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Fossil isopod crustaceans in the suborder Phreatoicidea have a known stratigraphic range from the Carboniferous to the Jurassic. Until now, all Mesozoic records of this group were thought to occur in fresh water habitats. A new phreatoicidean isopod fossil of the Triassic Luoping marine fauna, Yunnan Province, China, is described. The new species, based on several exceptionally complete specimens, is assigned to the genus Protamphisopus Nicholls and the family Amphisopidae Nicholls. This Chinese record is the first report of a Mesozoic-age phreatoicidean isopod outside of Gondwanan terranes, requiring a revision of known biogeographic patterns of the Phreatoicidea. Whether this record is from a marine habitat or is the result of a secondary deposition is not certain. Sottyella Racheboef, Schram and Vidal from the Carboniferous (Stephanian) Lagerstfitte of Montceaules- Mines that was assigned to this suborder may be a decapod. Therefore, it has no relationship to this new species.

In a large-scale outdoor mesocosm experiment we studied the effects of salinity on successional patterns, diversity, and relative abundances of Camargue (southern France) temporary pool crustaceans. Eighty mesocosms were inoculated with a mixed resting egg bank and exposed to four different salinity treatments (0.5, 1.0, 2.5, and 5.0 g [L.sup.-1]) for a period of 7 months. Salinity significantly altered crustacean communities hatching from the resting egg bank through a number of direct and indirect effects. Salinity had a significant negative effect on the establishment of large branchiopods and copepods. Both richness and density of cladocerans, especially chydorids, were positively related to salinity, possibly due to the absence of biotic interactions with large branchiopods at the highest salinity values. We hypothesize that the salinity-mediated presence of the large branchiopod keystone group can shift the whole wetland regime from a zooplankton-rich clear-water state to a zooplankton-poor turbid state. Crustacean succession was significantly altered by salinity, by slowing down development rates, population growth or maturation rates of some species. This suggests that in addition to salinity changes, any alteration of wetland hydroperiod (e.g., through aridification or inappropriate water management) could have a synergistic effect on community structure and diversity of invertebrate communities, including some keystone species. doi: 10.4319/10.2010.55.4.1712

Crown-group crustaceans (Eucrustacea) are common in the fossil record of the past 500 million years back to the early Ordovician period, and very rare representatives are also known from the [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2006.07.024 Byline: Tijana Copf (a)(b), Nicolas Rabet (c), Michalis Averof (a) Keywords: Hox gene regulation; Genital structures; Appendages; Homeosis Abstract: Hox genes play a central role in the specification of distinct segmental identities in the body of arthropods. The specificity of Hox genes depends on their restricted expression domains, their interaction with specific cofactors and selectivity for particular target genes. spalt genes are associated with the function of Hox genes in diverse species, but the nature of this association varies: in some cases, spalt collaborates with Hox genes to specify segmental identities, in others, it regulates Hox gene expression or acts as their target. Here we study the role of spalt in the branchiopod crustacean Artemia franciscana. We find that Artemia spalt is expressed in the pre-segmental 'growth zone' and in stripes in each of the trunk (thoracic, genital and post-genital) segments that emerge from this zone. Using RNA interference (RNAi), we show that knocking down the expression of spalt has pleiotropic effects, which include thoracic to genital (T[right arrow]G), genital to thoracic (G[right arrow]T) and post-genital to thoracic (PG[right arrow]T) homeotic transformations. These transformations are associated with a stochastic de-repression of Hox genes in the corresponding segments of RNAi-treated animals (AbdB for T[right arrow]G and Ubx/AbdA for G[right arrow]T and PG[right arrow]T transformations). We discuss a possible role of spalt in the maintenance of Hox gene repression in Artemia and in other animals. Author Affiliation: (a) Institute of Molecular Biology and Biotechnology (IMBB), 711 10 Iraklio Crete, Greece (b) Joint Graduate Programme in Molecular Biology and Biomedicine, Department of Biology, University of Crete, 714 09 Iraklio Crete, Greece (c) Universite Pierre et Marie Curie (UPMC), 9 quai St Bernard, 75 252 Paris, France Article History: Received 22 May 2006; Revised 21 July 2006; Accepted 22 July 2006

Kiricephalus coarctatus (Pentastomida, tongue worm) is known to utilize snakes as both second intermediate and definitive hosts throughout Central and North America (Riley & Self 1980). Eggs of K. coarctatus [...]

The feeding ecology of leptostracans is not well-known. In the present study, species of Nebalia (Crustacea: Leptostraca) were captured every month for 1 year from Lobster Bay, Hong Kong, using baited traps. Captured individuals fell into a size range of 0.36-3.64 mm and 0.95-5.52 mm in carapace and total lengths, respectively. They were divided into different reproductive stages based on the morphology of the second pair of antennae and thoracopods. Sexual dimorphism becomes apparent between 0.7-1.5 mm (CL) and 1.4-3.2 mm (TL). Most individuals collected were sexually differentiated, but immature (79.7% of the captured individuals), followed by post-ovigerous (11.4%) and ovigerous (8.9%) females. Sexually undifferentiated juveniles were rare (3.9%). The sex ratio of the immature individuals approached 1:1 with a propensity towards male dominance. Not one mature male was captured. Although females with setose thoracopod endopods, indicating that they were ovigerous, were captured frequently, only two were carrying eggs. The two brooding females had clutch sizes of 11 and 17 eggs. Alternate peaks in relative abundance of ovigerous and post-ovigerous females were identified, the latter following the former. Reproductive activities occurred mainly in April-May and October-December, indicating that two cohorts are recruited. Catches using baited traps could be explained by the reproductive season of Nebalia sp. High catches were usually associated with the months of highest reproductive activity, low catches with peaks in post-ovigerous females. It is therefore concluded that not all individuals at various reproductive stages are attracted to carrion and hence adopt a scavenging feeding mode. Catches of Nebalia sp. in Hong Kong possibly reflect their annual cycle of reproductive activity.

The feeding activity rhythm of Palaemonetes varians (Leach 1814) was studied by collecting stomachs over a 24-h cycle in four different seasons of 1996 and spring-summer of 1997 to assess a regulation of this behaviur dependent upon seasonal variations in photoperiod length. A total of 6,692 stomachs were collected from a population reared in an extensive earthen pond located in the Guadalquivir Estuary salt marshes (Spain). Stomach fullness (f) classification was performed with a stereomicroscope by means of a four-point visual qualitative scale. Results showed that a high proportion of stomachs were empty in all seasons considered and a great variability in the data occurred irrespective of the time of the day. The number of full stomachs at each catch were represented over 24-h for each sampling season. Time series showed the occurrence of a feeding activity rhythm phased at day-night transitions. The sunset peak occurred in all months of sampling, while the sunrise one occurred in summer. Results are discussed in relation to available data on behavior, moulting, and reproduction of this and other species of the same genus.

Changes in amino acid composition (AAC) during ontogeny of some planktonic crustacean species commonly found in fresh and brackish coastal waters were compared. For these comparisons two calanoid copepods (Eurvtemora velox and Calanipeda aquae-dulcis), two cyclopoid copepods (Diacyclops bicuspidatus odessanus and Acanthocyclops robustus) and two Daphnia (Daphnia pulicaria and Daphnia magna) species were selected. A discriminant analysis was performed to determine whether there were significant differences between the AAC of the different stages of each species. Results show gradual changes in AAC during ontogeny of the copepod species. Calanoids showed the greatest differences in AAC between stages, followed by cyclopoids. Gradual changes in AAC were due to the increase in some amino acids such as alanine, valine, glutamic acid, glycine, arginine, proline and tyrosine from nauplii to adults. The latter showed a remarkable increase in all copepod species. In contrast, Daphnia species showed a relatively constant AAC during development, with only minor changes being detected, and not related with ontogeny. Differences in the physico-chemical variables of the lagoons do not seem to be the cause of copepod ontogenic changes in AAC. Data suggest that AAC differences found between stages of copepod species could indicate a gradual change in diet during the life cycle of these copepods.

Northern shrimp Pandalus borealis (Kroyer) larvae hatch in the northern Gulf of St. Lawrence from early May to the end of June, and larval development occurs over a range of relatively cold water temperatures. Because of the long duration of the pelagic phase and the difficulty of sampling all successive larval stages at sea, we used laboratory experiments to assess the effects of water temperature on larval development and growth. In spring 2000, P. borealis larvae were reared from hatching to the first juvenile stages (i.e., stage VI and VII) at three temperatures (3, 5, and 8[degrees]C) representing conditions similar to those in spring in the northern Gulf of St. Lawrence. Larval development and growth were dependent on temperature, with longer duration and smaller size (cephalothorax length, CL, and dry mass, DM) at 3[degrees]C relative to the 5 and 8[degrees]C treatments. There were no significant differences in the morphological characters of the different stages among treatments, indicating that regular moults occurred at each temperature. The results suggest a negative impact of cold temperatures (lower intra-moult growth rates and smaller size) and, possibly, higher cumulative mortality due to longer development time that could affect the success of cohorts at sea. However, CL and DM for stage III and later larvae were smaller than those of larvae identified at the same developmental stage in field locations. It is possible that the diet offered to larvae in this experiment (Artemia nauplii, either newly hatched nauplii or live adults, depending on the developmental stage) was not optimal for growth, even though it is known to support successful P. borealis larval development. In the field, there is the possibility that phytoplankton contributes to the larval diet during the first stages and stimulates development of the digestive glands. Furthermore, the nutritional quality of the natural plankton diet (e.g., high protein content, fatty acid composition) might be superior and favourable to higher growth rates even at lower temperatures., Introduction The northern shrimp Pandalus borealis (Kroyer) is a dominant crustacean decapod species in the Estuary and the Gulf of St. Lawrence ecosystem, and the various stocks have supported an [...]

The current study determined behavioral and electrophysiological photosensitivities for three species of mesopelagic crustaceans: Pasiphaea multidentata Esmark, 1866 (Decapoda: Pasiphaeidae), Sergestes arcticus Kroyer, 1855 (Decapoda: Sergestidae), and Meganyctiphanes norvegica M. Sars, 1857 (Euphausiacea: Euphausiidae). In addition, in situ quantifications of the species' vertical distributions in relation to downwelling irradiances were also determined in two locations in the northwest Atlantic Ocean, Wilkinson Basin (WB) and Oceanographer Canyon (OC). Data are from six 2-week cruises between June and September from 1995 to 2001. P. multidentata and M. norvegica were the most abundant large crustaceans in WB, and S. arcticus and M. norvegica were the most abundant large crustaceans in OC. The behavioral light sensitivity thresholds of P. multidentata and M. norvegica from WB were both [10.sup.7] photons [cm.sup.-2][s.sup.-1] and those of S. arcticus and M. norvegica from OC were both [10.sup.8] photons [cm.sup.-2] [s.sup.-1]. Electrophysiologically, P. multidentata was significantly more sensitive than M. norvegica from either location, S. arcticus was significantly more sensitive than M. norvegica from OC, and M. norvegica from WB was significantly more sensitive than M. norvegica from OC. A correlation was found between electrophysiologically measured photosensitivity and downwelling irradiance, with the most sensitive species, P. multidentata and S. arcticus, associated with the lowest irradiance at daytime depths. The photosensitivities of M. norvegica collected from the clearer waters of OC were significantly lower than those of individuals collected from the more turbid WB waters. These results indicate that downwelling irradiance has a significant impact on interspecies and intraspecies vertical distribution patterns in the mesopelagic realm.

The integration of Geographic Information System (GIS) methodology within a phylogenetic and statistical framework provides a background against which to evaluate the relationship between biogeographic changes and evolution in the fossil record. A case study based on patterns in Middle and Late Devonian phyllocarids (Crustacea) illustrates the usefulness of this integrated approach. Using a combined approach enhances determination of rates of biodiversity change and the relationship between biogeographic and evolutionary changes. Because the interaction between speciation and extinction rates fundamentally determines biodiversity dynamics, and speciation and extinction rates are influenced by the geographic ranges of component taxa, the relationship between biogeography and evolution is important. Furthermore, GIS makes it possible to quantify paleobiogeographic ranges. Phylogenetic biogeography resolved patterns of both vicariance and geodispersal and revealed that range expansions were more abundant than range contractions in Devonian phyllocarids. In addition, statistical tests on GIS-constrained species ranges and evolutionary-rate data revealed a relationship between increasing species' ranges and increases in both speciation and extinction rates. Extinction rate, however, increased more rapidly than speciation rate in the phyllocarids. The pattern of extinction rate increasing faster than speciation rate in the phyllocarids may illuminate aspects of the Late Devonian biodiversity crisis in particular, and protracted biodiversity crises in general.

Increasing concerns over rising intersexuality in the animal kingdom and the ability of certain chemicals to disrupt the endocrine system have demanded a better understanding of the costs associated with such conditions. Whilst intersexuality appears relatively wide-spread throughout gonochoristic crustaceans, i.e. those crustacean species with two separate sexes, the 'fitness' costs have rarely been reported. Through comparable investigation of normal and intersex specimens of the highly abundant marine/estuarine amphipod Echinogammarus marinus (Leach) these 'fitness costs' were determined. Measurements taken to assess fitness costs included fecundity, fertility and embryonic development, maturation period, and any morphological deformities that might result in reduced pairing success. Results from this study suggest that intersex E.marinus suffer from reduced fecundity and fertility, and mature at a larger size than normal specimens. These fitness costs can also, to a certain extent, be related to the degree of intersexuality. It is suggested that the increased size and morphological abnormalities observed in intersexes may result in reduced pairing success. Investigations into intersex organisms, i.e. those organisms with known dysfunctional endocrine systems, and the costs associated with such conditions, should aid researchers in assessing effects at the population and community level.

With field, laboratory, and modeling approaches, we examined the interplay among habitat structure, intraguild predation (IGP), and parasitism in an ongoing species invasion. Native Gammarus duebeni celticus (Crustacea: Amphipoda) are often, but not always, replaced by the invader Gammarus pulex through differential IGP. The muscle-wasting microsporidian parasite Pleistophora mulleri infects the native but not the invader. We found a highly variable prevalence of P. mulleri in uninvaded rivers, with 0-91% of hosts parasitized per sample. In addition, unparasitized natives dominated fast-flowing riffle patches of river, whereas parasitized individuals dominated slower-flowing, pooled patches. We examined the survivorship of invader and native in single and mixed-species microcosms with high, intermediate, and zero parasite prevalence. G. pulex survivorship was high in all treatments, whereas G. duebeni subsp. celticus survivorship was significantly lower in the presence of the invader. Further, parasitized G. duebeni subsp. celticus experienced near-total elimination. Models of the species replacement process implied that parasite-enhanced IGP would make invasion by G. pulex more likely, regardless of habitat and parasite spatial structure. However, where heterogeneity in parasite prevalence creates a landscape of patches with different susceptibilities to invasion, G. pulex may succeed in cases where invasion would not be possible if patches were equivalent. The different responses of parasitized and unparasitized G. duebeni subsp. celticus to environmental heterogeneity potentially link landscape patterns to the success or failure of the invasion process.

Various mutants of molt-inhibiting hormone (MIH) are prepared and their molt-inhibiting activities on the molting hormones are assessed. This is done in order to test the hypothesis that the MIH peptide's functional site spanned the region encompassing the N-terminal alpha-helix and a portion of the C-terminus, both located sterically close to each other.

The effect of oxygen on 15 size spectra worldwide, established by compiling maximum length data of more than 2000 amphipod species is investigated. Data indicate that there is a small, but significant increase in minimum amphipod size with increasing oxygen.

Seasonal population dynamics of Mysis mixta Lilljeborg were studied from December 1998 to November 2000 at a 240 m deep site in Conception Bay, Newfoundland. At this depth, temperature was

Seasonal population dynamics of the gammarid Acanthostepheia malmgreni Goes in Conception Bay, Newfoundland, were examined from October 1998 to November 2000. This species exhibited a 2.5-year life span, with the reproductive cycle correlating with seasonal phytoplankton flux. Females were semelparous and died following a 5-month brooding period and the subsequent release of juveniles in April and May. The biennial life cycle of this population should result in the presence of two cohorts in the hyperbenthos at any given time. However, the cohorts alternated in strength from year to year, which affected annual density, biomass and production during the study period. Densities were 64 [+ or -] 87 ind. per 100 [m.sup.3] in 1999 and 491 [+ or -] 492 ind. per 100 [m.sup.3] (mean [+ or -] SD) in 2000. Secondary production was estimated at 18-44 mg C [m.sup.-2] in 1999 and 180-311 mg C [m.sup.-2] in 2000. The annual P/B ratios were 0.89 and 2.27 in 1999 and 2000, respectively. Growth varied both among and within cohorts, with different life-history stages exhibiting variable growth rates ranging from 0 to 12 mg dry mass [month.sup.-1].

Seasonal changes in abundance and development of Calanus pacificus Brodsky were investigated by analyzing samples of different depth strata (0-150 m and 0-1000 m) collected monthly in the Oyashio-Kuroshio Mixed Region. Copepodite stage 5 (C5) emerged from dormancy and matured in early summer. A new generation appeared in July and developed into C5 during summer to autumn. Some of the summer generation arrested development at C5 and persisted below 150 m depth until the following early summer. Although the remainder matured and reproduced in October, a new generation was not observed at the surface during winter. These results suggest that C. pacificus shows two different life-cycle patterns, i.e. one generation annually, with overwintering C5 in deep waters, and two generations annually, with surface development during autumn to winter. The complex life-cycle patterns may be an adaptation to the highly fluctuating surface environment in the Oyashio-Kuroshio Mixed Region.

Incremental (distance-dependent) costs and benefits of dispersal have received less attention than those that are qualitative. We present a dynamic programming model of settling behavior using parameters estimated from a field study of dispersal in desert isopods, Hemilepistus reaumuri, which walk up to thousands of meters before settling in new or already-established burrows each spring. The model shows that incremental costs of dispersal lead to right-skewed population dispersal patterns, in contrast to cost-free systems or those with unitary costs (i.e., a one-time cost of leaving a group or patch). In the model, continuous variation in habitat quality, as opposed to discrete suitable vs. unsuitable sites, allows for trade-offs with dispersal costs that lead to shifts in the likelihood of settling in a patch of a given quality. Thus, measurement of quantitative costs and benefits of movement are needed to understand population dispersal distributions. These costs or benefits may be observable during or after movement, and we examined both pre- and postsettling incremental consequences of dispersal. The daily mortality rate of traveling isopods was 4.2% during the dispersal season, higher than that of settled individuals. Successful settlers traveled more slowly, but burrows started in midseason were most likely to succeed. More distant burrows failed more often, suggesting either an additional cost of movement or a difference in the quality of individuals traveling different distances. The predicted mean dispersal duration from the simulations matched observed values closely, but was based on an unrealistic assumption of perfect knowledge of habitat quality, suggesting some other factor favors longer times before settling. Reproductive success was much higher in re-used burrows than in new burrows, making them a possible incentive for long-distance movements. Key words: behavior; condition; Crustacea; dispersal; Hemilepistus reaumuri; movement; prospecting; settling; terrestrial isopod.

Introduction Crustaceans exhibit a diverse array of metabolic and physiological responses to aquatic hypoxia (Reiber, 1995). Typically, hypoxic exposure results in a decreased heart rate (bradycardia) in decapod crustaceans (McMahon [...], The cardiovascular system is the first system to become functional in a developing animal and must perform key physiological functions even as it develops and grows. The ontogeny of cardiac physiology was studied throughout embryonic and larval developmental stages in the red swamp crayfish Procambarus clarkii using videomicroscopic dimensional analysis. The heart begins to contract by day 13 of development (at 25°C, 20 kPa [O.sub.2]). Cardiac output is primarily regulated by changes in heart rate because stroke volume remains relatively constant throughout embryogenesis. Prior to eclosion, heart rate and cardiac output decreased significantly. Previous data suggest that the decrease in cardiac parameters prior to hatching may be due to an oxygen limitation to the embryo. Throughout development, metabolizing mass and embryonic oxygen consumption increased, while egg surface area remained constant. The surface area of the egg membrane is a constraint on gas exchange: this limitation, in combination with the increasing oxygen demand of the embryo, results in an inadequate diffusive supply of oxygen to developing tissues. To determine if the decrease in cardiac function was the result of an internal hypoxia experienced during late embryonic development, early and late-stage embryos were exposed to hyperoxic water (P[O.sub.2] = 40 kPa [O.sub.2]). Heart rate in late-stage embryos exposed to hyperoxic water increased significantly over control values, which suggests that the suppression in cardiac function observed in late-stage embryos is due to a limited oxygen supply.

ABSTRACT. A new species of monstrilloid copepod, Monstrillopsis ferrarii n. sp., based on four adult female specimens collected in the White Sea, northern Russia, is described and illustrated. The new [...]

Crustacean motor neurons subserving locomotion are specialized for the type of activity in which they normally participate. Neurons responsible for maintained activity ('tonic' neurons) support moderate to high frequencies of nerve impulses intermittently or continuously during locomotion, while those recruited for short-lasting rapid responses ('phasic' neurons) generally fire a few impulses in a rapid burst during rapid locomotion and are otherwise silent. The synaptic responses of the two types, recorded at their respective neuromuscular junctions, differ enormously: phasic neurons exhibit much higher quantal release per synapse and per muscle fibre, along with more rapid synaptic depression and less short-term facilitation. We have analyzed the factors that are responsible for the large difference in initial release of nenrotransmitter. Several possibilities, including synapse and active zone size differences, entry of calcium at active zones, and immediately releasable vesicle pools, could not account for the large phasic-tonic difference in initial transmitter output. The most likely feature that differentiates synaptic release is the sensitivity of the exocytotic machinery to intracellular calcium. Molecular features of the phasic and tonic presynaptic nerve terminals are currently under investigation.

Abstract.--Decapod crustaceans are reported for the first time from the late middle to early late Miocene Puente Formation, Riverside County, California. A single specimen of penaeid shrimp and numerous cancrid [...]

Deep-water assemblages of suprabenthic peracarids were analyzed in the SW Balearic Islands (Algerian Basin, southwestern Mediterranean) between 249 and 1,622 m depth; the patterns of species composition, possible zonation, and trophic structure found in this area were compared with those exhibited by peracarids in the mainland side of the Catalan Sea slope (northwestern Mediterranean). One hundred and four peracarid species (plus one leptostracan) were identified on the Balearic Islands slope, amphipods being the most diversified taxon (45 species). On the Balearic slope, two distinct depth assemblages were distinguished: one at the upper slope (US), between 249 and 402 m depth and the second at the deep slope, between 543 and 1,620 m depth. A remarkable species substitution occurred at depths between 402 and 638 m. In the Catalan Sea, in addition to the US assemblage occupying depths between 208 and 408 m, a second boundary of faunal change was found around 1,250 m. Suprabenthos biomass increased from 242 to approximately 500 m. Suprabenthos attained the highest biomass values (100 g wet weight/10,000 m[sup.2]) at intermediate depths between 504 and 1,211 m, as also occurred with the associated zooplankton collected with suprabenthos (peak biomass between 502 m and 898 m). Suprabenthos biomass did not show any significant correlation with any environmental water-column variable. In contrast, zooplankton (especially small fish and dacapod crustaceans) showed a significant positive correlation with fluoromentry and turbidity at different levels of the water column. The feeding guilds of species showed important differences between the two areas only on the US, with a higher abundance of deposit feeders in the Catalan Sea (20.4%) than in the Balearic Islands (4.2%). The low contribution of deposit feeders in the SW Balearic Islands may ultimately be a consequence of the lack of river discharges in this area.

This review discusses relationship between the composition and expression of the Hox genes and morphological differentiation in the crustacean species as shown by morphological changes from the ancestral body plan that are linked to adaptation. Research findings suggest that a well-defined morphological change cannot be correlated wih a any single genetic change.

Nucleotide sequences for the 18S rDNA of 17 ostracod species, representing 4 extant orders and 12 superfamilies, were determined and compared with known sequences of other crustaceans. Resulting molecular phylogenetic trees based on maximum-likelihood, maximum-parsimony, and neighbor-joining methods consistently indicated that the Podocopida plus Platycopida forms a monophyletic group, but did not indicate monophyly of the Ostracoda consisting of the four orders, Podocopida, Platycopida, Kirkbyocopida, and Myodocopida. The tree topology and the crustacean fossil record suggest that the lineage of podocopidans and platycopidans, that of kirkbyocopidans, and that of myodocopidans should have separately been established already in the Cambrian, although there is no ostracod fossil record in that time period. Close relationships between the Bythocytheroidea and Cytheroidea and among the Macrocypridoidea, Pontocypridoidea, and Cypridoidea can safely be postulated, but other relationships among podocopidan and platycopidan superfamilies could not be resolved from the 18S rDNA data. The polychotomous relationship among five lineages of the podocopidan and platycopidan superfamilies, i.e. Cytherelloidea, Bairdioidea, Darwinuloidea, Bythocytheroidea plus Cytheroidea, and Macrocypridoidea plus Pontocypridoidea plus Cypridoidea, suggests that common ancestors of those lineages diverged from each other rapidly in short intervals in the early Paleozoic.

Embryos of the amphipod crustacean Orchestia cavimana are examined during cleavage, gastrulation, and segmentation by using in vivo labelling. Single blastomeres of the 8- and 16-cell stages were labelled with DiI to trace cell lineages. Early cleavage follows a distinct pattern and the a/p and d/v body axes are already determined at the 4- and 8-cell stages, respectively. In these stages, the germinal rudiment and the naupliar mesoderm can be traced back to a single blastomere each. In addition, the ectoderm and the postnaupliar mesoderm are separated into right and left components. At the 16-cell stage, naupliar ectoderm is divided from the postnaupliar ectoderm, and extraembryonic lineages are separated from postnaupliar mesoderm and endoderm. From our investigation, it is evident that the cleavage pattern and cell lineage of Orchestia cavimana are not of the spiral type. Furthermore, the results of the labelling show many differences to cleavage patterns and cell lineages in other crustaceans, in particular, other Malacostraca. The cleavage and cell lineage patterns of the amphipod Orchestia are certainly derived within Malacostraca, whose ancestral cleavage mode was most likely of the superficial type. On the other hand, Orchestia exhibits a stereotyped cell division pattern during formation and differentiation of the germ band that is typical for malacostracans. Hence, a derived (apomorphic) early cleavage pattern is the ontogenetic basis for an evolutionarily older cell division pattern of advanced developmental stages. O. cavimana offers the possibility to trace the lineages and the fates of cells from early developmental stages up to the formation of segmental structures, including neurogenesis at a level of resolution that is not matched by any other arthropod system. Key Words: Arthropoda; Malacostraca; germ band; mesoderm; ectoderm; cell fate; spiral cleavage; superficial cleavage.

The settlement behavior, antennulary biomechanics land morphology were investigated in the intertidal cypris larvae Balanus amphitrite. The very maneuverable antennule of the cyprid consists of four jointed segments, and it is the prime appendage for substratum exploration and final settlement. We recorded several previously undescribed settling behaviors, such as the 'tight direction change', for this intertidal species and discovered that the antennulary morphology is modified to facilitate such behaviors. Segment 2 has a modified lateral cuticle, which gives the segment an additional higher degree of maneuverability compared to non-intertidal cirripede species of Rhizocephala. Additional supporting muscle groups were also found in the antennule of our species, which were not found in the investigated rhizocephalan larvae. The results could very well be associated with the higher needs of substratum recognition in intertidal species, due to more heterogeneous habitats such as intertidal rock flats.

Life-history traits of Plesionika martia (Milne Edwards, 1883) were studied through data collected during six seasonal trawl surveys carried out in the Ionian Sea (eastern-central Mediterranean) between July 1997 and September 1998. P. martia was found at between 304 and 676 m depth, with the highest density in the 400-600 m range. Intraspecific, size-related depth segregation was shown. Recruitment occurred in summer at the shallowest depths. Juveniles moved to the deepest grounds as they grew. The largest female and male were 26 and 25 mm carapace length, respectively. The sex ratio was slightly in favour of females at depths >400 m. Although a seasonal spawning peak was shown, the reproduction appears to be rather prolonged throughout the year. Females with ripe gonads were found from spring to autumn. Ovigerous females with eggs in late maturity stage were found year round. Large females could spawn more than one time within their annual reproductive cycle. The size at first maturity (50% of the ovigerous females) was 15.5 mm CL. Average brood size of eggs with a well-developed embryo was 2,966 [+ or -] 1,521. Iteroparity, low fecundity and large egg size patterns were observed. Brood size increased according to the carapace length. Two main annual groups were found in the field population of the Ionian Sea. Estimates of the Von Bertalanffy growth parameters are: L[infinity]=30.5 mm, k=0.44 [year.sup.-1] in females; L[infinity]=28.0 mm, k=0.50 [year.sup.-1] in males. A negative allometry was detected mostly in the ovigerous females. The life cycle of P. martia is discussed in the light of life-history adaptations shown in other deep-water shrimp species. Keywords Crustacea Decapoda * Plesionika martia * distribution * reproduction * fecundity * population structure * growth * life cycle * Mediterranean Sea

Estimates of the assimilation and retention of trace elements from food by fish are useful for linking toxicity with the biogeochemical cycling of these elements through aquatic food webs. Here we use pulse-chase radiotracer techniques to estimate the assimilation and retention of Se and four trace metals, Ag, Am, Zn, and Cd, by 43- and 88-d-old juvenile striped bass, Morone saxatilis, from crustacean food. Brine shrimp nauplii, Artemia franciscana, or adult copepods, Acartia tonsa, were fed radiolabeled diatoms and then fed to juvenile striped bass. Assimilation efficiencies (AEs [+ or -] SD) for 43-d-old fish were 18 [+ or -] 2%, 6 [+ or -] 1%, 23 [+ or -] 4%, 33 [+ or -] 3%, and 23 [+ or -] 2% for Ag, Am, Cd, Se, and Zn, respectively. For 88-d-old fish, the AEs were 28 [+ or -] 1%, 42 [+ or -] 5%, and 40 [+ or -] 5% for Cd, Se, and Zn, respectively. The higher AEs in the older fish may result from longer gut passage times for larger fish. The 44-d-old fish excreted 5 [+ or -] 0.8%, 4 [+ or -] 2.0%, 7 [+ or -] 0.3%, 9 [+ or -] 0.4%, and 1.3 [+ or -] 0.9% of the Ag, Am, Cd, Se, and Zn, respectively, they ingested from food per day, whereas the 88-d-old fish excreted 3 [+ or -] 1.0%, 8 [+ or -] 0.5%, and 3 [+ or -] 0.5% of the assimilated Cd, Se, and Zn per day, respectively. Predictions of steady state Se concentrations in juvenile striped bass tissues made using a biokinetic model and the measured AE and efflux rates ranged from 1.8 to 3.0 [micro]g Se [g.sup.-1] dry wt for muscle tissue and 6.8 to 11.6 [micro]g Se [g.sup.-1] dry wt for gut tissue. These predictions agreed well with average values of 2.1 and 13 [micro]g Se [g.sup.-1] dry wt measured independently in North San Francisco Bay, where elevated Se concentrations are of concern. The model results imply that the planktonic food web, including juvenile striped bass, does not transfer Se as efficiently to top consumers as does the benthic food web., A report on the assimilation and retention by striped bass of selenium from the food chain is presented. Research results indicate the planktonic food chain does not transfer selenium efficiently to fish at the top of the chain.

We quantified the spatial and temporal variability of crustacean zooplankton abundance at annual time steps with 261 lake-years of data from 22 lakes in three regions of central North America. None of these lakes had been experimentally manipulated. Using a nested three-way analysis of variance, we apportioned variance among years, regions, lakes, and their interactions for 10 functional groups and 4 larger taxonomic aggregates. We proposed that relative variation in the abundance of zooplankton would be greatest among regions and lakes and least among years. We also explored how variability differed among functional groups and changed with taxonomic aggregation. Spatial sources of variation dominated the analysis, but a large interaction between lakes and years indicated that time cannot be ignored. Regional variation was half that found among lakes. Relative variance components differed widely among functional groups, which indicates that species will differ in their response to environmental controls and sensitivity to perturbation. Total explained variation also differed widely among zooplankton and decreased with increasing aggregation of taxa. Whether choosing ecological indicators or designing experiments and monitoring programs, these results clearly show that large-scale temporal and spatial variability will be an important consideration.

Numerous pygocephalomorph crustaceans occur with conchostracans, plants, fishes, amphibians, and amniotes in the Petrolia Formation (Leonardian Series, Lower Permian) of Baylor and Archer counties, Texas. Two pygocephalomorph species are represented; Mamayocaris serendipitous, new species, by hundreds of specimens that appear to be molted exoskeletons, and Paulocaris schrami, new species, by only a few specimens. Mamayocaris has been reported previously from the Lower Permian of Texas and South Dakota and the Upper Carboniferous of Illinois; Paulocaris was previously known only from South America. Associated plant assemblages are dominated by conifers accompanied by other Early Permian and some Late Carboniferous elements. Accompanying vertebrate remains include aquatic to fully terrestrial forms with close taxonomic ties to genera or families recorded in Upper Carboniferous deposits. The fossils are preserved in local deposits of thin (

Analysis of the mitochondrial DNA sequence in populations of Antarctic neritic krill species from widespread geographic areas reveals high genetic differences. However, the genetic differences do not correlate with the degree of geographic distribution.

Crustaceans in the California Current were examined for DNA variations and how their populations were related to zooplankton in the region. A single species of crustacea was collected and zooplankton biomass calculated on the basis of bioacoustic backscattering.

Middle and Upper Devonian members of the phyllocarid order Archaeostraca Claus, 1888, are analyzed in both a phylogenetic and biogeographic context. Results of the phylogenetic analysis show that the suborders Ceratiocaridina Clarke in Zittel, 1900, and Rhinocaridina Hall and Clarke, 1888, are paraphyletic as traditionally defined. The diagnoses of these suborders are revised and the use of the suborders Echinocaridina Clarke in Zittel, 1900, and Pephricaridina Van Straelen, 1933, is proposed. Ceratiocaridina now contains the family Ceratiocarididae Salter, 1860; Rhinocaridina contains the family Rhinocarididae Hall and Clarke, 1888; Echinocaridina includes the families Aristozoidae Gurich, 1929, Ptychocarididae n. fam., and Echinocarididae Clarke in Zittel, 1900; Pephricaridina includes the families Pephricarididae Van Straelen, 1933, and Ohiocarididae Rolfe, 1962. Generic definitions within the Rhinocarididae, in particular 'Rhinocaris' Clarke in Hall and Clarke, 1888, are revised. The genus Echinocaris is redefined to include a monophyletic assemblage of species. Each of these clades is supported by several synapomorphies. Two new genera, Paraechinocaris and Carinatacaris, are proposed. Biogeographic analysis of this group reveals an extremely low rate of vicariant speciation, while episodes of range expansion are frequent. All occurrences of vicariance preceded the Late Devonian mass extinction. This may suggest a relationship between increased dispersal, diminished speciation, and the Late Devonian biotic crisis. Parallels between the Late Devonian mass extinction and the modern biodiversity crisis are suggested by the frequency of episodes of range expansion indicative of invasive species.

The article examines maternally inherited Wolbachia bacteria responsible for feminization of genetic males in the terrestrial isopod Oniscus asellus. The negative effect of the bacteria on host fecundity and survival of infected offspring are described.

Acoustic techniques can be applied to increase the sampling resolution and the available information of zooplankton populations. Knowing an organism's acoustic target strength (TS) is essential for translating acoustic data into meaningful information. To evaluate the acoustic TS of Mysis relicta, several approaches were used, including in situ TS data and acoustic-based estimates of numerical abundance of mysids.

The activity of chitobiase or N-acetyl-beta-glucosaminidase in the epidermis and hepatopancreas of the fiddler crab Uca pugilator during the molting cycle was studied. Hepatopancreatic chitobiase activity was substantially higher than epidermal enzymatic activity in all the molt cycle stages tested except Postmolt Stage A-B. The patterns of chitobiase activity in the epidermis and hepatopancreas correlated well with the hemolymph titer of ecdysteroids in U. pugilator during the molting cycle. This indicates that chitobiase activity in both tissues is regulated at least partially by the steroid molting hormones.

The spermatozoal ultrastructure in two species of Hymenosomatidae, Odiomaris pilosus and O. estuarius, was studied to find out whether the sperm is characteristic of the Thoracotremata or has similarities with other brachyuran groups. The characteristics investigated include the presence of an epiopercular dome and separation of all but the central area of the operculum from the rest of the acrosome by an infra-opercular rim.

Introduction Our previous study (Kao and Chang, 1996) showed that autotransplantation of claw tissues into the autotomized stumps of crab walking legs can induce the stumps to regenerate claws or [...], The eyestalks of crabs were removed and various tissues of the limbs were autotransplanted into the empty eye sockets to study the capacity of the limb tissue to regenerate in a heterotopic site. Autotransplantation of walking leg tissues into the eye sockets was able to regenerate complete walking legs in the new site. Autotransplantation of tissues of claw digit (dactyl and pollex) or more proximal claw segments (ischium and merus/ carpus joint) could regenerate complete claws in the eye sockets. If the autotransplant of claw tissue was contralateral, claws could regenerate with host-site handedness. Sham operations or autotransplantation of frozen claw tissue did not induce regeneration in the eye sockets. These results demonstrate that complete crab claws can regenerate from the eye sockets by autotransplantation of live limb tissue and that the regeneration is not due to the traumatic effect of transplantation. The structure of the limbs regenerated in the eye sockets was determined by the source of the transplanted tissue. Complete claws resulted from autotransplantation of the tissues of the most distal claw segments (claw digits), and the most distal claw segments regenerated first, followed by the proximal claw segments in subsequent molts. Thus tissue from distal portions of crab claw can regenerate proximal portions of the claw in the eye sockets. Such a mode of regeneration is not consistent with the distalization rule of the polar coordinate model, which proposes that distal portions of the limb cannot regenerate proximal portions and that the direction of limb regeneration is always from proximal to distal.

Introduction Among crustaceans, bilateral asymmetry of the first pair of chelipeds is common; one of the paired claws is more enlarged and elaborate (major claw) than the other (minor claw). [...], In the paired asymmetric claws of adult snapping shrimp, Alpheus heterochelis, the minor, or pincer, claw may transform into a major, or snapper, claw if the existing snapper claw is damaged or lost, implying that an intact snapper claw normally inhibits the contralateral pincer claw from advancing to a snapper. We find that the pincer-to-snapper advancement in external form occurs almost immediately after the snapper is lost even as late as the premolt stage. The transforming claw in turn inhibits the newly regenerating pincer claw from becoming a snapper, but if the dactyl of the transforming claw is cut, then snapper-based inhibition is removed and the contralateral claw may regenerate as a snapper, resulting in shrimp with paired snapper claws. However, damaging an established snapper claw will not allow another snapper claw to regenerate at the pincer site, implying that less inhibition is required to restrict a newly regenerating claw to a pincer than to arrest an existing pincer claw. Inhibition may be manifested largely in terms of quantity of innervation. Hence the greater innervation of the snapper side over the pincer side would inhibit the pincer side, accounting for the regeneration of paired claws in their previous configuration following loss of both claws. Loss of the paired claws in two consecutive molts retards their development so that both claws often appear as pincers, but in succeeding molts one usually differentiates into a snapper and bilateral asymmetry is restored. In contrast, shrimp with paired snapper claws retain this configuration over several molts unless one or both of the claws are lost; in that case, regeneration restores bilateral asymmetry. Thus, bilateral asymmetry of the paired claws of adult shrimp is governed by a strong intrinsic lateralizing mechanism in which the snapper claw inhibits the pincer from advancing to another snapper.

Infrared time-lapsed video recording was used to study the behavioral responses to decreasing oxygen concentration of the three common macrobenthic crustaceans from the Baltic Sea. The amphipods studied were Monoporeia affinis, Pomtoporia femorata, and Saduria entomon. It was observed that a gradual decrease in oxygen significantly changed the behavior of the species investigated.

As an example of the relative impact of a specific ambient parameter on intraspecific phenotypic differentiation, the contribution of environmental sources of calcium on the geographic variation between alpine populations of the freshwater crustacean Gammarus fossarum was investigated through a comparative analysis of six different populations in the torrents of the Grenoble region of France. Major differences in water calcium levels were observed in correlation with lithological differences (average 13.6 mg/L in the crystalline massif of the Belledonne and 83.4 mg/L in the limestone areas of the Chartreuse and Vercors). The comparative analysis of the populations was performed through field and laboratory experimentation at morphometrical and ecophysiological levels. Uniform samples of male adult specimens from six different sites (two sites in the Belledonne, two sites in the Chartreuse, and two sites in the Vercors) were compared using three easily measurable parameters: maximum dry mass, duration of the molt cycle, and calcium balance during the molt cycle. Animals from waters that flow over limestone show a larger maximum size and a longer molt cycle than those from waters that flow over crystalline rocks. Spectrophotometrical analysis of their calcium balance during the molt cycle reveals that, whereas all animals are equally calcified during the intermolt, the decalcification during the premolt and the recalcification during the postmolt are more rapid in animals from limestone areas than in those from crystalline sites. Translocation experiments in both natural and artificially calcium-enriched waters confirm these differences. A significant increase in the duration of the molt cycle was observed in animals translocated to water of lower calcium concentration and vice versa, whereas no significant difference was observed between controls and animals translocated into water of comparable calcium concentration. Current results, supported by such a new synthetic experimental approach, indicate that variations in water calcium levels may generate important ecophysiological differentiation between populations, which may suggest a possible influence of environmental calcium on the geographic distribution of Gammarus fossarum. Key words: adaptive diversity; amphipods; calcium metabolism; experimental ecology; Gammarus fossarum; molt cycle., INTRODUCTION Knowledge of the contribution of the environment to intraspecific differentiation between neighboring populations is fundamental to understanding the ecological significance of geographic variation (for recent references, see Niewiarowski and [...]

The reproductive output of the burrowing shrimp Callianassa tyrrhena was studied using different biometric approaches. The parameters considered in the three methods used for such estimation included the size of the mother, the mother's weight loss due to oviposition and the loss of ovary weight due to oviposition. Each of the approaches provided insights about the complexity of the different events in the reproductive biology of C. tyrrhena in relation to the molting process or its inhibition. It appears, however, that molting just before oviposition and its inhibition during the yolk accumulation in the ovary are the major determinants of the reproductive output of C. tyrrhena.

A survey was conducted to study the spatial distribution and interannual variations in the megabenthic decapod crustacean assemblages on the Galician continental shelf and upper slope over the period 1980 to 1987. Forty species belonging to 19 families were identified among which depth and spatial structure were found to influence their community organizations. The results also showed that bathymetric zonation differentiates between species that are characteristic of the slope, shelf-slope edge and shelf. Spatial zonation was found to be related to changes in oceanography and sediment along the continental margin. 1980 to 1984 and 1985 to 1987 were the two periods identified based on interannual variation in assemblage structure.

The physiological effects of emersion of high or low level of humidity on Nephrops norvegicus were evaluated using seawater-soaked hessian with periodical flushes of seawater (high humidity, HH) or unprotected emersion (low humidity, LH). The quantitative measurements of haemolymph constituents such as ammonia, glucose and lactate as well as the assessment of respiratory conditions revealed that N. norvegicus can cope with emersion and that high humidity conditions have little effect on such adaptation to physiological stress.