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This study investigated the effect of partially replacing fish meal with krill and copepod meals in inert diets co-fed with shrimp on the growth and nutrient digestibility of long-snout seahorses (Hippocampus guttulatus). A control diet (Diet 1) using raw starch and four experimental diets with similar protein (≈44.8%) and energy (≈15.1 MJ/kg) levels were tested. Diet 2 used fish meal as the sole protein source, while in Diets 3–5, krill and copepod meals replaced 44% of the fish meal. Seahorses fed shrimp + Diets 2–5 showed significantly higher growth rates (p < 0.05) than those fed shrimp + Diet 1, though there were no significant growth differences among Diets 2–5. Digestibility of dry matter (46.1% to 72.2%), lipids (73.3% to 85.5%), crude protein (89.8% to 95.8%), energy (82% to 92.2%), and phosphorus (28.7% to 64.4%) varied with diet, being consistently lower in seahorses fed shrimp + Diet 1. As an agastric species, H. guttulatus did not exhibit impaired digestibility for any of the tested nutrients, minerals, or energy. This study suggests that crustacean meals can effectively substitute fish meal in inert diets for this species, contributing to the sustainability and optimization of captive seahorse husbandry practices. [ABSTRACT FROM AUTHOR]

This study investigated the tolerance of resting eggs of Eurytemora pacifica to storage under low temperatures, which is of particular interest in light of the recent use of nauplii as living food in aquaculture, other than conditions experienced also in the wild during winter cold events in the Northern Hemisphere. Sediment samples collected in August 2020 were used to store the resting eggs at two different freezing temperatures (−5 and −20 °C) for five different durations (1, 3, 6, 9, and 12 months). The mean hatching success rates of the resting eggs after one month of storage were 85.3 ± 1.5% (−5 °C) and 85.0 ± 3.6% (−20 °C), with no significant difference between freezing temperatures. However, significant differences emerged over time, with the mean hatching success rate remaining at 85.0 ± 3.6% at −5 °C after three months, while it dropped sharply to 1.7 ± 2.1% at −20 °C. For the non-freezing conditions, the hatching success at 10 °C increased gradually over the one-month incubation period, ultimately reaching 71.0%. These findings demonstrate the remarkable cold tolerance of E. pacifica but also indicate a limit to this tolerance at longer durations. These results underscore the importance of considering the adoption of storage freezing for resting eggs to be used for aquaculture and also suggest the possibility of the species better surviving the extreme weather events in comparison with other species. [ABSTRACT FROM AUTHOR]

The study was conducted to assess the species composition of copepods around Munroe Island of Kerala (South India) from October 2020 to September 2022. Copepod samples collected from the mangrove habitats around Munroe Island revealed 31 species belonging to 18 genera and 15 families. The order Calanoida was recognized as the most dominant taxon, with 23 species, followed by Harpacticoida (5 spp.) and Cyclopoida (3 spp.). Spatially, sampling station 3 (Palliyanthuruthu) had the highest species richness (28 spp.); in contrast, the lowest species richness was found at sampling station 1 (Villimangalam, 13 spp.). When exploring the seasonal effects on copepod richness it was found that the highest species richness was seen in the post-monsoon season (31 spp.) followed by the pre-monsoon season (29 spp.), while the least diversity was found during the monsoon season (28 spp.). Species such as Acartia bilobata, Paracalanus parvus, Pseudodiaptomus aurivillii, Pseudocalanus elongatus, Microsetella norvegica, and Oithona similis were found to be perennial in nature. The investigation calls for intensive surveys of copepods to reveal their ecology and diversity in the hitherto less studied region in South India. [ABSTRACT FROM AUTHOR]

Most studies on the feeding ecology of larvae and juveniles of commercially important pelagic fishes have used field-based approaches. However, due to possible biases related to net sampling, it is uncertain whether the results obtained from those studies truly represent the situation of live fish in the sea. Here we investigated the feeding ecology of pelagic fishes through a laboratory experiment minimizing the biases inherent in field net sampling. In the experiment, hatchery-reared juvenile chub mackerel (Scomber japonicus) and larval/juvenile Japanese anchovy (Engraulis japonicus) were fed with wild-caught zooplankton assemblages collected from around Hakatajima Island in the Seto Inland Sea, Japan. The relationships between fish size and prey number in the gut, and the selectivity on each prey organism were determined. As a result, in both species, prey number and size increased with body size, and the fish showed strong selectivity for crustaceans including copepodites and adults of copepods. Our data has also clearly indicated that both species can selectively prey on preferred foods that are rare while avoiding non-preferred foods that are abundant. These results, which substantially accord with reports from previous field studies, will not only help field scientists make a convincing interpretation of their data, but also open the possibility of further laboratory studies on detailed mechanisms of the feeding selectivity of larval/juvenile pelagic fishes. [ABSTRACT FROM AUTHOR]

One of the least understood trophic pathways on coral reefs is the linkage between highly productive cryptic motile invertebrates (herein: cryptofauna) and the predatory vertebrates that underpin reef fisheries. As cryptofauna are difficult to observe and quantify, particularly in coral rubble where they proliferate, the diets of invertivores that forage in rubble have largely been determined through relative gut content analyses. Without congruent quantification of prey diversity, biomass, and rates of predation specific to rubble, it remains challenging to develop models of productivity and energy transfer. We calculated bite rates of six wrasses (Labridae) and a goatfish (Mullidae) commonly found foraging in rubble, using in situ videography on a coral reef in Palau, Western Micronesia. Consumption rates (i.e. individuals consumed) and prey preferences were determined using tank-based feeding experiments, where individual fish were presented with a diverse rubble community characterised before and after 2 h feeding trials. The motile cryptofauna community and invertivore diet consisted predominantly of Arthropoda (83% and > 58%, respectively), with calanoid copepods and mysids positively selected and harpacticoids, decapods and ostracods negatively selected. The interspecific mean (± standard error) rate of consumption was 3.5 ± 0.2 ind. min−1 from rubble, estimated to equal 9.5 ± 0.9 mg min−1 of invertebrate biomass consumed per fish, with biased uptake of small fauna. Bite and consumption rates varied among species with the greatest efficiency in biomass uptake evident in Halichoeres melanurus. This study provides a first attempt at characterising diverse cryptofauna communities pre- and post-trial to identify feeding rates and preferences of coral reef invertivores from the rubble benthos, and highlights the importance of addressing the bioavailability of lower trophic entities in energy pathways. [ABSTRACT FROM AUTHOR]

We build on previous research describing correlative links between changes in the abundance of the copepod Calanus finmarchicus , a foundational zooplankton species of the pelagic food web, and diminishing recruitment of young-of-year American lobster (Homarus americanus) to benthic nurseries in the Gulf of Maine. Using parallel 31-year time series of lobster larvae and zooplankton collected on the New Hampshire coast between 1988 and 2018, we investigated how changes in phenology of stage I larval lobster and their putative copepod prey, C. finmarchicus , affect their temporal overlap and potential to interact during the larval season. We found that over the time series both the lobster egg hatch and first appearance of larvae began earlier in the season, a trend significantly correlated with ocean warming. The last appearance of larvae in late summer has been delayed, however, thereby extending the larval season. Even with the longer larval lobster season, the C. finmarchicus season has increasingly been ending before the peak abundance of stage I lobster larvae. The net effect is a widening mismatch in phenology of the two species, an outcome consistent with the hypothesis that changes in abundance and phenology of C. finmarchicus have contributed to recent declines in lobster recruitment. [ABSTRACT FROM AUTHOR]

Zooplankton is an important link between primary producers and lower trophic level organisms in the marine food web, and is an important biological basis for the formation of fishing grounds. Based on the Zooplankton samples collected by the fishery resources survey vessel "Songhang" of Shanghai Ocean University during the comprehensive scientific survey of fishery resources in the high seas of the Northwest Pacific Ocean from June to August in 2021 and 2022, the Zooplankton samples were analyzed in terms of their species composition, distributional characteristics, and their relationship with the environment. The results showed that a total of 174 Zooplankton species were collected in the surveyed area over the two years, belonging to 10 groups. Copepoda and planktonic larvae were the most abundant Zooplankton, with 95 and 22 species identified respectively, accounting for 54.6% and 12.6% of the total number of species, followed by ScyphoZoa, with 18 species identified, and Ostracoda, Tunicata, Chaetognatha, Euphausiacea, and Gastropoda with 11, 9, 6, 4 and 3 species respectively. Additionally, two species each of Polychaeta, Amphipoda, and Cladocera were identified. The dominant genes (species) included seven categories: Clausocalanus sp., Oncaea sp., Paracalanus sp., Calocalanus sp., Oithona plumifera, Oithona decipiens and Metridinidae larvae. The species diversity and dominant genes (species) composition were similar in both years. The mean Zooplankton abundance in 2021 was 732.89 ind./m³, lower than that in 2022 (1 418.88 ind./m³). The Shannon-Wiener index in 2021 was 1.57-3.16, the Evenness index was 0.54-0.91, and the abundance index was 0.84-3.36. All three indices were higher than those in 2022, which ranged from 0.66 to 2.92, 0.26 to 0.94, and 0.77 to 3.11, respectively. GAM analyses showed that Zooplankton abundance was significantly and negatively correlated with the sea-surface salinity and the water temperature in the 200 m layer, and the analyses suggested that the Kuroshio current and the Oyashio also had a certain effect on the temporal and spatial distributions of the abundance. The results of this study will provide basic information for the study of Zooplankton in the high seas of the Northwest Pacific Ocean. [ABSTRACT FROM AUTHOR]

We describe and analyze the mimetic behavior in juvenile Maracaibo leatherjack, Oligoplites palometa, establishing correlations with feeding diet composition during daytime. The relationships between behavioral patterns and the feeding diet of O. palometa were analyzed during daylight hours, considering seasonal and lunar cycle variations within a tidal channel in the estuary of the Caeté River, Northeastern Pará, Brazil. The two relatively well-defined seasons associated with the study area—rainy and dry seasons—have influenced the behavioral patterns and feeding diet of the fish. During the dry season, higher foraging frequencies were observed, consistently related to mimetic swimming behavior, and correlated with the abundance of food items found in the stomach contents. In contrast, during the rainy season, both behavioral and food item frequencies were lower, although the food items presented greater diversity. The fish have exhibited zooplanktivorous feeding habits, preferring copepods over other prey types. The lunar cycle may be associated with the temporal distribution of prey, whereas Brachyura, Clupeid larvae, and unidentified Crustacea are more related to the full, waning, and new moon phases, respectively. Our results clarify the dynamics between the environment and prey types, behavioral tactics, and feeding diets adopted by mimetic juvenile O. palometa. [ABSTRACT FROM AUTHOR]

Climate change may exacerbate the impact of invasive parasites from warmer climates through pre‐existing temperature adaptations. We investigated temperature impacts on two closely related marine parasitic copepod species that share the blue mussel (Mytilus edulis) as host: Mytilicola orientalis has invaded the system from a warmer climate <20 years ago, whereas its established congener Mytilicola intestinalis has had >90 years to adapt. In laboratory experiments with temperatures 10–26°C, covering current and future temperatures as well as heat waves, the development of both life cycle stages of both species accelerated with increasing temperature. In the parasitic stages, the growth of the established invader increased evenly from 10°C to 22°C, whereas the recent invader barely grew at all at 10°C and grew faster already at 18°C. In contrast, temperature had little effect on the transition success between life cycle stages. However, the highest temperature (26°C) limited the egg development success of the established invader and the host entry success of both species, whereas the infection success of the established invader increased at 18°C and 22°C. In general, our experiments indicate that the main effect of temperature on both species is through development speed and not life cycle stage transition success. Based on regional long‐term temperature data and predictions, the numbers of completed life cycles per year will increase for both parasites. The established invader seems better adapted for low current temperatures (around 10°C), whereas the more recent invader barely develops at these temperatures but can cope in high temperatures (around 26°C). Hence, pre‐existing temperature adaptations of the recent invader may allow the species to better cope with heat waves. [ABSTRACT FROM AUTHOR]

We investigated the species diversity of the demersal copepod genus Pseudodiaptomus in the coastal waters of northern Taiwan, and recorded four species new to Taiwanese waters: P. echinatus n. sp., P. ishigakiensis Nishida, 1985, P. philippinensis Walter, 1986, and P. zhengi Wang & Guo, 2019. Pseudodiaptomus echinatus n. sp. is distinguished from the allied species P. serricaudatus (Scott T., 1894) by the female genital double-somite, which is laterally swollen and of subequal length and width, and the male fifth leg, the right endopod of which is oval with a row of spinules increasing in size toward the tip, and the first exopod segment of which has a distomedial digitiform process with rounded tip. In addition, out of the 11 nominal species previously recorded from Taiwanese waters, we found only three species (P. annandalei Sewell, 1919, P. bispinosus Walter, 1984, P. trihamatus Wright, 1937). We were unable to confirm the presence of P. forbesi (Poppe & Richard, 1890), P. incisus Shen & Lee, 1963, P. inopinus Burckhardt, 1913, P. marinus Sato, 1913, P. pacificus Walter, 1986, P. penicillus Li & Huang, 1984, P. poplesia (Shen, 1955), and P. serricaudatus (T. Scott, 1894) by a critical review of available literature based on morphology, locality, habitat, etc. In this regard, it is necessary for a future study to try to verify the presence of these eight species in Taiwanese waters. [ABSTRACT FROM AUTHOR]

Appropriate diagnoses of parasites of apex marine predators are crucial to understand their biodiversity, host specificity, biogeography, and life cycles. Such diagnoses are also informative of ecological and biological characteristics of both host and environment in which the hosts and their parasites live. We here (i) investigate the parasite fauna of a bluntnose sixgill shark Hexanchus griseus (Bonnaterre, 1788) obtained from the Gulf of Naples (Tyrrhenian Sea), (ii) characterize molecularly all its metazoan parasites, and (iii) resurrect and report the main morphological features and phylogenetic position of Grillotia acanthoscolex, a cestode species previously synonymized with Grillotia adenoplusia. A rich parasite fauna represented by eight different taxa was found, including two monogeneans (Protocotyle grisea and Protocotyle taschenbergi), one digenean (Otodistomum veliporum), four cestodes (Crossobothrium dohrnii, Clistobothrium sp., G. acanthoscolex, and G. adenoplusia), and one copepod (Protodactylina pamelae). Sequencing of these samples accounts for an important molecular baseline to widen the knowledge on the parasitic fauna of bluntnose sixgill sharks worldwide and to reconstruct their correct food chains. The bluntnose sixgill shark was found to be a definitive host for all endoparasites found here, confirming that it occupies an apex trophic level in the Mediterranean Sea. The taxa composition of the trophic parasite fauna confirms that the bluntnose sixgill shark mostly feeds on teleost fish species. However, the occurrence of two phillobothrid cestodes (C. dohrnii and Clistobothrium sp.) suggests that it also feeds on squids. Finally, we emphasize the importance of using integrative taxonomic approaches in the study of parasites from definitive and intermediate hosts to elucidate biology and ecology of taxa generally understudied in the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

Reservoirs are ecologically important ecosystems. In the Brazilian semiarid region, these ecosystems are impacted by environmental changes resulting from the rainfall regime. Furthermore, the reservoirs boast a rich planktonic biodiversity, which is directly influenced by the ecological dynamics of each reservoir. Our aim was to analyse the impact of rapid changes between the dry and rainy seasons on the limnological variables in a Brazilian semiarid reservoir. Furthermore, we analysed the impact of this phenomenon on the microcrustacean community in the reservoir. We observed that the reservoir is significantly impacted by the region's rainfall regime. During the rainy season, the reservoir volume increases, resulting in higher pH and dissolved oxygen levels, and lower water temperature, electrical conductivity and total dissolved solids levels. The transition from the dry to the rainy season influenced the microcrustacean community. Our findings indicate that the transition from the dry to the rainy seasons in Brazilian semiarid region results in limnological changes in the reservoirs of this region. Furthermore, these changes also result in alterations to the microcrustacean community structure in these reservoirs. [ABSTRACT FROM AUTHOR]

The seasonal fluctuations of the copepod Eodiaptomus japonicus, which dominates the zooplankton community of Lake Biwa, have been disrupted several times over the past 45 years. The aim of this study was to clarify the primary environmental factor that caused the disrupted seasonal cycle in population density of E. japonicus. Here, we tested the hypothesis that the disruption in their seasonal cycle was due to the impacts of water temperature, food conditions, and predator pressure, using an individual-based model (IBM). Based on the experimental data from the literature, we described the growth and reproduction of E. japonicus using temperature- and food-dependent functions. Previously, the developmental time of this species was expressed using Bělehrádek's equation. In this study, we applied the Kontodimas equation, which successfully reproduced the effects of food scarcity at higher temperatures. Additionally, the influence of predators was incorporated into the survival rate of adult individuals. The long-term data set of Lake Biwa was input into the developed model to simulate the population fluctuations during the disruption period (1975–1979) and stable period (1995–1999) of their seasonal cycle. The combination of environmental data to be input was (1) water temperature, food availability, and predators; (2) water temperature and food availability; and (3) water temperature and predators. Disruptions in the seasonal cycle of the population were only observed in scenario (1) during the disruption period simulation, suggesting that the disrupted seasonal cycle of this species in Lake Biwa may have been caused by the effects of both food condition and predators. The results of simulation scenarios (2) and (3) indicated that predators have a stronger impact on the population than food availability. This time, we used common and simple indicators to describe food conditions and predators, but the model can be improved to be more complex and accurate as more data become available. Such models are important tools for understanding the relationship between environmental factors and the dynamics of diaptomid copepod populations. [ABSTRACT FROM AUTHOR]

Calanoid copepods have gained significant interest due to their rapid response to changes in environment. This study examined the seasonal variation in the size of calanoid copepods and their relationships to various environmental parameters in a tropical coast of India. Zooplankton samples were collected at Marina Beach, India, from January to December 2021. Ten calanoid species were selected based on their distribution to study the seasonal variation in the size, and the results showed a clear seasonal pattern, with smaller size of calanoid observed during summer months with high temperatures and larger sizes during the monsoon season associated with increased rainfall and nutrient availability. Negative correlations were observed between copepod size variation and temperature, while positive correlations were observed with dissolved oxygen, pH, salinity, and chlorophyll-a concentration. Acrocalanus gibber, Acrocalanus gracilis and Canthocalanus pauper showed changes that are more pronounced in body size (0.89–0.99, 1.12–1.23 mm and 1.41–1.52 mm, respectively) indicating species-specific responses to environmental fluctuations. These findings highlight the influence of environmental parameters in determining the size of calanoid copepods in tropical oceans. Moreover, this study contributes to our understanding of the ecological processes and global warming that determine copepod size variation in coastal ecosystems. [ABSTRACT FROM AUTHOR]

The present investigation was conducted to assess the species composition of Copepoda in Munroe Island from October 2020 to September 2022. As the information about the species composition of Copepoda is scarce in the mangrove habitats of the southern part of Kerala, their appraisal assumes greater significance. Copepod samples collected from the mangrove habitats of Munroe Island of Kerala (southern India) revealed 31 species belonging to 18 genera and 15 families. The order Calanoida was recognized as the most dominant taxa with 23 species, followed by Harpacticoida (five species) and Cyclopoida (three species). Among the 15 families encountered, Acartiidae, Centropagidae, Harpacticidae, Paracalanidae and Pseudodiaptomidae were the most diverse. Species such as Acartia bilobata, Paracalanus parvus, Pseudodiaptomus aurivillii, Pseudocalanus elongatus, Microsetella norvegica, and Oithona similis were found to be perennial. The investigation calls for intensive copepod surveys to reveal their ecology and diversity in the hitherto less-studied region in southern India. [ABSTRACT FROM AUTHOR]

Copepods are a major component of metazooplankton and important prey for fish and invertebrates such as crabs, shrimps, and flatworms. Certain bloom-forming dinoflagellates can kill copepods, but there is little research on the interactions between copepods and the bloom-forming dinoflagellates Karenia bicuneiformis and K. selliformis. In this study, the survival and ingestion rates of the calanoid copepod Acartia hongi feeding on K. bicuneiformis and K. selliformis were determined as a function of prey concentration. On day 2, the survival of A. hongi incubated with K. bicuneiformis was 90–100% at all the tested prey concentrations, while that with K. selliformis was 0–20% at ≥ 582 ng C mL−1. Compared to other harmful dinoflagellates from the literature, K. bicuneiformis caused low mortality of Acartia; however, K. selliformis caused almost the highest mortality at similar dinoflagellate concentrations. With increasing mean prey concentration, the ingestion rates of A. hongi feeding on K. bicuneiformis increased on day 1, but those on K. selliformis did not increase. Acartia hongi stopped feeding on K. bicuneiformis at mean prey concentrations of ≥ 341 ng C mL−1 and K. selliformis at all prey concentrations on day 2. At the prey concentration of 1000 ng C mL−1, the ingestion rate of A. hongi feeding on K. bicuneiformis was moderate among the rates of Acartia spp. feeding on harmful dinoflagellates; however, that on K. selliformis was the lowest. These results indicate that K. bicuneiformis and K. selliformis differentially affect the survival and ingestion rates of A. hongi. [ABSTRACT FROM AUTHOR]

The distribution and diversity of calanoid copepods were investigated using samples collected from 37 lakes in North-eastern (NE) China in 2019. A total of 10 calanoid copepods belonging to eight genera and three families were identified. Among them, Heterocope soldatovi Rylov, 1922 was recorded for the first time in China. Species from the family Centropagidae were more widespread than those from the families Temoridae and Diaptomidae. Sinocalanus doerrii (Brehm, 1909), previously not recorded in NE China, is now widespread alongside Boeckella triarticulata (Thomson G.M., 1883), and the latter species is also prevalent in that region. Canonical correspondence analysis (CCA) and redundancy analysis (RDA) revealed that calanoid copepods were significantly correlated with total phosphorus (TP), total nitrogen, conductivity, nitrate nitrogen, altitude, and dissolved organic carbon. TP was the most important environmental variable that impacted the distribution of calanoid copepods, including both fresh and saline–alkaline lakes. Integrating historical records, a total of 21 calanoid copepods were distributed in NE China, and we also gave comments on the ecology and distribution of these species. [ABSTRACT FROM AUTHOR]

The recent rise in ocean temperatures, accompanied by other environmental changes, has notably increased the occurrence and spread of diseases in Octocorallia, many species of which are integral to shallow tropical and subtropical coral reef ecosystems. This study focuses on the understanding of these diseases, which has been largely limited to symptomatic descriptions, with clear etiological factors identified in only a fraction of cases. A key example is the multifocal purple spots syndrome (MFPS) affecting the common Caribbean octocoral sea fan Gorgonia ventalina, linked to the gall-forming copepods of the genus Sphaerippe, a member of the widespread family, Lamippidae. The specialized nature of these copepods as endoparasites in octocorals suggests the potential for the discovery of similar diseases across this host spectrum. Our investigation employed four molecular markers to study disease hotspots in Saint Eustatius, Curaçao, northwest and southwest Cuba, and Bonaire. This led to the discovery of a group of copepod species in these varied Caribbean locations. Importantly, these species are morphologically indistinguishable through traditional methods, challenging established taxonomic approaches. The observed diversity of symbionts, despite the host species' genetic uniformity, is likely due to variations in larval dispersal mechanisms. Our phylogenetic analyses confirmed that the Lamippidae copepods belong to the order, Poecilostomatoida (Copepoda), and revealed their sister group relationship with the Anchimolgidae, Rhynchomolgidae, and Xarifiidae clades, known for their symbiotic relationships with scleractinian corals. These results add to our understanding of the evolutionary and ecological interactions of copepods and their hosts, and the diseases that they cause, and are important data in a changing climate. [ABSTRACT FROM AUTHOR]

The genus Mongolodiaptomus is widely distributed in stagnant water bodies in Southeast Asia. During a comprehensive collection of freshwater copepods from different areas in Thailand, a previously unknown species of calanoid copepod, Mongolodiaptomus phutakaensis sp. nov., was recorded. Representatives were found in a natural swamp located in the Kok Phutaka community forest in Khon Kaen Province, northeastern Thailand. The new species belongs to the "M. loeiensis species group" and most closely resembles M. loeiensis and M. mekongensis by having a distinct shape of the second exopodal segment of the male right P5, with enlarged proximal and distal parts of the outer margin as well as a bent and twisted principal lateral spine. The new species can be distinguished from its congeners by various characters in the males. The ventral surface of the right caudal ramus has two chitinous teeth and two knobs. The intercoxal plate is slightly produced distally and without any spine. The right P5 basis lacks a hyaline membrane on the inner margin but has a distinct spur-like chitinous process at the mid-distal margin on the posterior surface. The left P5 basis has a thin, longer hyaline lamella on the inner margin. The new species is rare, having been observed in only one out of approximately 5,000 surveyed locations in Thailand. A detailed morphological comparison and an up-to-date key to the Mongolodiaptomus species are presented. Their taxonomic characters, interspecies relationships, and biogeography are discussed. [ABSTRACT FROM AUTHOR]

Knowledge of recruitment to a fishery is particularly important in short-lived species, like most cephalopods, in which there is a complete turnover of individual every 1 or 2 years. In this study, age, body length, statolith length and growth rates of loliginid paralarvae (Alloteuthis media, A. subulata and Loligo vulgaris) were determined to evaluate the form of the growth curve and differences between species and hatching seasons. A total of 222 paralarvae collected in zooplankton samples along the Galician coast (NW Spain) were used to determine relationships between dorsal mantle length (DML), statolith length (SL) and the number of increments (NI)) deposited in the statolith. The paralarvae of L. vulgaris were between 1 and 35 days old, while both Alloteuthis species ranged in age from 1 to 54 days. Generalised additive models (GAMs) revealed non-linear growth in DML, with L. vulgaris exhibiting higher DML-at-age than Alloteuthis species. The best parametric model fit for these data was obtained using exponential regressions. The SL–NI relationship also differed between species, with L. vulgaris having larger statolith length at age. The paralarvae of L. vulgaris and A. media had two well-differentiated hatching peaks, one in late spring-early summer (beginning of the upwelling season) and another peak in late autumn (end of the upwelling season). Alloteuthis subulata had an earlier hatching peak in spring than in the other two loliginid species—and the second peak in autumn was barely visible, possibly because this species occurs further north in areas not sampled in autumn. [ABSTRACT FROM AUTHOR]

The dependence of the respiration rate (R) on an animal's weight (W) is described by the equation R = aW b, where the exponential coefficient b is usually taken equal to 3/4. However, several authors have indicated that the value of coefficient b may vary with temperature changes, as well as during ontogeny. In Arctic seas, copepods spend most of their lives at temperatures below or close to zero. Meanwhile, there are very few respiration rate measurements at temperature ≤ 0°C, which does not allow us to estimate the value of coefficient b at subzero temperature. The study was carried out on three cruises of the R/V Akademik Mstislav Keldysh in the Siberian Arctic seas in 2018–2020. Copepods caught from the sea were adapted to the experimental temperature and placed in tightly capped vials filled with filtered seawater for 24 h. The oxygen concentration was measured with a fiber-optic oxygen probe. The results of 120 respiration rate measurements and 111 body carbon measurements in five species of copepods at a temperature of –1.5°C are presented. The obtained relationship between body carbon content (W) and prosome length (L) is described by the equation W = 6.982L3.221, and the dependence of respiration on body weight is described by the equation R = 0.077W 0.753. No effect of subzero temperature on coefficient b was revealed. The parameters of regression R(W) did not change with the ontogenetic development of Calanus glacialis. [ABSTRACT FROM AUTHOR]

Analyses of feeding patterns of fish assemblages, common approaches for understanding their habitat use and habitat dependence, have been conducted infrequently in Japanese estuarine salt marshes. The present study, based on gut content analyses, revealed the food habits of fishes occurring in salt marsh estuaries in high- and low-salinity rivers with different sediment conditions (sandy mud and muddy bottoms) in the western Seto Inland Sea, Japan. Ontogenetic changes in food preference were recognized in six species (Lateolabrax japonicus, Acanthogobius flavimanus, Glossogobius olivaceus, Platycephalus sp. 2, Acanthopagrus latus and Gymnogobius breunigii) out of 22 species examined, small individuals generally feeding on calanoid and harpacticoid copepods, and terrestrial and aquatic insects, but subsequently switching to other larger prey items (e.g., crabs, shrimps, and fishes) with growth. A cluster analysis based on dietary overlaps showed that the fish assemblages of the two salt marshes comprised nine trophic groups (zooplankton, small crustacean, large crustacean, polychaete, mollusk, fish, insect, detritus, and plant feeders), large crustacean feeders being the most abundant, followed by fish feeders, compared with polychaete and mollusk feeders, represented by only two and one species, respectively. The most important food items for the overall assemblage comprised shrimps, fishes and detritus, represented by high gut volumes in all fishes and high consumption frequencies. Furthermore, the trophic structures of fish assemblages and important food items varied between the rivers, polychaete and insect feeders being more abundant, with increasing the consumption of their main food items in the low-salinity and muddy river. Some fishes also showed remarkably different diets between adjacent rivers, highlighting small spatial scale variations in food-use patterns of fishes at the community and species levels in salt marsh estuaries. [ABSTRACT FROM AUTHOR]

Substantial loss of biodiversity and the proliferation of invasive alien species can occur due to land cover anthropogenic transformations on islands. However, the effect of anthropogenic habitat modifications on the distribution of insular freshwater microcrustaceans is unknown. In the present paper, we examine the consequences of human activity on the insular diversity of microcrustaceans in the context of the theories of island biogeography and intermediate disturbances. The samples were collected in Madeira Island at 38 freshwater sampling sites with different anthropopressure. Morphology-based species identification of the copepods and cladocerans was supplemented with genetic analysis (COI) in some species. To estimate the species richness of the island, rarefaction, and extrapolation methods were used. Canonical Correspondence Analysis (CCA) was applied to assess the influence of geospatial and environmental variables on the species distribution. A total of 20 species belonging to six families were identified, of which 16 species are new to Madeira. There was low similarity between the fauna recorded and known previously on the island. The observed species richness was higher than the predictions by the island biogeography models for Madeira. CCA revealed a strong influence of anthropogenic land use on crustaceans. Anthropogenic transformations locally led to the depletion of fauna, but on the island scale they contributed to the increase of species richness including seven putative alien species. An increase in the artificial land cover and a decrease in the forest areas could lead to a further shift in the domination of non-indigenous microcrustaceans. [ABSTRACT FROM AUTHOR]

Objective: The White‐barred Goby Amblygobius phalaena is a popular ornamental fish in the marine aquarium market. To achieve successful commercial production, efficient larval rearing techniques are crucial. Previous studies have achieved successful cultivation of White‐barred Goby larvae by using a combination of three live feed organisms—the ciliate Euplotes sp., the rotifer Brachionus rotundiformis, and the copepod Apocyclops royi nauplii—during the first feeding stage. However, the specific contributions of these live feed organisms to larval survival and growth remain unclear. Moreover, the optimal feeding density for the critical initial live feed organism has not been determined experimentally. In this study, we aimed to enhance the larviculture protocol for White‐barred Goby by introducing Portuguese oyster Crassostrea angulata trochophores and by addressing these knowledge gaps. Methods: Larvae were initially cultured through individual and combined feeding with four live feed organisms: Euplotes sp., Portuguese oyster trochophores, B. rotundiformis, and A. royi nauplii. The objective was to identify the optimal initial live feed organism during the first feeding stage by assessing the survival and growth performance of larvae. Subsequently, using this optimal live feed organism, larvae were cultured at four feeding densities (2, 5, 10, and 20 individuals/mL). Through evaluating feeding incidence, feeding intensity, survival, and growth performance, the aim was to determine the optimal feeding density for the selected live prey. Result: Our experiments revealed that White‐barred Goby larvae could consume both oyster trochophores and Euplotes sp. during the first feeding stage. However, larvae exhibited superior survival and growth performance when fed oyster trochophores. The optimal feeding density of oyster trochophores was determined to be 10 individuals/mL, while a feeding density as high as 20 individuals/mL resulted in decreased larval feeding incidence. Conclusion: These findings have significant implications for enhancing larval production programs for marine ornamental gobies and promoting their sustainable commercialization. Impact statementOur study enhances the larval rearing of the popular marine ornamental fish, the White‐barred Goby. Feeding them with oyster trochophores at appropriate densities improves their survival and growth. This leads to more efficient commercial production, alleviating fishing pressure on wild populations. It marks a significant stride in preserving the diversity of coral reef fish and fostering a sustainable aquarium industry. [ABSTRACT FROM AUTHOR]

Invasion of non-native fishes threatens freshwater biodiversity worldwide. Yet, detailed estimates of population demography for invasive species, such as population size and body size, are rarely integrated in evaluating aquatic community responses. Our study capitalised on detailed brook trout population demographic data collected for a replicated whole lake ecosystem experiment involving experimental harvesting of exotic brook trout in nine mountain lakes. We applied environmental DNA (eDNA) metabarcoding and morphological taxonomy to examine the response of crustacean zooplankton and macroinvertebrate communities to gradients in brook trout effective density and lake elevation. Density-dependent effects of brook trout on crustacean zooplankton and macroinvertebrate communities were detected even decades after their first introductions (between 1926 & 1980). However, they were moderated by environmental factors such as elevation, lake maximum depth and dissolved organic carbon. Elevation was important in structuring crustacean zooplankton and macroinvertebrate community composition. While there were differences in explanatory variables when describing communities characterized by eDNA metabarcoding and morphological taxonomy, the principal environmental factors that structured the communities were similar. Our paper highlights persisting density-dependent impacts of exotic trout on invertebrate communities even decades after first introduction, and it considers the conservation implications for lake restoration. [ABSTRACT FROM AUTHOR]

A large adult (138 mm head length) of the grenadier genus Coryphaenoides is described. It is identified as C. affinis hitherto known only from two juvenile type specimens collected by HMS Challenger off Uruguay in 1876. The diagnosis of the species is revised to include the discovery of considerable ontogenetic changes in squamation. Spinulation on the body scales are reduced or lost with size, while the armament of the head scales become amplified. The larger of the syntype specimens is designated as the lectotype. All three known specimens of C. affinis were collected in the southwestern Atlantic at depths between 3500 and 4000 m. A key for identification for the species of the subgenus Nematonurus is provided. [ABSTRACT FROM AUTHOR]

We evaluated the potential of the euryhaline copepod Pseudodiaptomus inopinus as a prey to enhance the feeding activity of red sea bream Pagrus major larvae. Pseudodiaptomus inopinus was used to evaluate free amino acid composition and dietary effects on the rearing performance of fish larvae, in comparison to rotifers (control prey). Among free amino acids, alanine, arginine, and glycine were markedly higher in P. inopinus than in rotifers. Larvae were reared for 20 days post-hatching under three feeding treatments: rotifers (control), rotifers supplemented with copepods, and copepods only. Larvae fed copepods alone had a higher growth rate than those in the other treatments. However, the survival rates of these larvae were lower than those under control or copepod supplementation. While equivalent stocking densities of rotifers were employed in the rearing water for both larvae, whether supplemented with copepods or not, the supplemented treatment yielded diminished larval survival and failed to enhance growth rates. According to gut content analysis, larvae receiving supplemented treatment preferentially fed on copepods, and the number of ingested rotifers was reduced. As a result, total ingested mass was lower in the supplemented larvae. This study suggests that copepods containing free amino acid species negatively affect prey acceptance of fish larvae. [ABSTRACT FROM AUTHOR]

Orbitacolax kyphosi sp. nov. is described based on a single specimen of the female recovered from washing fluid of the brassy chub Kyphosus vaigiensis (Quoy & Gaimard, 1825) (Centrachiformes, Kyphosidae) in Japan. K. vaigiensis is a new host and Kyphosidae is a new host group for the genus. [ABSTRACT FROM AUTHOR]

Two new species of copepods of the genus Elaphoidella Chappuis, 1929 were discovered in a cave and a spring in northeastern Thailand. The first species, E. phuphamanensis sp. nov., belongs to species-group VII sensu Lang. It is most similar to E. turgisetosa Petkovski, 1980 in the armament of the male third exopod of the fourth swimming leg and the shape and armament of the fifth swimming leg in both sexes. However, it is easily distinguished from other congeners by the segmentation of the first swimming leg, the endopod of the fourth swimming leg, and the armature of the third exopod of swimming legs 2–4 in both sexes. The second species, E. propecabezasi sp. nov., is located in species-group I sensu Lang, where the male does not have a transformed seta on the third exopod of the fourth swimming leg and the female fifth swimming leg has four baseoendopodal robust setae, unequal in length. It is most similar to E. cabezasi Petkovski, 1982 and E. paraaffinis Watiroyram, Sanoamuang and Brancelj, 2017 in having the same armature formula as endopods 1–2 of female swimming legs 1–4. However, the ornamentation of the anal operculum, the shape of the caudal ramus, and the armature of the fifth swimming leg in both sexes distinguish them from each other. A rare gynandromorphic specimen of E. propecabezasi sp. nov. was recorded, and a revised key to Elaphoidella species in Southeast Asia is provided. [ABSTRACT FROM AUTHOR]

Thirteen new freshwater populations of the copepod genus Boeckella De Guerne & Richard, 1889 were found during three expeditions to New Caledonia ('La Planète Revisitée,' 2016-2018). The 12 populations from the Plaine des Lacs, which show remarkable genetic diversity among themselves, were identified as B. spinogibba Defaye, 1998 , the only species of its genus known from New Caledonia until now. The sole exception, the population from Mont-Dore 22 km further east, appeared genetically and morphologically distinct from the others and is described herein as a new species. The two species are distinguished from each other by the shapes of the male and female P5, female Th5, and body colour. A previously published key is amended to separate the species. Our concatenated COI+28S phylogeny places the two New Caledonia species as a new branch within Boeckella , distinct from the branches consisting of South American, Antarctic and Australasian species. All 13 Boeckella populations inhabit the extreme south of New Caledonia, an area known for endemism and high heavy metal concentrations in the soil. Extensive mining activity in this metal-rich area, begun in 1873, is now leading to conflict with conservation goals. By using aerial photographs to trace the fate of the pond that is the type locality of B. spinogibba , we confirmed that it disappeared between 2007 and 2014 as a result of the expansion of the Goro nickel mine. [ABSTRACT FROM AUTHOR]

The copepod family Shiinoidae Cressey, 1975 currently comprises nine species of teleost parasites with unusual morphology and a unique attachment mechanism. Female shiinoids possess greatly enlarged antennae that oppose a rostrum, an elongate outgrowth of cuticle that originates between the antennules. The antennae form a moveable clasp against the rostrum which they use to attach to their host. In this study, we use micro-computed tomography (microCT) to examine specimens of Shiinoa inauris Cressey, 1975 in situ attached to host tissue in order to characterize the functional morphology and specific muscles involved in this novel mode of attachment and to resolve uncertainty regarding the segmental composition of the regions of the body. We review the host and locality data for all reports of shiinoids, revise the generic diagnoses for both constituent genera Shiinoa Kabata, 1968 and Parashiinoa West, 1986, transfer Shiinoa rostrata Balaraman, Prabha & Pillai, 1984 to Parashiinoa as Parashiinoa rostrata (Balaraman, Prabha & Pillai, 1984) n. comb., and present keys to the females and males of both genera. [ABSTRACT FROM AUTHOR]

Purpose: The present paper describes two new genera and species of the parasitic copepod family Chondracanthidae Milne Edwards, 1840 based on specimens collected from two species of deep-sea fishes at a depth of 212 m off Suruga Bay, Japan. Avatar nishidaigen. et sp. nov. is described from the host fish Chaunax abei Le Danois, 1978 (Chaunacidae). Kokeshioides surugaensisgen. et sp. nov. is described from the host fish Setarches longimanus (Alcock, 1894) (Setarchidae). Methods: Fresh specimens of chondracanthids were collected from the buccal cavity of two species of deep-sea fishes (fish hosts were frozen), Chaunax abei Le Danois, 1978 (Lophiiformes: Chaunacidae) and Setarches longimanus (Alcock, 1894) (Perciformes: Setarchidae), caught at a depth of 212 m in Suruga Bay, Japan (34° 37′48.87″ N, 138° 43′2.958″ E). Both the species are described and illustrated based on ovigerous females. Results: The genus Avatargen. nov. can readily be distinguished from all other chondracanthid genera by the following combination of features: cephalothorax slightly wider than long with anterior pair of large and posterior pair of small lateral lobes, and two pairs of ventro-lateral processes; the very posteriormost part of the first pedigerous somite contributes to the neck; cylindrical trunk with two pairs of blunt proximal fusiform processes; antennule with small knob terminally; antenna bearing distal endopodal segment; labrum protruding ventrally; two pairs of biramous legs each with 2-segmented rami. Kokeshioidesgen. nov. has the following combinations of features that distinguish it from other chondracanthid genera: body flattened, without lateral processes; cephalothorax much wider than long, with paired anterolateral and posterolateral lobes, folded ventrally; the very posteriormost part of the first pedigerous somite contributes to the neck; mandible elongate; legs unique, heavily sclerotized, represented by two pairs of acutely pointed processes. Conclusion: With the addition of two new genera presently reported, the family Chondracanthidae currently includes 52 valid genera. Among the described genera Avatargen. nov. seems to be very primitive, while Kokeshioidesgen. nov. is highly advanced. The deduced evolutionary history of chondracanthid genera is also discussed. [ABSTRACT FROM AUTHOR]

2022 marked the third consecutive La Niña and extended the longest consecutive stretch of negative Oceanic Niño Index since 1998-2001. While physical and biological conditions in winter and spring largely adhered to prior La Niña conditions, summer and fall were very different. Similar to past La Niña events, in winter and spring coastal upwelling was either average or above average, temperature average or below average, salinity generally above average. In summer and fall, however, upwelling and temperature were generally average or slightly below average, salinity was close to average and chlorophyll a was close to average. Again, as during prior La Niña events, biomass of northern/southern copepods was above/below average off Oregon in winter, and body size of North Pacific krill in northern California was above average in winter. By contrast, later in the year the abundance of northern krill dropped off Oregon while southern copepods increased and body sizes of North Pacific krill fell in northern California. Off Oregon and Washington abundances of market squid and Pacific pompano (indicators of warm, non-typical La Niña conditions) were high. In the 20th century, Northern anchovy recruitment tended to be high during cold conditions, but despite mostly warm conditions from 2015-2021 anchovy populations boomed and remained high in 2022. Resident seabird reproductive success, which tended in the past to increase during productive La Niña conditions was highly variable throughout the system as common murre and pelagic cormorant, experienced complete reproductive failure at Yaquina Head, Oregon while Brandt's cormorant reproduction was average. At three sampling locations off central California, however, common murre reproduction was close to or above average while both pelagic and Brandt's cormorant were above average. California sealion reproduction has been above average each year since 2016, and pup weight was also above average in 2022, likely in response not to La Niña or El Niño but continuous high abundance of anchovy. The highly variable and often unpredictable physical and biological conditions in 2022 highlight a growing recognition of disconnects between basin-scale indices and local conditions in the CCE. "July-December 2022 is the biggest outlier from individual "strong" La Niña (events) ever going back to the 50s." - Nate Mantua. [ABSTRACT FROM AUTHOR]

Due to the recent increasing importance of microcharacters in copepod taxonomy, it has become evident that many species lacking detailed descriptions actually constitute to a species complex. In this study, Nitocra affinis is redescribed based on lectotype material from Lake Timsah (Egypt) which facilitated a thorough detailed comparison with specimens of N. affinis recorded from distantly related localities. The results unequivocally revealed that the specimens of N. affinis examined in this study belong to a different species. As a result, four new species, Nitocra sonmezi sp. nov. and Nitocra serdarsaki sp. nov. from the Turkish coast, Nitocra alperi sp. nov. from the Indian Ocean, and Nitocra loweae sp. nov. from Brighton, England are herein described as new to science. On the other hand, all subspecies of N. affinis, namely N. affinis rijekana Petkovski, 1954, N. affinis californica Lang, 1965, N. affinis stygia, Por. 1968, and N. affinis colombiensis Fuentes-Reinés & Suárez-Morales, 2014 are elevated to species rank. An updated key the species of the affinis group is also provided. [ABSTRACT FROM AUTHOR]

Simple Summary: In subtropical shallow lakes, large-scale changes in water temperature lead to seasonal succession of some cryptic rotifer species, and the temporal overlap of other cryptic rotifer species is a common phenomenon. However, in tropical shallow lakes, relatively stable water temperatures throughout the year may not lead to a seasonal succession of cryptic rotifer species, but evidence is scarce. Studies on the temporal distribution patterns of the cryptic Brachionus calyciflorus species in three lakes in China revealed that in the warm-temperate Lake Yunlong, B. fernandoi and B. calyciflorus s.s. underwent a seasonal succession, which was largely attributed to their differential adaptation to water temperature. In the subtropical Lake Jinghu, B. fernandoi, B. calyciflorus s.s., and B. dorcas exhibited both seasonal succession and temporal overlap. Seasonal successions were largely attributed to their differential adaptation to temperature, and temporal overlap resulted from their differential responses to algal food concentration. In the tropical Lake Jinniu, B. calyciflorus s.s. persisted throughout the year and overlapped with B. dorcas for 5 months. The temporal overlap resulted from their differential responses to copepod predation. These results indicated that the temporal distribution pattern of the cryptic B. calyciforus species and the mechanism that allows competitor coexistence vary with different climate zones. Sympatric distribution and temporal overlap of cryptic zooplankton species pose a challenge to the framework of the niche differentiation theory and the mechanisms allowing competitor coexistence. We applied the methods of phylogenetic analysis, DNA taxonomy, and statistical analysis to study the temporal distribution patterns of the cryptic B. calyciflorus species, an excellent model, in three lakes, and to explore the putative mechanisms for their seasonal succession and temporal overlap. The results showed that in the warm-temperate Lake Yunlong, B. fernandoi and B. calyciflorus s.s. underwent a seasonal succession, which was largely attributed to their differential adaptation to water temperature. In the subtropical Lake Jinghu, B. fernandoi, B. calyciflorus s.s., and B. dorcas exhibited both seasonal succession and temporal overlap. Seasonal successions were largely attributed to their differential adaptation to temperature, and temporal overlap resulted from their differential responses to algal food concentration. In the tropical Lake Jinniu, B. calyciflorus s.s. persisted throughout the year and overlapped with B. dorcas for 5 months. The temporal overlap resulted from their differential responses to copepod predation. These results indicated that the temporal distribution pattern of the cryptic B. calyciforus species and the mechanism that allows competitor coexistence vary with different climate zones. [ABSTRACT FROM AUTHOR]

Patagonian red octopus, Enteroctopus megalocyathus, an interesting species for Chilean aquaculture diversification, requires the improving of their experimental technology to obtain early juveniles. The first objective of the study was to enhance aspects of feeding and temperature management in broodstock, egg incubation, paralarvae rearing, and early juveniles' growth. The results indicated that female weight decreases up to 46.0 ± 8.6% during the egg incubation. Test of 8, 14, and 18°C during egg incubation shows that at 18°C embryos do not survive. Paralarvae reared under four diet treatments: (1) unfed, (2) enriched Artemia (Nannochloropsis sp.), (3) copepod (Acartia spp.), and (4) juvenile crabs (Petrolisthes spp.) showed survival quadruplication when they fed copepods and crabs instead of Artemia. Juveniles reared at 11, 13, and 15°C improved feed conversion and protein efficiency ratios at 15°C. The second objective was to analyze batches of paralarvae and early juveniles of two different periods to obtain their performance indicators and to compare them between productive periods. The results of growth rates, the relative weight condition coefficient, and morphometric relationships are discussed in the context of paralarvae culture from 1 to 90 days after hatching (DAH) and early juveniles from 1 to 135 days postsettlement (DPS). [ABSTRACT FROM AUTHOR]

Copepods are aquatic invertebrates with a key role at the basis of marine food webs due to their high biomass as well as their elevated fatty acid (FA) content. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are two FA abundant in copepods which have a well demonstrated role in growth and reproduction in marine organisms. While the majority of research has focused on planktonic copepod species, less is known for benthic species despite their high richness, abundance and their role as the main food source for many fish larvae. Temperature is a key driver of organism's fitness as well as ecosystem functioning and sea surface temperature is expected to rise under all CO2 emission scenarios. Thus, understanding how copepods will respond to such changes is crucial given their role in marine food webs. In this study we expose laboratory reared Tachidius discipes, an intertidal benthic copepod to a temperature gradient (12, 15, 18, 21 and 24 °C) including current seasonal variability as well as future scenarios. Survival, FA, growth rates and nauplii production were measured for each temperature. We found decreased survival, increased growth rates and detrimental effects for nauplii production with temperature increase. While relative EPA and DHA decreased with temperature this was not found on absolute levels of these FA. Changes in benthic copepods' biomass as well as their FA composition in response to temperature changes could amplify to higher trophic levels with consequences for food web functioning. [ABSTRACT FROM AUTHOR]

Cirracanthus monacanthi (Yamaguti, 1939) and Taeniacanthus balistae (Claus, 1864) are redescribed based on specimens recovered from Stephanolepis cirrhifer (Temminck & Schlegel, 1850) and Aluterus monoceros (Linnaeus, 1758) (Tetraodontiformes, Monacanthidae), respectively, in Japan. The description of the copepodid V female of T. balistae is the first time for the species. [ABSTRACT FROM AUTHOR]

This paper compiles the data regarding the first occurrence of Oithona davisae and O. atlantica in NW Spain, which is supported by morphological and molecular analysis. Additionally, we investigated the seasonal dynamics of the invasive O. davisae, revealing that its abundance is conditioned by upwelling-downwelling patterns in the Rías Baixas of Galicia. Temperature was the most correlated factor, with higher abundances in upwelling relaxation-downwelling events. More studies in long-term zooplankton dynamics and molecular analysis are needed to determine if O. davisae is displacing other native species of the same genus, such as O. atlantica, in Galician waters. [ABSTRACT FROM AUTHOR]

The recent distribution of the Ponto-Caspian calanoid copepod, Eurytemora velox, in Western and Eastern Europe has been well-documented; however, there are no studies on the genetic diversity of the recently discovered Western Siberian species population. To contribute towards filling this gap, genetic diversity and distribution were investigated for E. velox collected in the Urals and Western Siberia of the Russian Federation to compare with the European populations. In this study, 44 specimens were dissected for the morphological studies, and 22 specimens of E. velox from different geographical points were analyzed for mitochondrial cytochrome oxidase I (CO1), nuclear ITS1-ITS2 (nITS) and nuclear ribosomal RNA (18SrRNA) gene fragments. Analysis of the CO1 gene region showed that the studied populations from the Urals and Western Siberia differ significantly from European ones and represent a separate genetic line. However, the nuclear nITS and 18SrRNA genes, as well as the results of morphological analysis, did not show such isolation of the Trans-Ural populations from those in Europe. As in many studies on E. velox, we found atypical structural features of the fifth prosomal leg among females in the Ob Bay. Their share was 36% of the number of studied individuals. The CO1 shows that the divergence of genetic lines occurred approximately in the Middle Pleistocene, and the species itself is Paleogene–Neogene by origin. Based on these data, a different scenario of E. velox distribution or possible refuge survival is discussed. [ABSTRACT FROM AUTHOR]

The mesopelagic calanoid copepod Cephalophanes reflugens is characterized by its large eyes with semi-parabolic reflectors. It is hypothesized that the eyes aid in finding crustacean carcasses as food in poor deep-sea light and oligotrophic conditions. Here, the crustacean carcasses-associated luminous, chitin-degrading bacteria may play a vital role in detecting and digesting foods by the copepod. In this study, we collected adult female C. reflugens (n  = 9) from the mesopelagic layers off southwestern Japan in the Pacific Ocean and obtained a total of 47 bacterial isolates from the gut contents. None of the isolates were luminescent, but almost half of the isolates were chitinolytic. Based on the 16S rRNA gene sequences, these chitinolytic bacteria were identified as members of the genus Vibrio , Photobacterium and Pseudoalteromonas. In culture experiments at 15°C, most of the chitinolytic isolates efficiently utilized colloidal chitin as the sole carbon source and degraded the carapace strip of shrimp (Litopenaeus vannamei). Some isolates showed these chitinoclastic activities even at low temperatures (<5°C), equivalent to that of the deep-sea waters. The present results imply that chitin-degrading bacteria significantly contribute to chitin digestion in the gut of C. reflugens , whereas the involvement of luminous bacteria in the feeding mechanism remains unidentified. [ABSTRACT FROM AUTHOR]

Background: The present study explored the possibility of using live feed, as vector for supplementing the androgenic hormone in aquaculture seed production. Methods: The study consisted of five treatment doses of 17α-methyl testosterone namely; control (without hormone), T1 (20 mg L-1), T2 (40 mg L-1), T3 (60 mg L-1) and T4 (80 mg L-1) and each were triplicated. The doses were tested in the live feed of Artemia nauplii and rotifer by following completely randomized design. The Artemia nauplii (Artemia salina), collected by hatching the Artemiacyst and 5-8 days old rotifers, collected from mass culture unit of rotifer, were released in their respective treatment doses at 100 and 800 individuals/ml, respectively. Result: The study found significant difference in accumulation of hormone in the tissues of live feed at different time intervals. In Artemia, significantly higher amount of 17α-MT (15.33±0.09 mg L-1) was observed in 80 mg L-1 group at 24 h. In rotifer, significantly higher value of 17α-MT (17.42±0.06 mg L-1) was recorded in 60 mg L-1 group at 6 h. The level of 17α-MT in Artemia nauplii and rotifer started showing a decreasing trend in 24 h and 6 h, respectively. Overall the findings of the present study support that supplementation of hormone through live feed is possible as live feed accumulated 17α-MT in its tissue after enrichment which can be further explored for producing all-male population in a more sustainable way. [ABSTRACT FROM AUTHOR]

An illustrated redescription of the female and male of Moraria (Baikalomoraria) longicauda Borutzky, 1952, a harpacticoid species endemic to the littoral zone of Lake Baikal, Siberia, is presented based on new material. A neotype is designated, since the type material is lost. The morphology of this species has been studied in detail using scanning electron microscopy for the first time. An illustrated description of the mouthparts and antennules is given; the description of the swimming legs has been significantly expanded. The structure of the genital field is shown, and data on the morphological variability are presented. [ABSTRACT FROM AUTHOR]

An illustrated redescription of the female and male of Canthocamptus latus Borutzky, 1947, a mass endemic species of harpacticoids from the littoral zone of Lake Baikal, which plays an important role in the food chains of shallow waters, is given based on newly collected material. This species differs clearly from other endemic Baikal species of the genus Canthocamptus Westwood, 1836 in the structure of the caudal rami and swimming legs. Morphologically, the species seems to be especially close only to Canthocamptus bulbifer Borutzky, 1947. Data on the neotype are presented, since the type material is lost. The morphology of this species has been studied in detail using scanning electron microscopy for the first time. Illustrated descriptions of the mouthparts and antennules are given, while the description of the swimming legs is significantly expanded. The structure of the genital field is shown, and data on the morphological variability are presented. [ABSTRACT FROM AUTHOR]

The copepod species Acartia tonsa (Dana)(Crustacea) have the unique ability to induce quiescent embryonic dormancy if adverse environmental conditions occur; a characteristic shared by 41 other species belonging to the superfamily Centropagoida in the Calanoida order. However, the transcriptional changes characterizing this process are not known. Here, we compare the transcriptome of embryos in arrested quiescence with the normal development to identify pathways and differentially regulated transcripts involved in quiescent embryogenesis. Quiescence was induced by incubating eggs at 4 °C with anoxia for 26 h(hr), while eggs undergoing normal immediate development were incubated at 16.9 °C in normoxia for 7 h (where gastrulation occurs) or 14 h (where organogenesis occurs) before collecting for RNA extraction and analysis by RNA-sequencing. Results indicate that the expression profile of the quiescent embryo is not as different from the normal embryonic gastrulation as initially expected: None of the mapped transcripts is uniquely expressed in quiescence. Moreover, in quiescence a large proportion of the annotated transcripts display expression values halfway in-between the normal, immediate developmental stages of gastrulation and organogenesis. In depth comparison between the organogenesis stage and quiescent samples, reveal a high degree of divergence, confirming that a developmental arrest has been induced through quiescence. Specifically: Stress response transcripts are prominent in the quiescent phase with a transcript like the mammalian autophagy gene Sequestosome-1/p62 (SQSTM) being upregulated. The present analysis provides a better understanding of the molecular mechanisms characterizing the quiescent embryonic state of A. tonsa. [Display omitted] • Quiescent embryonic arrest of Acartia tonsa copepods was studied using RNA-sequencing and de novo transcriptome assembly. • Quiescence was induced by cold and anoxia and compared to gastrulation and organogenesis stages. • Quiescent embryonic arrest occurs in the gastrulation stage. • Quiescence is characterized by a profound stress response and induction of the autophagy gene Sequestosome (Sqstm). [ABSTRACT FROM AUTHOR]

Even in a biodiversity hotspot such as the Mediterranean basin, aspects relating to the distribution of some groups of microcrustaceans still need clarification. In this paper, we critically analyse the available information on diaptomid copepods in Tunisian inland waters and, based on the largest sampling campaign to date carried out in the country, report new data on their distribution. In the frame of this study, 248 crustacean samples were collected from 190 sites, and 10 diaptomid species belonging to 7 genera and 2 subfamilies were found in the samples. Their distribution follows a climate gradient determined by precipitation, and ecological variables mainly affect diaptomid distribution in the study area, while pure spatial factors are of negligible importance. Diaptomid biodiversity is therefore strongly linked to the diversity of inland waters that characterise the country. This is especially true in the wetlands of the Medjerda alluvial plain, where six diaptomid species co-occurred sympatrically, with up to four or five species coexisting syntopically and synchronically in some sites. Unfortunately, the natural water bodies of this plain are currently strongly threatened by urban expansion and agricultural reclamation, and the risk of local extinction for the species they host is increasingly high. [ABSTRACT FROM AUTHOR]

Quinquelaophonte is a genus of laophontid harpacticoid, including 13 valid species around the world. Many of them are known to possess inter- and/or intra-individual variations in their swimming legs. During a survey of the meiofaunal biodiversity of Jeju Island in Korea, specimens of Quinquelaophonte were collected from an intertidal zone off the west coast of Jeju Island. This study examined the morphological characteristics and amplified partial sequence of four genes (18S rRNA, 28S rRNA, COX1, and CYTB). As with other Quinquelaophonte species, specimens of this new species showed variability in the chaetotaxy of their swimming legs in both sexes. There was a setal arrangement pattern in females that could be considered a standard, whereas male individuals showed two sets of the chaetotaxy on the fourth swimming legs. The molecular data confirmed that individuals belonged to a single species, regardless of morphological variations. The result of the morphological comparison showed that the new Quinquelaohponte species shared some characteristics with congeneric species but included some specific morphological characters different from its congeners. The new species was named Quinquelaophonte sominer sp. nov. and was presented with detailed descriptions, illustrations, and confocal micrographs. Furthermore, phylogenetic analyses were conducted using newly obtained data plus the sequences of other copepods and two Quinquelaophonte species. The result suggested that Q. sominer sp. nov. and two congeners were classified as branched lineages. This discovery brings the total number of species to three in the Northwest Pacific region. [ABSTRACT FROM AUTHOR]

Diel vertical migration (DVM) is a widespread phenomenon in aquatic environments. The primary hypothesis explaining DVM is the predation‐avoidance hypothesis, which suggests that zooplankton migrate to deeper waters to avoid detection during daylight. Copepods are the predominant mesozooplankton undergoing these migrations; however, they display massive morphological variation. Visual risk also depends on a copepod's morphology. In this study, we investigate hypotheses related to morphology and DVM: (H1) as size increases visual risk, increases in body size will increase DVM magnitude and (H2) if copepod transparency can reduce visual risk, increases in transparency will reduce DVM magnitude. In situ copepod images were collected across several cruises in the Sargasso Sea using an Underwater Vision Profiler 5. Copepod morphology was characterized from these images and a dimension reduction approach. Although in situ imaging offers challenges for quantifying mesozooplankton behavior, we introduce a robust method for quantifying DVM. The results show a clear relationship in which larger copepods have a larger DVM signal. Darker copepods also have a larger DVM signal, however, only among the largest group of copepods and not smaller ones. These findings highlight the complexity of copepod morphology and DVM behavior. [ABSTRACT FROM AUTHOR]

The spatial and temporal variability in the dietary preferences of juvenile three-spined stickleback Gasterosteus aculeatus were studied across the typical coastal habitats of Keret Archipelago, Kandalaksha Bay(the White Sea). The sampling of fish using a beach seine was conducted in the late July–early August period and in late August. Additionally, zooplankton samples were collected to conduct a quantitative assessment of the abundance of potential prey items. The similarity percentage (SIMPER) analysis was applied to the data obtained from the stomach content and revealed the five planktonic taxa most prominently contributing to the diet of juvenile sticklebacks. Among these, the copepod Temora longicornis was the most important prey item at marine sites, while Acartia longiremis dominated the diet of fish in the marine lagoon. The calculation of the selectivity index revealed that some taxa (such as A. longiremis) were always avoided by juvenile fish, whereas the selectivity of some taxa increased in late August. In general, juvenile sticklebacks demonstrated a pronounced individual variation in their selectivity, even when a particular prey item was selected positively during the whole period of study. Our data highlight that despite the predominant consumption of easily available prey by juvenile sticklebacks, they demonstrate taxonomic- and size-specific prey selectivity. [ABSTRACT FROM AUTHOR]

A new harpacticoid species, Maraenobiotus skombrosus sp. n., is described based on specimens collected from groundwaters in the area of Dragalevtsi District, Vitosha Mountain, Bulgaria. According to the morphological characteristics, the specimens belong to the vejdovskyi-species group: mandibular palp one-segmented; distal segments of exopod P2 and P3 with five and six setae; distal segment of endopod P4 with four setae; baseoendopod P5 with four setae. Following these morphological characteristics, the specimens from Vitosha Mountain have been misidentified as the Palaearctic polymorphic and widely distributed M. vejdovskyi Mrázek, 1893 (s. l.). In this study, we describe the specimens from Vitosha Mountain as M. skombrosus sp. n. based on several features, among which are the morphology and size of the caudal rami, the presence of three lateral setae, the ornamentation of the anal operculum with six spinules as well as the ornamentation of the prosomе and urosomе. [ABSTRACT FROM AUTHOR]