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Abstract: In this study we compared DNA barcode-suggested species boundaries with morphology-based species identifications in the amphipod fauna of the southern European Atlantic coast. DNA sequences of the cytochrome c [...]

Bisphenol A (BPA) is an endocrine-disrupting compound that can enter aquatic systems through landfill leachate or wastewater effluent. Although impacts of BPA on vertebrates are well documented, its effects on invertebrates are less clear. Amphipods such as Gammarus pseudolimnaeus Bousfield, 1958 are often prevalent invertebrates in freshwater ecosystems and can provide a powerful invertebrate model system to investigate the endocrine-disruptive capabilities of BPA. However, techniques to assay hormone concentrations in amphipods, especially vertebrate-like steroid sex hormones, are not widespread. In this study, we (i) quantified estrogen concentrations in juveniles and in adult female amphipods; (ii) quantified testosterone concentrations in juveniles and in adult male amphipods; and (iii) delineated changes to estrogen and testosterone concentrations of adults and juveniles following a 9-day exposure to BPA at four levels: 0 (control), 10, 50, and 100 µg/L BPA. Tissue extracts from homogenized samples were analyzed for estrogen or testosterone concentrations via radioimmunoassay for each reproductive class of amphipod. Low concentrations of BPA significantly increased estrogen concentrations in adult females and in juveniles. Moderate and high concentrations of BPA significantly increased testosterone concentrations in adult males, and low and moderate concentrations of BPA significantly increased testosterone concentrations of juveniles. Key words: crustacean, amphipod, Gammarus pseudolimnaeus, bisphenol A, endocrine disruptor, estrogen, testosterone. Le bisphenol A (BPA) est un compose perturbateur du systeme endocrinien qui peut entrer dans les systemes aquatiques par le biais de lixiviat de sites d'enfouissement ou d'effluents d'eaux usees. Si les impacts du BPA sur les vertebres sont bien documentes, ses effets sur les invertebres le sont moins. Des amphipodes comme Gammarus pseudolimnaeus Bousfield, 1958 figurent souvent parmi les invertebres les plus abondants dans les ecosystemes d'eau douce et peuvent constituer un puissant modele invertebre pour l'etude des capacites de perturbation du systeme endocrinien du BPA. Les methodes d'analyse des concentrations d'hormones dans les amphipodes, particulierement celles d'hormones sexuelles stero'ides semblables a des hormones de vertebres, ne sont pas repandues. Dans l'etude, nous avons (i) quantifie les concentrations d'oestrogene dans des amphipodes juveniles et femelles adultes, (ii) quantifie les concentrations de testosterone dans des amphipodes juveniles et males adultes et (iii) delimite les changements des concentrations d'oestrogene et de testosterone d'adultes et de juveniles apres une exposition de 9 jours a du BPA en quatre concentrations differentes, a savoir: 0 (temoin), 10, 50 et 100 µg/L BPA. Des extraits de tissus tires d'echantillons homogeneises ont ete analyses par dosage radioimmunologique pour determiner les concentrations d'ostrogene et de testosterone pour chaque classe reproductrice d'amphipodes. De faibles concentrations de BPA entrainaient une augmentation significative des concentrations d'oestrogene chez les femelles adultes et chez les juveniles. Des concentrations moderees a elevees de BPA entrainaient une augmentation significative des concentrations de testosterone chez les males adultes, alors que des concentrations faibles a moderees de BPA entrainaient une augmentation significative des concentrations des testosterone chez les juveniles. Mots-cles: crustace, amphipodes, Gammarus pseudolimnaeus, bisphenol A, perturbateur du systeme endocrinien, ostrogene, testosterone. [Traduit par la Redaction], Introduction Endocrine-disrupting compounds stemming from certain pharmaceuticals, pesticides, and chemicals in industrial and commercial waste products have been linked to developmental and reproductive abnormalities in a wide range of vertebrate [...]

Among metazoans, crustaceans display the greatest disparity between body plans and are second only to the insects in overall species diversity. Within the crustaceans, the Amphipoda rank as one of the most speciose extant orders. Amphipods have successfully invaded a variety of ecosystems, including the pelagic midwater environment. Despite their abundance in varied and dissimilar habitats, and the use of traditional morphological and systematic comparative analyses, phylogenetic relationships among amphipods remain uncertain. The pelagic amphipods, hyperiids, have highly divergent life histories and morphological attributes in comparison to more familiar benthic, nearshore, intertidal, and terrestrial amphipods. Some of these adaptations are likely correlated with their pelagic life history and include features such as hypertrophied olfactory and visual systems, duplications of the eyes, and an array of modifications to the appendages. Many of these morphological features may represent homoplasies, thus masking the true phylogenetic relationships among extant hyperiid amphipods. Here, we sample a wide range of amphipod taxa for the COI gene and present the first preliminary molecular phylogeny among the hyperiids.

Abstract: The genome sizes of 8 species of amphipods collected from the Canadian Arctic were estimated by flow cytometry. Haploid genome sizes ranged from 2.94 [+ or -] 0.04 pg [...]

Recent reports have demonstrated a cost associated with intersexuality in Amphipoda, including reduced fecundity and fertility. In this study, the gross morphology of the gonads in normal and intersex Echinogammarus marinus (Amphipoda) were compared to determine whether resource allocation to gonadal tissue accounted for this reduced fitness. Evidence for the presence of the male sex-determining hormone, androgenic gland hormone (AGH), was compared between sexual phenotypes using MALDI mass spectrometry. Two distinct intersex phenotypes ('male' intersex and 'female' intersex) were found, with variation in gonadal structure corresponding with external phenotype. Examination of male intersexes revealed normal testicular development (testes, seminal vesicles and vas deferens), but also revealed the formation of an oviduct. Ovaries of intersex females showed normal ovarian development, but were reduced in length by approximately 20% due to the presence of vas deferens. The number of vas deferens in intersex females was equal to the number (one or two) of genital papillae. We hypothesise that the reduced ovarian length observed in intersex females is a likely cause of the reduced brood size previously reported in intersex females of this species. Variation in the sexual phenotype corresponded both to development of the androgenic gland and to expression of a peptide fragment corresponding to the A chain of androgenic gland hormone (AGH). Androgenic glands and a putative AGH peptide were present in males. However, in both normal and intersex females, the androgenic glands were only present in a rudiment form and the peptide was not detected. Intersex males were found to possess abnormal glands that appeared hypertrophied. However, AGH peptides were not detected, supporting the suggestion that the intersex phenotype is manifested via perturbations of AGH.

The amphipod crustacean Parhyale hawaiensis has been put forward as an attractive organism for evolutionary developmental comparisons, and considerable effort is being invested in isolating developmental genes and studying their expression patterns in this species. The scope of these studies could be significantly expanded by establishing means for genetic manipulation that would enable direct studies of gene functions to be carried out in this species. Here, we report the use of the Minos transposable element for the genetic transformation of P. hawaiensis. Transformed amphipods can be obtained from [approximately equal to] 30% of surviving individuals injected with both a Minos element carrying the 3xP3-DsRed fluorescent marker and with mRNA encoding the Minos transposase. Integral copies of the transposon are inserted into the host genome and are stably inherited through successive generations. We have used reporter constructs to identify a muscle-specific regulatory element from Parhyale, demonstrating that this transformation vector can be used to test the activity of cis-regulatory elements in this species. The relatively high efficiency of this transgenic methodology opens new opportunities for the direct study of cis-regulatory elements and gene functions in Parhyale, allowing functional studies to be carried out beyond previously established model systems in insects. arthropods | evolution | functional studies | transgenesis

We present here a morpho-functional and behavioural study of the feeding adaptations developed by a deep-sea invertebrate, the caprellid amphipod Parvipalpus major, in an environment temporarily deprived of external food supply. The animals were taken intact from bathyal muddy sediments using a classic Barnett multi-tub corer at depths ranging from 424 to 761 m. They were transferred to the laboratory, kept in tanks with their native sediment at a constant temperature (10[degrees]C) and their behaviour was studied by video analysis. Their morphology consists of elongated somites, with pereopods 5-7 ending in elongated curved dactyls, which are longer than those of more coastal species. Analysis of the literature shows that the largest caprellids inhabit the deepest and muddiest zones. This particular morpho-functional adaptation enables the species to adopt an originally erect and steady stance by fixing onto soft muddy sediment, thus improving its ability to prospect for food in its surrounding environment. For the most part, P. major balances its body at its anchorage point as it searches for food in the water column, but occasionally it bends down to the substrate, and tosses some sediment into the water column. Food is then selected from the particles that float down. Presumably, after exhausting the food supply in one area, the animal jumps into the water column and moves about a body length further on. This would appear to be an original strategy for foraging larger areas of organic matter from fixed, but temporary, positions. Finally, we show that caprellids are able to practise coprophagy. To conclude, we suggest that there is a positive correlation between body elongation and depth, with improved anchoring and coprophagy being an optimal way to conserve energy in conditions of limited diet and improve adaptation to life on deep-sea muddy bottoms., Introduction Studies on behavioural observations and the lifestyle of living deep-sea (> 200 m) benthic epifauna inhabiting soft bottoms, the dominant biotope in the deep-sea and the largest habitat on [...]

The toxic reactive oxygen species (ROS), produced naturally in an oxygenated environment, led to the development of antioxidant defenses by aerobic organisms to prevent tissue damage. Polar marine waters are regarded as a strongly prooxidant ecosystem, due to the high dissolved oxygen level and intense UV radiation during summer, while the deep waters are considered refuges against oxidative stress. In order to further elucidate the prooxidant and antioxidant forces associated with cold-water ecosystems and the implications of UV radiation, we sampled three amphipod species living at three different depths in the same water mass of the Arctic Ocean, characterized by low temperature (ca. 0[degrees]C), high oxygen level, and high ROS concentration in the surface water. The three species were the deep-sea amphipod Eurythenes gryllus, the benthic sublittoral amphipod Anonyx nugax and the surface-water species Gammarus wilkitzkii inhabiting the ice pack. The total oxyradical scavenging capacity (TOSC) was measured in the cytosolic fraction of the digestive gland and in the cell-free hemolymph of the three amphipod species. A significantly low TOSC toward peroxyl and peroxynitrite radicals (P0.05) was noted in G. wilkitzkii. These data suggest that A. nugax is highly susceptible to oxidative stress and that G. wilkitzkii is characterized by a mechanism that prevents the diffusion of exogenous ROS through the gills or allows excretion of internal [H.sub.2][O.sub.2] through the gills to the environment., Introduction Reactive oxygen species (ROS) naturally originate from the partial reduction of molecular oxygen during aerobic metabolism (see DiGiulio et al. 1989 for review). The main ROS produced during these [...]

Mitochondrial (mt) sequences from cytochrome oxidase subunit I to the subunit II gene (COI, COII) in crustacean talitrid amphipods were analyzed. The COI-NC-COII organizations and preliminary results, based on both COI-COII nucleotide and amino-acid sequence indicated monopoly of these talitrid taxa.

Research is presented on the ability of Peramphithoe parmerong, an herbivorous marine amphipod, to exhibit heritable variation in relation to two host macroalgae, Padina crassa and Sargassum linearifolium. While performance differed little between comparisons, ecological factors may explain P. parmerong's persistence on P. crassa, and phylogenetic factors may explain constraints on host use.

The freshwater amphipod Hyalella azteca appears to form at least two distinct species in southeast Michigan. A small-bodied ecotype occurs in habitats with predatory centrarchid fish, while a large-bodied ecotype is found in habitats without the predators. Gene flow between the ecotypes appears to be limited, with a high degree of reproductive isolation implied. No consistent genetic difference exists between the ecotypes, however.

The allozymic variation of four species of supralittoral amphipod including Talitrus saltator, Orchestia gammarellus, O. montagui and Talorchestia deshayesii, was explored in samples collected from five Aegean islands. Low levels of genetic variability were found with slight differences between the species. Data from intergeneric comparisons indicated a separation of the genus Orchestia from the other two genera. Gene flow levels were found to be generally low within T. saltator but generally high within O. montagui.

An analysis of the DNA sequence diversity in mitochondrial 16S ribosomal RNA gene of deep-sea amphipods Eurythenes gryllus shows that genetic homogeneity exists within the same depth zone on the scale of ocean basins. The genetically different cryptic taxa are distributed at different ocean depths, with the greatest diversity seen in the bathyal zones. Both physical and ecological conditions act as isolating mechanisms to cause the speciation of deep-sea amphipods.

In common with most cave-limited organisms, cave populations of the amphipod Gammarus minus have reduced eyes and pigmentation and elaborated extraoptic sensory structures relative to closely related surface populations (Holsinger [...]

In two large karst areas, one in West Virginia and the other in Virginia, populations of Gammarus minus (Amphipoda) in caves have significantly larger body size, longer antennae and significantly reduced eye size compared with populations occurring in springs. We examined genetic structure (allozyme variation) and morphological differentiation (ommatidia number) of cave- and spring-dwelling populations of G. minus in the Ward's Cove karst drainage in Virginia. We found that: (1) there is significant genetic and morphological differentiation between the hydrologically connected cave and spring populations, but (2) there is little genetic or morphologic differentiation between the two hydrologically connected cave populations. These patterns are essentially identical, both qualitatively and quantitatively, to those reported for the geographically disjunct West Virginia populations. These data support the hypothesis that the similar morphologies of cave-dwelling G. minus in West Virginia and Virginia are driven by similar selection pressures. These results also suggest that the taxonomic status of cave and spring populations, currently considered to be conspecific, should be re-evaluated.

Allozymic variation between spatially-disjunct populations of Ventiella sulfuris was investigated. Genetic diversity is not spread homogeneously throughout V. sulfuris, and the archipelagic arrangement of vent habitats on ridge axes results in genetic divergence between populations of V. sulfuris. Results show that genetic differences between East Pacific Rise and Galapagos Rift subpopulations are much larger, therefore it is necessary to separate the East Pacific Rise and Galapagos Rift populations at the species level.

A study was conducted to evaluate the relationship between glucosephosphate isomerase (Gpi) and fitness in two species of the genus Gammarus. Results show that fitness is highly correlated with enzyme activity, and below certain values of Gpi activity, the fitness of an organism is directly decreased. Moreover, G. aequicauda is adapted to thermal environments more marginal than those experienced by G. insensibilis. Mortality is not genotype dependent in G. aequicauda, but Gpi activity is higher than that of G. insensibilis.

The amphipod Gammarus minus is present in both caves and springs, with cave populations showing elaborated (size and antennae) and reduced (eye) characters relative to spring populations. Earlier studies have shown that cave populations resulted from independent invasions of hydrologically isolated subterranean drainages and that there is genetic variation for both elaborated and reduced characters. In this study we tested the hypothesis that a similar pattern of selection on isolated cave populations is responsible for the parallel evolution of cave morphologie We used variation in mating success and fecundity to test for the presence of directional selection on eye, antennal, and body size characters in a set of cave and spring populations during a series of seasonal cross-sectional samplings. We found significant directional selection for smaller eyes in caves and larger eyes in springs, which supports the hypothesis that selection is responsible for reduced eye size in cave populations. We also found selection for larger body and antennal size in cave populations, which is consistent with the hypothesis that paralLel patterns of selection in cav are responsible for the elaboration of body and antennal size. However, we found selection for larger body and antennal size in spring populations that is not consistent with the observed divergence of spring and cave populations. We suggest that unmeasured components of viability selection could be more important in springs than in caves and may act against the selection for larger size found in spring populations. Key words.--Caves, Gammarus minus, morphology, regressive evolution, selection, springs.

Gammarus paynei, a new species of amphipod crustacean, is described from the littoral benthos of the lower Mississippi River, West Feliciana Parish, Louisiana. The new species is morphologically similar to species of the Gammarus pecos complex (G. desperatus, G. hyalelloides and G. pecos) of southwestern Texas and southeastern New Mexico. Members of the G. pecos complex occur around the Pecos River, in an area formed by the Permian sedimentation. This area and the type locality of Gammarus paynei were inundated by the Midcontinental Seaway during the Late Cretaceous. It is likely that G. paynei and the G. pecos complex share a common, possibly marine, ancestor and speciated as a result of geographic isolation following recession of the seaway.

Populations of Gammarus minus (Amphipoda) at spring and stream sites of 54 small drainage basins in the mid-Appalachian Mountains of central Pennsylvania are highly differentiated genetically at three allozyme loci. Mean heterozygosity, H, is little affected by drainage area, stream density and mean stream gradient. However, H is significantly correlated with: (1) latitude, with a cline of increasing homozygosity running northward, and (2) distance from the regional trunk stream, with upstream populations most remote from large trunk streams lowest in H. Latitude and trunk stream influences have probably resulted from founder effect operating over recolonizations of vacated habitats. Frequency isopleth surfaces of high frequency alleles are less broadly regional than patterns of H. Some isopleths follow ridgelines, but their modal direction is transverse across valleys, especially along drainage divides. This pattern runs counter to environmental gradients and is inconsistent with the operation of natural selection. It supports the hypothesis that surface streams are the main avenues of migration. Spatial correlograms of H and allele frequencies in stream-connected graphs show positive autocorrelation diminishing with distance of 40-60 km. Beyond this radius, correlations are negative or absent.

A study was conducted to experimentally assess the sensitivity of a sexually selected trait (posterior gnathopod) to food resource stress in an amphipod species. The results suggested that the magnitude of ecological stress experienced by natural populations strongly impacts condition dependency of sexually selected traits and could play an important role in shaping trait variation and hence the opportunity of sexual selection.

The investigation of mitochondrial DNA sequence performed to study the genetic diversity and phylogeographic population structure in the highly adaptable marine gammarid amphipod, Gammarus duebeni, across its broad latitudinal distribution in the NE and NW Atlantic is illustrated.

The geographical range of the amphipod Echinogammarus ischnus has expanded from the Ponto-Caspian region to Western Europe and North America. The phylogeographic patterns of this amphipod across its current distribution based on the nucleotide diversity is explored.

Coastal macroalgal communities provide a rich source of nutrients and a variety of habitats for associated mesograzers. Benthic macroalgae dominate biomass in near-shore Antarctic Peninsular communities. We examined the distribution and abundance of gammarid amphipods associated with 8 common species of Antarctic macroalgae. Divers collected ten individuals of each targeted algal species in a mesh bag (< 1 mm) and the associated epifauna later washed on to a sieve mesh (1.4 mm) and sorted. Algal morphometrics considered included canopy and thallus volume, and the order and number of branches. A total of 28 species of amphipods were identified with mean abundances ranging from 0.02 2.3 individuals/g algal wet wt. Cluster analysis revealed that the three algal species that were most highly branched harbored the greatest abundance and diversity of amphipods. Palatability assays using the common omnivorous amphipod (Gondogeneia antarctica) presented fresh thalli and finely ground dried algal tissues embedded in alginate food pellets revealed no correlation between palatability and amphipod-algal associations. In a parallel study, we found that those algal species harboring the greatest abundance and diversity of amphipods were chemically defended against amphipod herbivory. Thus our findings suggest that both algal morphology and chemical defenses influence the distribution and abundance of macroalgal-associated amphipods in Antarctic Peninsular marine communities. Supported by the Office of Polar Programs, NSF.