| Budget Amount *help |
¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1998: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
Paralithodes camtschaticus and P.brevipes (Decapoda : Anomura : Lithodidae : Paralithodes) are commecially important king crabs in the North Pacific Ocean and Okhotsuk Sea. The present study has elucidated, for the first time, that the glaucothoe, metamorphose stage, does not feed. (1) The mouthparts of zoea, glaucothoe and juveniles were compared. The mandibles of the glaucothe, especially the lateral lobes showed reduction in size. The gnathal processes are uncalcified, lacking denticles. The endites and endopods of the maxillae are rudimentally having minute setae. (2) The setae which presented in the foregut of zoea are reduced and the filter press is poorly developed in glaucothoe. The complex gastric mill is absent, which is well developed in the first juvenile. These facts suggest that feeding and food processing are not functional in the glaucothoe.
The newly hatched zoea has lipid reserve in the epithelial cells (resorptive cells) of the midgut gland. Accumulation of lipids is
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observed in the medial portion of the midgut gland with feeding cultured diatom Thalassiosira sp. and Artemia nauplii during all zoea stages. The large lipid droplets obseved in the early glaucothoe disappeared in the late glaucothoe. Small lipid droplets distribute abundantly in the outer margin of the epithelial cells of the midgut gland tables in the late glaucothoe. Fatty acids analysis showed an increase of neutral and polar lipids contents at 41 and 84 ug/dry weight mg for the newly hatched zoea of P.camtschaticus to about 100 and 110 ug/mg at the final zoea and the early glaucothoe. The lipids content decreased to 60 and 80 ug/mg at the mid-stage glaucothoe, 25, 50 ug/mg at the late-stage, and 15.30 ug/mg at the first juvenile Neutral lipids content increased/decreased remarkably compared to polar lipids content. These facts indicate that the lipids are used as energy source during the non-feeding glaucothoe stage. The fat body, which presents in the hemocoel of the puerulus, was not observed in the glaucothoe. This may imply relatively short distance migration in glaucothoe compared to long distance migration in puerulus during coastal recruitment. Less
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