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The growing impact of human activities on the biosphere requires research into the effects of exposure to hazardous toxic substances on aquatic ecosystems. The ecophysiological parameters of the amphipod Gammarus oceanicus Segerstråle, 1947, such as rates of food consumption, oxygen consumption, and phosphate excretion (excreted in the urine), were studied in order to determine the responses of these crustaceans to the influence of a little-studied micropollutant of anthropogenic origin, xenoextrogen, 4-tert-octylphenol (4t-OP). After 28 days of exposure to the lowest concentrations of 4t-OP (0.25 μg/L), a decrease in the feeding and excretory activity of crustaceans was detected, while the level of oxygen consumption was similar to the values in control individuals. All the parameters of the tested animals studied changed significantly after the same time of exposure to 2.5 μg/L 4t-OP, showing an adverse effect on the functioning of the crustacean organism. The data obtained can be used to develop criteria for quality control of the aquatic environment. [ABSTRACT FROM AUTHOR]

A central goal of molecular studies on ancient lake faunas is to resolve the origin and phylogeny of their strikingly diverse endemic species flocks. Another equally intriguing goal is to understand the integrity of individual morphologically diagnosed species, which should help to perceive the nature and speed of the speciation process, and the true biological species diversity. In the uniquely diverse Lake Baikal amphipod crustaceans, molecular data from shallow-water species have often disclosed their cryptic subdivision into geographically segregated genetic lineages, but the evidence so far is mainly based on mitochondrial DNA. We now present a lake-wide parallel survey of both mitochondrial and multilocus nuclear genetic structuring in the common shoreline amphipod Eulimnogammarus verrucosus, known to comprise three deep, parapatric mtDNA lineages. Allele frequencies of seven nuclear allozyme loci divide the data into three main groups whose distributions exactly match the distributions of the main mitochondrial lineages S, W, and E and involve a further division of the W cluster into two subgroups. The inter-group differences involve one to four diagnostic loci and additional group-specific alleles. The transition zones are either abrupt (1 km), occur over a long segment of uninhabitable shoreline, or may be gradual with non-coincident clinal change at different loci. Mitochondrial variation is hierarchically structured, each main lineage further subdivided into 2–4 parapatric sublineages or phylogroups, and patterns of further local segregation are seen in some of them. Despite the recurring observations of cryptic diversity in Baikalian amphipods, the geographical subdivisions and clade depths do not match in different taxa, defying a common explanation for the diversification in environmental history. [ABSTRACT FROM AUTHOR]

This study investigated the presence of ectoparasites in stranded cetaceans along the coast of Sergipe, Brazil. The parasitological material, dates and informations about the hosts was obtained from a biological collection. Were analysed four Megaptera novaeangliae, one of Sotalia guianensis, and one of Peponocephala electra. A total of 264 ectoparasites were collected from these carcasses – 263 amphipods of the species Cyamus boopis and Syncyamus ilheusensis, and a single cymothoid isopod, identified as Livoneca redmanii. C. boopis showed a average intensity of 77.0 parasites per host, and a prevalence of 100% in the analysed humpback whale carcasses, representing the first record of this louse species on humpback whales in the region. S. ilheusensis appears to have a rare occurrence and specificity to the host P. electra, being its third report in the scientific literature. Additionally, the discovery of the isopod L. redmanii on Sotalia guianensis is unprecedented, being the first report of an isopod parasitizing this cetacean and expanding our knowledge about the host flexibility of this ectoparasite. The attachment of the isopod to the dolphin's skin was likely favored by the absence of mucus, as found in fish. These findings provide new insights into the ecology of these ectoparasites. [ABSTRACT FROM AUTHOR]

Deep-sea amphipods constitute an important part of the ocean benthos, although their species richness is far from fully known. During a survey of the project 'Avaliação da Biota Bentônica e Planctônica na porção offshore das Bacias Potiguar e Ceará' (BPOT), four new species and two new records of amphipods were reported from north-eastern Brazil. The material was collected by bottom trawl nets at depths from 150 to 2057 m in the Potiguar Basin. The species Adeliella debroyerisp. n., Alexandrella cedricisp. n., Epimeria colemanisp. n. and Tectovalopsis potiguara sp. n. are established based on morphological comparisons with their congeners, properly illustrated and discussed. We present the first record of the family Adeliellidae Lowry and Myers, 2017 and genus Adeliella Nicholls, 1938 for the South Atlantic Ocean and the first report of the family Stilipedidae from Brazil. The species Cyphocaris johnsoni Shoemaker, 1934 is herein first recorded from Brazil, providing a geographic and depth range extension, and Parandania boecki (Stebbing, 1888) is reported for the first time in the Rio Grande do Norte state. Additionally, identification keys are provided for global species of Adeliella, Tectovalopsis J.L. Barnard and Ingram, 1990, and Alexandrella Chevreux, 1911, and one for Atlantic species of Epimeria Costa in Hope, 1851. [ABSTRACT FROM AUTHOR]

Baikal amphipods are one of the most unique freshwater species flocks of over 350 morphological species and subspecies playing multiple ecological roles in this ancient lake. However, molecular phylogeny studies accumulate evidence that this number is underestimated. Previously, we showed that an abundant littoral species Eulimnogammarus verrucosus comprised at least three genetic lineages: southern (S), western (W), and eastern (E), inhabiting corresponding parts of Baikal shore. The Angara River is the only outflow of the lake and is inhabited by amphipods originating from Baikal, which were previously analysed only morphologically. The river has parts with strong current or closed bays as opposed to sea‐like conditions of Lake Baikal, which raises the question of which species were able to adapt here. Here we studied the phylogeny of E. verrucosus from the Angara River, which could be reached by two lineages, S and W. We analysed 17 sites from 0.6 to 650 km from the outflow. Cytochrome c oxidase subunit I (COI) and 18S rRNA analysis showed that the sites closest to Baikal were inhabited by the S and W lineages sympatrically. The other sites were inhabited by the S lineage at both banks and also by the novel A (Angara) lineage. The A lineage was the first to split up from the last common ancestor of all E. verrucosus. Our data confirm the importance of considering cryptic diversity in ecological monitoring, and in order to simplify the identification of the genetic lineage, we developed a web‐app speCOIdent. [ABSTRACT FROM AUTHOR]

The processing of organic matter is a central ecosystem function in freshwater ecosystems that allows the integration of terrestrial plant material into aquatic heterotrophic food webs. From an energetic perspective, many temperate aquatic systems fundamentally depend on such allochthonous inputs. Current research established that this central ecosystem function may be linked to population density of few yet dominant invertebrate detritivores, showing a negative density‐dependent relationship. Here, we extended the current knowledge and experimentally assessed the processing of leaf litter by freshwater amphipods, using broad density gradients, interspecific competition, and laboratory and field experiments. We used two species of dominant amphipods, namely the native Gammarus fossarum and the non‐native Gammarus roeselii, varying their density by two orders of magnitude, both in single‐species and two‐species treatments. Results from 252 mesocosms in the lab and 97 mesocosms in a natural stream show that per capita leaf litter processing rates are strongly negatively dependant on population density in monocultures. Interspecific competition in two‐species treatments corroborated the negative density‐dependent ecosystem function and highlighted the functional redundancy of the two detritivore species. We identified a flattening in the processing rates at previously unreported but well‐defined breakpoints. These breakpoints may reflect minimal metabolic requirements at which survival takes precedence over any other process, such as interference competition. The breakpoints were consistent across both species, indicating that they must process leaf litter equalling one fifth to one fourth of their dry body weight per day as a minimal nutritional threshold. Our results suggest the need for integrating nonlinear density‐dependencies and breakpoint population densities in key ecosystem functions in aquatic ecosystem modelling alongside classical biodiversity–ecosystem functioning relationships. Depending on the population density the corresponding ecosystem functioning could differ significantly. This corroborates the need to better understand biodiversity–abundance relationships when protecting aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Numerous and diverse groundwater habitats suitable for sustaining aquatic invertebrate communities exist across Australia. These habitats include enclosed subterranean aquifer systems, fractured rock, alluvial aquifers, perched aquifers, artesian springs, and spring-fed seeps and marshes. Crustaceans are a dominant member of these groundwater-associated invertebrate communities, and amphipods, both stygobiont and associated epigean species, are particularly diverse yet are still relatively poorly known. We review both the diversity and distributions of Australian amphipods associated with groundwater habitats, describing hotspots of diversity, providing notes on the unique Australian habitats, and examining the extraordinary species diversity and endemism of the Australian species. Our review highlights the significance of Australian groundwater ecosystems, their associated biodiversity, and the importance in considering these ecosystems in groundwater conservation management plans. [ABSTRACT FROM AUTHOR]

The nature of symbiotic relationships between organisms can be difficult to assess and may range from commensalism, to mutualism, and parasitism. Trophic linkage and feeding ecology are essential to disentangle symbiont-host relationships/interactions. Amphipods of the genus Dactylopleustes are known as urchin symbionts. Though their ecology remains largely unknown, Dactylopleustes was recently reported to aggregate on diseased hosts, suggesting that Dactylopleustes feeds on diseased urchins' tissues and uses urchins as both a habitat and prey. We investigated by DNA metabarcoding analyses, the feeding ecology of Dactylopleustes yoshimurai in relation to growth and disease status of the host (Strongylocentrotus intermedius). Contrary to our hypothesis, sequence reads from the gut contents were dominated by planktonic copepods regardless of body size or host disease status. These results suggest that they mainly feed on copepod fecal pellets deposited on sediments, and do not have a strong trophic linkage with their host. Large individuals on diseased urchins feed more on urchins than those on healthy urchins. However, their main prey still remains copepods, implying that host disease has a limited effect on the feeding behavior. In conclusion, our study indicates that this species is mainly commensal, but also may parasitize its host depending on the situation. [ABSTRACT FROM AUTHOR]

This article discusses the association between argonauts, a group of octopods, and various substrates in the ocean. The study used images shared by recreational divers on social media to quantify the diversity of substrates used by argonauts for movement. The images showed that argonauts were attached to plastic waste, vegetal debris, and pelagic animals, with gelatinous plankton being the most abundant substrate. The study also observed accompanying fauna sharing the same substrate with the argonauts. The findings highlight the value of citizen science and the use of high-quality images obtained during blackwater dives for studying the behavior and interactions of oceanic pelagic organisms. [Extracted from the article]

A new deep-sea species of the genus Bathypisella was collected from bathyal soft bottoms, SW Gulf of Mexico. This new species represents the second Bathypisella species known worldwide, which is characterised by head subequal in length to pereonal segments 1–2 combined, eyes absent, toothed pleonal and urosomal segments, 4-articulate accessory flagellum, coxae 1–4 posteroventral area slightly notched; coxa 4 posterior lobe absent, maxilliped palp article 3 in right angle, maxilla 1 inner plate with five lateral setae, left mandible with three teeth on lacinia mobilis, gnathopod 1 palmar margin convex, gnathopod 2 propodus palmar margin concave, one long, robust seta in palmar angle, epimeron 3 with trifid posteroventral margin, and telson cleft half its length. Besides a complete description of the new species, a dichotomous key to identify both Bathypisella species is provided. [ABSTRACT FROM AUTHOR]

New records of deep-sea marine amphipods are presented. Three families, three genera and three species (Chuneola paradoxa, Epimeria ortizi and Trischizostoma nicaeense) are recorded for the first time for the Gulf of Mexico. Another species, T. raschi, is recorded for the first time from the Florida Keys, the Lesser Antilles, and the eastern Atlantic Ocean.

The crustacean family Ampithoidae is one of the most abundant invertebrate families associated with macroalgae in shallow marine waters. Ampithoe, the largest genus, was previously documented as non‐monophyletic by phylogenetic analyses based on morphological and molecular characters. Here, we reconstructed a multi‐gene phylogeny of Ampithoidae with the first data of the southwestern Atlantic Ocean. We performed the first biogeographic analyses for the family, which indicated its origin in the Indo‐West Pacific, with subsequent dispersion to the Atlantic Ocean around the Eocene. Divergence times suggest that the diversification of Ampithoidae is congruent with the brown algae crown radiation, which allowed the colonization of new environments. [ABSTRACT FROM AUTHOR]

Kelp forests support species-rich food webs that predator-prey interactions may sustain. Here, we analyze prey availability and stomach contents of the predatory fish Prolatilus jugularis in an unexplored subtidal kelp forest of Lessonia trabeculata in south-central Chile. In the kelp forest, 42 invertebrate taxa and 1016 individuals were observed. In the diet of P. jugularis, 21 taxa and 130 individuals were identified. Crustacea, particularly amphipods, were the dominant and more frequent taxa in the kelp forest and stomach contents. Annelida and Mollusca were also present in the kelp forest and diets but were less abundant. We did not find a statistically significant correlation between kelp forest and stomach-content prey abundances and frequencies. Also, dominance structure significantly differed between kelps and stomach contents. Our results indicate that P. jugularis could feed in other habitats outside the survey area. Seven predatory fish were sampled in the kelp forest. Pinguipes chilensis was the dominant fish, with 65% of the total fish biomass, followed by P. jugularis with 20%. [ABSTRACT FROM AUTHOR]

A species' expansion beyond the native range is often assumed to be associated with an increased dietary niche breadth. However, empirical evidence remains limited due to a scarcity of studies comparing both the parental and invaded ranges. Here, we test the trophic niche expansion hypothesis by examining stable isotopes and functional morphology across native (NW Black Sea) and invaded (SE Baltic Sea) ranges of two amphipods, Dikerogammarus villosus and Pontogammarus robustoides, originating from the Ponto‐Caspian region—a major source of species invading Holarctic inland waters. Stable isotopes revealed that both species underwent a marked dietary niche contraction by becoming less carnivorous in the invaded range. This dietary shift was morphologically mirrored by an overall reduction of functional traits related to predation. The magnitude of dietary and morphological change was greater in D. villosus. Our findings indicate that previous experimental reports of aggressive predation in D. villosus reflect opportunistic foraging and align with local stable isotope studies which generally indicate a low trophic position. We conclude that Ponto‐Caspian species can undergo rapid dietary changes outside the native range, and that dietary niche expansion is not a prerequisite for successful non‐native establishment. [ABSTRACT FROM AUTHOR]

Parasite infections are increasingly reported to change the microbiome of the parasitized hosts, while parasites bring their own microbes to what can be a multi-dimensional interaction. For instance, a recent hypothesis suggests that the microbial communities harboured by parasites may play a role in the well-documented ability of many parasites to manipulate host phenotype, and explain why the degree to which host phenotype is altered varies among conspecific parasites. Here, we explored whether the microbiomes of both hosts and parasites are associated with variation in host manipulation by parasites. Using colour quantification methods applied to digital images, we investigated colour variation among uninfected Transorchestia serrulata amphipods, as well as amphipods infected with Plagiorhynchus allisonae acanthocephalans and with a dilepidid cestode. We then characterized the bacteriota of amphipod hosts and of their parasites, looking for correlations between host phenotype and the bacterial taxa associated with hosts and parasites. We found large variation in amphipod colours, and weak support for a direct impact of parasites on the colour of their hosts. Conversely, and most interestingly, the parasite's bacteriota was more strongly correlated with colour variation among their amphipod hosts, with potential impact of amphipod-associated bacteria as well. Some bacterial taxa found associated with amphipods and parasites may have the ability to synthesize pigments, and we propose they may interact with colour determination in the amphipods. This study provides correlational support for an association between the parasite's microbiome and the evolution of host manipulation by parasites and host–parasite interactions more generally. [ABSTRACT FROM AUTHOR]

A new amphipod species belonging to the genus Gammarus was identified in the rivers of the Eastern Black Sea Region of Türkiye: G. sezgini sp. nov. The authors described the new species using a taxonomic approach that combines morphological and molecular data. The newly identified species belongs to the G. komareki species complex because of the setation of antenna 2, pereopods 3 and 4, and the uropod 3. Some of its characteristic features are as follows: A medium-large species (holotype male, 9.8 mm). The body is yellowish; no dorsal keel or hump; eyes well developed, kidney-shaped; extremities not elongated; the second antenna bears numerous groups of long setae on the peduncle and flagellar segments; antennal gland cone long, not curved; the posterior margin of pereopod 3 is densely setose; the setae on the posterior edge of pereopod 4 are shorter and fewer in number; the anterior margins of pereopods 5 to 7 bear spines in the male; epimeral plates are not pointed. The newly identified species looks similar to G. komareki but differs from it by having a longer antennal gland cone, having fewer D-setae (33) in the third segment of the mandible palp, having shorter setae on the ventral part of the peduncular segment of the antenna 2, and having longer antenna 1, having fewer setae along the posterior margins of pereopods 3 and 4, and the absence of setae along the anterior margins of merus and carpus of pereopod 7. The new species is distinct from its relatives by high genetic distance (COI : 17.10% and 28S: 0.88%) and was resolved from them as an independent lineage with high support (ML : 78%, NJ : 70%, and BI : 1.0) in all phylogenetic results, based on the concatenated dataset (28S+ COI). Additionally, species delimitation analyses (ASAP and PTP) based on the COI gene supported the conclusion that the new species constitutes an independent lineage. Detailed descriptions and drawings of the male holotype and the female allotype are given, and the morphology of the newly identified species is compared with that of its relatives. [ABSTRACT FROM AUTHOR]

Isolation of desert springs often leads to the evolution of unique biodiversity. We investigated the taxonomy and evolutionary relationships of members of the Gammarus pecos complex, an assemblage of narrowly endemic amphipod species in the Chihuahuan Desert of the USA. Morphological and molecular phylogenetic analyses, including newly obtained COI sequences from the now-extinct type population of Gammarus desperatus , reveal the presence of two undescribed species and lead to redescription of G. desperatus. Gammarus acerbatus sp. nov. is split from G. desperatus and Gammarus balmorhea sp. nov. is split from G. hyalelloides. Each of these species is endemic to a single spring system. Speciation in the Gammarus pecos complex was likely promoted by the lineage's ties to marine/riverine systems and geological events during the Oligocene/Miocene. The additional diversity discovered within the complex highlights the effects of both habitat and evolutionary history on the processes of speciation at local and regional spatial scales. The entire complex of at least six species is imperilled due to the narrow ranges occupied by each species and human water-use that threatens the existence of their spring habitats. [ABSTRACT FROM AUTHOR]

Seamounts can have a strong influence on the distribution and diversity of species, creating an oasis effect that may favour diversification. In order to assess how and to what extent supra- and epibenthic crustaceans can colonise these environments, the eucarid and peracarid fauna collected from the summit of the Valencia Seamount (VS), a small deep seamount (summit depth: 1056 m), rising from a depth of ca. 1850 m, in the oligotrophic Balearic Basin, was analysed. Based on a first sampling (beam trawls, plankton nets and stomach contents), and a faunal reconstruction from a sediment core (MC2, at 1151 m), the supra(epi)benthic crustaceans at the VS summit (to 1300 m) were composed of nine Eucarida and 25 Peracarida. Polycheles typhlops, Munida tenuimana, and Aristeus antennatus were the dominant species among eucarids. Among Peracarida the most abundant species were the Mysida Boreomysis arctica, the Amphipoda Rhachtropis caeca, and the Isopoda Munnopsurus atlanticus. Among Decapoda, a species with a wide amplitude in their depth distribution and small eggs (i.e., with planktotrophic larvae), showed a higher colonisation capacity. In the absence of larvae, the colonisation of peracarids depends on the amplitude of their depth distribution and only those species that reach the highest depths in the entire Balearic Basin, at least 1600–1800 m, were able to colonise the summit of VS. The natatory capacity of the species also has some influence and whole groups with low natatory capacity, such as the Desmosomatidae, were completely absent on the VS summit; however, they are distributed throughout the Balearic Basin to depths (up to about 1500 m) exceeding the depth of the seamount summit. Therefore, colonisation by peracarids must not have occurred by swimming through the entire water column, but by swimming along or just above the bottom. Remains of some suprabenthic species (mainly the isopod M. atlanticus) in MC2 and another core collected in NW Mallorca (MC3, 1114 m), i.e., out of the VS, showed how isopod diversity and size distribution changed historically. Also, after the 1960s, a decrease in primary production due to a decrease in rainfall and river runoff associated with river damming could have reduced the abundance of M. atlanticus. These types of historical studies can be useful in interpreting long-term changes in deep-sea communities and optimising the management of these vulnerable areas. [ABSTRACT FROM AUTHOR]

During two expeditions to the seamounts in the Yap-Caroline area of the Western Pacific, a new genus, Phoxirostus gen. nov., in the family Laphystiopsidae Stebbing, 1899, is erected for two new species, P. longicarpus sp. nov. (type species) and P. yapensis sp. nov. The new genus can be distinguished from the other three laphystiopsid genera by the acute rostrum not overreaching the distal end of the first peduncular article of antenna 1, the outer plate of maxilla 1 bearing 10–11 spines, and the elongated carpus of pereopods 3–7 being distinctly longer than half the length of the propodus. Phoxirostus longicarpus sp. nov. differs from P. yapensis sp. nov. by the shape of the eyes and coxa 4, the presence of posterodistal protrusions on pleonite 1, and the number of posterodistal protrusions on pleonite 2. Generic analysis of one mitochondrial (COI) and one nuclear (H3) gene using maximum likelihood and Bayesian inference clarified the phylogenetic position of the Laphystiopsidae within the superfamily Iphimedioidea Boeck, 1871. [ABSTRACT FROM AUTHOR]

Within the hyper-diverse group of the amphipods, little is known about deep-sea benthic species that still represent an unknown reservoir of species to be discovered, particularly in remote regions of the southwestern Pacific. Herein, we are describing three new deep-sea species of Rhachotropis from Papua New Guinea, Solomon archipelago, and Vanuatu using an integrative taxonomy approach, combining morphological and molecular characters with biological and ecological information. Nomenclatural comments and a key to Rhachotropis species occurring in the bathyal provinces from the southwestern Pacific are also provided. Comments on the sex ratio and fecundity of the genus are also discussed. The biogeography and distribution of the newly described species as well as congeneric species occurring in the area are discussed, and new DNA data are shedding new light on the global phylogenetic relationships (geography, depth range) of the deep-sea genus Rhachotropis. [ABSTRACT FROM AUTHOR]

Conservation translocations may be a useful tool for the restoration of declining freshwater invertebrates, but they are poorly represented in the literature. We conducted a before‐after/control‐impact (BACI) experiment to test the efficacy of conservation translocation for re‐establishing abundant populations of the amphipod Gammarus lacustris, a declining species and wildlife food resource in depressional wetlands in the upper Midwest of the United States of America. Each study site (n = 19) contained at least one treatment wetland receiving translocated G. lacustris from a local donor and one control wetland. We selected study wetlands based on a suite of wetland characteristics and randomly assigned recipient versus control treatment. Gammarus lacustris was detected post‐translocation at only 2 of 22 recipient wetlands (1 of 19 sites). Overall, there was a statistical increase in G. lacustris density in recipient wetlands compared to controls; however, the results were of minimal biological significance due to being driven by a single site with low G. lacustris densities. Accordingly, our results suggest that future conservation translocations of amphipods might be successful if limited to recently restored wetlands or informed by a more complex habitat suitability model to differentiate dispersal limitations from habitat limitations. To develop such a model would involve identifying the fewest, most influential physical and biological factors (e.g. wetland size/structure, fish, aquatic vegetation, and water chemistry) from the numerous inter‐related factors that correlate with the abundance of naturally occurring G. lacustris; candidate wetlands to receive amphipods would be those for which the model predicts abundant G. lacustris but in which they do not presently occur. [ABSTRACT FROM AUTHOR]

Southern Ocean zooplankton provide globally significant ecosystem services through their role in carbon sequestration, nutrient cycling and food webs. However, the remote and extreme nature of the Southern Ocean creates significant logistical difficulties for studying zooplankton all year round. Here, for the first time in the Southern Ocean, we present the seasonal occurrence of the zooplankton assemblage in the Northeast Scotia Sea using a sediment trap deployed throughout 2018 (P3 observation site, 52.80˚ S, 40.14˚ W). Results show that copepods and pteropods dominated trap abundance, representing 25.0–68.3% and 13.4–72.5% respectively, followed by amphipods (1.0–7.2%) and hydrozoa (0.2–15.6%). The dominant signal in copepods was consistent with previous observations using traditional (net) sampling methods while the relative contribution of pteropods, amphipods and hydrozoa was increased in our trap. Further, zooplankton showed taxon-specific seasonal signals, with a relatively high number of individuals throughout winter, including an increase in hydrozoa occurrences. This observation highlights the importance of zooplankton as source of nutrition for the benthic community in the winter. Our data reiterate the utility of sediment traps for observing zooplankton in remote locations and sampling specific taxa that might be otherwise understudied. [ABSTRACT FROM AUTHOR]

The ability of aquatic mesofauna representatives involved in trophic chains to sorb and accumulate toxicants is important for understanding the functioning of aquatic ecosystems and for fishing industry. This study investigated the capacity of marine amphipod Gammarus oceanicus and freshwater amphipods Eulimnogammarus vittatus and Gammarus lacustris to absorb the DNA-alkylating agent methyl methanesulfonate (MMS). The presence of alkylating agents in the environment and in the tissues of the amphipods was determined using whole-cell lux-biosensor Escherichia coli MG1655 pAlkA-lux, in which the luxCDABE genes from Photorhabdus luminescens, enabling the luminescence of the cell culture, are controlled by the PalkA promoter of DNA glycosylase. It was shown that within one day of incubation in water containing MMS at a concentration above 10 μM, the amphipods absorbed the toxicant and their tissues produce more alkylation damage to biosensor cells than the surrounding water. Concentrations of MMS above 1 mM in the environment caused the death of the amphipods before the toxicant could be significantly concentrated in their tissues. The sensitivity and the capacity to absorb MMS were found to be approximately the same for the marine amphipod G. oceanicus and the freshwater amphipods E. vittatus and G. lacustris. [ABSTRACT FROM AUTHOR]

Calceoli are putative sensory organs which are known in limnic, marine, and subterranean amphipods for almost 200 years. Despite an otherwise comprehensive understanding of the sensory organs of crustaceans, we still have not unambiguously understood their function. Since calceoli are mainly found on the antennae of male animals, previous studies suggested a chemosensory function mainly related to reproduction. Here, we use a combination of light and electron microscopic techniques to examine the calceoli of Gammarus locusta (Linnaeus 1758) and Oediceroides calmani (Walker 1906), to provide an overview over these structures, and in addition reveal nervous tissue in close proximity to the calceoli. The calceoli of both species are cuticular structures and consist of proximal and distal elements, a stalk and a receptacle that connects both regions. The two studied calceoli differ in the structure of their proximal and distal element, as well as in their receptacle. This study provides new insight into the functional morphology of the antenna and calceolus. Histological sections through the antennae and the calceoli indicate that the calceoli might possess a mechanosensory function. [ABSTRACT FROM AUTHOR]

This article discusses the feeding behavior of Atlantic herring in coastal waters, specifically in Greifswald Bay in the Baltic Sea. The researchers found that adult herring caught in the fall had unexpectedly consumed demersal fishes and large invertebrates, rather than the expected zooplankton. This behavior was consistent over multiple years of sampling. In contrast, herring stomachs in the spring were mostly empty. The study highlights the importance of considering the feeding traits of marine fish in population models and the need for more holistic approaches in food web science. [Extracted from the article]

The global spread of non-native species is leading to an increasing frequency of multiple co-occurring non-native species. We examined the co-occurrence of the bivalve mollusc Dreissena polymorpha (zebra mussel) with three Ponto-Caspian amphipods (Dikerogammarus villosus, Dikerogammarus haemobaphes, and Chelicorophium curvispinum) across England and Wales in association with in-situ substrate size. For all three amphipod species, substrate grain size where amphipods co-occurred with D. polymorpha was significantly finer than when recorded in isolation. Subsequently, we confirmed this via aquarium experiments. We examined the occurrence of D. villosus with D. polymorpha when present with cobbles, gravel, or sand from three population sources (co-location with abundant D. polymorpha populations, co-location with low populations, and naïve). Experiments demonstrated that D. villosus actively sought shelter on or near D. polymorpha, with their co-location being significantly more prevalent in finer grained substrates (sand > gravel > cobble). The strength of this co-location differed by population source, with those co-located with high D. polymorpha densities demonstrating a greater association. Our analyses and experiments indicate that D. polymorpha may facilitate Ponto-Caspian amphipod establishment in otherwise suboptimal locations, whereby mussel shells provide favourable structural habitat for the amphipods, analogous to the presence of coarse-grained benthic sediment. [ABSTRACT FROM AUTHOR]

The trophic relationships between bats (Chiroptera) and Lake Baikal biota have been assessed based on microscopic studies of Myotis petax feces (n = 22). From 82 to 86% of samples had fragments of exoskeletons of caddis flies (Trichoptera) and dipterans (Diptera). These taxa include mainly aquatic and semiaquatic species. Many species from these taxa are endemic to Lake Baikal. Terrestrial insects are found in studied samples less frequently (Hymenoptera 41%, Neuroptera 27%, and Heteroptera 9%). Morphological analysis has revealed fragments of Baikal amphipods in two fecal samples of M. pretax. Further molecular studies will make it possible to detect greater invertebrate taxa diversity in fecal samples of bats feeding near Lake Baikal. [ABSTRACT FROM AUTHOR]

The results of studies of bottom biocenoses in three types of littoral zone (rocky biotope, gravel-sand biotope, and surf zone with thickets of higher aquatic vegetation) of Lake Onego in 2013 and 2014 are presented. Our data show that, among the three types of coastal zone, the macrozoobenthos biomass is maximal in the rocky littoral zone (3.4–6.6 g/m2) and is minimal in the sandy zone (0.1–0.2 g/m2). The invasive species Gmelinoides fasciatus (Stebbing 1899) (CRUSTACEA: AMPHIPODA) has successfully naturalized in all types of littoral zones of the reservoir in recent decades. This species dominates both in number and biomass in the rocky type of biotope. [ABSTRACT FROM AUTHOR]

Pollution by active ingredients is one of the most significant and widespread forms of pollution on Earth. Medicines can have a negative impact on ecosystems, and contamination can have unpredictable consequences. An urgent and unexplored task is to study the Lake Baikal ecosystem and its organisms for the presence of trace concentrations of active pharmaceutical ingredients. Our study aimed to conduct a qualitative analysis of active pharmaceutical ingredients, and quantitative analysis of ibuprofen in endemic amphipods of Lake Baikal, using methods of high-performance liquid chromatography and mass spectrometry (HPLC-MS). Acetylsalicylic acid (aspirin), ibuprofen, acetaminophen, azithromycin, dimetridazole, metronidazole, amikacin, spiramycin, and some tetracycline antibiotics were detected in the studied littoral amphipods. We also detected different annual loads of active pharmaceutical ingredients on amphipods. Using the multiple reaction monitoring (MRM) mode mentioned in GOST International Technical Standards, we detected molecules, fragmented as amikacin, chlortetracycline, doxycycline, oxytetracycline, dimetridazole, metronidazole and spiramycin. Thus, we first revealed that invertebrates of Lake Baikal can uptake pharmaceutical contaminants in the environment. [ABSTRACT FROM AUTHOR]

Fishes have spread into previously fishless wetlands, likely affecting other species. In the Prairie Pothole Region of North America, the invasion of fish into wetlands is facilitated by interactions of altered land use, climate, and hydrology. We aimed to understand the effects of fishes on amphipods, which are macroinvertebrates that vertebrates rely on as forage. We hypothesized the presence and abundance of fish, particularly benthivores, would have detrimental effects on amphipod abundance. Our study design targeted a large gradient of amphipod abundances among wetlands, including very high abundances of two amphipod species: Gammarus lacustris and Hyalella azteca. We found that fishless basins had twice as many amphipods as those with fish, on average. Gammarus lacustris were not detected in the presence of Black Bullhead Ameiurus melas. The abundance of both amphipod species had negative associations with the most common fishes, Fathead Minnow Pimephales promelas and Brook Stickleback Culaea inconstans. A multivariate community analysis showed the benthivore-fish functional feeding guild was negatively associated with the amphipod community, as hypothesized. However, our study design captured several wetlands with anomalies of high abundances of both fish and amphipods, obscuring their relationships. Our results aid resource managers by confirming several fish guilds and species are associated with lower abundances of amphipods. These findings can inform resource managers who make decisions about managing for fish and wildlife; for example, they may choose to manage existing fish populations or protect existing wetlands with high amphipod densities from new fish invasions. [ABSTRACT FROM AUTHOR]

Benthic amphipod feeding groups are a well-established trophic classification that is mostly based on field observations and laboratory tests and are used in ecological studies to monitor the ecological state of benthic ecosystems. Globally, carbon and nitrogen stable isotope ratio investigations have provided confirmation of, and novel insights into, the trophic ecology of benthic animals, such as polychaetes. However, stable isotopic examinations of benthic amphipods have been limited. Here, we used microgram samples to compare the species-specific dietary sources, trophic positions, and isotopic niche overlap of selected benthic amphipods from the Gulf of Kachchh, Marine National Park, using elemental analyser-isotopic ratio mass spectrometry (EA-IRMS) of carbon and nitrogen. Overall, all primary carbon sources presented wide variation in the isotopic values of δ13C (6.3‰) and δ15N (greater than 13‰). Conversely, the amphipod taxa displayed relatively narrow range for δ13C (3.9‰) and wider range for δ15N (more than 10‰). The results of the Bayesian mixing model revealed that the benthic amphipods had species-specific feeding preferences. However, the predominant carbon source was organic matter in sediment which reinforced benthic pathways for energy flow for most species. According to the estimated trophic level values (1.62–3.39), these species play a significant role as primary and secondary consumers serving as crucial trophic intermediaries in the food chain, connecting the base to the top consumers. High overlapping ecological niche amongst species was detected by SIBER analysis which indicated co-existence of the benthic amphipods in their respective microhabitats. This signifies wider utilisation of resources and inter-specific feeding preferences with minimal competition amongst amphipod species. [ABSTRACT FROM AUTHOR]

The Ponto-Caspian radiation of gammaroid amphipods is one of the world's most diverse lacustrine crustacean radiations as well as the only lacustrine amphipod radiation with a fossil record (dating back 9 Ma). However, the phyletic relationship between fossils and extant species was never formally investigated, hampering our evolutionary understanding of this diverse clade. Here, we present the first morphology-based phylogeny (114 characters) of Ponto-Caspian gammaroids that includes 99% of extant taxa, all previously known fossils, as well as newly discovered fossil specimens from the Late Miocene (10.5 Ma) of eastern Romania. Our phylogenetic and phenetic results strongly support the monophyly of all fossil taxa. However, despite its widespread Late Miocene distribution throughout the Paratethys Sea, this fossil clade left no modern descendants. Its exact phylogenetic position is ambiguous, although it is nested in the radiation's crown group. Morphometric analyses further indicate that fossil species occupy a narrower and peripheral morphospace relative to extant taxa. Our results support the assignment of the newly discovered Romanian fossils to a new genus, Eogmelina gen. nov. with two new species Eogmelina moldavica gen. et sp. nov. and Eogmelina prisca gen. et sp. nov. Finally, our findings call for a fundamental systematic restructuring of Ponto-Caspian gammaroids at genus and family level. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to describe a new species of Antarctic amphipod of the genus Orchomenella Sars, 1890, Orchomenella rinamontiae sp. nov. and to investigate whether high-resolution images of the surface anatomy obtained ' in situ ' with synchrotron radiation X-ray phase-contrast micro-tomography (SR-PhC micro-CT) can replace classical approaches to describe a new species. The phylogenetic analyses based on the gene COI support the morphologically based taxonomic assignment. The SR-PhC micro-CT was useful for viewing the three-dimensional reconstructions, with the great advantages that the specimen could be rotated around all axes and that it was possible digitally to remove sections of the image that might have obscured areas of the amphipod on which we were focusing. However, it is not yet a completely reliable technique to describe a new species fully. Classical descriptions using light microscopy and scanning electron microscopy are still necessary. Nevertheless, SR-PhC micro-CT is a promising technique that has the potential to revolutionize the way we study biological samples, accelerating the study of biodiversity. [ABSTRACT FROM AUTHOR]

In the hypersaline lakes of Crimea, only 5–7 species of animals are common including Gammarus aequicauda (Amphipoda) and Eucypris mareotica (Ostracoda). Two experiments were carried out to characterize the trophic interactions between these species. In one, G. aequicauda were used freshly caught from the lake, and in the other, after they were starved for 2.5 days in the laboratory. The experimental options were one male or female G. aequicauda and either 10, 20, or 30 ostracods. The gammarids actively fed on the ostracods, and significant differences were between females and males. The feeding intensity of males was higher than that of females. However, ostracods are not passive prey, they can actively attack their predator and are capable of causing them harm. Ostracods attacked a Gammarus only if it had captured one of the ostracods. Sex differences in G. aequicauda were also evident in the reaction to the group's aggressive behavior of ostracods. Interactions between Ostracoda and Gammarids cannot be considered unidirectional; they both may be prey or predators depending on the situation. Research Highlights: Seagrass Ruppia influence on zooplankton in a hypersaline lake but direct or reverse to different species.From 2019 to 2023, the average number of Ruppia shoots gradually increased but the total abundance of zooplankton decreased. [ABSTRACT FROM AUTHOR]

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Idunella spinifera (Dauvin and Gentil, 1983) (Crustacea: Amphipoda: Liljeborgiidae) is reported for the first time after the original description that was based on one immature female. Specimens were collected in the Ría de Muros (NW Iberian Peninsula) during the course of a study on macrofauna diversity in shallow sublittoral biogenic sands along a one-year period. The male and the ovigerous female are fully described, and the data on ecology and temporal variation of abundance is provided as well. [ABSTRACT FROM AUTHOR]

One of the most important steps in identifying priority areas for conservation is the assessment of species richness and their extinction risks. While most species remain undescribed, the identification of cryptic lineages is frequent in phylogenetic and phylogeographic studies. This is particularly common in troglobites, exclusively subterranean organisms. The Jandaíra Formation, in the Brazilian semiarid, combines the occurrence of extensive karstic areas with hundreds of caves and subterranean aquifers in a region with intense paleoclimatic changes. This region is recognized for the richness of troglobitic species, some of which are widely distributed in heterogeneous areas. This suggests cryptic lineages that can be differentially exposed to anthropogenic threats, with distinct extinction risks regarding the nominal taxa of which they putatively belong. To test it, a large sampling was conducted and, by means of lineage delimitation analyses, the genetic structure of four troglobitic taxa, three aquatic and one terrestrial, was evaluated. In addition, the extinction risk of these lineages was assessed and priority areas for conservation were identified. The results indicated that while Cirolanidae sp. 1 (Isopoda) is a single species widely distributed, Cirolanidae sp. 2, Potiberaba porakuara (Amphipoda) and Kinnapotiguara troglobia (Hemiptera) present an extensive diversity of cryptic and endemic lineages, most of which are likely new threatened species. Furthermore, two priority areas for conservation of these lineages were identified. Thus, comparative phylogeography may represent a first step in the conservation of subterranean taxa, indicating areas that should be prioritized in a context of increasing threats and dwindling conservation resources. [ABSTRACT FROM AUTHOR]

Globally, stable isotopic methods are rapidly being employed in food web studies to quantify the relative proportions of diverse primary carbon sources in an animal diet. Tropical estuarine ecosystems, one of the vital marine habitats, harbor complex food webs due to the multiplicity of habitats and resources. The complex system of inputs and exchanges of organic matter sometimes complicate identification of the carbon sources that support the higher trophic levels. To assess the primary food sources of four abundant amphipod species in the anthropogenically influenced upper Vashishti estuary, Carbon and Nitrogen stable isotopes were employed. Seasonal variations were significant for δ13C and δ15N of suspended particulate organic matter (SPOM) and also for δ13C of sediment organic matter (SOM), but not for the isotopic values of individual amphipod species. Significant variations in the δ13C and δ15N values between amphipods suggested species-specific diets. Mixing model output indicated discrepancies in seasonal variations of food preferences between species. Trophic level values of all amphipod species indicated seasonality with lower values during post-monsoon. The low δ15N values of SPOM, SOM, and amphipod species were possibly due to the anthropogenic input of nitrogen in the estuary. [ABSTRACT FROM AUTHOR]

Amphipods in the parvorder Lysianassidira are scavengers, often collected in sediment, coral rubble, algae, or among other invertebrates. Members of the parvorder have a head that is deeper than long, large coxae, lacinia mobilis present only on the left molar, and a mitten-shaped gnathopod 2 propodus with a long ischium. Nine species from two families within the parvorder are documented from Bocas del Toro, Panama. This research documents range extensions for eight species and an identification key to the species of Caribbean Lysianassidira of Panama is provided. [ABSTRACT FROM AUTHOR]

Eye loss has been a long‐standing interest in evolutionary biology. Many organisms that inhabit environments without light penetration, for example the deep sea, exhibit eye loss and thus become blind. However, water‐depth distribution of eyes in marine organisms is poorly understood. Ostracods are widely distributed crustaceans, and many sighted marine ostracods have eye tubercles (lenses) on their shells. Since eye tubercles are visible on the shells illustrated in much literature, it is easy to determine their presence or absence via a literature survey. Here, we used a large Arctic‐wide ostracod census dataset (Arctic Ostracode Database) to calculate the eye index (the percentage of species with eyes), and compare them with water depth and light availability. As water depth increases, eye index values decrease and become constantly zero in water deeper than 1000 m. Similar decline of sighted species with increasing depth is also known in isopods and amphipods, suggesting that it may be common in other crustaceans and perhaps in deep‐sea organisms in general. We also show that eye index values increase as light availability increases. This study is the first to quantify how distributions of sighted and blind species change with light availability, giving baseline information on vision in the deep sea. [ABSTRACT FROM AUTHOR]

The groundwater fauna in northwestern Iran remains insufficiently studied. A previous molecular investigation utilizing COI and 28S detected several putative Niphargus species. However, due to the lack of formal nomenclature for these discoveries, we are currently unable to implement practical measures for their protection and management. This paper aims to address this knowledge gap by conducting a morphological analysis of one of the identified species. Additionally, we diagnose and describe a novel species under the name N. azerbaijanensis sp. nov. The results showed that N. azerbaijanensis sp. nov. can be easily distinguished from other species by having triangular gnathopods propodi and rounded epimeral plates I-III. Additionally, the morphological characters of the new species were compared to those of Iranian species, including N. daniali, N. alisadri, N. persicus, N. ilamensis, N. hosseiniei, N. urmiensis and N. tauri from Turkey.The groundwater fauna in northwestern Iran remains insufficiently studied. A previous molecular investigation utilizing COI and 28S detected several putative Niphargus species. However, due to the lack of formal nomenclature for these discoveries, we are currently unable to implement practical measures for their protection and management. This paper aims to address this knowledge gap by conducting a morphological analysis of one of the identified species. Additionally, we diagnose and describe a novel species under the name N. azerbaijanensis sp. nov. The results showed that N. azerbaijanensis sp. nov. can be easily distinguished from other species by having triangular gnathopods propodi and rounded epimeral plates I-III. Additionally, the morphological characters of the new species were compared to those of Iranian species, including N. daniali, N. alisadri, N. persicus, N. ilamensis, N. hosseiniei, N. urmiensis and N. tauri from Turkey. [ABSTRACT FROM AUTHOR]

Black corals are important components of mesophotic and deep-water marine habitats. Their presence at great depths (e.g., 50 to 200 m) makes accessibility difficult, limiting our understanding of the associated biodiversity. Amphipods dominate vagile epifauna in marine habitats around the world, fulfilling important ecosystem functions. However, there are no studies on amphipods exclusively associated with black corals, including relationships between their ecological patterns (e.g., abundances) and the size of coral colonies. We investigated the epifaunal composition and abundance associated with black coral colonies of Antipathella wollastoni in the subtropical eastern Atlantic Ocean. In total, 1,736 epifaunal individuals were identified, of which 1,706 (98.27%) were amphipods, belonging to 6 taxa. We identified and described a new amphipod genus and species within the Stenothoidae family, Wollastenothoe minuta gen. nov., sp. nov., which outnumbered the amphipod assemblage (86.15%) and provided a complete taxonomic key of Stenothoidae family including this new finding. For the first time, the association between an amphipod species and a black coral was described, including a strong correlation between coral colony size and amphipod abundances. This study demonstrates that epifauna associated with mesophotic black corals remains largely undescribed. [ABSTRACT FROM AUTHOR]

A new species of the amphipod family Stenothoidae found living in association with tubulariid hydroids in British Columbia, Canada is described. Stenula traudlae sp. nov. , which has a rounded naked telson, a rounded posterodistal tooth on Ep3, and a heavily spinose P5, is described morphologically. We also include an updated key to world species of Stenula s.l. Associations of amphipods with tubulariids and other small hosts are discussed. [ABSTRACT FROM AUTHOR]

Charles Spence Bate (1818–1889) was one of the more influential mid to late 19th century crustacean taxonomists, with broad interests spanning several taxonomic groups, such as Amphipoda and Decapoda. Despite several contemporary obituaries, no full publication list for him has ever been assembled. In the present contribution, we provide a complete listing of publications and all species- and genus-level crustacean taxa described by Spence Bate, and indicate their current status. Corrections to publication dates are listed, and several decisions are made to stabilise crustacean nomenclature. In a scientific career spanning almost 50 years (1850–1889), Spence Bate described a total of 402 species and 70 genera in Decapoda, 181 species and 46 genera in Amphipoda, as well as eight genera and eight species of Cumacea, four genera and 16 species of Isopoda, three of Tanaidacea and one of Cirripedia. Of these, 36.2% of species and 45.7% of genera are still considered as the accepted names for their taxa today. [ABSTRACT FROM AUTHOR]

The ocean's midwater is a uniquely challenging yet predictable and simple visual environment. The need to see without being seen in this dim, open habitat has led to extraordinary visual adaptations. To understand these adaptations, we compared the morphological and functional differences between the eyes of three hyperiid amphipods—Hyperia galba, Streetsia challengeri and Phronima sedentaria. Combining micro-CT data with computational modelling, we mapped visual field topography and predicted detection distances for visual targets viewed in different directions through mesopelagic depths. Hyperia's eyes provide a wide visual field optimized for spatial vision over short distances, while Phronima's and Streetsia's eyes have the potential to achieve greater sensitivity and longer detection distances using spatial summation. These improvements come at the cost of smaller visual fields, but this loss is compensated for by a second pair of eyes in Phronima and by behaviour in Streetsia. The need to improve sensitivity while minimizing visible eye size to maintain crypsis has likely driven the evolution of hyperiid eye diversity. Our results provide an integrative look at how these elusive animals have adapted to the unique visual challenges of the mesopelagic. [ABSTRACT FROM AUTHOR]

A new intertidal species of the melitid amphipod, Melita panda, from the Wakayama Prefecture, Japan, is identified and described. Melita panda sp. nov. differs from the similar M. koreana and M. nagatai by its black-and-white body color, well-developed anterodistal projection of the male gnathopod 1 propodus, and telson armature. Molecular phylogenetic analyses based on the nuclear 28S rRNA and mitochondrial COI genes support that M. panda sp. nov. is closely related to M. koreana and M. nagatai. [ABSTRACT FROM AUTHOR]

The long-term dynamics of production of the glacial relict amphipod Monoporeia affinis was examined in a small subarctic lake. The aims of this study were: (1) to compare the production of amphipods with their biomass; (2) to relate the changes in amphipod population with environmental variables. I hypothesized secondary production could provide better insight into M. affinis population dynamics, than abundance and biomass alone. Production (increment-summation method) and its standard error were estimated based on benthic samples taken at a sublittoral site from June 2002 to May 2019 (as a rule, 4–5 times a year). Production and biomass were highly correlated with each other. The annual P/B ratio varied twofold. However, the majority of estimates did not differ significantly from the mean P/B value for the study period. Effects of environmental variables (water temperature and chlorophyll-a concentration) were pronounced for offspring and juvenile amphipods only. The older amphipods showed no significant correlation with any environmental variables. Despite the initial prediction, no reliable evidence was found that production revealed greater insight into population dynamics of M. affinis. This long-term study confirms that benthic production is mainly a function of biomass. [ABSTRACT FROM AUTHOR]

Improve the knowledge base on the ecomorphological adaptation of teleost species to different environments, trying to reconstruct how habitat can shape sagittae, is essential for conservational purposes, evolutionary evaluations, and population dynamics studies. Here is provided a comparative study between sagittae features, growth rates and age composition of two Scorpaena porcus populations inhabiting the Mediterranean waters, one from the Strait of Messina (Central Mediterranean Sea) and one from the Split area (Adriatic Sea). Additionally, the stomach contents of the Messina specimens have also been analysed to provide some preliminary information on the diet of S. porcus. A total of ninety individuals, half from each area, have been obtained from two extremely different environments. Results showed an overall different morphology, shape, and morphometry of sagittae among the size classes of the two investigated populations. Samples from Messina were characterized by a most elliptical and slender shape, with a more regular serration of margins than those from Split, which exhibited a wider sagitta, with a most enhanced anti-rostrum and longer rostrum. Concerning diet, specimens from Messina showed a preference for Crustacea (especially Brachyura and Amphipoda) and Teleost species, showing some differences with literature data from other geographical areas (Split one included). Results have confirmed the reliability of sagittae to detect the interpopulation variability of S. porcus from different geographical areas, an essential tool for stock assessment, population studies and investigation on ecomorphological adaptation of teleost species to different habitats. [ABSTRACT FROM AUTHOR]

Pontocrates genus has been assigned to the family Oedicerotidae since 1871. The five species recognized within this family share a similar biogeographical distribution in cold and temperate seawater of Europe and the northern Mediterranean Sea. However, this genus has never been recorded from tropical or subtropical waters elsewhere. The present collected materials from the northern Red Sea (Egyptian coast) indicated an expansion of the distribution area to cover warmer waters. The present species is distinguished from the other congeners by having long dactyl of pereopod six in both male and female, which is the longest among the other species of the genus and subequal to propodus length. A detailed description and fully illustrated material of this species, along with an identification key of worldwide species of Pontocrates, are provided. [ABSTRACT FROM AUTHOR]