Fiddler crabs are generally considered polygamous as they tend to live in dense mixed sex colonies with numerous neighbours and individually defended territories. We show that the Australian fiddler crab, Uca capricornis, is socially monogamous based on behavioural experiments and observations of neighbouring males and females. The unusual relationship between neighbouring males and females in U. capricornis is selected for and maintained by intrasexual aggression and the ability to recognise and defend their partner.

Males of several fiddler crab species sometimes construct sand structures (referred to as “hoods” in Uca lactea) at the entrance to their burrow, to which they attract females. Like the bowers of bowerbirds, sand structures of fiddler crabs are external ornaments that exist physically apart from the animals. Despite the mating benefit gained by possessing a structure, many males do not construct structures and some males even destroy their own structures. Structure destruction cannot be explained by the time and energy costs associated with structure construction or maintenance. This implies that the possession of a structure alone can be costly. In the present study on U. lactea, I experimentally planted hoods at the burrows of males that did not have hoods, and compared their frequency of hood destruction with that of control males (builders whose hoods were replaced with those of other males). Non-builders destroyed planted hoods more frequently than control males. Females, which do not construct hoods, also destroyed experimentally planted hoods more frequently than control males. Hoods are able to attract females, but the possession of hoods may incur some costs for crabs, probably because hoods also attract males and non-receptive females. Hence, only males that can afford the costs are likely to construct hoods.

Estuarine intertidal zones are characterized by variable salinity regimes due to seasonal and daily fluctuations. Salt-marsh inhabitants, such as the mud fiddler crab Uca pugnax, are physiologically adapted to this habitat. Crustacean growth and development are energy demanding and sensitive hormonal processes which are susceptible to natural stressors. This study investigated physiological and metabolic changes in the molt cycle of U. pugnax in response to different salinity levels by assessing the survival, respiration, and post-molt tissue protein and carbohydrate content. Crabs were subjected to a limb regeneration and ecdysis challenge under four different salinity regimes. For the study, a limb was removed and its regenerative growth was photographed every two days. After ecdysis, crabs were dissected, and the tissues collected were analyzed for their protein and carbohydrate contents. Crabs held at 60 and 75 ppt seawater showed 100% mortality. Crabs at 60 ppt did not undergo basal limb growth. During limb regeneration, abnormal limb growth occurred solely in males. Post-molt 40 ppt crabs showed elevated respiration rates compared to 10 ppt crabs. Females and 25 ppt crabs had significantly more free carbohydrates in epithelial tissue than males and crabs at 10 and 40 ppt. As salinity decreased, epithelial protein content in females decreased while males experienced no change. Salinity did not affect the amount of acid, water or base-soluble exoskeleton protein. These physiological responses indicate that U. pugnax males and individuals exposed to extreme salinities are more likely to be impacted by salinity stress during limb regeneration and ecdysis.

Marine isopods of the genus Bathynomus are important scavengers. We studied the microscopic structure of setae on the antennule and antenna of Bathynomus pelor using scanning electron microscopy. The animals were caught in baited traps off the Northwest Shelf of Australia and brought to the surface by a remotely operated vehicle (ROV). The peduncles of the antennule and antenna displayed pits with simple setae and some penicillate setae located outside these pits. The ventral side of the antennule flagella houses a furrow, bordered by knob shaped projections and filled with aesthetascs. Bifurcated and penicillate setae are also present on this flagellum. Clustered and branched setae were found on the flagellum of the antenna. These structures indicate that B. pelor possesses a set of complex setae on its antennule and antenna that it may use for sensory perception.

Allometric growth analysis on chelae dimensions vs. carapace length (CL) was employed to estimate average size at the onset of morphometric maturity (= puberty molt) and sexual dimorphism regarding the pair of chelae in Aegla franca. Males attain morphometric maturity (12.15 mm of CL) at a larger size than females (10.93 mm of CL). After the puberty molt, an additional change in the allometry level regarding chelae dimensions was detected in adult males (average CL = 19.00 mm). As a result, two sequential morphotype groups of adult males, herein designated as morphotype I and morphotype II, were recognized according to the state of development of the pair of claws. We postulate that the second change in this allometry level is related to functional maturity in this sex, based on the following observations: 1) temporal variation in the proportion between the two morphotype groups reveals that morphotype II individuals make up most of adult males in the population at the beginning of the seasonal reproductive period of the species, and 2) morphotype II males show a more robust pair of claws as compared to the predecessor morphotype, which might represent an advantageous trait in reproductive competition. Males and females of Aegla franca are heterochelous with handedness preponderance of the left chela. Claw size is a distinct dimorphic trait in this species, being significantly larger in male specimens.

Inducible defenses are phenotypically plastic traits in which individuals or colonies develop a predator/herbivore-resistant trait in response to a cue. The barnacle Chthamalus fissus, commonly found in the upper intertidal of southern California and Baja California, Mexico, exhibits three morphs: one with an oval operculum, one with a narrow, slit-like operculum, and a relatively uncommon bent form with the operculum opening on one side. A previous study suggested that the narrow and bent morphs are defended from attack by the predatory snail Mexcanthina lugubris lugubris. In the present study, predator exposure and predator exclusion experiments revealed that operculum morphology of C. fissus is a plastic trait: individuals exposed to M. lugubris lugubris develop into the narrow operculum morph or, less commonly, the bent morph. While some species of marine invertebrates exhibit either a generalized plasticity response to various predators or plastic traits that are specific to the type of predator to which they have been exposed, the observation in this study appears to be the first demonstration of the occurrence of alternative inducible defenses to the same predator within a single species of marine invertebrate.

Species assemblages of Alpheus of similar morphology occur along the tropical and subtropical margins of all world oceans. We studied sympatric populations of Alpheus belonging to three color morphs recognized along an intertidal gradient at Cabo Branco beach, State of Paraíba, Brazil. Morphological measurements of populations sampled monthly during a year were used to obtain indexes of size and fluctuating asymmetry. Standard statistical analyses were used in order to verify if the stress gradient established along the intertidal region affects spatial distribution, size and body symmetry in these three sympatric populations. Alpheus armillatus sensu stricto, the most frequent species, was predominant in the upper meso-littoral zone, being significantly smaller in the lower zone. A. cf. angulosus was predominant in the middle zone, while A. cf. heterochaelis was restricted to the upper zone. Individuals of A. cf. angulosus were significantly smaller than those of the other two morphs. Males were larger than females in all morphotypes, while cheliped dimensions show allometric growth. Couples invariably belong to a same morph. We obtained indications that competition between morphs are favoring the establishment of larger individuals in the most disputed zones of the middle and upper meso-littoral, although we were not able to confirm whether wave action was the main environmental factor responsible for these gradients in body size and symmetry along the intertidal region. Our data provide further ecological and biological evidence for the three color morphs representing distinct species, whose sympatric populations may be further recognized by additional morphological criteria. However, we are unsure about the constancy of these auxiliary distinguishing characters for allopatric populations from throughout their full western Atlantic ranges.

Macrobrachium carcinus, one of the largest freshwater shrimp of the east coast of the Americas, is commercially fished in certain parts of the region. We present data concerning the reproductive biology of the species, and compare findings with those published for other species of Macrobrachium. Ovigerous females were collected monthly between March 2004 and April 2005 in the San Juan River, northern Costa Rica. Egg bearing females ranged in size from 120.1 to 190.1 mm total length. Fecundity increased with female size and, up to 242,437 eggs, can be considered as high compared to other species of Macrobrachium. Average egg volume increased gradually during embryogenesis from 0.065 to 0.088 mm³, representing an overall increase of 35.4%. Eggs can be considered as small, typical for Macrobrachium species depending on brackish water to complete larval development. Reproductive output of M. carcinus varied between 4.0% and 21.0%, and was independent of female size; these values are within the range reported for other species of Macrobrachium and other marine caridean shrimp.

The green crab Carcinus maenas invaded the Gulf of Maine over a hundred years ago and has become a well-established member of coastal ecosystems. Carcinus is most abundant in the intertidal zone despite higher availability of invertebrate prey in the nearby shallow subtidal. A previous study revealed a higher mortality rate for Carcinus in the subtidal than in the intertidal zone. Two other decapods, the American lobster Homarus americanus and Jonah crab Cancer borealis, have their highest abundance in the shallow subtidal. These three species have similar diets and predation among and within species occurs. We performed a laboratory experiment to investigate the effects of H. americanus, C. borealis, and larger conspecifics on mortality and behavior of Carcinus. Homarus americanus was the most effective predator on Carcinus, consuming 27% within 24 h. In contrast, only 5% of Carcinus were eaten by C. borealis and none by conspecifics. The presence of American lobsters had dramatic effects on Carcinus behaviors: hiding and climbing increased while walking and standing on the open substrate decreased. In contrast, Carcinus showed no significant changes of behavior in the presence of C. borealis or larger conspecifics. The consumptive and non-consumptive (behavioral) effects of lobsters on Carcinus appear to be one major cause of the scarcity of Carcinus in subtidal communities. These effects are also likely to reduce Carcinus predation on the small invertebrates that are common prey for all the large decapods in this ecosystem.

This study examines egg development in American lobster (Homarus americanus) ovigerous females caught off the Magdalen Islands (MI), Québec, in September 2002 and kept in tanks for 10-11 months under a simulated natural temperature cycle. The study compares egg development trajectories of 7 early-spawners (ES) that had a well-defined pigmented eye area (Perkins eye index, PEI: 190-246 µm) at the time of capture and 8 late-spawners (LS) with no visible pigmented eye at the time of capture. Eggs from ES achieved about 80% of their development in the fall, followed by a circa 6-months rest period. Eggs from LS reached approximately 50% development by late fall, and unlike eggs from ES, continued development during winter even at temperatures of 1.0-1.5°C. The two groups experienced different numbers of effective (> 3.4°C) degree-days (ES: 1440.7, LS: 1308.0) for complete embryonic development and late spawning translated into late hatching. Additional observations made on a group of 72 ovigerous MI females caught in September 2006 indicate that early spawning is mainly associated to larger females, most likely multiparous, with a 2-year reproductive cycle, and late spawning mainly to smaller females, most likely primiparous, with a 1-year cycle, molting and spawning the same year. Larvae from ES/multiparous and LS/primiparous may therefore encounter different environmental conditions for survival at hatching and during larval development. The occurrence of females having different patterns of egg development trajectories in American lobster populations can help spread larval production over time. This can be viewed as a mechanism for coping with environmental uncertainty.

On the Brazilian coast, ten species of fiddler crabs occur in the estuaries and mangrove systems. The larval development of only five of these species is completely known. Here we describe the first zoeal stage and megalopa of Uca (Uca s. str.) maracoani. Ovigerous females and megalopae were obtained at Jabaquara Beach, Paraty, state of Rio de Janeiro, Brazil. The first zoeal stage was obtained from ovigerous females in the laboratory, and the megalopae directly from the field. Both zoeae and megalopae were raised in laboratory conditions. The megalopae survived until the eighth juvenile stage, when they could be identified to species. The larval morphology was analyzed and compared with the species already known for the Brazilian coast, and some other species, such as the southeast Atlantic fiddler crab, Uca tangeri. The comparison showed that U. maracoani has some characteristics that are more similar to U. tangeri than the previously studied species from the Brazilian coast. This is the first description of the zoea and megalopa morphology of a member of the genus Uca from the southwest Atlantic, of which the adult has a narrow front sensu Crane (1975), and it is helpful for taxonomic, systematic and ecological purposes.

Discovery of a single specimen of cirolanid isopod from the Late Cretaceous of Lebanon permits definition of a new species, Cirolana garassinoi. Preservation with the ventral surface exposed is unique among isopod fossils. The evidence of a thin, apparently transparent cuticle and three pairs of dermoliths suggests that the specimen died while in the pre-molt condition. The ability to sequester calcium and possibly other mineral salts in a marine isopod may indicate a preadaptation to terrestrial lifestyles where the process is common in extant forms.

Two glutamate dehydrogenase (GDH) cDNA sequences encoding 474 (GDH A, a truncated gene) and 552 amino acids (GDH B) were discovered in the Pacific white shrimp, Litopenaeus vannamei. Both GDH A and GDH B were fairly conserved as shown by the amino acid alignment. The two cDNAs differed only at the C-terminal sequences. The quantitative real time polymerase chain reaction (qPCR) assay was developed to estimate the specific expression on different tissues. Both GDH A and B were mainly expressed in shrimp muscle, followed by in the gill and epithelium, while the expression in shrimp hepatopancreas was the lowest when compared with other tissues. Though no significant difference was observed among all the test tissues, the ratio of GDH B to GDH A transcription was kept at a very high level ranging from 32.04 in the eyestalk to 64.52 in the muscle, indicating that GDH B was largely expressed in L.vannamei. The GDH activity in the muscle of L.vannamei was also the highest followed by in the epithelium, eyestalk and gill. The GDH activity in hepatopancreas was significantly lower than that in other tissues. As a control, the tissue expression of Na -K ATPase was also determined. This enzyme was mainly expressed in the gill, followed by in the muscle and epithelium. Our results provide baseline data in physiological expressions of GDH and Na -K ATPase for osmoregulation in L.vannamei. The research protocol offers a practical guideline for the analysis of gene expression in shrimp. The sequences and techniques developed in this study will also contribute to the GDH gene research in other crustacean species.

We have adapted an actin-myosin motility assay to examine the interactions in vitro between actin cables isolated from the giant internodal cells of the freshwater alga, Nitella, and pigment granules extracted from red ovarian chromatophores of the freshwater palaemonid shrimp, Macrobrachium olfersi. The chromatophore pigment mass consists of large (0.5–1.0-µm diameter) membrane-bounded granules, and small (140-nm diameter), amembranous granules, both structurally continuous with the abundant smooth endoplasmic reticulum. Our previous immunocytochemical studies show a myosin motor to be stably associated with the pigment mass; however, to which granule type or membrane the myosin motor is attached is unclear. Here, we show that sodium vanadate, a myosin ATPase inhibitor, markedly increases the affinity of isolated, large, membrane-bounded granules for Nitella actin cables to which they become permanently attached. This interaction does not occur in granule preparations containing ATP with uninhibited, active myosin without vanadate. We propose that a stable state of elevated affinity is established between the granule-located myosin motor and the Nitella actin cables, resulting from a vanadate-inhibited acto-myosin-ADP complex. This finding provides further evidence for a myosin motor positioned on the surface of the membrane-bounded pigment granules in shrimp ovarian chromatophores.

Snow crabs, Chionoecetes opilio, were obtained approximately bimonthly from the eastern Bering Sea and sampled for biometric information and biochemical analysis of ovaries, which included determination of moisture, ash, total lipid, protein content, fatty acid and lipid profiles. Development of the ovary during the reproductive cycle largely followed the pattern seen in other crustaceans, namely an increase in size and lipid content. However, the increase in lipid content occurred early in the development cycle and was stable thereafter. Both the lipid and fatty acid profiles were relatively stable throughout development. The fatty acid profile of the ovary of C. opilio differs from other crustaceans by having relatively high percentages of eicosapentaenoic (EPA) and docosahexaenoic acid (DHA), and low percentage of arachidonic acid (ARA). Forward stepwise general discriminant analysis of fatty acid profile indicated that it can be used to classify the development of ovaries at least during the last five months of the yearly reproductive cycle.

Using 15 species of freshwater prawns (Macrobrachium Bate, 1868) from Taiwan as the study material, characters of mitochondrial 16S rDNA sequences (16S) and nuclear 28S rDNA sequences (28S) were examined. Their phylogenetic analyses were conducted with Bayesian (BI), maximum likelihood (ML), maximum parsimony (MP), and minimum evolution and neighbor-joining (MENJ) methods. The 16S extracted was smaller in sequence length, rich in adenine, poor in cyctosine, and biased strongly to transitions in the nucleotide substitutions, whereas the 28S extracted was larger, rich in guanine, and biased to transversions. In the separate analyses of the two genes, the phylogenetic trees derived from the 28S had appreciably higher topological resolution with deeper branching (less polytomies) and higher topological confidence with stronger phylogenetic signals than the 16S trees. The poor resolution and confidence of the 16S trees were attributable primarily to its poor sequence divergences associated with high transition/transversion (ts/tv) ratios and low α-values of the gamma distributions. The result was a severe convergence of taxa within a narrow range of small genetic distances, so that their bifurcation could not be determined unambiguously. The 28S was highly diverged and had larger genetic distances with low ts/tv ratios and high α-values, resulting in much less convergence of the taxa. The 28S tree reconstructed with BI produced the best topological resolution and confidence in the separate analyses. The partition homogeneity test indicated that the 16S and 28S data sets were congruent. Their combined analyses with ML, MP, and MENJ showed no improvement in both topological resolution and confidence from the separate analyses of the 28S. With BI the combined analysis produced mixed results; improved the estimates of phylogenies for some of the taxa but confused or even obscured for the others.

A total of twenty microsatellite loci included dinucleotide, trinucleotide, and tetranucleotide microsatellite loci were isolated for Sinopotamon yangtsekiense using the FIASCO protocol. Genotyping of 30 individuals showed that the number of alleles ranged from 2 to 22, with observed heterozygosity ranging from 0.103 to 0.900 and expected heterozygosity ranging from 0.100 to 0.957. The polymorphism information content per locus ranged from 0.093 to 0.932. Cross-species amplification was investigated in seven related taxa. The results suggested that the developed microsatellite loci are specific to Sinopotamon and have potential for limited use in cross-genus amplification within Potamidae. These microsatellite markers should prove valuable tools for population genetic studies of the species Sinopotamon.

Two new troglobitic species of the freshwater crab genus Sundathelphusa (Parathelphusidae), S. waray, n. sp., and S. lobo, n. sp., are described from two caves in Samar, Philippines. This discovery brings the number of cavernicolous species of Sundathelphusa in the Philippines to nine. It is the first record of freshwater and true cavernicolous crab species from Samar. These two new species are morphologically closely related to S. cavernicola Takeda, 1983 and S. hades Takeda and Ng, 2001, but differ distinctly in the shape of carapace and the presence of long corneous spines in the dactyli. The new species are characterized by the non-pigmented body, greatly reduced eyes and long ambulatory legs that are associated with previously known troglobitic crabs. The presence of corneous spines on the distal two segments of the ambulatory legs is suggested as troglomorphic adaptation to subterranean habitat. A key to the cavernicolous freshwater crabs of the Philippines is also provided.