Populations of the high altitude anostracan Branchinecta papillota from the type locality in the Atacama Altiplano (Iquique province, Chile) and from the Cumbres Calchaquíes (Tucumán province, Argentina) and specimens of B. achalensis from the type locality (La Posta, Pampa de Achala, Córdoba province, Argentina) were compared and new observations on the morphological diversity of the species were made. A basal branching in the male antenna 2 distal article, only observed in one branchinectid to date, was found in the Argentinean populations of both species.

Morphology of the masticatory surface of the mandibles, branchiae on pereiopods, and gill formulae have phylogenetic implications in freshwater crayfishes of the Northern Hemisphere (Astacidae, Cambaridae in Asia and North America). Here the mandibles and branchiae are described and illustrated for all four species of Cambaroides (Decapoda: Cambaridae). The mandible, gill, and gill formulae are similar in morphology in all four species of Cambaroides (Asian Cambaridae). However, the masticatory surfaces on the mandible of the members of Asian Cambaridae differ from those of the Astacidae and Cambaridae occurring in North America (American Cambaridae). The morphology and formula of the branchiae of Cambaroides show similarity to those observed in the members of Astacidae and American Cambaridae. However, the all species of Cambaroides differ from both Astacidae and American Cambaridae in lacking pleurocoxal lappet (= pendant) on the fourth pereiopod. These findings support phylogenetic results from molecular analyses.

Marine wood-borers and burrowers can substantially alter habitats and human-created structures in the marine environment. While many marine borers and burrowers occur only in a few substrata, burrowing sphaeromatid isopods can damage a variety of substrata. On the Pacific coast of North America, burrowing by the non-native isopod, Sphaeroma quoianum, accelerates shoreline erosion and damages marine structures. We conducted a lab experiment to quantify the per capita burrowing effect of S. quoianum on four common estuarine substrata. After two months, isopods created longer and more voluminous burrows and removed the most material (per capita) in marsh banks and Styrofoam followed by sandstone and non-decayed wood. We also examined the burrow morphology (length, diameter, volume) of burrows of S. quoianum from those four substrata collected in the field. We observed longer and more voluminous burrows in marsh bank and Styrofoam substrata, although we only detected a significant difference in length between substrata. Based on our lab results, we estimate a population of 100 000 adult isopods burrowing for two months could remove approximately 176 liters of marsh bank, 103 1 of Styrofoam, 72 1 of sandstone, or 29 1 of non-decayed wood. While the per capita bioerosion effects are lower than some bioeroders, e.g., the shipworm Bankia setacea, the pholad Penitella penita, high densities and wide distributions of S. quoianum suggest it is a substantial bioeroder within the intertidal and shallow subtidal in temperate Coos Bay, Oregon, and perhaps the other estuaries it has invaded.

The mating behavior of the spider crab Libinia spinosa Milne Edwards 1834 was studied in the laboratory. Two male morphotypes as morphometrically immature (MI) with small chelae and morphometrically mature (MM) with large chelae were used in non competitive and competitive mating trials. The liberation of putative hormones by receptive females to attract males was studied. We examined whether male body or cheliped size influence mate acquisition and copulation. The liberation of putative hormones by receptive females could not be demonstrated because males did not behave differently among four treatments exposed to water from 1) ovigerous females, 2) non ovigerous females, 3) males, and 4) a control of water unexposed to crabs. Under non competitive and competitive scenarios, copulation occurred immediately after physical contact between partners, thus a contact pheromone could be involved. The copulatory behavior and the time of copulation were similar between both male morphotypes. In non-competitive mating trials, MI males copulated successfully with females, and immediately after the mating pairs decoupled. By contrast, MM males displayed a post-copulatory guarding behavior that consisted of holding the female with the major cheliped and carrying her around the aquarium. In a competitive scenario, MM males guarded females for several hours by either caging them within the legs, or holding them out of the water when MI males approached. MI males of larger sizes than MM males did not gain mates and avoided agonistic interactions with MM males; thus, large chelae size is a more decisive trait than large body size for mate acquisition.

Given the limitations of the short life span and the highly unpredictable environment of branchiopods, a spatial differentiation strategy may become an immediate issue rather than a long-term life history adaptation to potential interspecific competition for a multi-species branchiopod community. We found an ephemeral pool in northern Taiwan with three sympatric branchiopods, Branchinella kugenumaensis (Ishikawa, 1895), Eulimnadia braueriana (Ishikawa, 1895), and Lynceus biformis (Ishikawa, 1895), and thus we aim to explore the spatial distribution patterns among these three species. We measured the density distributions of these species during two inundation episodes (2008P1 and 2008P2) that lasted for 6 and 32 days respectively. Significant differences in both horizontal and vertical distribution of these species were observed. Horizontally, each species showed its own spatial hotspots, but the hotspots changed irregularly every day. Vertically, while B. kugenumaensis gathered in the upper strata, L. biformis spread over a wide range of depths, with increasing dominance towards the deeper layers. Eulimnadia braueriana, on the other hand, showed no significant pattern of vertical distribution due to its small population size. We suggest that the significant differences in the spatial distribution of these sympatric branchiopod populations can be an adaptive strategy under the selective stresses of high unpredictability and variability.

Blue crabs Callinectes sapidus Rathbun, 1896 support large commercial and recreational fisheries along the Atlantic coast and in the Gulf of Mexico (GOM). Female blue crabs are traditionally believed to produce one to six broods in their lifetime. However, recent evidence has shown that females have the ability to spawn up to eight broods in a single spawning season, with as many as 18 broods over their lifespan. In this study, fecundity and egg diameter were examined by brood class (primiparous, multiparous) in the spring and summer/fall. Mean carapace width of females was significantly different between brood class and season, with the largest females in the spring. There was a positive relationship between fecundity and carapace width. Although primiparous spring females were the most fecund (3.2 ± 1.5 million eggs), no statistically significant differences in fecundity by brood class and season were found. Loss of eggs occurred during embryonic development; primiparous females lost ∼0.9 million eggs whereas multiparous females lost ∼0.1 million. Egg diameter and carapace width of the female were positively correlated. There was no difference in egg diameter between brood classes, but eggs were 9.9% larger in diameter during the spring than summer/fall. There was an inverse relationship between fecundity and egg diameter. Seasonality appeared to play an important role in the reproductive life history of blue crabs in the northern GOM. Larger crabs and larger eggs in the spring may be related to quality and quantity of available food and temperature conditions for optimal growth.

The reproductive traits of three coastal grapsoid crabs from the southwestern Atlantic, Neohelice granulata (Dana, 1851), Cyrtograpsus angulatus Dana, 1851 and C. altimanus Rathbun, 1914, were compared under the hypothesis that more energy is diverted to maintenance (and less to reproduction) in the upper intertidal and/or in estuaries than in the lower marine intertidal or subtidal, in order to cope with the harsh, and frequently variable, environmental conditions of semiterrestrial and brackish water habitats. Each species occupies a different habitat along intertidal, as well as estuarine gradients: N. granulata lives in the upper and middle intertidal of salt marshes and mud flats, especially in estuarine waters; C. angulatus lives in the low intertidal and subtidal of estuarine and marine habitats, and C. altimanus is predominantly an intertidal and subtidal marine crab. Results suggested that energy demands imposed by the harsh environmental conditions of the estuarine and semiterrestrial habitats resulted in less energy available for reproduction in N. granulata, evidenced by a shorter breeding season, a reduced reproductive output per clutch and an increased clutch interval. The opposite occurred with C. altimanus: less energy was necessary to cope with the stable marine water, allowing the presence of a long breeding season, a higher reproductive output per clutch and a very short clutch interval. Differences observed between marine and estuarine populations of C. angulatus are comparable with differences between C. altimanus, and N. granulata.

A new species of clawed lobster, Dinochelus steeplensis, is reported from the London Clay (Eocene: Ypresian) of England. This is the first report of Dinochelus from the fossil record. The genus was previously known by one recent, deep-water species. Four genera, the fossil Oncopareia and extant Thaumastocheles, Thaumastochelopsis and Dinochelus, comprise the thaumastochelid lobsters, a cladistically cohesive group (minus Dinochelus) formerly given family-level status as Thaumastochelidae Bate, 1888. These lobsters are united, and readily distinguished from other nephropids, by their short, quadrate, pleonal pleura and by their major claw morphology (a short, bulb-like palm and very long, slender fingers bearing acicular dentition). Also described herein is an occurrence of Thaumastocheles sp. from the Miocene of Chile. We now have a monophyletic group of lobsters with a fossil record extending back 90 million years and, with the new fossils reported herein, morphologic end members connected by a range of intermediates. It seems certain that Oncopareia is the least derived of the thaumastochelids, and it is reasonable to conclude that Dinochelus and Thaumastocheles are intermediate between Oncopareia and the most derived genus, Thaumastochelopsis. The new fossil species, D. steeplensis, shows that the carapace and minor claw form of recent thaumastochelids had evolved by the early Eocene (ca. 52–58 mya), and that thaumastochelids were living in outer shelf depths at that time. The new species, being morphologically, stratigraphically, and bathymetrically intermediate between previously known fossil Oncopareia and recent thaumastochelids, is at least consistent with the previously hypothesized retreat of the thaumastochelids off of the shelf and into deeper waters in the Cenozoic.

Biochemical profiles and proximate analysis of three species of fairy shrimps from Thailand, Streptocephalus sirindhornae, S. siamensis, and Branchinella thailandensis are characterized and compared. The nutritional analysis reveals that all three species contain high protein levels, particularly essential amino acids that are needed for growth and reproduction. Streptocephalus sirindhornae contains significantly higher crude protein (74.41%) than B. thailandensis (64.65%) and S. siamensis (50.24%). The highest percent of crude lipid (9.34%) and carbohydrate (32.69%) contents are found in S. siamensis. The highest amino acid content is recorded in S. sirindhornae (784.92 mg g^-1 dw) followed by that of B. thailandensis (596.12 mg g^-1 dw) and S. siamensis (439.58 mg g^-1 dw). Predominant amino acids found in all three species are lysine, phenylalanine, leucine, tyrosine, and glutamic acid. For fatty acids, palmitic acid C16:0, oleic acid C18:1n9, stearic acid C18:0, linolenic acid C18:3n3, and linoleic acid C18:2n6 are found to be major components. Branchinella thailandensis has the highest carotenoid content of 254.41 µg g^-1, followed by S. siamensis (211.92 µg g^-1) and S. sirindhornae (128.93 µg g^-1). Carotenoid content analysis show the presence of dominant groups consisting of β-carotene, canthaxanthin, astaxanthin, and lutein. The presence of essential fatty acids, amino acids, and carotenoids is the principal factor that determines the food value of Thai fairy shrimps for aquaculture application. These biochemical attributes make these Thai fairy shrimps ideal as feed for aquaculture.

In view of the relationship between shifts in diet composition and the activity of digestive enzymes in penaeid shrimp, the present study focused on the analysis of digestive trypsin and α-amylase activities of wild Farfantepenaeus duorarum (Burkenroad, 1939) juveniles and their changes in phenotypic expression, during the molt cycle as endogenous factor and their changes due to different feeding regimes (exogenous factor) in relation with δ¹³C and δ¹⁵N isotopic signature as an index of food assimilation induced by the seasonal availability of food items in the nursery area. Wild juveniles of F. duorarum were captured from April 2007 to February 2008, in the Celestun coastal lagoon, Yucatan, Mexico. Samplings were carried out considering all quarters of the lunar cycle and in each of the recognized seasons for this region: dry, rainy, and the Nortes (North Wind). Copepods and amphipods were the main source of food for juveniles of F. duorarum. Values of δ¹³C in the muscular tissue were near -20‰ hence the feeding regime of F. duorarum in the lagoon was composed by material of marine origin. Isotopic signature differences were found between the three annual seasons. It is an opportunist generalist organism that is located in the 4^th trophic level. The digestive enzymatic activities of both trypsin and α-amylase in fresh hepatopancreas tissue showed an interaction between season and molt stages (p < 0.05). Activity of the trypsin was highest during the Nortes at molt stage C (140 mU mg^-1 HP) and activity of α-amylase was higher in the Nortes at stage B2 (674 mU mg^-1 HP). The amylase/trypsin ratio also showed significant interaction between season and molt stages (p < 0.05), with higher values in premolt stages during the rainy and Nortes seasons. Isoforms of these digestive enzymes differed in expression according to the molt stage and also to the season with expression generally being greater at stage C.

We measured concentrations of Ca² in tissues (hemolymph, hepatopancreas, cuticle, and muscle) of the whiteleg shrimp Litopenaeus vannamei (Boone, 1931) and recorded changes in tissue calcium levels at molting stages and different salinities. Calcium in tissues varied significantly with molting stage (p < 0.05). Salinity also affected Ca² concentrations in tissues (p < 0.05). The highest Ca² concentrations were found in the cuticle, followed by the hepatopancreas. Ratios of Ca² /Na in tissues (except for muscle) varied with the molting stage and were higher in 4 g L^-1 than in other salinities. Calcium entering the shrimp may initially be mineralized in the cuticle or stored in the hemolymph and hepatopancreas, after which it is released to support mineralization in the post-molt period. Muscles may take part in the growth of L. vannamei by storing calcium during the molting cycle.

One of the most threatened ecosystems on many islands may be anchialine habitats, or coastal land-locked water bodies with no surface connection to the sea yet containing brackish water that fluctuates with the tides. To better manage these habitats, it is important to develop a broader understanding of the biodiversity within them since such knowledge plays critical roles in establishing conservation strategies. In this study, the genetic variation and population structure of an anchialine atyid shrimp, Caridina rubella Fujino and Shokita, 1975 was investigated in the Southern Ryukyu Archipelago, Japan. Given a planktotrophic larval stage and its potential amphidromous life cycle, populations of C. rubella on the island of Miyako-jima (to which it is apparently restricted) were hypothesized to have little to no structure across the island. To test this, 61 individuals were collected from four anchialine caves and sequence variation examined at the cytochrome c oxidase subunit I (COI) region of the mitochondrial DNA (mtDNA). Surprisingly, significant genetic structure was exhibited across distances ranging from <20 m to > 10 km. Additionally, deep (∼17% p-distance) genetic divergence correlating with distinct variation in rostrum lengths was found between closely situated, but more-or-less completely isolated, populations. This implies “C. rubella” may actually represent two distinct species on Miyako-jima. Given that this atyid is already listed as a threatened species by the Japanese government, the results presented here are useful in the formulation and implementation of future conservation plans for populations of C. rubella on Miyako-jima.

Ecological and phylogeographical investigations were made of disjunct populations of Deiratonotus kaoriae Miura, Kawane and Wada, 2007 in the Kumanoe (Miyazaki Prefecture) and Miyagawa (Mie Prefecture) Rivers, so as to compare life history patterns and elucidate genetic relationships between them. The relationship of carapace width with sex and occurrence of ovigerous females revealed a similar life history pattern throughout, new recruits occurring in spring and summer, reaching maturity the following autumn, and breeding in winter and spring. Large-sized individuals disappeared before the next breeding season, indicating longevity to be around 1.5 years. However, genetic analysis suggested an absence of present-day larval migration between the two populations. Two genetic groups present in the Miyagawa population were estimated to have diverged from the Kumanoe population in the Pleistocene.

Lack of an ischium on pereiopods 1–6 was previously considered a synapomorphy for the tanaidacean superfamily Tanaoidea, although descriptions of Arctotanais alascensis (Richardson, 1899), the sole species in Arctotanais, indicated presence or absence of the ischium. To resolve this ambiguity, we examined newly collected specimens of A. alascensis (including males, which had not previously been described) from Hokkaido, Japan, using light and scanning electron microscopy. We also conducted molecular phylogenetic analyses based on partial sequences of the 18S rRNA gene to examine the phylogenetic position of A. alascensis. Here we describe in detail the morphology of the male of A. alascensis, which proved to be similar to that of the females. This species bears an ischium on pereiopods 1–6, which contradicts the current diagnoses of Tanaoidea and Tanaidae, although other synapomorphies remain valid. Molecular phylogenetic analyses strongly supported the placement of A. alascensis in Tanaoidea, and consequently we amended the diagnoses for Tanaoidea and Tanaidae to include either presence or absence of the ischium on the pereiopods.

Milnepanopeus n. gen. is proposed to accommodate the western Atlantic brachyuran crab, Hexapanopeus lobipes. Characters of the carapace, sternal groove, carpus of the ambulatory pereiopods, and male first gonopod define this presently monospecific genus. Recent molecular analyses support removal of H. lobipes from Hexapanopeus, and segregate this genus as a distinct lineage of Panopeidae Ortmann, 1893. The species is redescribed as Milnepanopeus lobipes, n. comb., on the basis of the holotype and supplementary material from deep banks in the Gulf of Mexico. Variations in morphology are addressed along with morphological comparisons to related genera of the family.