a safer site. Our goal was to test this hypothesis by exploring the burrow-site selection of different-sized desert isopods ( Hemilepistus reaumuri ) near and away from a scorpion burrow. We found that larger females are more likely to occupy burrows than smaller females, regardless of whether these burrows were close or away from scorpion burrows. We also found that larger females stayed longer in safer burrows and that smaller females tended to stay longer in riskier sites even in the absence of direct competition, implying a prudent burrow-site selection. We found no association between male size and the tendency to occupy or to spend time in a burrow, regardless of whether these burrows were close or away from scorpion burrows. Our work highlights the need to consider intraspecific competition when exploring how predators regulate prey behaviour.

Exploratory activity is an essential component of animal behavior, including among invertebrate species. This study examined the effects of hydric deprivation and their possible modulation by light exposure on locomotion and rearing-up behavior in two woodlice species, Porcellio scaber (Latreille 1804) and Armadillidium vulgare (Latreille 1804). It was also an attempt to replicate previous findings on the stimulation of these behaviors in P. scaber, exposed to (pseudo)random vs. regular visual and tactile patterns in a small enclosure. In Experiment 1, two groups of P. scaber and two groups of A. vulgare were exposed to randomly vs. regularly distributed visual (black and white) and tactile (grained and smooth) patterns for approximately 20 min. No rewards were present in the environment and the woodlice were tested without preliminary hydric deprivation. In Experiment 2, the same procedure was used but the woodlice were tested following a 20-min hydric deprivation under a bottle cap (darkness). Experiment 3 replicated this procedure with the 20-min hydric deprivation spent in a plastic cup (light exposure). The results of Experiments 1 and 3 provide partial replication with A. vulgare, but not P. scaber, of the previous findings: Random patterns stimulate rearing-up behavior on the apparatus' vertical walls more than regular patterns. Also, a more aversive stimulation in Experiment 3 compared to Experiment 2, increased locomotion, especially in the random environment. The role of hydric deprivation and light exposure in the process of escaping from a hostile environment is discussed, as well as the effects of the treatments used in these experiments., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Climate changes and metal contamination are pervasive stressors for soil ecosystems. Mercury (Hg), one of the most toxic metals, has been reported to interact with temperature. However, compared to aquatic biota, little is known about how temperature affects Hg toxicity and bioaccumulation to soil organisms. Here, toxicity and bioaccumulation experiments were replicated at 15 °C, 20 °C, and 25 °C to understand how sub-optimal temperatures affect the toxicokinetics and toxicodynamics of Hg via soil. Genotoxicity and energy reserves were also assessed to disclose potential trade-offs in life-history traits. Results underpin the complexity of temperature-Hg interactions. Survival was determined mainly by toxicokinetics, but toxicodynamics also played a significant role in defining survival probability during early stages. The processes determining survival probability were faster at 25 °C: General Unified Threshold of Survival (GUTS) model identified an earlier/steeper decline in survival, compared to 20 °C or 15 °C, but it also approached the threshold faster. Despite potentiation of Hg genotoxicity, temperature promoted faster detoxification, either increasing toxicokinetics rates or damage repair mechanisms. This metabolism-driven increase in detoxification led to higher depletion of energy reserves and likely triggered stress response pathways. This work emphasized the need for comprehensive experimental approaches that can integrate the multiple processes involved in temperature-metal interactions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Tire particles pose a potential threat to terrestrial organisms because they are deposited in large quantities in the soil by tire wear abrasion, and moreover their chemical complexity poses an additional risk. Microplastics can affect several physiological processes in organisms, including those related to immunity. Therefore, we investigated the expression profile of selected immune-related genes (MnSod, Manganese Superoxide dismutase; Cat, Catalase; CypG, Cyclophilin G; Nos, Nitric oxide synthase; Ppae2a, Prophenoloxidase-activating enzyme 2a; Dscam, Down syndrome cell adhesion molecule; Myd88, Myeloid-differentiation factor 88; Toll4, Toll-like receptor 4; Mas-like, Masquerade-like protein) in haemocytes and the digestive gland hepatopancreas of terrestrial crustacean Porcellio scaber after two different time exposures (4 and 14 days) to tire particles in soil. Our results reveal for the first time the response of P. scaber after microplastic exposure at the transcriptome level. We observed time- and tissue-dependent changes in the expression of the analysed genes, with more pronounced alterations in haemocytes after 14 days of exposure. Some minor changes were also observed in hepatopancreas after 4 days. Changes in the expression profile of the analysed genes are a direct indication of a modulated immune status of the test organism, which, however, does not represent an adverse effect on the test organism under the given conditions. Nevertheless, the question remains whether the observed change in immune status affects the immunocompetence of the test organism., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Most bopyrid isopod parasites, which are crustaceans themselves, settle in the branchial chamber of decapod crustaceans and feed on host haemolymph. Here we report the results of an experiment on the common prawn Palaemon serratus and the parasite Bopyrus squillarum. Infected and uninfected prawns were stimulated with pokes of a plastic rod until an escape response was triggered; the number of pokes was recorded as an indicator of prawn responsiveness, whereas the time spent moving following stimulation was used as an indicator of prawn activity. Our results show that bopyrid infection affects both prawn responsiveness and activity, with infected prawns requiring more pokes to move, and moving for less time compared to uninfected prawns. In nature, such behavioural changes may impact defence mechanisms and survival of infected prawns. This could contribute to decreases in P. serratus abundance, thereby affecting the coastal ecosystems home to this species and the fisheries reliant on it, such as the Irish shrimp fishery.

Turn alternation (TA) is the tendency to turn in the opposite direction of an immediately preceding turn when moving forward, resulting in an overall linear trajectory. TA has been observed in many animals, and terrestrial isopods are considered model organisms for studying TA. Optimizing their fleeing speed and trajectory helps isopods efficiently escape from predatory threats. However, since reproduction induces morphological and physiological changes, individuals might adjust their trajectories depending on their altered mobility. In this study, we investigated the effect of reproduction-related factors on the frequency of TA, which enables linearity, in the common rough woodlouse Porcellio scaber. The results showed that breeding females enhanced their linearity more than nonbreeding females and males. Furthermore, females without access to a potential mate enhanced their linearity more than females and males with access to a potential mate and maintained a high linearity for approximately 40 days. In terrestrial isopods, continuous TA for linearity may be used to avoid reproductive failure because of lack of encounters with the potential mate or to compensate for low running ability due to physical or physiological loads. Conversely, individuals that do not need to worry about reproductive failures or individuals with small loads could perform the random turn that does not require learning or memory. This is the first study to show that the events involved in reproduction affect the linearity shown by continuous TA in terrestrial isopods., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Tachaea chinensis, a parasitic isopod, negatively affects the production of several commercially important shrimp species. To better understand the interaction between shrimp immunity and isopod infection, we performed a transcriptome analysis of the hepatopancreas of Palaemonetes sinensis challenged with T. chinensis. After assembly and annotation, 75,980 high-quality unigenes were obtained using RNA-seq data. Differential gene expression analysis revealed 896 significantly differently expressed genes (DEGs) after infection, with 452 and 444 upregulated and downregulated genes, respectively. Specifically, expression levels of genes involved in detoxification, such as the interferon regulatory factor, venom carboxylesterase-6, serine proteinase inhibitor, and cytochrome P450, were upregulated. Furthermore, expression levels of genes corresponding to retinol dehydrogenase, triosephosphate isomerase, variant ionotropic glutamate receptor, and phosphoenolpyruvate carboxykinase were significantly upregulated after isopod parasitization, indicating that the shrimp's visual system was influenced by isopod parasitization. Moreover, quantitative real-time PCR of 10 DEGs helped validate the RNA-seq findings. These results provide a valuable basis for future studies on the elucidation of immune responses of P. sinensis to T. chinensis infection., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Cinusa nippon n. sp. is described as the second species of the genus from ovigerous females and adult males found in the buccal cavity of three species of coastal puffers [vermiculated puffer, Takifugu snyderi (Abe, 1989) (type host); panther puffer, Takifugu pardalis (Temminck and Schlegel, 1850); and fine patterned puffer, Takifugu flavipterus Matsuura, 2017], in the southern Sea of Japan off western Honshu, Japan. The female of the new species is distinguished from that of its single congener, Cinusa tetrodontis Schioedte and Meinert, 1884, by the shape of pereonite 1 (straight lateral margins with slightly produced anterolateral angles in the new species vs. rounded anterolateral sides and angles in C. tetrodontis ). The number of recurved robust setae on the female's maxilliped article 3 is also different between the two species: C. nippon n. sp. has two robust setae, while C. tetrodontis has three robust setae. Moreover, the male of the new species is differentiated from that of C. tetrodontis in the number of antennal articles and recurved robust setae on the maxilla and maxilliped. Cinusa nippon n. sp. represents the first specimen-based record of the genus from the Pacific region. An amended diagnosis of the genus is provided.

Terrestrial isopods have evolved adaptations to reduce water loss, which is necessary for life in low humidity environments. However, the evolution of a waterproofed cuticle to prevent loss of water to the environment could also impede oxygen uptake from the environment. We therefore postulate an evolutionary trade-off between water retention and gas exchange in this group of soil animals. The outcome of this trade-off is expected to be affected by both differences across species (different types of lung) and differences within species (body size and resulting surface area to volume ratios). To test these ideas, we compared two sympatric isopods: Porcellio scaber and Oniscus asellus. While P. scaber possesses covered lungs typical for drier habitats, O. asellus has simple open respiratory fields which are in direct contact with external air. For each species, we assessed how individuals across a broad range in body size differed in their hypoxia and desiccation tolerance. In addition, we assessed how hypoxia and low humidity affected their thermal preference. We found clear effects of species identity and body size on tolerance to hypoxia and low humidity. Desiccation resistance was tightly linked to water loss rates (R 2  = 0.96) and strongly resembled the interspecific pattern across 20 isopod species. However, our results did not support the postulated trade-off. Tolerance to hypoxia and low humidity covaried, both increasing with body size and being higher in P. scaber. Thermal preference was affected by both hypoxia and low humidity, but not by body size. Our study increases understanding of the ecophysiology of both species, which can be useful in explaining the geographical distribution and use of microhabitats of isopod species in a climate change context., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Bopyrid isopods and rhizocephalan barnacles are obligate parasite crustaceans which harm their decapod hosts. However, to the best of our knowledge, studies have not compared which of these parasites has a greater parasitic effect on its hosts. Here, the parasitic effect of the bopyrid isopod, Allokepon hendersoni, and an unidentified sacculinid rhizocephalan species, infesting the same population of portunid crabs, Charybdis bimaculata, was investigated and compared for the first time. Samples were collected from the bycatch of a trawl fishery in Tosa Bay, Japan. A total of 2601 crabs were collected, of which 14 (0.55%) were parasitized by the bopyrid and 21 (0.82%) by the rhizocephalan. One of the two female crabs parasitized by the bopyrid was ovigerous (with much fewer eggs than unparasitized females). No ovigerous crab was found from the eight females parasitized by the rhizocephalan. Because only two female crabs were parasitized by the bopyrid, the following analyses were made using the male crabs. Both parasites reduced the wet weight (crab condition) and the cheliped size (secondary growth) of C. bimaculata, but the impact of the parasitism did not differ between the parasite species. The size of the abdominal flap of male hosts was reduced by the bopyrid infestation; however, rhizocephalan infestation caused enlargement of the abdominal flap, which is an indication of feminization. The present study provides information on how the effect of these two parasitic castrators on the same host crab varies. A moderate decrease in crab condition and cheliped development was common among the parasites, suggesting that the degree of impact might be favorable for the survival of the two parasites species., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Cirolana khamensis sp. nov. and C. parawongat sp. nov. are described from specimens collected in the western Gulf of Thailand at depths of 8 metres and 1 metre, respectively. Both species belong to the Cirolana 'pleonastica-group' with tubercles on the dorsal surfaces, transverse sutures on the pereonites, pleonite 3 not posteriorly produced and pleonite 4 posterolaeral margin rounded. Cirolana khamensis sp. nov. can be distinguished from other species of Cirolana 'pleonastica-group' by lateral margin of uropodal exopod having five robust seatae and a continuous row of plumose marginal setae, pereonites 1-3 each with a single transverse impressed line; antennula peduncle with articles 1 and 2 distinct and articulated peduncle; pleotelson dorsal surface with two sub-median longitudinal carinae, each of which has four prominent tubercles. Cirolana parawongat sp. nov. can be distinguished by pereonites 1-3 without a single transverse impressed line and having nine tubercles on pleonite 4 and 5. A dichotomous key to Cirolana 'pleonastica-group' in South-East Asia region is given.

Crustaceans provide a fascinating opportunity for studying adaptations to a terrestrial lifestyle because within this group, the conquest of land has occurred at least ten times convergently. The evolutionary transition from water to land demands various morphological and physiological adaptations of tissues and organs including the sensory and nervous system. In this review, we aim to compare the brain architecture between selected terrestrial and closely related marine representatives of the crustacean taxa Amphipoda, Isopoda, Brachyura, and Anomala with an emphasis on the elements of the olfactory pathway including receptor molecules. Our comparison of neuroanatomical structures between terrestrial members and their close aquatic relatives suggests that during the convergent evolution of terrestrial life-styles, the elements of the olfactory pathway were subject to different morphological transformations. In terrestrial anomalans (Coenobitidae), the elements of the primary olfactory pathway (antennules and olfactory lobes) are in general considerably enlarged whereas they are smaller in terrestrial brachyurans compared to their aquatic relatives. Studies on the repertoire of receptor molecules in Coenobitidae do not point to specific terrestrial adaptations but suggest that perireceptor events - processes in the receptor environment before the stimuli bind - may play an important role for aerial olfaction in this group. In terrestrial members of amphipods (Amphipoda: Talitridae) as well as of isopods (Isopoda: Oniscidea), however, the antennules and olfactory sensilla (aesthetascs) are largely reduced and miniaturized. Consequently, their primary olfactory processing centers are suggested to have been lost during the evolution of a life on land. Nevertheless, in terrestrial Peracarida, the (second) antennae as well as their associated tritocerebral processing structures are presumed to compensate for this loss or rather considerable reduction of the (deutocerebral) primary olfactory pathway. We conclude that after the evolutionary transition from water to land, it is not trivial for arthropods to establish aerial olfaction. If we consider insects as an ingroup of Crustacea, then the Coenobitidae and Insecta may be seen as the most successful crustacean representatives in this respect., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Invasive terrestrial isopods are likely to have altered leaf litter decomposition processes in North American forests, but the mechanisms underlying these alterations and the degree to which they differ among isopod species are poorly characterized. Using mixed-deciduous leaf litter microcosms, we quantified the effects of two common, invasive isopods (Oniscus asellus and Porcellio scaber) on short-term leaf litter decomposition and microbial community structure and function. Microcosms containing ground litter and a microbial inoculant were exposed to one of the two isopod species or no isopods for 21 days. Mass loss was then quantified as the change in litter dry mass after leaching, and microbial respiration was quantified as the mass of CO 2 absorbed by soda lime. Litter leachates were plated on agar to quantify culturable bacterial and fungal abundance, and denaturing gradient gel electrophoresis of amplified leachate microbial DNA was used to characterize shifts in microbial community structure. Isopod presence increased litter mass loss by a modest ~ 6%, but did not affect litter microbial respiration. Bacterial abundance increased significantly in the presence of isopods, while fungal abundance was either unchanged or reduced. Overall litter microbial species richness was reduced by isopods, with O. asellus specifically reducing fungal abundance and diversity. Isopods modified the microbial community structure by suppressing four bacterial and one fungal species, while promoting growth of four other bacterial species (two unique to each isopod species) and two fungal species (one which was unique to O. asellus).

To survive in its extreme habitat, the cuticle of the burrowing desert isopod Hemilepistus reaumuri requires properties distinct from isopods living in moist or mesic habitats. In particular, the anterior tergites are exposed to high mechanical loads and temperatures when individuals guard the entrance of their burrow. We have, therefore, investigated the architecture, composition, calcite texture and local mechanical properties of the tergite cuticle, with particular emphasis on large anterior cuticle tubercles and differences between the anterior and posterior tergite. Unexpectedly, structure and thickness of the epicuticle resemble those in mesic isopod species. The anterior tergite has a thicker endocuticle and a higher local stiffness than the posterior tergite. Calcite distribution in the cuticle is unusual, because in addition to the exocuticle the endocuticle distally also contains calcite. The calcite consists of a distal layer of dense and highly co-oriented crystal-units, followed proximally by irregularly distributed and, with respect to each other, misoriented calcite crystallites. The calcite layer at the tip of the tubercle is thicker relative to the tubercle slopes, and its crystallites are more misoriented to each other. A steep decrease of local stiffness and hardness is observed within a distal region of the cuticle, likely caused by a successive increase in the ACC/calcite ratio rather than changes in the degree of mineralisation. Comparison of the results with other isopods reveals a much lower ACC/calcite ratio in H. reaumuri and a correlation between the degree of terrestriality of isopod species and the magnesium content of the cuticle., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The dorsal surface of the woodlouse Porcellionides pruinosus is covered with minute spheres, providing its characteristic powdered appearance. Little has been known about their composition and formation. A previously suggested function of these structures was to increase the hydrophobicity of the cuticular surface. We studied the ultrastructure, composition and formation of the spheres as well as tested whether they affect the hydrophobicity of the cuticle. We determined the composition of the spheres with histochemistry and scanning electron microscopy after applying various chemicals. We studied the process of their formation with transmission electron microscopy and assessed the hydrophobicity of the cuticle by measuring contact angles of water droplets with its surface. Our results show that the spheres are largely organic. They contain proteins and glycoproteins or possibly polysaccharides without detectable amounts of lipids. By studying the formation of the spheres we established that they are epicuticular structures. They are deposited early in the premolt stage of the molt cycle around branching extensions of epidermal cells. The sphere-covered cuticle of P. pruinosus is more hydrophobic than the cuticle with experimentally removed spheres as well as the scale-covered cuticle in a related species., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Phoresy is a behavior in which an organism, the phoront, travels from one location to another by 'hitching a ride' on the body of a host as it disperses. Some phoronts are generalists, taking advantage of any available host. Others are specialists and travel only when specific hosts are located using chemical cues to identify and move (chemotax) toward the preferred host. Free-living nematodes, like Caenorhabditis elegans, are often found in natural environments that contain terrestrial isopods and other invertebrates. Additionally, the C. elegans wild strain PB306 was isolated associated with the isopod Porcellio scaber. However, it is currently unclear if C. elegans is a phoront of terrestrial isopods, and if so, whether it is a specialist, generalist, or developmental stage-specific combination of both strategies. Because the relevant chemical stimuli might be secreted compounds or volatile odorants, we used different types of chemotaxis assays across diverse extractions of compounds or odorants to test whether C. elegans is attracted to P. scaber. We show that two different strains-the wild isolate PB306 and the laboratory-adapted strain N2 -are not attracted to P. scaber during either the dauer or adult life stages. Our results indicate that C. elegans was not attracted to chemical compounds or volatile odorants from P. scaber, providing valuable empirical evidence to suggest that any associations between these two species are likely opportunistic rather than specific phoresy., Competing Interests: The authors have declared that no competing interests exist.

Tachaea chinensis is a parasitic isopod that negatively affects the production of several commercially important shrimp species in China. To date, there have been no reports on the antioxidant and immune responses of host shrimps to isopod parasite infection or their underlying molecular mechanisms. In this study, we examined the specific activities of the immune and antioxidant enzymes of the shrimp Macrobrachium nipponense during the course of a 15-day isopod infection and evaluated expression of related genes. Acid phosphatase (ACP) and alkaline phosphatase (AKP) activities and malondialdehyde (MDA) levels showed significant peaks over 15 days of exposure in both the hepatopancreas and muscle (P < 0.05), whereas catalase (CAT) activity increased continuously during infection (P < 0.05), and lysozyme (LZM) activity increased only in the hepatopancreas (P < 0.05). After 6 days of exposure, expressions of glutathione S-transferase (GST), ACP, and AKP were significantly higher than at 12 days. Compared with the control group, at 12 days, S-(hydroxymethyl) glutathione dehydrogenase activity and glutathione metabolism pathways were significantly inhibited (P < 0.05). Furthermore, the NOD-like receptor signaling pathway and antigen processing and presentation pathways were also significantly inhibited at 12 days compared with that at 6 days (P < 0.05), indicating that T. chinensis parasitism could perturb the antioxidant and immune systems of shrimp hosts during the latter stages of infection. Additionally, the molting and mortality rates of M. nipponense increased the duration of parasitism. These findings indicate that M. nipponense can activate antioxidant and immune defense systems during the early period during isopod parasitism, whereas the parasite can negatively affect these host defense systems during the latter period. Our findings accordingly provide valuable insights into the antioxidant defense systems and immune function characterizing parasite-host interactions., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Terrestrial isopods have evolved pleopodal lungs that provide access to the rich aerial supply of oxygen. However, isopods occupy conditions with wide and unpredictable thermal and oxygen gradients, suggesting that they might have evolved adaptive developmental plasticity in their respiratory organs to help meet metabolic demand over a wide range of oxygen conditions. To explore this plasticity, we conducted an experiment in which we reared common rough woodlice (Porcellio scaber) from eggs to maturation at different temperatures (15 and 22 °C) combined with different oxygen levels (10% and 22% O 2 ). We sampled animals during development (only females) and then examined mature adults (both sexes). We compared woodlice between treatments with respect to the area of their pleopod exopodites (our proxy of lung size) and the shape of Bertalanffy's equations (our proxy of individual growth curves). Generally, males exhibited larger lungs than females relative to body size. Woodlice also grew relatively fast but achieved a decreased asymptotic body mass in response to warm conditions; the oxygen did not affect growth. Under hypoxia, growing females developed larger lungs compared to under normoxia, but only in the late stage of development. Among mature animals, this effect was present only in males. Woodlice reared under warm conditions had relatively small lungs, in both developing females (the effect was increased in relatively large females) and among mature males and females. Our results demonstrated that woodlice exhibit phenotypic plasticity in their lung size. We suggest that this plasticity helps woodlice equilibrate their gas exchange capacity to differences in the oxygen supply and metabolic demand along environmental temperature and oxygen gradients. The complex pattern of plasticity might indicate the effects of a balance between water conservation and oxygen uptake, which would be especially pronounced in mature females that need to generate an aqueous environment inside their brood pouch., Competing Interests: Declaration of competing interest The authors declare no conflicting interests., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

This study investigated the water balance physiology of Venezillo arizonicus, a land isopod endemic to the Southwest Desert Ecoregion of North America. Evaporative water losses were measured in two ways: gravimetric in dry air, and by perfusing animals with dry air in a respirometry chamber and monitoring downstream relative humidity (RH). The respective mean loss flux estimates were 0.140 and 0.177 μg h -1 cm -2 Pa -1 , lower than other N. American Oniscidea described to date (≥0.491 μg h -1 cm -2 Pa -1 ). Humidity monitoring revealed intermittent sharp peaks in RH, attributed to the release of maxillary urine. Whole-animal flux increased as a function of temperature, with a critical temperature (T c ) between 38 and 42 °C identifiable by a clear Arrhenius break point. Hexane-rinsed whole animals yielded straight-chain, saturated hydrocarbons (C 21 -C 33 ). The surface density of extracted alkanes (0.64 µg cm -2 ) was somewhat higher than previously determined values for mesic species, although modest compared to insects and arachnids. Dehydrated animals exposed to high RH (>88%) demonstrated active water vapor absorption (WVA) like other Crinocheta, with an extrapolated uptake threshold of approximately 85% RH (A w  = 0.85), the lowest value reported for Oniscidea. The maximum uptake flux increased linearly as a function of ambient RH. Mass-specific uptake in 100% RH was 49% d -1 , similar to values determined previously for Armadillidium vulgare and Porcellio scaber. The low WVA threshold of V. arizonicus, and the species' low permeability, are consistent with its known range in the arid desert southwest and the desiccation stress of its typical aeolian sand and seasonal wash habitats., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Sex can influence patterns of parasitism because males and females can differ in encounter with, and susceptibility to, parasites. We investigate an isopod parasite (Hemioniscus balani) that consumes ovarian fluid, blocking female function of its barnacle host, a simultaneous hermaphrodite. As a hermaphrodite, sex is fluid, and individuals may allocate energy differentially to male versus female reproduction. We predicted the relationship between barnacle size and female reproductive function influences the distribution of parasites within barnacle populations. We surveyed 12 populations spanning ~400 km of coastline of southern California and found intermediate-sized barnacles where most likely to be actively functioning as females. While it is unclear why larger individuals are less likely to be actively reproducing as females, we suggest this reduced likelihood is driven by increased investment in male reproductive effort at larger sizes. The female function-size relationship was mirrored by the relationship between size and parasitism. We suggest parasitism by Hemioniscus balani imposes a cost to female function, reinforcing the lack of investment in female function by the largest individuals. Within the subset of suitable (=female) hosts, infection probability increased with size. Hence, the distribution of female function, combined with selection for larger hosts, primarily dictated patterns of infection.

The capability of producing sounds and vibrations is well known in insects and is thought to be a form of intra- and interspecific communication. Sounds and vibrations are used and modulated for several aims such as interacting with conspecifics, getting information from the environment, and defending against predators. This phenomenon is less known but also present in other arthropods, including a few roller-type terrestrial isopods. In this study, we used a Y-shape test apparatus to investigate the behavior of adult individuals of Armadillo officinalis Duméril, 1816 (Crustacea: Isopoda: Oniscidea) when exposed to two particular vibrational stimuli, namely species-specific stridulations and non-specific substrate-borne vibrations. Our results showed that adults of A. officinalis significantly react to the presence of both types of vibrational stimuli, by moving away from the vibrational source as if they experienced these vibrations as a sign of danger or disturbance. A. officinalis can produce stridulations only when it rolls into a ball during the so-called conglobation, a possible defense mechanism against predators. Stridulation might thus be a secondary form of defense used during conglobation to deter a predator following contact with it and might be experienced as an alert by conspecifics nearby. The high sensitivity to non-specific substrate-borne vibrations might provide A. officinalis with the possibility to anticipate dangers and adverse conditions, giving it a better chance of survival.

Ingestion of microplastics can impair nutrition of marine invertebrates. In a laboratory study, we tested whether microplastics affect ingestion rates and gastrointestinal enzyme activities in the marine isopod Idotea emarginata. Isopods were fed for eight days with one out of four different food formulations: natural food (the brown alga Fucus vesiculosus) or synthetic diet consisting of freeze-dried algal powder embedded in agarose, both, with or without microplastic particles (fluorescent polymethyl methacrylate, 10-100 μm) at a concentration of 40 items per mg of food. The isopods accepted both types of food but consumed significantly more (average 3.1-fold) of the agar based synthetic food. I. emarginata responded to the reduced content of digestible organic matter in the synthetic food by a compensatory adjustment of the ingestion rates. Addition of microplastics had no effect on ingestion rates in natural food whereas the feeding rates for synthetic food varied in response to microplastics. Similarly, activity patterns of digestive enzymes, particularly those of esterases, changed significantly in the treatment with synthetic food. Isopods fed with synthetic food alone showed elevated esterase activities in the gut while those isopods fed with synthetic food and microplastics showed elevated esterase activities in the midgut gland but not in the gut. Apparently, not the exposure to microplastic alone, but the combined effects of reduced nutrient availability and microplastic ingestion caused considerable biochemical reactions in the digestive organs of the isopods., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Very few studies have characterized the concentrations of pollutants in bioturbating species. These species are considered as ecosystem engineers and characterizing stressors, such as contaminants, that impact them could lead to a better understanding of the functioning of ecosystems. In addition to contaminants, bioturbators are affected by a wide range of stressors, which can influence their physiological status and their ability to accumulate pollutants. Among these stressors, parasitism is of particular concern due to the ubiquity of parasites in natural environments and their influence on the fitness of their host. This study aims to assess the relationship between parasitism and metal accumulation in the bioturbating mud shrimp Upogebia cf. pusilla. A one-year seasonal survey was conducted in Arcachon Bay, France, with the aims of (1) characterizing the levels of metals in the mud shrimp and (2) evaluating the influence of two macroparasites (a bopyrid isopod and a trematode) on the variation of the metal content in mud shrimp. The bopyrid parasite castrates its female host and a particular attention has therefore been paid to the reproductive cycle of female mud shrimp by quantifying the expression of the vitellogenin gene that encodes the major yolk protein in female crustaceans. The levels of contaminants in mud shrimp appeared low compared to those reported in other crustaceans in areas of higher pollution. Even at these low contamination levels, we observed a significant impact by the bopyrid parasite that depends on season: bopyrid-infested organisms are generally more contaminated than their uninfested conspecifics except in summer when the opposite trend was observed. We suggest that the bopyrid indirectly interferes with the metal accumulation process by altering the reproductive capabilities of the mud shrimp. On the opposite, very low influence of the trematode parasite on the metal content of the host was found., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Parasite attachment structures are critical traits that influence effective host exploitation and survival. Morphology of attachment structures can reinforce host specificity and niche specialisation, or even enable host switching. Therefore, it is important to understand the determinants of variation in attachment structures. Cymothoid isopods are striking ectoparasites of fishes that include the infamous 'tongue-biters.' They are known to parasitise hosts in one of four qualitatively distinct anatomical regions. Here, we quantify variation in cymothoid attachment structures - hook-like appendages called dactyli - and test whether differences in dactylus shape are correlated with parasite mode (where they attach), allometry, or both, using multivariate ordinary least squares regression. We also assess the influence of shared ancestry on shape using a molecular phylogeny to weight our models using phylogenetic generalised least squares regression., Results: We find clear differences in shape between externally-attaching and internally-attaching cymothoids but also between anterior and posterior dactyli across various species with the same attachment mode. Allometric effects are significant for anterior but not posterior dactyli. Mouth-attaching species show greater shape variability than gill- and mouth-attaching species. We find no evidence that there are clade-specific patterns of association between parasite mode and dactylus shape., Conclusions: Parasite mode appears to be the main driver of attachment morphology. This likely reflects several components of parasite ecology including feeding and functional demands of attachment in different microhabitats. Geometric morphometric approaches to the quantification of shape variation of simple structures is an effective tool that provides new insights into the evolvability of parasite attachment.

Nutrient cycling in most terrestrial ecosystems is controlled by moisture-dependent decomposer activity. In arid ecosystems, plant litter cycling exceeds rates predicted based on precipitation amounts, suggesting that additional factors are involved. Attempts to reveal these factors have focused on abiotic degradation, soil-litter mixing and alternative moisture sources. Our aim was to explore an additional hypothesis that macro-detritivores control litter cycling in deserts. We quantified the role different organisms play in clearing plant detritus from the desert surface, using litter baskets with different mesh sizes that allow selective entry of micro-, meso- or macrofauna. We also measured soil nutrient concentrations in increasing distances from the burrows of a highly abundant macro-detritivore, the desert isopod Hemilepistus reaumuri . Macro-detritivores controlled the clearing of plant litter in our field site. The highest rates of litter removal were measured during the hot and dry summer when isopod activity peaks and microbial activity is minimal. We also found substantial enrichment of inorganic nitrogen and phosphorous near isopod burrows. We conclude that burrowing macro-detritivores are important regulators of litter cycling in this arid ecosystem, providing a plausible general mechanism that explains the unexpectedly high rates of plant litter cycling in deserts.

Anthropogenic substances pollute freshwater systems worldwide, with serious, long-lasting effects to aquatic biota. Present methods of detecting elevated levels of trace metal pollutants are typically accurate but expensive, and therefore not suitable for applications requiring high spatial resolution. Additionally, these methods are not efficient solutions for the determination of long-term averages of pollution concentration. This is the rationale for the implementation of a biomonitoring programme as an alternative means of pollutant detection. This review summarises recent literature concerning the past and potential uses of the benthic isopod Asellus aquaticus as a biomonitor for pollution in freshwater systems. Recent studies indicate that A. aquaticus is well suited for this purpose. However, the mechanisms by which it bioaccumulates toxins have yet to be fully understood. In particular, the interactions between coexisting trace metal pollutants in the aquatic environment have only recently been considered, and it remains unclear how a biomonitoring programme should adapt to the effects of these interactions. It is evident that failing to account for these additional stressors will result in an ineffective biomonitoring programme; for this reason, a comprehensive understanding of the bioaccumulation mechanisms is required in order to reliably anticipate the effects of any interferences on the outcome., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Organisms with a parasitic lifestyle comprise a high proportion of biodiversity in aquatic and terrestrial environments. However, there is considerable variation in the ways in which they acquire nutrients. Hematophagy is a common consumption strategy utilized by some terrestrial, aquatic, and marine organisms whereby the parasite removes and digests blood from a host. Gnathiid isopods are marine hematophagous parasites that live in benthic substrates from the intertidal to the abyss. Although ecologically similar to ticks and mosquitoes, they feed only during each of 3 juvenile stages and adults do not feed. They have long been considered as generalist fish parasites and to date, there have been no reports of their successfully feeding on invertebrates. Based on observations of gnathiids attached to soft-bodied invertebrates collected from light traps, we conducted a laboratory experiment in which we collected and individually housed various common Caribbean invertebrates and placed them in containers with gnathiids to see if the gnathiids would feed on them. All fed gnathiids were subsequently removed from containers and given the opportunity to metamorphose to the next developmental stage. In total, 10 out of the 260 gnathiids that were presented with 1 of 4 species of potential invertebrate hosts had fed by the next morning. Specifically, 9 of a possible 120 gnathiids fed on lettuce sea slugs ( Elysia crispata ), and 1 of a possible 20 fed on a bearded fireworm ( Hermodice carunculata ). Eight of these 10 fed gnathiids metamorphosed to the next stage (5 to adult male, 2 to adult female, and 1 to third-stage juvenile). Even though feeding rates on invertebrates were considerably lower than observed for laboratory studies on fishes, this study provides the first documented case of gnathiids' feeding on and metamorphosing from invertebrate meals. These findings suggest that when fish hosts are not readily available, gnathiids could switch to soft-bodied invertebrates. They further provide insights into the evolution of feeding on fluids from live hosts in members of this family.

Isopods of the genus Ceratothoa (Cymothoidae) are one of the largest invertebrates parasitic on a variety of fishes, which include commercially important species. Nevertheless, the parasitic effects on fish body condition have been studied only in a few Ceratothoa species, particularly those living in the Mediterranean and Australian waters. Findings from these previous studies suggest the hypothesis that effects of parasitism by Ceratothoa species are benign on native host condition in the wild. In this study, to test this hypothesis on another Ceratothoa-fish relationship in different region, we examined the effects of Ceratothoa arimae on the body condition of the yellowstriped butterfish, Labracoglossa argenteiventris, a commercial fish important to local fisheries particularly in the remote islands of Tokyo, Japan. Ceratothoa arimae was found in 8 out of 23 fish examined (prevalence: 34.8%). Although infected and uninfected fish were similar in standard length, the body condition index (relative weight) of infected fish was significantly lower than that of uninfected fish. The observed weight of infected fish was an average of 89.2% of the expected weight. These results are inconsistent with the hypothesis and suggest that the potential effects of Ceratothoa parasites need to be considered carefully in fishery management plan of host fish., (Copyright © 2019. Published by Elsevier B.V.)

The flow regime of a river is an important driver of many ecosystem components. However, few studies explore how differences in flow rates and water chemistry can influence communities of parasites and their hosts. Here, we investigate the impact of dissolved oxygen, pH, salinity, water temperature, and river flow on the abundance and prevalence of cymothoid isopod parasitism ( Lironeca ovalis ) of the Bay Anchovy ( Anchoa mitchilli ) in the Alafia and Hillsborough rivers of Tampa Bay (Florida). We also explore seasonality by comparing monthly samples preserved throughout 2005-2007. Although both the Alafia and Hillsborough rivers had similar average water temperatures and salinity, and similar wet and dry season cycles, the upstream damming of the Hillsborough River had numerous negative effects on water flow rate, dissolved oxygen content, and acidity. This disruption in water quality corresponded with a lower abundance of anchovy hosts, fewer free-swimming cymothoids, and low prevalence of anchovy parasitism. Anchovies were much more abundant in the Alafia River, but flow negatively affected abundance-a negative effect that could be mitigated by positive changes in water temperature, salinity, and pH. Flow rates also negatively affected free-swimming cymothoid abundance; however, water flow was less important in predicting their parasitism of anchovies. In Alafia, fewer anchovies were parasitized when dissolved oxygen was high and water acidity was low, but more were parasitized during the wet season. These findings corroborate predictions that flow can moderate habitat stability and complexity which, in turn, can impact opportunities for parasitism of host communities.

In the present study the model isopod, Cyathura carinata were exposed to four pH NIST treatments (control: 7.9; 7.5, 7, 6.5) in order to determine the tolerance and pH threshold value this estuarine species withstand under future acidification scenarios. Seawater acidification significantly affected the lifespan of C. carinata, where population density was remarkably reduced at the lowest pH treatment. The longevity, survivorship and swimming activity (related to the acquisition of energy) of these isopods decreased with decreasing pH. Furthermore, to determine the possible metabolic plasticity of this species, the swimming activity, the Na+/K + -ATPase activity (relevant for osmoregulation process), and the RNA:DNA ratio (an indicator of fitness) were measure from two populations of C. carinata, one inhabiting a stable environment (pH NIST 7.5-8.0) and one inhabiting a fluctuating pCO 2 regimes (pH 3.3-8.5) subjected to three pH treatments (7.9, 7.0 and 6.5). The population from high fluctuating pCO 2 conditions showed capacity to withstand to pH 6.5, as well as higher longevity and metabolic plasticity, when compared with the population from the habitat with slight pCO 2 variation. These results indicate that Cyathura population from stable environments could be vulnerable to ocean acidification because it could trigger detrimental effects on its survival energy budget, and growth. However, ocean acidification has limited effect on the energy budget and survival of C. carinata population from highly variable habitats, suggesting that they are able to cope with the elevated energy demand. The difference showed between populations is likely an indication of genetic differentiation in tolerance to ocean acidification, possibly attributable to local adaptations, which could provide the raw material necessary for adaptation to future conditions. In addition, our results suggest that when assessing marine crustacean responses to changing environments on a global scale, variability in population and metabolic responses need to be considered., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This study aimed at determining the competition of cadmium (Cd), lead (Pb), zinc (Zn) and copper (Cu) on their assimilation, on the food consumption and the growth of terrestrial isopod Porcellio laevis. Individuals were exposed to artificially contaminated litter of Quercus for 4 weeks and were weekly weighed. At the end of the experiment, the concentration of Cd, Pb, Zn and Cu in individuals were measured by atomic absorption spectrometry. Biological parameters such as growth, and bioaccumulation factor (BAF) were calculated and results from the various treatments were compared. Depending on metals, weight loss or gain were recorded for isopods during the four weeks of exposure. A weight loss was measured on individuals exposed to Cd-contaminated litter whereas a weight gain was highlighted for those exposed to the Zn-contaminated litter. BAF values revealed that P. laevis was macroconcentrator of Zn and Cu and deconcentrator of Cd and Pb.

Environmental temperatures and oxygen availability are important for the balance between oxygen supply and demand. Terrestrial organisms are generally perceived to be less limited by access to oxygen than their aquatic counterparts. Nevertheless, even terrestrial environments can be deficient in oxygen, especially for organisms occurring in soil, litter, wood, rotten fruit or at high elevations. While isopods are the best adapted to a terrestrial lifestyle among crustaceans, many species, including woodlice, occupy environmental gradients of temperature and oxygen. To investigate whether mismatches between oxygen supply and demand can result in a loss of performance in a terrestrial organism, we studied the effects of atmospheric oxygen concentration on the thermal performance of the common rough woodlouse (Porcellio scaber). We compared the thermal preference, thermal sensitivity of running speed, and tolerance to extreme temperatures of woodlice exposed to one of two oxygen concentrations (21% - normoxia, 7% - hypoxia). Under hypoxia, P. scaber preferred microhabitats with temperatures that were on average 3°C lower than those preferred under normoxia. The running speed tended to reach its maximum at a lower temperature under hypoxia than under normoxia (25.13°C vs 28.87°C, respectively, although p was equal to 0.09), and normoxic woodlice ran approximately 1.5-fold faster than hypoxic woodlice at the point of maximum speed. Heat tolerance was significantly lower under hypoxia (38.9°C) than under normoxia (40.7°C), but there was no difference in cold tolerance (5.81°C under normoxia and 5.44°C under hypoxia). Overall, our results indicate that environmental gradients of temperature and oxygen may shape the physiological performance of terrestrial ectotherms, likely via their effects on the balance between oxygen supply and demand, which may have fitness consequences for these organisms in nature., Competing Interests: The authors have declared that no competing interests exist.

Background: Anilocra capensis Leach, 1818 is the only named species of Anilocra Leach, 1818 from South Africa. Anilocra is a large genus (> 40 species) with high levels of diversity reported from the Caribbean and Indo-West Pacific. Considering it is highly unlikely that all records of Anilocra from South Africa can be of a single species, the aim of this study was to better understand the diversity of Anilocra from this region and continent., Methods: To redescribe A. capensis, the syntypes of A. capensis and specimens recorded as A. capensis from Africa were borrowed from the Natural History Museum, London, UK, and The iZiko South African Museum, Cape Town. Newly collected fresh samples of A. capensis were collected from off Cape Town, South Africa. Morphological redescriptions of the syntypes, and other museum and fresh material were conducted. Fresh samples were used to characterise molecularly A. capensis using the mitochondrial cytochrome c oxidase subunit 1 gene (cox1)., Results: Morphological analyses demonstrated that apart from A. capensis there are six Anilocra species new to science from Africa: Anilocra ianhudsoni n. sp., Anilocra bunkleywilliamsae n. sp., Anilocra paulsikkeli n. sp., Anilocra jovanasi n. sp., Anilocra angeladaviesae n. sp. and Anilocra hadfieldae n. sp. Of the species under study, specimens of A. capensis appear to demonstrate the most individual variation, which occurs in pleonite width, pleotelson form and uropod length. We determined that African species of Anilocra can be primarily differentiated by the proportional shape and size of the full body in dorsal view and pereonites 1, 6 and 7. Other defining morphological traits include proportional shape and size of the pereopods, and the antenna and antennula peduncles. Lastly, the molecular characterisation of A. capensis is provided and the interspecific divergence with Mediterranean species is smaller than that with Caribbean species., Conclusions: The results of this study provide a detailed redescription of A. capensis and the first molecular barcode for this organism. Six new species of Anilocra from Africa are described, establishing that the diversity of Anilocra in this region is greater than previously known. With this new understanding of species differences, we can accurately conduct detailed molecular and ecological analyses of Anilocra from Africa with certainty of the organism under study.

Background: Juvenile gnathiid isopods are common ectoparasites of marine fishes. Each of the three juvenile stages briefly attach to a host to obtain a blood meal but spend most of their time living in the substrate, thus making it difficult to determine patterns of host exploitation. Sequencing of host blood meals from wild-caught specimens is a promising tool to determine host identity. Although established protocols for this approach exist, certain challenges must be overcome when samples are subjected to typical field conditions that may contribute to DNA degradation. The goal of this study was to address a key methodological issue associated with molecular-based host identification from free-living, blood-engorged gnathiid isopods-the degradation of host DNA within blood meals. Here we have assessed the length of time host DNA within gnathiid blood meals can remain viable for positive host identification., Methods: Juvenile gnathiids were allowed to feed on fish of known species and subsets were preserved at 4-h intervals over 24 h and then every 24 h up to 5 days post-feeding. Host DNA extracted from gnathiid blood meals was sequenced to validate the integrity of host DNA at each time interval. DNA was also extracted from blood meals of wild-fed gnathiids for comparison. Attempts were also made to extract host DNA from metamorphosed juveniles., Results: Using a cox1 universal fish primer set, known fish host DNA sequences were successfully identified for nearly 100% of third-stage juvenile gnathiid blood meals, digested for up to 5 days post-feeding. For second-stage juveniles, host identification was 100% successful when gnathiids were preserved within 24 h of collection. Fish hosts were positively identified for 69% of sequences from wild-fed gnathiid isopods. Of the 31% of sequences not receiving a ≥ 98 % match to a sequence in GenBank, 25 sequences were of possible invertebrate origin., Conclusions: To our knowledge, this is the first study to examine the degradation rate of gnathiid isopod blood meals. Determining the rate at which gnathiids digest their blood meal is an important step in ensuring the successful host identification by DNA-based methods in large field studies.

Geoplanidae (Platyhelminthes: Tricladida) feed on soil invertebrates. Observations of their predatory behavior in nature are scarce, and most of the information has been obtained from food preference experiments. Although these experiments are based on a wide variety of prey, this catalog is often far from being representative of the fauna present in the natural habitat of planarians. As some geoplanid species have recently become invasive, obtaining accurate knowledge about their feeding habits is crucial for the development of plans to control and prevent their expansion. Using high throughput sequencing data, we perform a metagenomic analysis to identify the in situ diet of two endemic and codistributed species of geoplanids from the Brazilian Atlantic Forest: Imbira marcusi and Cephaloflexa bergi. We have tested four different methods of taxonomic assignment and find that phylogenetic-based assignment methods outperform those based on similarity. The results show that the diet of I. marcusi is restricted to earthworms, whereas C. bergi preys on spiders, harvestmen, woodlice, grasshoppers, Hymenoptera, Lepidoptera and possibly other geoplanids. Furthermore, both species change their feeding habits among the different sample locations. In conclusion, the integration of metagenomics with phylogenetics should be considered when establishing studies on the feeding habits of invertebrates.

The effects of CO 2 -related acidification on two crustacean populations, the isopod Cyathura carinata and the amphipod Elasmopus rapax, were studied. Three pH levels were tested: artificial seawater without CO 2 injection and two levels of reduced pH. Even though RNA:DNA ratio was reduced for both species, no statistical significant differences were found between the control and the treatments. Both species experienced a reduction in survivorship, longevity and the body length of surviving animals; although the impairment observed in E. rapax was more severe than in C. carinata. The long life span isopod and the short life span amphipod experienced a high degree of impairment in the reproduction, likely due to the reallocation of resources from reproduction to body maintenance and increasing survival by postponing the brood production. Regardless of the underlying processes and the energetic pathways, both experienced failure to reproduce, which could lead to the local extinction of these species., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Shelter-seeking is a vital behavior for stress reduction and survival in a range of animals. It comes at the cost of reduced foraging, mate finding, dispersal and territoriality, and is expected to reflect the trade-off between fitness costs and benefits. One way to test this hypothesis is to compare shelter-seeking behavior in surface habitats and in caves where external threat factors are largely reduced. We did so using the freshwater isopod Asellus aquaticus from the Postojna-Planina Cave System and surrounding surface waters. Animals from two distinct, replicated pairs of surface and cave populations were individually offered a choice between shelter and open area. The thigmotatic sensation of a transparent plastic plate was the only stimulus that could trigger the sheltering behavior. Video recordings showed a clear reduction of shelter-seeking behavior in the cave ecomorph in one population pair (Pivka). There were no changes in the other population pair (Rak), where the behavioral response had a much higher variance. Our results were partly in agreement with the hypothesis that shelter-seeking behavior should be selected against in an environment with reduced external threats. It is nevertheless too early for generalizations as the results in the second population pair were inconclusive. Additionally, we showed that for benthic walkers like A. aquaticus the use of rough substrate is crucial to obtain unbiased behavioral responses. Results of some previous studies using smooth glass or plastic substratum could be affected by unnatural behavior of animals constantly trying to find firm contact with the ground., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Coastal habitats, in particular sandy beaches, are becoming increasingly exposed to artificial light pollution at night (ALAN). Yet, only a few studies have this far assessed the effects of ALAN on the species inhabiting these ecosystems. In this study we assessed the effects of ALAN on Tylos spinulosus, a prominent wrack-consumer isopod living in sandy beaches of north-central Chile. This species burrows in the sand during daylight and emerges at night to migrate down-shore, so we argue it can be used as a model species for the study of ALAN effects on coastal nocturnal species. We assessed whether ALAN alters the distribution and locomotor activity of this isopod using a light system placed in upper shore sediments close to the edge of the dunes, mimicking light intensities measured near public lighting. The response of the isopods was compared to control transects located farther away and not exposed to artificial light. In parallel, we measured the isopods' locomotor activity in the laboratory using actographs that recorded their movement within mesocosms simulating the beach surface. Measurements in the field indicated a clear reduction in isopod abundance near the source of the light and a restriction of their tidal distribution range, as compared to control transects. Meanwhile, the laboratory experiments showed that in mesocosms exposed to ALAN, isopods exhibited reduced activity and a circadian rhythm that was altered and even lost after a few days. Such changes with respect to control mesocosms with a natural day/night cycle suggest that the changes observed in the field were directly related to a disruption in the locomotor activity of the isopods. All together these results provide causal evidence of negative ALAN effects on this species, and call for further research on other nocturnal sandy beach species that might become increasingly affected by ALAN., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Only a few insect species are known to engage in symbiotic associations with antibiotic-producing Actinobacteria and profit from this kind of protection against pathogens. However, it still remains elusive how widespread the symbiotic interactions with Actinobacteria in other organisms are and how these partnerships benefit the hosts in terms of the growth and survival. We characterized a drastic temperature-induced change in the occurrence of Actinobacteria in the gut of the terrestrial isopod Porcellio scaber reared under two different temperature (15 °C and 22 °C) and oxygen conditions (10% and 22% O 2 ) using 16S rRNA gene sequencing. We show that the relative abundance of actinobacterial gut symbionts correlates with increased host growth at lower temperature. Actinobacterial symbionts were almost completely absent at 22 °C under both high and low oxygen conditions. In addition, we identified members of nearly half of the known actinobacterial families in the isopod microbiome, and most of these include members that are known to produce antibiotics. Our study suggests that hosting diverse actinobacterial symbionts may provide conditions favorable for host growth. These findings show how a temperature-driven decline in microbiome diversity may cause a loss of beneficial functions with negative effects on ectotherms., (Copyright © 2019 Elsevier Ltd. All rights reserved.)