Two new species of Tortanus (Atortus), T. (A.) ampliramus and T. (A.) nishidai, are described from the northern Red Sea and the Gulf of Aden, respectively. These new species evidently belong to the recticauda species group in the recticauda species complex. The species group has a distinct distribution in the western Indian Ocean, extending from South Africa. The functional morphology of spermatophores of Tortanus is also discussed. A semelparous reproductive strategy may be employed in some species of Tortanus, whereas others adopt an iteroparous strategy as do most of centropagoideans. The formation of swarms was found exclusively in the subgenus Atortus which inhabits clear waters. Swarms of T. (A.) erabuensis may utilize swarms of another small copepod, Oithona oculata as prey.

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The period during postembryonic development in which the androgenic gland hormone can masculinize female secondary characters was studied, with emphasis on the sexually undifferentiated period, in Armadillidium vulgare. Genetic females were implanted with androgenic glands at various developmental stages to induce masculinization. Instead of injection of androgenic gland extracts, androgenic glands were implanted after treatment with ethanol. Each genetic female received a total of three gland implants at stages 2-8. Masculinization of female endopodites of the first pair of abdominal legs was used to show sensitivity to the androgenic gland hormone. All the female recipients showed at least some masculinization of their endopodites at the first and second molts after receiving the implants regardless of the developmental stages. However, masculinization of their endopodites did not continue at subsequent molts. Only the genetic females, which received implants during the sex differentiation period, had endopodites that had fully developed into male copulatory organs. These results show that the secondary sexual characters of genetic females are sensitive to the androgenic gland hormone not only during the sex differentiation period but also during the sexually undifferentiated period. The effects of the androgenic gland implants on female secondary characters and gonadal development are discussed and an ovary-differentiating factor is hypothesized.

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The body sizes of individuals of the freshwater prawn Macrobrachium nipponense at sexual maturity (1year-old females) were investigated in 23 local populations residing in diverse environments from estuaries to inland fresh waters. The body size of females at maturity was significantly smaller in populations inhabiting fresh waters (37.5 mm in modal body length), owing to the slower growth of individuals, than that found in populations inhabiting brackish-water lakes (57.5 mm) or estuaries (52.5 mm). In the laboratory, however, females from an estuarine population spawned at a body size much smaller (37.5 mm) than observed in nature, and this body size was very close to that observed in freshwater populations under both natural and experimental conditions. The great phenotypic plasticity of body size at maturity in estuarine populations would have played an important role in the colonization, by this species, of inland fresh waters.

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A new species of the pandalid shrimp genus Pandalopsis is reported from the Kuril Islands. Pandalopsis spinosior new species is closely related to P. miyakei Hayashi, 1986, particularly in the rostral formula and the spine arrangement of the ambulatory legs. However, the new species is immediately distinguished from the latter by having the anteriormost spine of the dorsal rostral series (except subapical ones) situated anterior to the antennular peduncle, the pleuron of the fourth abdominal somite with a posteroventral spine and the telson armed with a greater number of dorsolateral spines.

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A range extension to Japanese waters is recorded for three crangonid shrimps: Lissosabinea indica (De Man, 1918) previously only known from the Philippines and Indonesia; Parapontocaris levigata Chace, 1984 known from the Indo-West Pacific up to Taiwan; and Rhynocrangon sharpi (Ortmann, 1895) known from the northern North Pacific including the Far East Russian coast of the Sea of Japan. The first two species are the only members of their genera recorded from Japan. Diagnosis and illustrations are given for L. indica and P. levigata for the species recognition. Rhynocrangon sharpi is fully redescribed and illustrated, because there is no detail description of this species.

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A new alpheid shrimp, Betaeus gelasinifer, is described and illustrated from the Pacific coast of central Honshu, Japan. The new species is characterized by a set of the following characters: the frontal margin of the carapace is moderately indented; the palm of the first pereiopod is relatively deep and usually bears a shallow excavation on the ventral surface; the lateral surface of the palm of the first pereiopod lacks granules, tubercles or setae; the mesial spine at the posterolateral corner of the telson is noticeably elongate; and the endopod of the uropod overreaches the posterior margin of the telson by 0.3 of its length. It represents a second species of the genus from Japanese waters. A brief note on the taxonomy of the genus is provided.

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The male of a species described as Pagurus miyakei Baba, 1986 is described from a specimen collected from deep water off the northeast coast of Taiwan, a new geographical record for this species. Close examination of the gills revealed a quadriserial condition, and the presence of reduced and rudimentary pleurobranchs above the second and third pereopods respectively, requiring the reassignment of this species to the genus Propagurus McLaughlin & de Saint Laurent, 1998.

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The hatchling larval stage of the symmetrical and primitive hermit crab Pomatocheles Jeffreysii Miers, 1879 was obtained under laboratory conditions. This is the first recorded pylochelid larva. It has a mass of yolk granules and the body is covered with a thin embryonic cuticle, showing a prezoea-like appearance. The antennal exopod and mouthparts are reduced, while pereiopods, pleopods and the uropod are already well developed at the time of hatching. These features strongly suggest that the larval development of P. jeffreysii is abbreviated.

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The Japanese species of Pylopaguropsis Alcock, 1905 are reviewed. The genus is rediagnosed, and the gill structure within the genus is discussed. Seven species are recognized, including two species new to science, P, furuset, new species and P. granulata, new species and one species new to the Japanese fauna, P. keijii McLaughlin & Haig, 1989. Taxonomic problems concerning Japanese representative of P. zebra (Henderson, 1893) are discussed. Detailed descriptions and illustrations of the two new species and brief diagnoses and illustrations of the other species are included, together with a key to the Japanese species of Pylopaguropsis.

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Population density and structure of the intertidal mud crab Macrophthalrnus japonicus were compared among five stations in June, August and November 1984. Population density was higher where sediment particles were finer and nitrogen content was higher than at other stations. However, large crabs were more abundant in stations with coarser sediments and lower nitrogen, indicating higher survival rate in these stations. Stations with fine sediments and higher nitrogen had higher percentage of ovigerous females in both June (early breeding season) and August (late breeding season). But in other stations, it was higher only in August. These differences indicate that high food availability may enable large reproductive effort throughout the breeding season, but also may cause high mortality under high population density. In habitats where food availability was high but crab survivorship low, early and large reproductive effort may be advantageous because probability of further reproduction may be very low.

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Daily sand pellet production by the fiddler crab Uca lactea (De Haan, 1935) that lived in cages in the natural habitat was examined for five months in 1971. In 1972 and 1973 a study was done to determine the number of days per month that crabs are active. Females were less active in July and August because they were incubating broods underground. The average number of active days per year was 100.6 for males and 92.5 for females. Using their two chelipeds, females scooped 55-57% more frequently than did males, who have only one cheliped that is useful for sediment feeding. The length of dactyl and width of claw tip of the male cheliped are about 10% larger than those of the female cheliped. The total number of sand pellets produced in one year is estimated to be 34,967 in males and 38,675 in females. Pellets dry weights are 1,011 g in both males and females with the carapace width of 16.0 mm.

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The number of setae on the merus of the first and second maxillipeds of the fiddler crab, Uca lactea (De Haan, 1835), was examined. The whole outer face of the first maxilliped is covered with numerous arrow-headed, slender setae. On the inner side of the second maxillipeds there are two kinds of spoontipped setae; short- and long-stalked. Adjacent to these, plumose setae grow on the proximal region. There were no statistically significant sexual differences in the number of setae on the first and the second maxillipeds by the sex. Also, no differences were found in the length and width of the two maxillipeds by sex. Male and female U. lactea are equipped with mouthparts that have the same size and func tion.

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Several megalopae of the plagusiid crab Plagusia dentipes were collected from Tateyama at the Pacific coast of Japan. The comparison of these specimens with previous descriptions of this stage from Japan, revealed a lack of detail in the earlier morphological accounts. Therefore, the megalopal stage of Plagusia dentipes is redescribed and once again illustrated. The new set of morphological characters for this stage is used for a detailed comparison with other known megalopae of the genus Plagusia. The results allow preliminary conclusions on phylogenetic relationships within this genus of rafting crabs.

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Larval development of the sesarmine crab, Perisesarma bidens (De Haan) was studied in the laboratory at salinities 0-35‰ at 23.5-25.5℃. Larvae survived to first crab stage at salinities between 10 and 35‰. In 0 and 5‰ S larvae died within 12 h after exposure without moulting to the next stage. Total duration required for development to first crab stage was 32, 28, 25, 18, 22 and 30 days at 10, 15, 20, 25, 30 and 35‰ S, respectively. Significant differences (P<0.05) of survival rate were found among the salinities tested. The best survival was recorded between 20 and 30‰S (P<0.05), and 25‰S was found to be optimal for complete larval development of P. bidens.

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Effects of temperatures (9, 13, 17, 20, 23℃) on the production of Acanthomysis mitsukurii were investigated in the laboratory under unlimited food conditions. The intermolt period increased with body length (BL) and decreased with increasing temperature. Growth factor (the percentage increase in BL between successive molts) declined with BL and the rate of the decline increased with temperature increase. Mysids reached zero growth at a smaller size under high temperatures, hence the maximum size was largest at the lowest temperature. Growth models as a discontinuous stepwise process at each experimental temperature were developed using a regression equation between the intermolt period and BL, and between the growth factor and BL, and BL on Day 0. The incubation time of young in the marsupium was significantly related to the temperature but not to the female BL. Although the number of offspring per brood (brood size) was greater at lower temperatures, incubation time was shorter at higher temperatures, resulting in a greater reproduction rate (brood size/incubation time) at the higher temperatures. There were no differences in the productivity parameters between 20℃ and 23℃ and because the survival rate of juvenile mysids to maturation was lower at 23℃ than at 20℃, the optimal temperature for population production of this species was concluded to be approximately 20℃.

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