Relative growth of the chelae of the Japanese mitten crab Eriocheir japonica during the juvenile stages was investigated by laboratory rearing. Regression of chela propodus height (CPH) on carapace width (CW) suggested that two growth phases are present in juveniles (CW<40 mm) of both sexes. These two phases are separated by an inflection at approximately 11 mm CW in both sexes. Between the first and second phases, there are significant differences in the slope and Y-intercept of the regression lines for each sex. Significant differences between sexes were not detected for the first phase, but were detected for the second phase. With the addition of data for sub-adult and adult stages a complete growth pattern of E. japonica chela could be estimated. In addition to the first phase three other phases in the males and two phases in females were observed.

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The holotype of Natatolanajaponensis (Richardson, 1904) is redescribed and re-illustrated. New figures of paratype specimens of Natatolana miyamotoi Nunomura, 1991 are also presented. Comparison of the type material of the two nominal taxa indicates that there are no significant differences between them and N. miyamotoi is a junior subjective synonym of N. japonensis. This reduces the number of species of Natatolana recorded from Japan to two, N. japonensis and N. albicaudata (Stebbing, 1900).

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The intertidal ocypodid crab Ilyoplax pusilla builds a mound at the burrow entrance, by piling mud excavated from the burrow or gathered from the nearby surface. Mounds located separate from the burrow entrance were built predominantly by hard carapace males, while mounds adjoining or enclosing burrow entrances were mainly built by ovigerous females and heterosexual pairs. During heavy rain, when surface activity was lowered, the proportion of burrows with a separate mound decreased whereas that of burrows with a mound adjoining the burrow entrance increased. Females with a mound adjoining the burrow entrance showed shorter surface activity, compared with females without a mound. Between males with a separate mound and males without a mound, the duration of surface activity was not different.

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The occurrence of the sandy beach mysids Archaeomysis spp. (Mysidacea) with epibiontic peritrich ciliates (Protozoa) has been studied. Epibiontic peritrich infestations were found on four Archaeomysis species collected from the western North Pacific. This study provided the evidence of existence of a previously undescribed symbiontic association between mysids and epibiontic ciliates. Overall incidence of infestation for Archaeomysis sp., A. kokuboi, A. vulgaris, and A. japonica hosting peritrichs averaged 74.7, 75.6, 22.3, and 1.2%, respectively, with higher incidence in the northern populations for the genus. No mysids carrying peritrichs were found in specimens taken from central to southwestern Japan. Thus, the attached ciliates were considered to have a cold water affinity. Seasonal observations over one year suggested that the mysid-ciliate association in the northern waters of Japan was a year-round phenomenon. The incidence of infested mysids in the harsh zone of sandy beaches was noticeably higher than that in the infralittoral bottoms, suggesting that the habitat of host mysids may be a factor affecting the infestation success of the peritrichs.

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Foregut contents of Eurynolambrus australis from the intertidal zone at Kaikoura, New Zealand, showed that a coralline alga (Corallina officinalis) was the most important dietary component, occurring in 94.6% of the crabs examined (constituting 55.0% of diet). Isopods, amphipods, decapods, as well as red, green and brown algae were also common components of the diet. There were no differences in diet between male and female crabs, or crabs collected from different sites. Ontogenetic differences in diet were observed, with larger crabs consuming more decapods, gastropods, coralline and brown algae, while small and medium-sized crabs consumed more amphipods. Much of the animal component of the diet can be attributed to specialist grazing on a coralline alga which may also be a source of pigments helping to camouflage the crab.

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Population structures and reproductive activities of two intertidal ocypodid crabs, Ilyoplax pingi and I. dentimerosa, were compared at Kanghwa Island, western Korea. Density at abundantly populated area was higher in I. pingi (mean = 238 per m^2) than in I. dentimerosa (159 per m^2). Ovigerous females of I. pingi occurred from May to August, with the peak in August, resembling other temperate ocypodids, whereas females of I. dentimerosa brooded from April to August, with the marked peak in April. Females of both species appear to commence breeding at age of 1 year. Female I. dentimerosa carried eggs of larger size (mean = 0.3753 mm × 0.3543 mm) and smaller number (mean = 1136 eggs) than female I. pingi (0.2869 mm × 0.2725 mm, 2192 eggs). Pair formation of both species was completed by entry of the male and the female into the same burrow; in I. pingi the female usually entered the male's burrow, while the reverse case occurred more often in I. dentimerosa.

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The pea crab Pinnotheres bidentatus Sakai, 1939, previously known only from the type locality of Wakayama, Japan, is recorded for the first time from a coastal area in west central Taiwan. Its swimming ability and color patterns on the dorsal carapace are also noted.

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A new intertidal species of hermit crab, Pagurus nigrofascia, is described and illustrated on the basis of materials from three separate localities in Japan, Hakodate Bay (southern Hokkaido), Amakusa Matsushima (Kyushu), and Wakayama at the mouth of Osaka Bay (Kinki district of Honshu). The new species is compared with P. samuelis (Stimpson, 1857), P. hirsutiusculus (Dana, 1851) and P. venturensis Coffin, 1957, from the west coast of North America, and P. filholi De Man, 1887, from Asian waters. It is suggested that Stimpson's (1858) Eupagurus hirsutiusculus from Hakodate Bay might acutually be this new species. The new species is one of the most common intertidal hermit crabs in Hakodate Bay.

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An ultrastructural investigation of the porcellanid crabs, Aliaporcellana suluensis and Pisidia longicornis reveals that they possess small, spherical to ovoid, pedunculate spermatophores containing a few extremely elongate spermatozoa wound spirally inside the ampulla. In each species the ampulla is divided into two halves which join at a structurally complex, thickened lateral ridge. The spermatozoa of both species have small complex acrosomal vesicles with a perforate operculum and complex, concentric acrosome zonation. Several of these internal acrosome zones are autapomorphic characters for the spermatozoa of the Porcellanidae, when compared with previously studied anomuran spermatozoa. The elongate spermatozoa have a long tail-region composed of a central core of microtubules (autapomorphy) which has a collar of cytoplasm proximally and distally a nuclear sleeve. This central microtubular core splits distally to produce more than four external microtubular arms. The elongate, almost "flagellate", appearance of the spermatozoa of Aliaporcellana and Pisidia is unique for the investigated Decapoda.

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The distribution and reproductive biology of the hermit crab Pagurus nigrofascia Komai, 1996, were studied from March 1992 to May 1995 at Kattoshi, Hakodate Bay, northern Japan. The species was distributed in the upper intertidal zone, mainly at pebble-covered areas on the shoreline. Ovigerous females were observed from April to February. Developmental stages of incubated eggs were synchronized within the population. The appearance of ovigerous females and examination of developmental stages of eggs revealed that the main spawning month was May, females oviposited once a year, and eggs were incubated for about nine months through the hot summer and cold winter. This long incubation period is a striking reproductive characteristic compared with other Pagurus spp., and suggests a wide variety of reproductive features may exist within the same genus Pagurus, even among species living in the same habitat.

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The rate of chromatophore color fading of first zoeae of the amphidromous atyid shrimp Caridina japonica was studied using eight different preservatives (1%, 3%, and 5% formalin, 1%, 3%, and 5% neutral formalin, 50% ethylene glycol, and 2.5% glutaraldehyde) at two different temperature regimes (2℃ and 30℃) giving a total of sixteen trials. The degree of preservation of abdominal chromatophores were periodically observed until 120 days after initial preservation. Differences between temperature regimes were more marked than between preservatives, with 1% formalin at 2℃ being the most effective preservative to minimize pigment loss. Significant differences in the vulnerability of color fading were noted between different chromatophores on the abdomen.

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A new species of freshwater atyid shrimp, Caridina mengaeoides from Hunan Province, China is described and illustrated. Caridina mengaeoides is distinguished from other species of the genus Caridina by the following set of characters: short and slender rostrum, unarmed dorsally; pereiopod shape, spination and segment ratios; shape and spination of the posterior margin of telson; and shape of the endopod of the first male pleopod.

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The larval development of Helice leachi Hess, 1865, consists of five zoeal stages and one megalopal stage. The morphology of all larval stages and the first crab stage is described and illustrated. The morphological characters of the larvae of H. leachi are compared with those of H. japonica and H. tridens. The zoeae of H. leachi are unique among the species of Helice in lacking a lateral carapace spine.

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A predominantly vertical reef face adjacent to the Banda Marine Laboratory of Tokyo University of Fisheries, Chiba Prefecture, Japan, was regularly surveyed for pueruli and juvenile Panulirusjaponicus (Von Siebold) over a 21 month period. The height above the sea bed and the incline of the reef face at which pueruli and juvenile lobsters occurred in holes during the daytime were recorded. The rock face (53.2m^2) ranged in height from 0.9-1.4m above the sea bed, however &ap; 85% was between 1.0-1.1m. Pueruli (postlarvae) and first instar juveniles were distributed non-randomly on the rock face, with near horizontal sections of the reef and areas immediately adjacent to the sand sediment being less favored than more vertical sections of the reef. Small juveniles [8-20mm carapace length (CL)] generally showed similar shelter preferences as pueruli and first instar juveniles. Larger juveniles (20-40mm CL), however, showed a reduced shelter preference in relation to both height above the sea bed and the angle of rock face incline and this appears to be related to limitations in the availability of holes for this size group on the reef face. Most pueruli and first instar juveniles were observed in an inverted (ventral side up) position (91.5%) in holes, this percentage decreased markedly as lobsters grew.

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Aega komai sp. nov. from Japanese waters, is described and figured from the single known specimen. Brief comments are given on the relationship of Aega komai sp. nov. to other species of the genus. The species is characterised by the plate-like expansion of antennule articles 1 and 2, the flattened and expanded antenna article 5, short, truncate and deeply serrate pleotelson, together with deeply serrate uropods, and the presence of a conspicuously large spine of pereopod 3 only.

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Previously, the species Tritodynamia intermedia has been distinguished from T. horvathi based on the number of teeth on the dactylus of the cheliped. However, it was reviewed that T. intermedia is synonymous with T. horvathi. The number of teeth on the chelipeds of T. horvathi with growth was investigated in the laboratory and the field. Crabs from the first to the third stages had two teeth on the proximal section of the dactylus of the cheliped whilst the fifth or later stage crabs had only one tooth at the same site on the cheliped. Both types of chelipeds were observed in the fourth stage crabs. In the natural population, carapace width of crabs with 2 teeth chelipeds were less than 12.3 mm, and that with one tooth chelipeds larger than 5.4 mm. Furthermore, sexual differences in the width of the abdomen occurred at the fourth crab stage.

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Characteristic outgrowths developed from wounded surfaces on the lateral faces of chelipeds of the crayfish Procambarus clarkii. These outgrowths formed as separated projections, fused at the base but branched at the distal end, or projections that were completely fused (without hooks or serrations). Outgrowths were usually a paired projection, with the individual projections developing from the proximal and distal surfaces of the wound, respectively, as mirror images. The two projections fused if the distance between them was small. The variations in the shapes of the outgrowths were due to differences in the frequency of fusion.

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In the western Atlantic Charybdis hellerii was first discovered as an exotic species in the Caribbean Sea (1987 and 1988), northeastern Venezuela (1987) and eastern Florida (1995). The species is now recorded from the southeastern Brazilian coast (Rio de Janeiro). Its occurrence in Brazil and the introduction of seven other exotic marine decapods in Brazil are discussed.

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Temporal size variation of precopulatory guarding males and females of the hermit crab Pagurus middendorffii were described from field data collected during a single breeding season, and the advantage of large size to males competing for mates was examined in a laboratory experiment. Larger males won in mate competition, and size assortative mating occurred in the peak and the late periods of the breeding season, but not in the early period. Both mating male and female sizes declined with time during the breeding period. The decrease in size of mating males with time might be caused by the trade-off between the present and future reproductive success, or by physiological constraints. Decreasing size of breeding females might be due to size-dependent variation in the allocation of reproduction and growth, or to physiological constraints experienced by small females.

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