The complete larval development of the Botan shrimp, Pandalus nipponensis Yokoya, 1933, is described and illustrated based on laboratoryreared material. Four larval stages (stage 1-4) and two postlarval stages (stages 5, 6) were recognized. The larvae started to feed on Artemia nauplii from stage 2. Starved larvae survived until stage 3. According to Gore's (1985) classification of the developmental types of decapods, the development of P. nipponensis is of an advanced and lecithotrophic type.

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The complete larval development of the poisonous crab Atergatis floridus (Linnaeus, 1767) is described and illustrated, based on laboratoryreared material. The larval development consists of four zoeal and one megalopal stage. The morphological characters of the larvae ofA. floridus are compared with those of Zosimus and Lophozozymus species, and generic diagnostic larval characters are identified.

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Parabetaeus culliereti Coutiere, 1896, the type species of the genus Parabetaeus Coutiere, 1896, is redescribed and illustrated based on recently collected specimens from southern Japan and Papua New Guinea, and the taxonomic status of the genus Parabetaeus Coutiere is clarified. Parabetaeus culliereti appears to exhibit large variation in the development of the rostrum and orbital teeth. This type of variation has not been previously reported in the family Alpheidae. As a result, the genus Neoalpheopsis Banner, 1953 is synonymized with Parabetaeus, and a new combination, Parabetaeus euryone (De Man, 1910) is proposed. Differences between P. culliereti and P. euryone are also discussed.

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The shell use pattern between sexes of Pagurus filholi was described, at Kattoshi, northern Japan. Line transect sampling showed that the shells available to P. filholi in this area were mainly composed of four species, Reticunassa fraterculus, Homalopoma sangarense, Batillaria cumingi and Littorina brevicula. The former three shell species were used by small crabs, and the pattern of shell use significantly differed between sexes. Almost all large crabs of either sex used Littorina brevicula shell. The abundance of empty shells was about 10% of total hermit abundance. Shell size suitability of crabs decreased as crab size increased, suggesting that shell limitation was more severe in large-sized crabs than in small ones. However, this trend differed between sexes. Males used unsuitable-sized shell relative to similar-sized females in Reticunassa and Homalopoma species. The population sex ratio was biased towards females, and showed an anomalous pattern as a function of crab size that was initially from male bias to female bias with increasing size, but was biased towards males again with a further increase in size. Sexual differences in shell preference, competitive ability and growth rate were discussed as causal explanations for the present pattern.

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A new shallow-water mysid, Heteromysoides simplex, is reported from submarine caves of Okinawa, southwestern Japan. The new species is distinguished from all the known species of the genus by a sharp process on the eyes, a distally truncated subtriangular telson with three pairs of lateral spines, and the third thoracic endopod with a simple, not subchelate, termination. A key to the world species of Heteromysoides is provided.

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Annual reproductive cycle of the helmet crab Telmessus cheiragonus was investigated based on the histological observations of the ovary and the gonadosomatic indices (GSI = ovarian weight x 100 / body weight). The ovarian maturity was divided into five phases (Phase I-V). Minimum mature size of female was 36.0 mm in carapace length. The annual reproductive cycle in the adult females (more than 36.0 mm carapace length) consisted of the incubating period (October-March) and the maturing period (April-September). During the incubating period, the ovarian maturity was Phase I-II (mean GSI±SD = 3.8±4.7 %) when most of the females were ovigerous. During the maturing period, the ovarian maturity increased to Phase V (GSI ≤ 21.6 %) when the females seemed to be frequently copulating, because the soft shell adult females, which could copulate, occurred with highest frequency. The spawning of most females seemed to occur at the end of the maturing period. These results suggest that the ovarian maturation cycle requires one year, and during the incubation period ovaries are immature.

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One of the three syntypes of Pagurus lepidochirus (Doflein, 1902) was reexamined. This female syntype was found to possess paired first pleopods modified as gonopods, broadly separated ocular acicles and subequal chelipeds, suggesting reassignment of this species to either the genus Nematopagurus A. Milne-Edwards & Bouvier, 1892, or to Ceratopagurus Yokoya, 1933. Study of supplemental material has revealed the presence of a long, filamentous right sexual tube in males, requiring reassignment of this species to Nematopagurus,_ Further comparisons have shown that Doflein's taxon is identical with a species reported from Japanese waters as N. squamichelis Alcock, 1905. Nematopagurus lepidochirus is redescribed and illustrated in detail on the basis of the lectotype, herein selected, and supplemental material. Differences between this species and other closely allied taxa, including the true N. squamichelis, are discussed.

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The purpose of this series of papers is to clarify the identity of each Calcinus species from Japan and adjacent waters and to establish a descriptive catalogue of the species. There has been much and serious taxonomic confusion and misidentifications in the literature. This report considers Calcinus pulcher Forest and C. lineapropodus Morgan & Forest. Since the original as well as subsequent descriptions of C. pulcher have been brief and insufficient, a detailed redescription and illustrations are provided. Confusion between C. pulcher and C. anani is clarified. Calcinus lineapropodus, a species very closely related to C. pulcher, and a taxonomic enigma in Japanese literature, is redescribed in detail. Minor but reliable morphological distinctions between C. pulcher and C. lineapropodus are provided. Mouthparts of the two species are described for the first time.

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The complete larval development of Galathea inflata Potts, 1915, a symbiont of comatulid crinoids, is described and illustrated from laboratoryreared material. The zoeas of G. inflata are easily distinguished from those of G. rostrata and G. intermedia by an abdomen, including a telson, that is covered with very minute spines in all zoeal stages, a rostrum that bears lateral teeth in the second to fifth zoeal stages, and by the setations of the maxillule and first and second maxillipeds. This species had five zoeal stages and one megalopal stage. However, the fifth zoeal stage may be abnormal because it possesses a mixture of zoeal and megalopal characters. It is suggested that the fourth stage zoeas possibly molt directly to the megalopa under favorable conditions.

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We performed short-term cultivation of alive interna fragments of Sacculina polygenea Liitzen & Takahashi, 1997 isolated from the organism of its host, the coastal crab Hemigrapsus sanguineus (De Haan) and studied the histology of parasitic interna and their relationships with the gut and gonads of the host. It is shown that the colonial interna of S. polygenea comprises an extensive trophic system (roots and trunks) and a reproductive system represented by numerous primordia of externae at different stages of development. We observed asexual reproduction (blastogenesis) in the interna beginning with the development of numerous nuclei, dense aggregations of non-differentiated embryonic cells surrounded by a simple epithelium; later on each nucleus develops a primordium of a trophic module. An ovary with paired colleteric glands, paired male receptacles, and mantle with inner cavity and mantle opening arise in the anlagen of externae prior to their emerging to body surface of the crab, i.e., in the interna. The process of oogenesis begins in the primordium of the ovary; in late primordial externae we have found vitellogenic oocytes. Cells performing functions of ingestion, treatment, and accumulation of nutrients are located in the distal parts (rootlets) of the trophic system; the cells filled with nutrients then release the latter into root lumen, where the nutrients are conveyed toward the primordia and, later on, adult externae. Thus, we have visualized the colonial structure of S. polygenea interim comprising numerous elements of reproductive and trophic systems.

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Uroptychus japonicus Ortmann, 1892 and Munidopsis taurulus Ortmann, 1892, both known only from Japan, are redescribed based upon the type material, now in the collection of the Musee Zoologique, Strasbourg. Munidopsis hastifer Benedict, 1902, another species known only by the type material from Japan, is synonymized with M. taurulus.

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Examination of the morphology and distribution of setae of Pugettia quadridens quadridens, using SEM and stereomicroscopy reveals two types of setae (hooked and simple) distributed in different areas on the dorsal surface of the carapace. Hooked setae bear regularly arranged oblique striae with both spinules and a median groove along the inner curve. These setae are loosely arranged in double rows along the rostrum, in the orbital region, and at the anterolateral border of the carapace. Simple setae are not curved and are found in the gastric, mesobranchial and intestinal regions of the carapace. The distribution of hooked setae on the carapace varies considerably according to crab size and sex. They are more widely distributed on the dorsal carapace of smaller crabs than on larger ones, and on females compared to males. These spider crabs can be classified into four types based on setal distribution pattern.

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Based on material collected from shallow hydrothermal vent fields in Kagoshima Bay, southern Japan, a new species of the sub family Pontoniinae, Periclimenes thermohydrophilus, is described and illustrated. A combination of several characters distinguishes the present new species from all other members of this genus. A short and narrow rostrum without basal crest, an isolated epigastric spine, a submarginal antennal spine and a long carpus of the second pereopod are characteristics of the new species. The relationship between this shrimp and host tube worms is briefly discussed.

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