Masatsune Takeda

A NATURAL HYBRID MUD CRAB (DECAPODA, PORTUNIDAE) FROM JAPAN

Abstract A presumed hybrid mud crab of the genus Scylla was examined. The presumed hybrid could not be easily separated morphologically from the three Japanese Scylla species, S. serrata, S. paramamosain, and S. olivacea. An analysis of the first internal transcribed spacer (ITS-1) of the nuclear DNA revealed that the hybrid carried genomic DNA from both S. serrata and S. olivacea. Analysis of the maternally inherited 16S rDNA of the mitochondrial DNA demonstrated that the presumed hybrid carried S. olivacea mtDNA. Based on these results, we conclude that the examined animal is indeed the hybrid offspring of a female S. olivacea and a male S. serrata. The degree of genetic isolation among these species, and the possible causes of hybridization are discussed.

Pair formation in Spongicola japonica (Crustacea : Stenopodidea : Spongicolidae), a shrimp associated with deep-sea hexactinellid sponges

The population structure of the deep-sea sponge-associated shrimp Spongicola japonica was investigated, and the mechanism of pair formation analysed from field samples. The composition pattern of shrimp in host sponges was divided into three patterns by sex and number as follows: solitary, a solitary inhabitant; sexually paired, a pair with a male and a female; grouped, multiple individuals excluding those designated as sexually paired. Juveniles usually remained grouped or solitary in a host cavity until the size at which gonadal maturity starts. Before forming sexual pairs, shrimp appear to have a free-living period outside the host, when the ovarian stages of females correspond to early to late vitellogenesis. Re-invasion is just before the first spawning, when females are in the ovarian stage of late vitellogenesis.

Skeletal growth of the deep-sea hexactinellid sponge Euplectella oweni , and host selection by the symbiotic shrimp Spongicola japonica (Crustacea: Decapoda: Spongicolidae)

Aspects of the skeletal growth of the deep-sea hexactinellid sponge Euplectella oweni Herklots and Marshall, and host size and type selection by the symbiotic shrimp Spongicola japonica Kubo were investigated using field-collected material. Two phases, flexible and stiff, were observed in the framework of the sponges. In the flexible sponges, the circular, longitudinal and oblique systems of the skeletal beams that constitute the principal framework were not fused to each other, and the parietal ledges running circularly, or sometimes obliquely, on the wall were not developed. The skeletal wall was fragile in texture, readily torn by any external force. The wall was much sturdier in the stiff sponges, in which the systems of the skeletal beams were coarse, fused to each other to make the principal framework tough in texture, and pareital ledges developed so as to reinforce the sponge wall. The flexible phase is mainly seen in smaller and younger sponges, while the stiff phase was seen in the larger (or dead) ones. Almost all the solitary and young pairs of shrimps were collected from flexible sponges.

ABBREVIATED LARVAL DEVELOPMENT OF A FRESH-WATER PRAWN, MACROBRACHIUM NIPHANAE SHOKITA AND TAKEDA (DECAPODA: PALAEMONIDAE), FROM THAILAND

The abbreviated larval development of a fresh-water prawn from Thailand, Macrobrachium niphanae Shokita and Takeda, is described and illustrated in detail. Two zoeal, 1 megalopal, and 2 juvenile stages are distinguished, and their characteristics are compared with those of related species which have an abbreviated larval life.

Hermit crabs (Crustacea: Decapoda: Anomura: Paguroidea) from submarine caves in the Ryukyu Islands, south-western Japan

Hermit crabs collected from submarine caves in the Ryukyu Islands, south-western Japan, were represented by one species of the Diogenidae and six species of the Paguridae, including two new species of Catapaguroides A. Milne-Edwards and Bouvier, 1892. Two new species named Catapaguroides iejimensis and C. kasei are described and illustrated in detail. These taxa appear most closely allied to C. foresti McLaughlin, 2002a, in the shape of carpus and chela of the right cheliped and completely unarmed left chela. However, C. iejimensis is immediately distinguished from C. foresti and C. kasei by having slightly dilated and semisphere-shaped corneas of the ocular peduncles (in the latter two species, reduced and cone-shaped corneas) and two or three spines proximally on the dorsal surface of the palm of the right cheliped (in the latter two species, unarmed on the dorsal surface of the right palm). Catapaguroides kasei closely resembles C. foresti, but differs from the latter in the length of the carpus of the left cheliped. This unusual species has tapering ocular peduncles with reduced and cone-shaped corneas, very long antennular peduncles, and antennal flagella with numerous long, simple setae; these characters are presumed to be adaptations for the dark and oligotrophic environment of submarine caves. Paguristes jalur Morgan, 1992 is redescribed in order to supplement the original description. Intraspecific morphological variations in Pagurixus nomurai Komai and Asakura, 1995 and Catapagurus tuberculosus (Asakura, 1999) are noted.

A new xanthid crab (Decapoda, Brachyura) from a submarine cave in the Philippines

A new species of the family Xanthidae, Gaillardiellus holthuisi , is described based on a single male from a submarine cave in Cebu, the Philippines. Gaillardiellus holthuisi sp. nov. differs from its congeners in having thickened and peculiarly curved cheliped fingers, with each immovable finger armed with a large triangular tooth. The specimen examined is preserved in the collection of National Museum of Nature and Science, Tokyo (NSMT). The size of the specimen is indicated by cb (breadth of carapace) and cl (length of carapace). Keywords: Gaillardiellus holthuisi ; NSMT; Philippines; submarine cave; Xanthidae

Two new species of the genus Heteronucia (Crustacea: Decapoda: Brachyura: Leucosiidae) from Japan

ABSTRACT Two new species of leucosiid crabs, Heteronucia toyoshioae and H. granulata, are described from the offshore banks of the Ryukyu Islands in southern Japan and the Izu Islands in central Japan. Heteronucia toyoshioae may be distinguished from all the known species of Heteronucia Alcock, 1896 by having seven tubercles on the carapace, a median triangular tooth on the sixth segment of the male abdomen, and the shape of the male first pleopod. Heteronucia granulata is similar to H. globata Sakai, 1963 and H. perlata (Sakai, 1963) from East Asia but can be distinguished by the presence of a small tubercle on the pterygostomian margin, a ridged row of granules on the branchial region, and a triangular tubercle on the posterolateral margin of the carapace.

On Merocryptoides, a Leucosiid Crab Genus (Crustacea: Decapoda: Brachyura) Endemic to Japan, with Description of Two New Species

Abstract The taxonomy of the leucosiid crab genus Merocryptoides Sakai, 1963 is revised, and two new species, M. ohtsukai and M. peteri are described from Japan. These new species resemble the type species of the genus, M. frontalis Sakai, 1963 from Japan, but can be distinguished from it by the form of the cardiac tubercle, male abdomen, male telson and first male pleopods. Merocryptoides ohtsukai is also distinguished from M. peteri by the broadly V-shaped ridge on the gastric tubercle, the lateral margin of the hepatic region not ridged and the form of the median tooth of the epibranchial margin.

Pilumnus Planus Edmondson and Leptodius Leptodon Forest & Guinot as Synonyms of Forestia Depressa (White) and Leptodius Davaoensis Ward (Decapoda, Brachyura)

organic material. This material may have been a mixture of sediment and semidigested tissue or detritus. The ingestion of sediment, detritus and associated bacteria has been demonstrated to be important to the nutrition of some crusta ceans (Fenchel & Jorgensen, 1977; Moriarty, 1976; Rieper, 1978). Marukawa (1933) suggests that the megalopa of king crab feed on detritus and bryozoans in the Bering Sea. In Cook Inlet, post-larval king crab ingest substantial quan tities of detritus and some bryozoans, but the crab are also capable of capturing ostracods and harpacticoid copepods. The ability of post-larval king crab to utilize detritus or bacteria as food needs to be investigated. Acknowledgements. ? This study was supported under contract # 03-5-022-56 between the University of Alaska and NOAA, Department of Commerce through the Outer Continental Shelf Environmental Assessment Program to which funds were provided by the Bureau of Land Management, Department of Interior. This work is Contribution No. 392 from the Institute of Marine Science, University of Alaska. Specimens were collected by the Alaska Department of Fish and Game and Marine/Coastal Habitat Management Group.