The spermatozoal morphology of Loxopagurus loxochelis exhibits characters shared by other paguroids: complex concentrically zoned acrosome vesicle, capped by an electron-dense operculum and posteriorly penetrated by a large perforatorial chamber, and three microtubular arms emanating from the cytoplasm. The general sperm cell dimensions and arrangement of the acrosome in L. loxochelis are similar to those previously described for three species of Calcinus. However, Loxopagurus lacks a defining autapomorphy of this genus: splitting of the anterior end of the perforatorial chamber into many obvious fingers. The only unique character observed in the sperm of Loxopagurus is the presence, in the cytoplasm, of a bulge filled with small tubules on the side of the acrosome. This structure could be an artifact or possibly a parasitic bacterial infection. In conclusion, L. loxochelis sperm morphology does not demonstrate any clear autapomorphies, but seems to separate from the other genera in the Diogenidae by the absence of their defining sperm characters (e.g. anterior perforatorial fingers and microvillar projections). It appears most similar to the genus Calcinus, and more superficially Strigopagurus, although its spermatophore morphology seems to indicate a doser relationship with Clibanarius. The combination of spermatophore and spermatozoal characters clearly places it in the Diogenidae, and supports its monotypic status.

We describe for the first time the male reproductive apparatus, spermatophore and sperm of Calcinus tubularis, analysing them under interference phase microscopy, scanning electron microscopy and transmission electron microscopy. The testes merge into a tubular duct made up of four zones. In the proximal zone, the ampulla of the spermatophore starts to be formed. In the medial zone, the ampulla is completed, the stalk lengthens and the foot develops. The two halves making up the ampulla meet at the lateral ridge, which shows a mostly fibrillar ultrastructure. Spermatozoa are composed of an almost spherical acrosomal vesicle, capped by a conical operculum, a cytoplasm, a nucleus and three microtubular arms. The acrosomal vesicle is posteriorly penetrated by the perforatorial chamber and shows an inner acrosome zone, a thick ray zone and an electron dense outer acrosomal zone. The great importance of paguroid male reproductive apparatus morphology and ultrastructure for phylogenetic analysis is confirmed.

Each January for 7 years (1999-2005), tubes of the polychaete Chaetopterus sp. were excavated at low tide from Dog Island, Florida, in the northern Gulf of Mexico, and examined for the presence of two common crab commensals, the anomuran Polyonyx gibbesi and the brachyuran Pinnixa chaetopterana. Of 114 tubes examined, 4 (3.5%) had no crabs, 77 (67.5%) had Pinnixa-only, 23 (20%) had Polyonyx-only, and 10 (9%) contained both species. For Pinnixa-only tubes, 90% contained a mixed-sex pair; for Polyonyx-only, 57% contained a mixed-sex pair and the remainder a single crab. All tubes containing both species had either one or two adult Pinnixa and a small Polyonyx (CW < 3.5 mm, 9 tubes) or a single adult Polyonyx and a small Pinnixa (CW < 3 mm, 1 tube). No tubes contained adults of both species. Among adult females, 24% of the Pinnixa and 44% of the Polyonyx were ovigerous. The Polyonyx-Pinnixa ratio of 20:80 showed a greater relative abundance of Pinnixa compared to other reports of this association from elsewhere along the Atlantic coast of the United States or the Gulf of Mexico. Experiments introducing single adult intruder crabs of either species into in situ tubes showed that adult crabs of either species evict same-sex conspecifics or heterospecifics; with time most tubes have a mixed-sex pair of a single species.

Material belonging to three species of hermit crabs [Paguristes bakeri Holmes, 1900, Pagurus gladius (Benedict, 1892), and Pagurus smithi (Benedict, 1892)] was collected during a series of research cruises along the Pacific coast of Mexico. In many cases, environmental conditions (i.e., depth, substrate, epibenthic water temperature and dissolved oxygen concentration) were measured. The geographic distribution of these species is reviewed, new sampling localities are provided (8 for Pgsts. bakeri; 10 for Pg. gladius; 4 for Pg. smithi), and the aboudance of the species is analyzed in relation to these environmental conditions. There is a clear tendency for Pg. gladius to occur on sediments with a larger sand component and in higher dissolved oxygen concentration than in the case of the two other species. Temperature gradient does not appear as a factor influencing the abundance of any of the three species studied, while depth seems to act as a segregation factor.

The present study investigated if Dardanus insignis abundance along the southern region of Brazil is maintained by their reproductive potential characteristics. Crabs were collected monthly from July 2001 to June 2003 offshore of Ubatuba and Caraguatatuba regions, Brazil. Females with eggs at an early stage of development were selected for fecundity analysis. This species presented a discontinuons or seasonal reproduction with peak in spring in the Southern Hemisphere. Relatively more females with eggs in the initial developmental stages were collected than those with eggs in late developmental stages, suggesting that brood time was shorter than other species of hermit crabs. Fecundity of individuals was not influenced by the species of shells occupied. Fecundity also increased with increasing crab size. Strategically, the relatively small size of eggs was compensated for by the larger number of eggs produced per brood as well as the possibility that individuals spawned multiple times during the reproductive season. The reproductive activity of D. insignis was characterized by a low frequency of ovigerous females, a seasonal pattern of egg production, a large number of eggs produced per ovigerous female, a relatively low commitment of metabolic reserves to reproduction, a high reproductive output, and a relatively brief embryonic development. These parameters contribute to the maintenance of the population in the study area, but do not explain the success of the species as evidenced by the large numbers of individuals observed in the study area.

Hermit crabs are one of the most abundant taxa in the intertidal habitats of tropical estuarine areas. Despite this situation, many aspects concerning their population ecology and reproduction are still poorly known. In this study, the reproductive biology of the diogenid hermit crab, Calcinus laevimanus was studied with emphasis on size structure, sex ratio, recruitment, breeding season and fecundity. Monthly samplings were conducted between January and December 2003 at Inhaca Island, southern Mozambique. A total of 1966 crabs were collected, represented by 760 males and 1206 females. The size frequency distribution of the present population showed an unimodal pattern skewed to the right, suggesting increased mortality in the largest size classes. Sexual dimorphism was evidenced by the larger sizes attained by males in relation to females. Moreover, sex ratios were femalebiased during most of the study period. Juvenile recruitment was constant with major peaks in March and May, ovigerous females were present year-round peaking February and April and egg number increased with female size. The present results show that reproduction and recruitment of Calcinus laevimanus displays high reproductive activity in the study area, as evidenced by the constant presence of ovigerous females and the high number of eggs carried by females.

Little is known about the typical behaviors of the pelagic red crab Pleuroncodes planipes (family Galatheidae). The crabs were observed in an aquarium to determine the typical repertoire of behaviors. An activity budget was developed to address two important questions: 1) how important are locomotory behaviors among overall red crab behavior; and 2) what additional non-locomotory behaviors comprise the behavioral repertoire of red crabs. Locomotory behaviors executed by the crabs were only 15% of the total observed behaviors and were divided into active (90.4%) and passive (9.6%), or benthic (41.9%) and water column (58.1%) components. Active locomotory behaviors included “power swimmin,” “hovering,” “walking” and “climbing,” while “sinking slowly” was the only passive behavior. The crabs spent nearly 79% of their time in feeding and grooming their exoskeleton and 6.1% interacting with other crabs. The locomotory behaviors of captive red crabs are correlated well with in situ observations where they feed on planktonic organisms in the surface waters during early stages of their life, alternately swimming to the surface and sinking down in the water.

Sexual differences in shell exploitation behavior of the hermit crab Pagurus filholi were investigated in the laboratory. Prior to this study, the size of shells preferred by crabs of a given size was estimated by free-shell choice experiments and was used for the present experiment. Crabs collected from the field were removed from their original shells and put in Littorina brevicula shells smaller or larger than preferred, or in shells with preferred size. Each of crabs was put in an aquarium provided with 100 L. brevicula shells, and, to maintain the motivational state of crabs constant during the experiments, the aperture of each shell was blocked by glass balls to prevent crabs from exchanging shells. We counted the number and size of shells assessed by each crab. Results were that females more frequently assessed shells than males did during the observation time, and were not affected by the difference in size adequacy of their occupying shell. The sizes of shells explored by females were similar to their preferred size, however, males tended to assess shells that were larger than preferred. This sexual difference was not affected by size of their original occupying shells. The female's higher activity in shell exploitation behavior and their better shell size suitability in the field suggested that acquirement of empty shells , for which opportunity is rare in the field, could be an important process for improving their shell size suitability in the field.

The hermit crab Pagurus filholi shows precopulatory guarding behavior in which males drag the shells occupied by ripe females. It bas been suggested by our previous study on male mate choice in this species that males would adopt a mating strategy of pairing with the first ripe female they encounter. If it is true, we would expect random pairing by size in a field population. However, we observed positive size assortative pairing in the actual field population; larger males tended to mate with larger females and smaller males with smaller females. In this study, field observations and laboratory experiments were conducted to examine the following possible causes of the size assortative mating: 1) mate choice, 2) mate availability, and 3) constraints of size and/or weight of possible partners. The results were: 1) no strong preference for larger females was found in males; 2) males often took over females guarded by smaller males; 3) smaller males could not drag larger females and thus did not pair; and 4) larger females often rejected smaller males. These results suggest that the loading constraint of size and/or weight of the partners and female's rejection of pairing with smaller males explain size assortative mating by P. filholi.

Shell fighting, mating and aggressive behavior are reported in five species of intertidal and shallow water hermit crabs found in temperate Japan, viz., Pagurus filholi, P. maculosus, P. minutus, P. gracilipes (Paguridae) and Clibanarius virescens (Diogenidae). Shell fighting behavior was observed in all species. Rapping is the major component in shell fighting, but, unlike some Atlantic pagurid species reported by Hazlett (1966), spasmodic shaking behavior was not observed in the above pagurids except for P. gracilipes. Precopulatory guarding was observed in all five species. Before copulation, the male grasped the female by its minor cheliped in these four pagurids. However, in C. virescens, the male inserted both chelipeds into the shell of the female and maintained a position such that the shells of both were firmly approximated in a face-to-face position. Male-male fighting for a female during precopulatory guarding was observed in these pagurid species but not in C. virescens.

This study describes aspects of the biology of heat shock proteins 90kDa (hsp90) in terrestrial decapods, Coenobita purpureus, C. brevimanus (Anomura: Coenobitidae) and Chiromantes haematocheir (Brachyura: Sesarmidae). These species possess highly developed terrestrial adaptations on both morphological and physiological levels. We have analyzed the pattern of expression for the gene coding hsp90: molecular chaperon in both embryos and the muscle tissues of adults of these species in response to heat stress. While the minimum temperature for initiation of the synthesis of excess of hsp90 mRNA was different between embryos and adults from the different climatic regions, the range of resistance to high temperature shock was nearly the same (6-7℃). Furthermore, the structure of the stress-factor binding domain in hsp90 coding gene showed convergent patterns by possessing a conservative amino acid sequence in decapods experiencing the same annual temperature regimes in the subtropical, temperate and boreal climatic regions.

Male gonopores on most hermit crabs (Paguroidea) occur as circular or oval apertures on the coxae of the fifth pereopods , are flush with the surrounding coxal segment, may be covered by a membrane or a calcified operculum, and are normally associated with numerous complex setae. In many male paguroids of the families Paguridae and Coenobitidae, elongate tubelike extensions called sexual tubes are found on the coxae. The sexual tubes of C. perlatus and C. clypeatus of the Coenobitidae are here investigated at the histological and SEM level for the first time. Coenobita clypeatus has two short, squarish, equal/subequal extensions of the coxae with the densely hirsute gonopore directed ventrally. In contrast, C. perlatus has large, unequal, tubular extensions of the coxae, directed posteriorly, and with the hirsute gonopores terminally on the tubes. The right sexual tube is the longest, and curves across the mid-line of the body. The left sexual tube is much shorter and extends posteriorly from the coxa. In both, the sexual tubes have various coarse setae of several different morphotypes. Histological sectioning reveals a vas deferens terminating at the gonopore, and that sexual tubes are as heavily calcified and muscular as the coxal segments they emanate from. This differs markedly from previously investigated sexual tubes in other paguroids.

In decapod crustaceans, coloration is often useful in taxonomic studies for separating species that are difficult to distinguish by morphological characters but are reproductively isolated. In this paper, color patterns are described for eight pagurid species with sexual tubes; Catapaguroides cristimanus de Saint Laurent, 1968, Turleania senticosa (McLaughlin and Haig, 1996), Catapagurus hirayamai (Asakura, 2001), Catapagurus kosugei (Asakura, 2001), Nematopagurus gardineri Alcock, 1905a, Anapagurus japonicus Ortmann, 1892, Boninpagurus acanthocheles Asakura & Tachikawa, 2004, and Trichopagurus trichophthalmus (Forest, 1954). These patterns are based on color photographs of live animals or specimens in which color patterns were well preserved.

We obtained 47 partial sequences of the mitochondrial 16S rRNA gene for 20 western Atlantic, three amphi-American, and two eastern Pacific species of porcellanids, grouped into eight genera. Neighbor Joining, Maximum Parsimony, Maximum Likelihood, and Bayesian Analysis were the methods used to infer phylogenetic relationships between and within the genera. The family is divided into two main clades, one with Polyonyx and Porcellana, and the other with the remaining six genera treated here. Larval, sperm, and spermatophore morphology largely support this obvious dichotomy. Species of Clastotoechus were grouped closely together, which raises questions regarding the validity of the monotypic genus Madarateuchus recently proposed for Clastotoechus vanderhorsti. Intrageneric divergence in Megalobrachium suggests the possible need for resurrection of Porcellanopsis. Megalobrachium soriatum appears to contain a cryptic species. Neopisosoma is supported as a genus distinct from Pachycheles, which contained two independent lineages. Petrolisthes is resolved into two clades , as supported by previous morphological and molecular evidence. In one clade, Petrolisthes violaceus is closely related to P. tridentatus, P. quadratus, P. lewisi, and P. magdalenensis. The second clade contains three lineages: one with Petrolisthes armatus, P. marginatus, and P. politus as a subclade; another with P. rosariensis as an independent lineage; and lastly the Petrolisthes galathinus-complex, with P. caribensis, P. galathinus (with cryptic species), and Parapetrolisthes tortugensis.

Lithodid crab isheries began before 1900 in Japan and spread across the North Pacific Ocean by 1940. Fisheries targeted red king crab (Paralithodes camtschaticus) with lesser amounts of blue king crab (P. platypus) and brown king crab (P. brevipes). Paralithodes spp., especially red king crabs, have always dominated lithodid fisheries. Golden king crab (Lithodes aequispinus) became important in North Pacific Ocean waters after major declines in red king crab fisheries in the early 1980's. Southern king crab (Lithodes santolla) are fished in southern South America along with softshell red crab (Paralomis granulosa). These five species accounted for more than 89% of lithodid landings for 1984-2003. World lithodid landings peaked at 150,100 metric tons (t) in 1966 after development in pre-World War II Asia and rapid post-1950 expansion in Alaska and Asia. The world lithodid landings fell to 60,540 t in 1973 but rebounded to 104,970 t in 1980, due to abundant eastern Bering Sea red king crab stocks. Eastern Bering Sea and Gulf of Alaska red king crab stocks soon collapsed, and landings fell to a low of 40,920 t in 1983. The world Iithodid landings reached 81,390 t in 1997 with increased Russian landings, but have declined sharply to only 32,610 t. In the 1960's, Russian scientists successfully introduced red king crabs to the Atlantic Ocean and resultant fisheries currently provide 9% of world lithodid landings. Elsewhere , Paralithodes spp. landings trend downward, white other lithodid species are stable or increasing.

Observations on the lithodid crab, Paralomis spinosissima, were taken during the first exploratory crab fishing near South Georgia Island. We examined P. spinosissima from waters near South Georgia Island (4,970 crabs) and from waters near Shag Rocks (190 crabs). Morphometric measurements, reproductive characteristics, incidence of rhizocephalan parasites and the occurrence of microsporidan infections were recorded. Gross examination showed that rhizocephalans infected 15% of the specimens examined, while microsporidans infected 0.5%. Rhizocephalan parasites were hyper-parasitized by an undescribed species of isopod. Morphometrically, rhizocephalan-infected males resembled females, but parasitized and unparasitized females were similar. Examination of females showed that 50% were ovigerous at 62 mm carapace length in both areas, but ovigerous females at South Georgia Island were larger than those at Shag Rocks. Ovigerous females carried embryos in diverse developmental stages, indicating a protracted spawning period, perhaps lasting throughout the year. Chela allometry showed males matured at 75 mm carapace length at South Georgia Island and 66 mm at Shag Rocks. Fecundity estimated from preserved egg clutches ranged from 2,569 to 13,745 eggs per female. Eggs averaged 2.08 mm length and 1.88 mm width, which is considerably larger than that typical shallow water Paralithodes spp. but is smaller than that typical of Lithodes spp.