Amphipod Crustaceans Research Articles

Moon orientation in sandhoppers: effects of lighting treatments on the persistence of orientation ability

The moon orientation rhythm persists in sandhoppers removed from environmental entrainments relative to moon periodicity. In order to investigate the underlying mechanism, the crustacean amphipods Talorchestia capensis and Talitrus saltator were collected at new moon and exposed in the laboratory to an artificial light during the day, but to a variety of lighting treatments during the night: (1) continuous dark, (2) dim light in phase with the natural moon, (3) continuous dim light. The animals were tested under the moon 9–21 days later by using a new type of arena. The ability to orientate in a direction perpendicular to the shore persisted in sandhoppers under treatments 1 and 2, but not under treatment 3. A disturbance due to a phototactic tendency in Talorchestia was also observed in animals captured on the day of the test when exposed to unnatural lighting, but not when they were kept under natural light. The present findings show that the timing mechanism allowing compensation for changes in the moon’s position also persists in animals that have been long removed from entraining factors. The dependence of this orientation ability on nocturnal lighting and the disturbing effect of sudden changes in light intensity support the idea that the phasal lighting of the moon, and perhaps sunrise and sunset act as resetting factors for the moon’s orientation rhythm.

DNA barcoding reveals extraordinary cryptic diversity in an amphipod genus: implications for desert spring conservation

DNA barcoding has revealed unrecognized species in several animal groups. In this study we have employed DNA barcoding to examine Hyalella, a taxonomically difficult genus of amphipod crustaceans, from sites in the southern Great Basin of California and Nevada, USA. We assessed the extent of species diversity using a species screening threshold (SST) set at 10 times the average intrapopulation cytochrome c oxidase subunit I (COI) haplotype divergence. Despite the fact that this threshold approach is more conservative in delineating provisional species than the phylogenetic species concept, our analyses revealed extraordinary levels of cryptic diversity and endemism. The SST discriminated two provisional species within Hyalella sandra, and 33 provisional species within Hyalella azteca. COI nucleotide divergences among these provisional species ranged from 4.4% to 29.9%. These results have important implications for the conservation of life in desert springs - habitats that are threatened as a result of groundwater over-exploitation.

Expression of otd orthologs in the amphipod crustacean, Parhyale hawaiensis

The arthropod head is a complex metameric structure. In insects, orthodenticle (otd) functions as a 'head gap gene' and plays a significant role in patterning and development of the anterior head ectoderm, the protocerebrum, and the ventral midline. In this study, we characterize the structure and developmental deployment of two otd paralogs in the amphipod crustacean, Parhyale hawaiensis. Photd1 is initially expressed at gastrulation through germband stages in a bilaterally symmetric, restricted region of the anterior head ectoderm and also in a single column of cells along the ventral midline. Late in embryogenesis, Photd1 is expressed within the developing anterior brain and the expression along the embryonic midline has become restricted to a stereotypic group of segmentally reiterated cells. The second ortholog Photd2, however, has a unique temporal-spatial expression pattern and is not detected until after the head lobes have been organized in the developing ectoderm of the germband during late germband stages. Anteriorly, Photd2 is coincident with the Photd1 head expression domain; however, Photd2 is not detected along the ventral midline during formation of the germband and only appears in the ventral midline late in embryonic development in a restricted group of cells distinct from those expressing Photd1. The early expression of Photd1 in the anterior head ectoderm is consistent with a role as a head gap gene. The more posterior expression of Photd1 is suggestive of a role in patterning the embryonic ventral midline. Photd2 expression appears too late to play a role in early head patterning but may contribute to latter patterning in restricted regions of both the head and the ventral midline. The comparative analysis of otd reveals the divergence of gene expression and gene function associated with duplication of this important developmental gene.

New families and subfamilies of amphipod crustaceans

Cleonardopsis K.H. Barnard, 1916, has been incorrectly placed in the Eusiridae. Based on mouthpart morphology, body carination and the shape of the gnathopods it is reassigned to the Amathillopsidae in the new subfamily Cleonardopsinae. Cleonardopsinae is cosmopolitan in the deep sea. Parepimeria Chevreux, 1911, has been incorrectly placed in the Epimeriidae. Coleman & Barnard (1991) suggested that it be moved to the Pleustidae. Bousfield & Hendrycks (1994) rejected this suggestion. It is excluded from the Pleustidae because of the progressively larger and ventrally acute coxae 1 to 4, simple first and second gnathopods and carinate urosomites. Parepimeria appears to be a sister taxon of Amathillopsis Heller, 1875, and forms the basis of a new monotypic subfamily, Parepimeriinae, within the Amathillopsidae. Parepimeriinae appears to be a Southern Ocean endemic. Miramarassa Ortiz, Lalana & Lio (1999) was originally placed in the Aristiidae mainly because it has an elongate ischium on gnathopod 2. It is excluded from the aristiids and the lysianassoids, because of the slender antenna 1 which is characteristically non-lysianassoid, the mandibular incisor which is curved and serrate and the lacinia mobilis which occurs on both mandibles. A monotypic family, Miramarassidae, is established which may have affinities with iphimedioid taxa. Miramarassidae is currently known only from Cuba. Regalia K.H. Barnard (1930) has generally been considered as a calliopiid amphipod, although some workers have discussed its similarity to the Pleustidae. A fresh evaluation of the genus has shown that characters not considered by earlier workers, such as a callynophore on antenna 1, brush setae on antenna 2 and a straight, minutely serrate incisor on the mandible, indicate that Regalia cannot be a calliopiid or a pleustid. Regalia appears to be most similar to members of the Pardaliscidae, but a number of characters such as the lack of an accessory flagellum, the presence of a left and right lacinia mobilis, a well developed molar and lateral ridging on the pleosome exclude it from this family. Consequently Regaliidae is established as a new monotypic family for Regalia, with an Indo-West Pacific distribution. Sancho Stebbing, 1897, has most recently been placed in the Eusiridae (sensu lato), but might be more suited to the Calliopiidae (sensu stricto) because of its entire telson. Unlike eusirids or calliopiids, species of Sancho have a non-recessed head and a dorsoventrally flattened urosome. Sanchoidae is established as a new monotypic family for Sancho, currently known from shallow water in south-eastern Australia.

Feeding habits and their implications for the conservation of the endangered semiaquatic frog Atelognathus patagonicus (Anura, Neobatrachia) in a northwestern Patagonian pond

Feeding habits and their implications for the conservation of the endangered semiaquatic frog Atelognathus patagonicus (Anura, Neobatrachia) in a northwestern Patagonian pond. Atelognathus patagonicus (Gallardo, 1962) is an endemic frog species whose distribution is restricted to an endorheic pond system in basaltic basins in the northwest of the Argentinean Patagonia. Atelognathus patagonicus has two morphotypes: aquatic and littoral. This study presents data on the diet of A. patagonicus in Laguna del Burro, in Neuquén Province. Digestive tracts were analyzed for 20 specimens: 17 of the aquatic form and 3 of the littoral form. Diversity and trophic niche breadth, and index of relative importance (IRI) were calculated for the aquatic form. Nine food categories were found in the stomachs and intestine with the most important being Odonate naiads (Rhionaeschna sp.; IRI% = 86.57) and amphipod crustaceans (Hyalella sp.; IRI% = 12.89). There was not a statistically significant correlation between snout-vent length and mouth width of the frogs and mean prey lengths. For the littoral form of A. patagonicus, 25 prey categories were found, and all preys were adult terrestrial arthropods. Conclusions about the feeding habits of Atelognathus patagonicus and their implications for the design of conservation programs for the species are also given.

Two new genera and two new species of the subterranean family Bogidiellidae (Crustacea, Amphipoda) from groundwaters in northern Oman, with notes on the geographic distribution of the family

The bogidiellid amphipod crustaceans Stockigi diella aequim ana new genus and species and Om angidiella p arvid actyl a new genus and species are described from subterranean groundwater habitats in the Sultanate of Oman on the Arabian Peninsula. Stockigidiell a is easily distinguished by a row of long, deeply bifid setae on pereopods 5 and 6, whereas Omangidiell a is distinguished by a greatly reduced propodus of gnathopod 2 and elongate oostegites; it also possesses a third coxal lobe on the maxilliped, a unique character noted only in three other bogidiellid genera from northern and eastern Africa. At present, the family Bogidiellidae contains 35 genera and 105 species but a significant number of provisionally recognized new species and possibly several new genera await description. The geographic distribution of the family Bogidiellidae is nearly circumglobal, but species tend to be clustered in discontinuous regions. A number of important questions regarding the origin and biogeographic history of the family remains unanswered.

Interlaboratory assessment of marine bioassays to evaluate the environmental quality of coastal sediments in Spain. IV. Whole sediment toxicity test using crustacean amphipods

Interlaboratory variability was studied for the bioassay using crustacean amphipods. Nine series of data were obtained from different laboratories using four different species (Ampelisca brevicornis, Corophium volutator, Corophium multisetosum and Microdeutopus gryllotalpa), all previously used for sediment toxicity assessment in Spain. Results were studied for interlaboratory variability and according to different confounding factors. The coefficients of variation were similar to those previously reported for this bioassay and sample classification was homogeneous among the laboratories that succesfully completed the exercise. No significant tendencies related to test species were identified and it seems that the factor most critically affecting test results and the classification of samples is storage time before testing.

The discriminatory power of two biomonitors of trace metal bioavailabilities in freshwater streams

The relative discriminatory powers of two trace metal biomonitors in European streams (the amphipod crustacean Gammarus fossarum and mayfly larvae of the genus Baetis— B. rhodani and B. vernus) are compared by discriminant function analysis using data from streams draining a zinc and lead mining area of Upper Silesia, Poland. The mayfly larvae (whether or not distinguished into the two separate species) had the better discriminatory power to distinguish between sites on the basis of local bioavailabilities of cadmium, copper, iron, lead and zinc. The bioavailabilities of the two metals lead and cadmium were the major local contributing factors to the stronger discrimination shown by the Baetis larvae.

Dikerogammarus villosus (Sowinsky, 1894) (Crustacea, Amphipoda, Gammaridae) for the first time in Italy

The recent discovery in Lake Garda, and in other watercourses of northern Italy, of Dikerogammarus villosus, an amphipod crustacean from the Ponto‐Caspian region, is a worrying confirmation of how it is rapidly spreading in Europe. In Lake Garda, the species is present, with high population density, in the southern basin, where it is the only gammarid of the littoral benthos, and in the northern basin, with lower population density, where it still coexists with the native species Echinogammarus stammeri. Ovigerous females and juveniles are present most of the year in all the explored areas. Considering that the species has often replaced the native gammarids in invaded waters in most European regions, we want to raise the alarm for a possible progressive elimination of the native species E. stammeri by the invading one from the Garda littoral benthos.

Bactrurus speleopolis, a new species of subterranean amphipod crustacean (Crangonyctidae) from caves in northern Arkansas

Bactrurus speleopolis, a large stygobitic amphipod crustacean in the family Crangonyctidae is described from specimens collected from a lake in Cave City Cave, Sharp County, Arkansas, and is the second species of Bactrurus Hay, 1902 recorded to date from the state. This species may also occur in Marble Falls Cave in Marion County, but sexually mature specimens are needed to verify that occurrence. The description of B. speleopolis raises the total number of species in Bactrurus to eight. The genus is widespread in subterranean groundwaters of the east-central United States and is also recorded from a few localities farther east in the southern Appalachians.

Amphipod crustaceans (Gammaridea) from Beijing, P. R. China

Seven freshwater and terrestrial amphipod species from Beijing, including one new species, Jesogammarus (Annanogammarus) debilis, are reported. A detailed description and illustrations of this new species are given and differences between these seven species are discussed. A key to the amphipods of Beijing and their distribution data are also presented.

The use of tracers to evaluate the importance of bioturbation in remobilising contaminants in Baltic sediments

Large areas of the bottom sediments of the Baltic Sea are temporarily or permanently anoxic. These sediments are also an important sink for a variety of contaminants. Reoxygenation of bottom waters allows recolonisation by benthic infauna, which may have important implications for the fate of buried contaminants. This study used tracers to experimentally examine the role of bioturbation by benthic infauna in transporting sediment-associated contaminants in the Baltic Sea. Three different tracer methods were used in two experiments, using three key Baltic macrofaunal species: the amphipod crustacean Monoporeia affinis; the Baltic clam Macoma baltica; and the priapulid worm Halicryptus spinulosus. In the first experiment, a reoxygenation–recolonisation scenario was recreated in the laboratory, using hypoxic sediment cores collected in the field, to determine if there was remobilisation of buried 137Cs from the Chernobyl nuclear accident in 1986. The potential for the infauna to bury newly settled surface contamination was also investigated, using a fluorescent particle tracer. In the second experiment, artificially-created radiolabelled tracer layers ( 14C and 51Cr) were used to quantify both upward and downward movements of organic matter and sediment-associated contaminants by bioturbation. In both experiments there were clear visual differences between the sediment effects of the three species. Halicryptus spinulosus buried deepest into the sediment, creating a network of burrows, Monoporeia affinis burrowed actively in the upper few centimeters of the sediment, and Macoma baltica was quite stationary, but appeared to filter- and deposit feed at the sediment surface. Mixing depths in the hypoxic sediment varied from 4.0 ± 3.5 cm for M. baltica to 7.8 ± 2.1 cm for H. spinulosus. Biodiffusion rates ( D b) were similar for all treatments but biotransport rates ( r) were significantly different between treatments, mainly due to a high r value for H. spinulosus. In the experiment with radiolabelled tracer layers, 51Cr was transported more than 14C, and tracer originally at the surface transported more than tracer buried 4 cm below the surface. There was also transport of all tracers in treatments without added macrofauna. The most likely explanation is bioturbation by the meiofauna that were undoubtedly present in both experiments. Bioturbation by macrofauna both buries surface contaminants and remobilises those that are buried, but the effects are small and on a similar scale to transport caused by meiofauna. In addition, 137Cs profiles at the hypoxic site indicated that resuspension and redeposition of sediment by physical processes had occurred, and also showed that contaminants from the last 40 years were still present in the top 5–10 cm of the sediment, well within active mixing depths. At this site, as at many others in the Baltic, physical processes are likely to be far more important than biological processes in the redistribution of contaminants on a decadal timescale.

The acanthocephalan parasite Polymorphus minutus alters the geotactic and clinging behaviours of two sympatric amphipod hosts: the native Gammarus pulex and the invasive Gammarus roeseli

AbstractAcanthocephala are parasites with complex life cycles involving arthropod intermediate hosts and vertebrate final hosts. They use predation as a means of transmission, and some species have developed the ability to modify behaviour of their intermediate hosts to enhance the probability of ingestion by the definitive host. Knowledge of how a single parasite species is adapted to modify the behaviour of different intermediate host species is important for the understanding of parasitic transmission in host communities. In Burgundy, the freshwater amphipod crustaceans Gammarus pulex (native species) and Gammarus roeseli (eastern European invader) are both intermediate hosts for the acanthocephalan Polymorphus minutus. The influence of this bird parasite on the geotaxis of G. roeseli was evaluated and it was found that when infected, individuals of this host species have a negative geotaxis compared to uninfected individuals. There were two components to the behavioural changes: swimming to the top of the water column, and clinging to surface material. These changes were comparable to those observed in the local host species G. pulex, but lower in magnitude. This result contrasts with a previous study on the influence of the fish parasite Pomphorhynchus laevis, which is able to alter the native species' behaviour, but not that of the invasive host. Parasite adaptations to local vs invasive intermediate host species are discussed in terms of their dispersal range (i.e. dispersal of their definitive hosts): the wider the dispersal, the greater should be the spectrum of intermediate hosts.

Shallow benthic fauna communities of South Georgia Island

Benthic communities in several fjords and sheltered bays of the north coast of South Georgia Island were examined using SCUBA and shore sampling in November 2004. It is one of the most northerly islands within the Polar Front and its well studied, terrestrial biota is described as sub Antarctic. The intertidal and subtidal zones and their fauna are, by comparison, little known. We describe the composition of the substratum and benthic communities of sites in several northern bays, including an exceptional community in the extremely sheltered Moraine Fjord with a 2 m sill at its entrance. In this, like those in some other fjordic systems, some taxa occur shallower than elsewhere, and in this instance, get large and are probably old. Elsewhere, we found the coastal fauna was fairly similar to Antarctic shallow communities in the southern Scotia Arc and Peninsula region. Of the taxa we found, we identified 53 to genus and 41 to species. Most of these were typical Antarctic shallow benthic taxa. Certain flatworms, nemerteans, bivalve and gastropod molluscs, amphipod and isopod crustaceans, asteroid echinoderms and stalked ascidians were very abundant, but some normally common Antarctic higher taxa and species were notably absent or rare.

New species and new records of weckeliid amphipod crustaceans (Hadziidae) from caves in northern Mexico, with descriptions of the new genera Paraholsingerius and Tamaweckelia

Two new genera, Paraholsingerius and Tamaweckelia, and two new species, P. mexicanus and T. apalpa are described from caves in eastern Coahuila and southern Tamaulipas, Mexico, respectively. Holsingerius smaragdinus, previously known from a single cave in Val Verde County, Texas, is placed in the new genus Paraholsingerius, and a second population of P. smaragdinus is recorded from northern Coahuila, Mexico. A new record for Paramexiweckelia in north-central Coahuila is documented.

Selective predation by the zoarcid fish Thermarces cerberus at hydrothermal vents

This study investigates predation by the vent zoarcid fish Thermarces cerberus through gastrointestinal analyses of 27 specimens collected with the submersible ALVIN at vents at 9°50′N on the East Pacific Rise. T. cerberus fed most frequently on gastropod mollusks (mainly Lepetodrilus elevatus) and amphipod crustaceans (mainly Ventiella sulfuris). Species found occasionally in high abundance included the swarming amphipod Halice hesmonectes and the snail Cyathermia naticoides. Other items also found in gastrointestinal tracts, but in very low numbers, included polychaete worms, crustaceans and unidentified tissue clumps. The comparison between the size distribution of L. elevatus limpets ingested by T. cerberus and those found attached to vestimentiferan tubes suggest that the fish may selectively prey on large limpets. If the selective removal of large Lepetodrilus spp. limpets by T. cerberus does occur, then it would have potential community-level consequences at hydrothermal vents, since these mobile gastropods appear to inhibit the settlement of sessile vent species, including tube-building worms. Our results suggest possible direct and indirect effects of T. cerberus on benthic community structure at hydrothermal vents on the East Pacific Rise.

Kinetics of zinc uptake from solution, accumulation and excretion by the decapod crustacean Penaeus indicus

Juveniles of the dendrobranchiate decapod Penaeus indicus take up radiolabelled zinc from solution at all exposure concentrations studied from 5.6 to 100 μg l−1, with an uptake rate constant of 0.045 l g−1 day−1 at 15 salinity and 25°C. Over the first 10 days of zinc exposure, the new zinc taken up is added to the existing zinc content of the prawn with no significant excretion; over this period the rate of accumulation of radiolabelled zinc is a measure of the absolute zinc uptake rate from solution. Over the next 10 days of zinc exposure to 10 μg Zn l−1, however, zinc is excreted at about half the rate of uptake resulting in a raised body concentration of zinc. Moulting had no significant effect on the accumulation of zinc. Newly accumulated zinc is distributed to all organs with the highest proportions of body content being found in the exoskeleton, followed by the muscle, the hepatopancreas and the antennal organs. Radiolabelled zinc is subsequently lost from all organs. Unlike caridean shrimps or prawns (pleocyemate decapods), therefore, penaeids (dendrobranchiate decapods) do not show regulation of zinc body concentrations to a constant level over a range of dissolved zinc bioavailabilities by matching zinc excretion to zinc uptake. Nevertheless, unlike amphipod crustaceans, P. indicus does excrete some of the zinc newly accumulated from solution after a time delay. Unlike their caridean counterparts, penaeid prawns inhabiting anthropogenically contaminated coastal waters with raised zinc bioavailabilities can be expected to contain raised body concentrations of zinc.

New Species of Amphipod Crustaceans in the Genera Tegano and Melita (Hadzioidea: Melitidae) from Subterranean Groundwaters in Guam, Palau, and the Philippines

Abstract Three new species of Tegano are described, two from caves on Panglao Island, Bohol, Philippines, and one from a cave on Peleliu Island, Palau. Sriha vagabunda from Sri Lanka is reassigned to the genus Tegano based primarily on the high degree of similarity between Sriha vagabunda and species of Tegano and the fact that these species exhibit a great deal of variation in the reduction of the mandibular palp. A new species of Melita with characters intermediate between those defining the genera Abludomelita, Melita, and Paraniphargus is described from a spring on Guam. The characters of the new species and studies by previous authors suggest that Abludomelita may not be as distinct from Melita as previously believed. The troglomorphic genus Paraniphargus from the Andaman Islands and Java is re-evaluated and synonymized with Melita.

The fate of isolated blastomeres with respect to germ cell formation in the amphipod crustacean Parhyale hawaiensis

Germ cells may be specified through the localization of germ line determinants to specific cells in early embryogenesis, or by inductive signals from neighboring cells to germ cell precursors in later embryogenesis. Such determinants can be produced and localized during or after oogenesis, either autonomously by oocytes or by associated nutritive cells. In Drosophila, each oocyte is connected to nurse cells by cytoplasmic bridges, and determinants synthesized in nurse cells are transported through these bridges to the oocyte. However, the Drosophila model may not be applicable to all arthropods, since in many species of all four extant arthropod classes, gametogenesis functions without nurse cells. In this paper, I use immunodetection of Vasa protein to study germ cell development in the amphipod crustacean Parhyale hawaiensis, a species whose ovaries lack nurse cells and whose eggs lack obvious polarity. Previous cell lineage analyses have shown that all three germ layers and the germ line are exclusively specified by third cleavage. In the present study, I use a molecular marker to follow germ cell development during P. hawaiensis embryogenesis. I determine the capacity of individual blastomeres to form germ cells by isolating blastomeres at early cleavage stages and provide experimental evidence for localized germ cell determinants at the two-cell stage in P. hawaiensis. These experiments indicate that many aspects of early amphipod development, including timing and symmetry of cell division, the transition from holoblastic to superficial cleavage, and possibly some gastrulation movements, are cell autonomous following first cleavage.

A new species of amphipod crustacean, Pleusymtes comitari sp. nov., associated with gorgonians on deep-water coral reefs off Ireland

A new species of pleustid amphipod of the genus Pleusymtes is described from the west coast of Ireland. It was found to be common in association with an Acanthogorgia sp. gorgonian at 725 and 900 m depth on coral habitats in the continental shelf-break areas of the Porcupine Seabight and Porcupine Bank. It is assumed to be a commensal due to its modified pereopod dactyls.