Relative to other economically important marine animals, there is limited knowledge of the reproductive characteristics of the male Australian red claw crayfish Cherax quadricarinatus. In this study, the structure of the male reproductive system of C. quadricarinatus and the progression of spermatogenesis were examined histologically and using transmission electron microscopy (TEM). The male reproductive system of C. quadricarinatus is composed of paired testes, vasa deferentia, and genital appendixes. Each testis has a non-branched collecting duct and numerous attached seminal acini. Spermatogenesis occurs mainly in the seminal acini. Germ cell development is synchronous within each acinus, but not between different acini. Spermatids, formed after meiosis, undergo a complicated metamorphosis until the aflagellate spermatozoa are finally formed. Early in the metamorphosis, a highly convoluted membrane lamellar system is assembled in the cytoplasm as the chromatin begins to condense. The convoluted membrane lamellae split into numerous small vesicles which amass together and condense to construct a helmet-shaped acrosome cap, the concave side of which forms an acrosomal vesicle. In the meantime, the chromatin's decondensing expands the nucleus, while granular material, mitochondria, and membrane lamellae remain in the cytoplasm. Finally, the acrosomal cap and vesicle move to the surface and protrude through to the outside of the spermatid. The chromatin condenses again, enabling the nuclear volume to decrease and thereby forming a mature aflagellate spermatozoon.

How do certain characteristics of organisms, such as sex or species, and certain ecological factors, such as interaction with congeneric individuals, influence the variability of body architecture in an environmental setting over a small spatial scale? Using geometric morphometrics we performed a morphological comparison of the dorsal surface of the carapace of a congeneric guild formed by Aegla araucaniensis, A. denticulata denticulata, and A. abtao. Additionally, we evaluated whether the segregation of microhabitat by congeneric interactions generates variations in the shape of the cephalothorax in A. araucaniensis, comparing a population belonging to the congeneric guild with a close population without congeneric interactions. Changes in cephalothoracic shape are regulated primarily by intrinsic factors, such as the differences between species and sex of individuals. In addition, the congeneric interactions do not affect the expression of the carapace shape in either of the populations of A. araucaniensis. The patterns of variation in cephalothoracic architecture are similar to previous reports based on geometric morphometrics, traditional morphology and descriptive morphology. The interspecific variations are caused mainly by the configuration of the spinous processes at the borders of the carapace, while the variation due to sexual dimorphism is due to an expansion of the longitudinal axis in males and the caudal end of the carapace in females. Morphological responses in A. araucaniensis differ from previous comparisons made with other species of Aegla under similar environmental contexts but over distinct spatial scales. We discuss the sexual dimorphism from an adaptive perspective and propose that the architecture of the cephalothorax in aeglids is a trait conserved and regulated significantly throughout the evolutionary history of the group.

Sand crabs (Lepidopa benedicti) are highly specialized digging animals that spend the vast majority of their adult life submerged in fine sand. The carapace color of L. benedicti varies from gray to white. Given that the environment in which they live is uniform and dark, most of the functional scenarios to explain color variation seem unlikely to apply. Carapace color has a bimodal distribution, indicating that it is better characterized as a polymorphism than simply as normal variation. Gray crabs are larger and more common than white ones. Crabs mostly swim ventral-side up, which suggests that countershading does not explain the apparent advantage of having a gray carapace.

Stomach content analysis and behavioral observations reveal that the horned shrimp Paracrangon echinata is a lie-in-wait predator on smaller organisms, especially amphipods, polychaetes, and caridean shrimp. Prey is detected using the extremely thin third pair of pereiopods, captured with the subchelate first pereiopods, and ingested whole.

I observed and obtained video footage of swimming behavior in Metoporhaphis calcarata. The behavior is described and illustrated by tracings of video stills over a one-second interval. The fifth pereiopods do not end in paddles, as do those of crabs in Portunidae, but rather are fringed with pinnate setae. On the sea floor, these crabs can form a “stockade” consisting of the acute rostrum and a circle of thorns on the distal surfaces of the pereiopods.

Maintaining a sustainable egg bank through rapid maturation and the production of large clutches is an important strategy for large branchiopods surviving in ephemeral habitats, and such egg banks can only be replenished by the recruitment of hatched eggs as a function of fitness (F). The ability to reach a threshold F represents a key adaptation to selection pressures. We investigated daily changes in the population density/size and hatching numbers of fairy shrimp, Branchinella kugenumaensis, and estimated their F values in an ephemeral pool, Siangtian Pond, in northern Taiwan during 2005, and four cohorts were observed. The number of hatchings per cohort ranged from to , representing a hatching density between 1.42 and 2.83 , and the number of newly produced eggs per cohort ranged from to , representing a high level of recruitment, ranging from 10,631 to 37,425 in the sediment, which yielded a mean fitness of 2.05 produced eggs per hatching (CI  =  1.82 ∼ 2.35). The threshold F for replenishing the hatched portion of the egg bank was derived theoretically and ranges from 1.39 to 2.36, varying with the probability of reproduction failure and the rate of egg mortality. Because only a small fraction of the egg bank hatches during each inundation episode, the observed F may not be sufficient for replenishing the remaining egg bank. Therefore, additional strategies for long-term persistence are required, which may be achieved by exhibiting occasional indeterminate growth in addition to the regular determinate growth pattern of this species.

We studied copepod assemblage variability among years, seasons, and tidal states in the Mucuri River estuary (Bahia State, Brazil). Zooplankton samples were collected seasonally through five years (2002-2006) at three sampling stations, one of which was sampled over a complete tidal cycle (two ebb and two flood tides). Temperature, salinity, river flux, and rainfall data were collected. Winter and summer represented dry and wet seasons, respectively. Copepod abundances ranged from 40 to 63% of the total zooplankton assemblage and comprised 46 taxa, among which, common estuarine species such as Temora turbinata (first record for the studied area), Parvocalanus crassirostris, Acartia lilljeborgi, Oithona hebes were the most abundant (euryhaline species). Interannual and seasonal variations were most marked in stenohaline species, e.g., Notodiaptomus sp. and Thermocyclops minutus; density variations of euryhaline species, which made up the majority of the abundant taxa, were most closely related to tides. Diversity and richness also followed an intertidal pattern of variation.

The macrocrustacean community of brackish polder waters in Flanders was investigated based on a twenty year survey comprising 430 biological samples taken at 218 different locations. A clear shift in the gammarid community could be observed. After its introduction, the alien Gammarus tigrinus, originating from North America, reached high abundances and became widely spread in the polder waters within a few years. Simultaneously, a decrease in the prevalence of the indigenous brackish water gammarids G. duebeni and G. zaddachi occurred. However, at the same time a decrease in the salinity of the polder waters also was observed. Uni- and multivariate data analysis revealed a clear difference in the environmental preferences of G. tigrinus, G. duebeni, and G. zaddachi. The alien species preferred lower salinities, lower orthophosphate concentrations, and a higher oxygen concentration compared to the two indigenous species. Besides the decrease in prevalence of the native gammarids, a decrease was also observed in prevalence of two other indigenous brackish water crustaceans: Palaemonetes varians and Neomysis integer. It appears that the decrease in salinity is the most important factor causing the decline of the indigenous gammarids and not the introduction of the alien G. tigrinus.

The freshwater shrimp Caridina gracilipes is widely distributed in the Indo-Pacific, and both landlocked and amphidromous populations occur in southern Taiwan. In this study, we collected monthly samples between September 2006 and August 2008 from a lake and a stream, representing landlocked and amphidromous populations, respectively. We found the amphidromous individuals were larger and grew faster than the landlocked individuals. The mature females in the landlocked population are in general small compared to the amphidromous population, and their eggs were larger but fewer than the amphidromous females. Ovigerous females could be found year-round in both populations, but the main recruitment was in September. The life span of females was longer than males; that of amphidromous were longer than landlocked populations. We found that populations of C. gracilipes in the subtropical region have evolved different biological and reproductive strategies based on their landlocked and amphidromous life histories.

Previous studies on two species of the genus Rhynchocinetes (“hingebeak” shrimps) have described mating systems in which large dominant “robustus” males, with hypertrophied cheliped and third maxilliped weaponry, guard and defend smaller females during copulation. The sexual system of these species is gonochoric (separate sexes). In this preliminary study on the sexual biology of R. uritai, we report observations indicating a very different sexual and mating system for Rhynchocinetes. A sample of R. uritai taken off Shimoda, Japan, revealed a population structure with small males and large females with no overlap in size. Two intermediate-sized individuals showed transitional sexual characteristics indicating sex change from male to female (protandrous sequential hermaphroditism). Transitional individuals had male sexual appendices but also were developing female “breeding dress” (incubatory) characters. Furthermore, these individuals had large vitellogenic oocytes in the gonads, typical of maturing ovaries. Mating observations were made on three receptive females to examine whether the smaller males employ the “pure searching” mating strategy. Matings occurred at night after female molting. Mating behavior was brief and simple: males approached and attempted to grasp the newly molted female, followed by a brief (∼ 2 sec) copulation, with no evidence of the complex “caging” (guarding) behavior described in two other Rhynchocinetes species. These observations on R. uritai suggest a “pure searching” mating system, in which mating is brief with little pre- or postcopulatory interaction between male and female and little or no agonistic behavior among males. Such a mating system is characteristic of decapod shrimp species with small males and larger females, i.e., the population structure observed in our sample.

The present distribution of two hermit crabs, Clibanarius vittatus and Pagurus maclaughlinae, was assessed for comparison with a study done more than 30 yr ago on decapods of the region. Clibanarius vittatus presently occurs in low or moderate density only at Sebastian Inlet. Retreat of C. vittatus from sites that it formerly occupied is attributed to intolerance of its larvae to low salinities recorded in the lagoon during recent reproductive seasons. Pagurus maclaughlinae remains the most abundant and widespread hermit crab in the lagoon. Its present distribution seems unchanged from the reference study despite prolonged periods, sometimes years, during which salinities declined to 12-25 in many areas distant from inlets.

The Bering Strait marks the northern species boundary for blue king crabs (Paralithodes platypus), but the life history of the population at this latitude has never been described in scientific literature. Blue king crabs were collected in shallow (10-23 m) waters near King Island (n: males  =  199; females  =  260) in July of 2005 and from near Little Diomede Island (n: males  =  40; females  =  19) in April of 2007 for morphometric, fecundity and hatch timing information. Crabs from Little Diomede and King Islands showed no significant difference in male carapace length (CL) by location and were smaller than blue king crabs from more southern parts of the state (mean CL ± SE: 108.45 ± 0.70 mm). Females from King Island (mean CL ± SE: 99.47 ± 0.52 mm) were significantly larger than female crabs collected from Little Diomede Island (mean CL ± SE: 93.11 ± 2.96 mm) and male crabs (mean CL ± SE: King  =  107.98 ± 0.73; Diomede  =  110.13 ± 2.24) were significantly larger than female crabs at both locations. Weight of female crabs (mean ± SE: 810.0 ± 61.9 g) increased with CL according to a non-linear function; Crab weight  =  0.00165*(CL)^2.8995 (r²  =  0.86). Fecundity estimates based egg counts (mean ± SE: 62,955.6 ± 4981.2) were slightly higher than visual estimates of hatched larvae (mean ± SE: 56,570 ± 6690). Timing of larval release differed significantly between female crabs held in the laboratory for 1 and 13 months. Crabs held for 1 month began hatching in mid-May 2008 with more larvae released per day and over a shorter duration (12 d). Crabs held for 13 month released fewer larvae per day over a longer duration (20 d) starting in mid-February 2009. Long-term laboratory holding may impact hatch timing due to differences in ambient temperature and perhaps other suppressed seasonal effects of the artificial environment.

The Dungeness crab, Cancer magister, is classed as a weak osmoregulator. Nevertheless, this species will enter into low salinity regimes of estuaries during times of high food abundance. The present study investigated the possible regulatory role of neurohormones on feeding behaviour during acute low salinity exposure. When the crab's eyestalks were ablated, removing the terminal medulla and the associated X-organ/sinus gland complex, they consumed more food and fed for a longer period of time compared with intact animals. Eyestalk ablated animals would even attempt to feed in freshwater, whereas intact animals would only consume food in salinities above 40% SW. The results suggest that feeding behaviour during low salinity exposure in C. magister is regulated by an inhibitory neurohormonal mechanism. This mechanism may help animals balance the demands of competing physiological processes.

Re-examination of the holotype of Ibacus cottreaui Roger, 1946, originally considered to be a scyllarid decapod, confirms that it is an isopod referable to the genus Cirolana Leach, 1818.

Description of a new genus and species of crayfish from the Eocene McAbee beds in southern British Columbia, Canada, marks the first occurrence of Parastacoidea Huxley, 1879, in the Northern Hemisphere. The superfamily is widely distributed in modern aquatic environments in the Southern Hemisphere, except in Africa and Antarctica, as well as in Australia, New Zealand, and South America in the fossil record. The occurrence of a single species in the Eocene of North America suggests a Cretaceous or Paleogene dispersal from the Southern Hemisphere through eastern Asia. Remarkable preservation of the specimens reveals traces of muscles, the endophragmal skeleton, and the intestinal tract.

The freshwater amphipod Gammarus pulex is widely distributed in freshwater streams and rivers of Europe. This amphipod also has isolated hypogean populations, which are transparent in appearance, suggestive of adaptation to their cave environment. Since cave habitats are often food limited, physiological adaptations have been observed that reduce the energy expenditure of cave organisms. Osmoregulation is an energetically expensive mechanism that allows gammarids to survive in fresh water. This study tested the hypothesis that differences in osmoregulation existed between hypogean and epigean populations of G. pulex. The osmoregulatory parameters measured were haemolymph cation concentrations, water and sodium fluxes and gill Na /K -ATPase activity. The hypogean G. pulex had significantly lower haemolymph sodium and potassium concentrations, but had a significantly higher haemolymph ammonium concentration than the epigean G. pulex. The low food availability in the hypogean environment was considered to be the underlying cause for these differences in haemolymph ion concentrations.

Reanalysis of aligned sequence data from the mitochondrial cytochrome oxidase I gene region across Crustacea has generated a number of new insights into how we can interpret genetic variation in these species. Some insights, such as the relationship between genetic diversity and the latitudinal biodiversity gradient, have been predicted in earlier studies. Other patterns – such as the bias toward more ‘rare’ allelic variants than expected under null models – across the 255 data sets analyzed here suggest that a more nuanced understanding of molecular evolution is necessary for interpreting the phylogeography and population biology of species in this group.

Ferritin is an important protein for iron storage in cells. A hepatopancreas cDNA library from the mud crab Scylla paramamosain was constructed using the SMART technique. A complete cDNA sequence that showed high identity with the conserved sequence of the ferritin gene was cloned from the cDNA library and subjected to further investigation. The full-length ferritin gene of Scylla paramamosain (SpFer) consists of 767 bp and contains a complete open reading frame of 513 bp and a 26-bp iron-respective element in the 5′-untranslated region. The gene encodes a polypeptide of 170 amino acids, constituting a predicted molecular weight of 19.44 kDa and a theoretical isoelectric point of 5.24. The deduced protein shares 84% identity with the ferritin protein of the crab Eriocheir sinensis. Quantitative real-time PCR analyses revealed that the expression of ferritin was ubiquitous in different organs of S. paramamosain, including muscle, heart, ovary, testis, and hepatopancreas. The highest expression level was found in the heart, while testis tissue showed the lowest level. Ferritin mRNA expression in continuous developmental stages in zoeal phases, including Z1, Z2, Z3, Z4, and Z5, as well as megalopa and juvenile crab I stages, were also examined by quantitative real-time PCR. The expression level of ferritin was highest in the Z1 stage and lowest in the megalopa stage. This study provides useful information regarding the structure and function of ferritin and will play an important role in immunity and resistance research in S. paramamosain.

Alpheid snapping shrimp are one of the most diverse groups of coral-reef fauna, and sponge-dwelling shrimp in the genus Synalpheus (gambarelloides species group) have in particular become a model system for studying the evolution of social biology and host use in marine invertebrates. Despite recent advances in understanding the evolution and systematics of Synalpheus, the taxonomy and phylogenetic relationships within this group remain challenging. More than 20 new species in the S. gambarelloides species group have been described over the past two decades, primarily within several cryptic species complexes, which has doubled the known diversity of this group in the West Atlantic. Here we construct a new phylogenetic tree describing relationships between 40 different species from the S. gambarelloides-group (119 individuals from across the Caribbean), using a combined dataset consisting of two mitochondrial loci (16S and COI), one nuclear protein-coding gene (elongation-factor 2), and 33 morphological characters. Putative conspecific specimens of Synalpheus from multiple locations across the Caribbean were always monophyletic (with one exception), providing strong support for the validity of species concepts based on morphology. Our study also provides further evidence for the monophyly of the S. gambarelloides-group in the Caribbean, resolves the molecular relationships within many recently described species complexes, and provides a new phylogenetic framework for future evolutionary studies of this group.

Compilation of lists of all genera of decapods and all species of fossil decapods has prompted erection of replacement names for junior synonyms. Duncanitrix replaces Duncania Portell and Collins, 2004; Gwana replaces Wanga Hu and Tao, 1996; Loerenthoplumopsa replaces Loerentheya Beurlen, in Lo˝renthey and Beurlen (1929); Paradoxilissopsa replaces Lissopsis Fritch and Kafka, 1887; Pseudomicippella replaces Pseudomicippe Pelseneer, 1886; Rathbunites replaces Rathbunella Collins, in Collins et al., 2009; and Syphaxiella replaces Syphax A. Milne-Edwards, 1864.

Survival, metabolic and reproductive activity of Itunella muelleri was tested in several combinations of temperatures (2°-30°C) and salinities (from fresh water to salinity of 34‰). Proportions of individuals alive after 18 or 22 days was high in all experimental combinations except in fresh water at 2°C and at 30°C at salinities of 4 and 16‰. Metabolic activity, as measured by the production of faecal pellets, was low in fresh water regardless of temperature. Metabolic activity was also very low at 2°C regardless of salinity. Maximum activity was found at 20°C and 22°C with little difference between salinities of 4, 8, 16, and 32‰. Production of nauplii during the first 29 days was nil in fresh water regardless of temperature, and also nil at 2°C and 30°C regardless of salinities. The maximum production was found in the combination of 22°C and salinity of 16‰. The results are discussed in relation to expected ambient conditions in the natural habitat of the species.

Heretofore, the pinnotherid crab, Afropinnotheres monodi, had been recorded only from African waters. The range is now extended into European waters with discovery of material in the Gulf of Cádiz. Furthermore, early collections of material had occurred only in open water; now three hosts can be assigned, the clams Scrobicularia plana, Ruditapes decussatus and Cerastoderma glaucum. Further discoveries of this pinnotherid may now be expected, especially along the coast of Portugal.

A specimen of a gladiator box crab, Acanthocarpus alexandri Stimpson, 1871, was captured off the northeast coast of Newfoundland during June 2009. This is the first report of the species in Canadian Atlantic waters, and represents a major northern expansion in the distributional range by approximately 800-900 kilometres. The known distribution of this western Atlantic species now extends from Newfoundland to Brazil, encompassing tropical, temperate, and sub-arctic marine ecosystems.

A recent phylogenomic analysis of arthropod relationships (Regier et al., 2010) produced several surprising clades within Tetraconata (Pancrustacea). The first discussion of these heterodox findings in the carcinological literature was published in the Journal of Crustacean Biology by Ferrari (2010). Ferrari criticized the findings of Regier et al. from three perspectives: 1) that morphological and developmental evidence was not considered by Regier et al., thus casting doubt on their results; 2) that Regier et al.'s tree implies incredible transformations in crustacean body plans; and 3) that Regier et al.'s results could be a methodological artifact. I show that none of these criticisms can withstand scrutiny. One should take care in structuring a phylogenetic critique. Not doing so may well be counterproductive if the aim is to increase respect for non-molecular evidence in phylogenetics.