In an effort to use aspects of the cuticle as taxonomic characters in phylogenies of fossil and extant decapods, variation due to gender, growth, sample location on the carapace, and molt cycle must be understood so that taxonomically important characters can be identified. In this study, effects of sample location on the carapace and carapace size were examined. A series of male Callinectes sapidus Rathbun, 1896, specimens from 2-6 cm in length were collected on the Rhode River of the Chesapeake Bay, MD, USA. To study the effects of sample location and carapace size on parameters of the cuticle, the cuticle was examined in thin section and on the surface of the dorsal carapace. The distributional density of setal pits and nodes and node size were measured on the surface. In thin section, thickness of the cuticle and construction of the nodes and setal pits was examined. Thickness of the cuticle, node size, and setal pit density increased during growth of the crab. Node density decreased with growth. Construction of nodes and setal pits remained constant in all specimens and sample locations. Morphometric parameters of the cuticle were consistent with previously reported growth rates of the carapace in C. sapidus. Differences in the rate of change for the cuticle metrics studied occurred at carapace sizes that are attained upon reaching sexual maturity. Growth rates of cuticular features provide context for comparison with similar data in other species. In addition, the change in growth rates of these features, if recognized in fossil crab populations, may allow the determination of population age structures and size at maturity.

Shell hardness was measured with a durometer for female red king crabs, Paralithodes camtschaticus, held in the laboratory over variable periods up to 107 days after molting. The data were fit best by a hyperbolic equation, with parameters β₀ = 0.216 and β₁ = 0.019 (R² = 0.976, n = 199), and an asymptotic value of 50.7 durometer units (DU). The time required to reach 90% of complete shell hardness (H₉₀ = 45.6 DU) was calculated to be 74.2 days. Molting dates for all crabs were hindcast using the last measurement that was less than H₉₀ and were within 2.5 ± 6.4 days (mean ± SE, n = 34) of the actual molting date.

Until about 20 years ago, the well-established gammarid amphipod Gammarus roeselii, originating from the Balkan Peninsula, was widespread and often the dominant amphipod species in rivers, canals, and big lakes of Germany and adjacent countries. Since 1989 Dikerogammarus villosus, a Ponto-Caspian pontogammarid, has successfully invaded the aquatic systems of mid and western Europe reducing and even eliminating native and earlier established gammarideans including G. roeselii. Field observations and laboratory experiments indicate that these two gammaridean species have different feeding habits. In our SEM study we wanted to test the hypothesis that different modes of food acquisition are expressed in differences in the morphology of the mouthparts and other structures involved in feeding, such as the antennae and gnathopods, possibly are indicative of the success of D. villosus over G. roeselii. Although both gammarideans have tools for omnivorous feeding, comparisons indeed revealed obvious differences in appendages involved in food acquisition. In G. roeselii, the molar surfaces of the mandibles are structured like rasps, suggesting they are well suited for grinding firm plant material, whereas those of D. villosus are only weakly structured. In G. roeselii, the basipodal endites of the maxillulae are armed with chisel-like cuspidate setae, and the maxillipeds bear flattened cuspidate setae, possibly a specialization of these mouthparts for scraping off adherent food from the substrate. We did not find such modifications on the maxillulae and maxillipeds of D. villosus. Compared to D. villosus, the setation of the antennae and the gnathopods in G. roeselii is sparse and short. Therefore, filter feeding, one of the feeding modes of D. villosus, seems to play a minor role in the nutrition of G. roeselii.

This study examined 24 hour activity patterns of a diurnally refuge seeking palaemonid, Macrobrachium australiense. The results obtained improve our understanding of the mechanistic processes that are likely to underlie observed patterns of anti-predatory refuge usage, and diurnal inactivity, in a wide range of crustaceans. When introduced to a novel environment M. australiense altered their searching behaviours in response to changes in available refugia. These behaviours were consistent with attempts to reduce exposure to predation. They altered in response to variation in stalk density of a vegetated refuge, environmental conditions, and individual body size. When settled in the environment all vegetated refuges were attractive to the test species, though higher stalk densities were preferred. M. australiense demonstrated both an active and a passive strategy of mediating exposure to predation. Like numerous other prawn species they substantially reduced activity during periods of high light. The underlying preferences and behavioural mechanisms displayed by the test animals were consistent with the theory that diurnal inactivity is a form of antipredator behaviour, even in the absence of predators. Upon subsequent exposure to predation, refuge seeking behaviour altered depending on the current activity level of the individual: during periods of low activity there was no significant change in behaviour. The presence of a predator had no significant impact upon the occurrence of periods of high activity. However, during these periods the presence of the predator caused an increase in the time prawns spent within the refuge, and decreased the number of transitions between the refuge and the open area.

We investigated the sex differences in the spatiotemporal distribution, body length, and gut contents of adult Neocervinia itoi, the most abundant cerviniid harpacticoid in Sagami Bay, Japan. Two other cerviniid species, Cerviniopsis sp. A and Cervinia bradyi, were also examined for comparison. The density of N. itoi tended to be higher at stations in or below sea bights with steep slopes in the bay, although there was no correlation between their distribution and chloroplastic pigment equivalent (CPE) in the sediment. In general, the sex ratio was strongly biased toward females in this species; the overall mean percentage of males was approximately 23% of adults. The sex ratio seemed to fluctuate temporally, even at the same site, although this fluctuation was not statistically significant. Comparisons of body size and sex ratio between the three species suggest that sampling bias was not the only cause for the observed skewed sex ratio. Distinct sex differences were observed in gut contents of N. itoi. Detritus-like gut contents were clearly observed in the urosomes of almost all females, whereas few males had gut contents. This result suggests that males do not forage during the adult stage. This non-feeding habit of males may result in a shorter lifespan than that of females and may be one cause of the skewed sex ratio. It remains unknown, however, whether this is a general trend among cerviniid species.

The nature of the sexual system (protandry, gonochory) and the frequency of female spawning (semelparous, iteroparous annual, iteroparous biennial) in the crangonid Sclerocrangon boreas remain uncertain. We addressed these questions by examining population sex ratio, anatomy and histology, and gonad and oöcyte sizes. Gonochory is supported by several facts: sex ratio was balanced at the smallest shrimp sizes, no intermediate sex form was found, and there was no evidence of degeneration of male gonad at the sizes where this might have been expected to occur. A majority of larger females, if not all, had a structure linking the ovary to the base of the fifth pereiopod but the presence of this structure on small females suggests it is not a degenerate vas deferens. Iteroparity is supported by the presence of two generations of oöcytes in females, including those gravid, and female biennial spawning is supported by the small size of ovaries/oöcytes in gravid females.

The objective of the current study is to understand population characteristics of the grass shrimp Palaemonetes pugio by describing growth, population structure, mortality, fecundity, and size at sexual maturity from a lagoon system inlet in the southwestern Gulf of Mexico. The shrimps were collected between January and December 2007 by otter trawl of 1-mm mesh size; salinity and water temperature were recorded simultaneously. Regressions were applied between total length (TL) and total weight (TW) of females and males. Growth parameters were estimated by length-frequency distributions with 0.01-mm length interval of carapace using the von Bertalanffy growth function (VBGF), mortality was calculated with an exponential model. To represent fecundity, the potential model was selected. The average salinity and temperature values were 6.39 ± 2.49 ppt and 27.63 ± 1.59°C, respectively. The number of females was higher than for males in winter and spring, suggesting a reproductive strategy that increases the probability for the male of finding a receptive female. The K (Bertalanffy growth coefficient) values were 0.48 for males and 0.43 for females. This could indicate a reduction of female energy investment in growth, directing it rather to reproduction. The instantaneous mortality estimates (Z) suggest a relationship with the reproductive period; the highest mortality was encountered from April to September. Female size at sexual maturity was estimated to be 2.41 cm TL, showing that ovarian development starts in winter and continues until early spring. Consequently, P. pugio showed faster growth, a seasonally oscillating growth pattern, a rather short life span, a somewhat high mortality, and an early onset of sexual maturity, which is considered to be similar to r selected species.

We evaluated the effectiveness of four sampling methods for freshwater crayfish in five aquatic habitat types in Congaree National Park, South Carolina, USA. Electrofishing was the most successful technique in terms of the diversity of species collected, the number of individuals collected, and the widest range of sizes collected. Seine netting was the next most successful method. Baited minnow traps were biased towards form I males and larger individuals, while dip netting was biased towards smaller individuals. The relative success of techniques depended somewhat upon species. For two stream dwelling species, Procambarus acutus and P. chacei, electrofishing collected significantly more individuals than any other technique. For P. troglodytes, the most abundant species and a habitat generalist, electrofishing was superior to dip netting in some habitats, but did not significantly differ from traps or seine netting. For Fallicambarus fodiens, no significant differences among the effectiveness of any sampling methods were detected.

Thirty-seven crabs (8 males and 29 females) of the genus Arcotheres, which inhabit the sessile bivalve Barbatia virescens (Reeve, 1844), were reared for 135 days in the laboratory and their morphological development was described. There was a strong size correlation between female crabs and their host bivalves. During laboratory culture, seven males and 18 females molted once, and one male and four females molted twice. The crabs showed little growth, perhaps because the crabs and bivalves were not fed during the study and because crab growth may be restricted by the host size. One small female molted from pre-hard stage to hard stage and progressed further to Stage II. Some adult females in Stage III or IV developed swimming setae following the molt. In past studies, only one metamorphosis was detected within a crab, and adult females were not thought to develop swimming setae. Thus, our study is the first to detect successive changes in body form within a crab. Furthermore, this study confirmed that adult females can develop swimming setae.

A panbiogeographic analysis of the distributional patterns of 196 species of eastern Pacific Isopoda led to the recognition of three generalized tracks, which correspond to major biotic components. The northern cold-temperate track extends from 62° to 35°N, in the northern cold-temperate sub-region (Aleutian Islands, Gulf of Alaska and coast of British Columbia, Washington, Oregon and northern California). The 57 endemic species assigned to it belong mainly to suborders Flabellifera, Valvifera and Asellota, although species of Oniscidea, Epicarida, Anthuridea, and Gnathiidea are also present. The northern warm-temperate/ tropical track extends from 33°N to 1°S, covering the Warm-Temperate and Tropical sub-regions, i.e., southern California to about halfway south into Ecuador. The 27 endemic species assigned to it belong mainly to the Flabellifera, most of them Cirolanidae and Cymothoidae, and Sphaeromatidae, Valvifera, Anthuridea, Asellota, Epicaridea, Oniscidea, and Gnathiidea are also present. The southern warm/cold-temperate track extends from 19° to 52°S, covering the Southern Warm and Cold-Temperate sub-regions, i.e., coast of Chile south to the Magellan Strait. The 27 endemic species assigned to it belong mostly to the Flabellifera, Asellota, and Valvifera.

Freshwater prawns of the genus Macrobrachium of Taiwan are diverse, rich in amphidromous species, but poor in land-locked and endemic species. The fauna showed higher similarity to those of the Philippine Islands and Ryukyu Islands than that of the China mainland. Based on their geographical distribution patterns in the Indo-Pacific region and their phylogenetic relations reconstructed from the nuclear 28S rDNA sequences, we hypothesize their most likely biogeographical origins and dispersion routes. For the 16 known species of Macrobrachium of Taiwan, 13 species were amphidromous. Their biogeographical origins were: 1) in the eastern region of tropical Southeast Asia islands, dispersing to Taiwan through the Philippines islands for M. australe, M. lar, M. latimanus, M. gracilirostre, M. jaroense, M. esculentum, M. lepidactyloides, and M. placidulum; 2) in the western region of tropical Southeast Asia islands, dispersing to Taiwan through the Philippines and/or mainland China for M. equidens, M. latidactylus, and M. mammillodactylus; 3) in mainland China for M. formosense; and 4) on the island of Taiwan for M. japonicum. For the remaining three species, M. asperulum, a land-locked prawn, and M. nipponense, a non-obligatory amphidromous prawn, originated in mainland China. M. shaoi is the only endemic prawn to Taiwan and its life cycle is still unknown.

Eocyzicus is defined as those cyzicid spinicaudatans with a round condylus dorso-posteriorly on the head, a wide space between the head and trunk, and the male rostrum spatulate. Furthermore, most if not all species have a dorsal columnar lobe on the posterior-most trunk segments terminating in a single spine. Eocyzicus parooensis Richter and Timms is widespread in Australian inland hyposaline waters, and Eocyzicus argillaquus n. sp. also occurs across the inland but generally in turbid freshwater clay pans. The two species differ morphologically in number of trunk segments, head structure, features of the caudal furcae, and in a number of minor features.

A new crangonid genus, Placopsicrangon, is established for an unusual new species, P. formosa, which is described on the basis of material from off Taiwan in the northwestern Pacific, at the abyssal depths of 4412-4824 m. This new genus has a large and reflective plate-like eye that is unknown in decapod crustaceans before but similar to the eyes of the deep-sea grideye fish of the genus Ipnops Günther, 1878. The new genus is also unique within Crangonidae by having a laterally compressed rostrum with dentate dorsal margin, and the presence of a transverse row of sharp teeth adjacent to the posteroventral margin of the sixth pleonal sternite. Placopsicrangon appears closest to Sabinea in the general pattern of the carination on the carapace and pleon, and the substantially reduced non-chelate second pereiopod. This new taxon is the sixth representative of Crangonidae inhabiting the abyssal zone.

Fairy shrimps (Anostraca) live in temporary waters. Dominant among their predators are aquatic insects, especially diving beetles (Dytiscidae). Mastication of the eggs of the fairy shrimp Branchipus schaefferi and their passage through the digestive tract of smaller beetles, like Ilybius fenestratus, has a positive effect on hatching afterwards. Dytiscidae could be important vectors for aerial dispersal of diaspores among ponds which are not directly connected to a stream channel. Such long-distance dispersal can be of critical importance for population survival and gene flow among communities living in temporary habitats.

Intermolt to premolt males of Hemigrapsus takanoi were exposed to salinities of 0, 10, 20 (control), 30, and 40 ppt. After 2, 4, and 6 h of exposure, oxygen consumption and ammonia excretion were measured. Hemolymph osmolality was measured at the end of 8 h. No mortalities were observed until hemolymph sampling. Hemolymph osmolality was maintained between 570 to 840 mmol/kg. Oxygen consumption increased significantly only at 0 ppt, compared to the control (20 ppt). Ammonia excretion levels showed a remarkable increase at 0 ppt. These results indicate that this species expends increased metabolic effort to tolerate abrupt salinity changes to freshwater compared to brackish or seawater.

Microsatellite markers were developed for the fiddler crab Uca mjoebergi for use in paternity assignment. Five highly variable loci were found to amplify reliably in U. mjoebergi, although one locus exhibited evidence for the presence of null alleles, and two loci exhibited evidence of linkage. The number of alleles, expected heterozygosity and probability of paternity exclusion (P > 0.999) suggest that these markers when combined provide sufficient power to determine paternity by exclusion in this species. Three primer pairs were found to also amplify PCR products from three additional fiddler crab species (U. dampieri, U. flammula and U. seismella), and will prove useful for phylogeography and behavioural ecology of fiddler crabs.