Abstract: Jelly-like substances secreted by a lysaretid polychaete, the“ akamushi” Halla okudai, while handling and feeding on prey were shown to have paralytic and digestive activities, and the active factors were partially purified and characterized. An extract of the handling-phase jelly exhibited a paralytic activity against Japanese killifish as well as short-necked clams. Only the supernatant after precipitation of the extract with 75% saturated ammonium sulfate retained this property. Gel filtration of the supernatant produced two active fractions of 14-68 kDa and less than 0.9 kDa, respectively. Anion exchange chromatography of the higher-molecular-weight active fraction produced nine protein peaks, of which only the third, not adsorbed to the anion exchange column, exhibited the activity. The molecular weight of this fraction was shown to be 62 or 54 kDa by SDS-PAGE. On the other hand, an extract of the feeding-phase jelly showed a protein-digestive activity. The precipitate of this extract with 50% saturated ammonium sulfate also had this property, and it exerted an activity even at 4°, but not after heating at 56° for 30 minutes. These results suggest that the jelly-like substance produced while handling prey contains components with a paralytic activity that provides for efficient handling of the prey, while that produced while feeding contains digestive enzymes for quick ingestion of the prey.

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Abstract: Differences in shell preference and utilization patterns among sympatric species of hermit crabs and between males and females of Pagurus lanuginosus were investigated. The shell utilization pattern of P. lanuginosus differed from those of three other species. While P. middendorffii and P. filholi crabs of≤3mm in shield length frequently occupied shells of Reticunassa fraterculus, comparably-sized P. lanuginosus did not. Most P. lanuginosus occupied shells of Chlorostoma lischkei and Homalopoma sangarense. The order of shell species preference was similar in both males and females of P. lanuginosus of>3mm in shield length; slight sexual differences were found in the shell preferences of smaller crabs. In shell size preference experiments, the relationships between crab size and size of chosen shell were similar between sexes for each shell species tested. The similarity in shell-size and-species preference and utilization patterns between males and females might be due to weak sexual selection for male body size.

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Abstract: Newly obtained material from Tokyo Bay, central Japan, enables a redescription of the poorly known upogebiid mud shrimp Upogebia imperfecta Sakai, 1982, which has been represented only by the holotype from the Yellow Sea, China. Remarkable sexual dimorphism of the rostral armament and morphology of the first pereopod is found in this species. The present material extends the known geographical range of the species to the Pacific coast of central Japan. A brief note on the taxonomy of Japanese Upogebiidae is provided.

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Abstract: Recently, most populations of amphioxus in Japan, consisting of the species Branchiostoma belcheri Gray, have been thought to be in decline or already disappeared, because there have been few collection records in their known habitats. In the offing of Koajiro Bay and Moroiso Bay at Misaki on the Miura Peninsula in Kanagawa Prefecture, amphioxi were again found in 1996 almost twenty years after their last collection. Three juveniles settled in the bottom of Moroiso Bay were collected by dredging in November 1996, and swimming larvae were collected by towing a plankton net in October 1996 and September 1997. The sediment condition in the offing of Misaki was analyzed on the basis of dredge samples and observed using an underwater video camera. These investigations suggest that many habitats of amphioxus still exist along the Japanese coasts.

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Abstract: We studied the functional interaction between hermit crabs' preferences for gastropod shells based on shell size and species. The effect of decreasing shell size suitability on the shell species preferences of males, non-ovigerous females, and ovigerous females of the hermit crab Pagurus filholi was determined for several shell species. Crabs that inhabited ideal-size shells of less preferred species were offered shells from preferred species that were not of ideal size. In every case, shell species preference changed with changing shell size suitability, and preferences for shells larger and smaller than the ideal differed among males, non-ovigerous females, and ovigerous females. The different shell selection strategies noted between the sexes may reflect the relative importance of the demands for their fitness components from the aspects of reproduction and growth.

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