The first five variable microsatellite DNA loci for mangrove crab, Scylla paramanosain, were developed. Allelic variation and other characteristics at these loci were examined in this species captured at the Urado Bay, Japan. The number of alleles per locus ranged from 24 to 44. The expected heterozygosity across loci ranged from 0.900 to 0.999 and probability of identity (PI) ranged from 2.8 × 10−3 to 1.7 × 10−2. Therefore, these microsatellite markers could be useful for estimating effect of stock enhancement release and population genetic structure of mangrove crab.

Two sympatric forms ( I and II ) of the estuarine grapsid crab Hemigrapsus penicillatus from the Nanakita River (Sendai, Japan) were detected by starch gel electrophoresis. Form I consists of individuals possessing the allele 6PgdB, while Form II has the allele 6PgdC. Heterozygote individuals (genotype of B/C ) were not observed at the 6Pgd locus. Form I is also characterized by the alleles Aat-2C and PgmA, while Form II has the alleles Aat-2B and PgmB. Morphological analysis revealed that the patch of soft hairs on the male chela in Form II individuals is much larger than that in Form I . The above results suggest that the two sympatric forms are reproductively isolated and represent sibling species.

We described the relationship between the mass mortality of megalops and the morphogenesis of zoeas in the seed production of the swimming crab Portunus trituberculatus. The survival rate of larvae from the last (fourth) zoeal stage to theˆrst crab stage was lower than that from theˆrst to fourth zoeal stage. Survival rate tended to decrease with increasing frequency of abnormal molting during the metamorphosis to megalops. The relationship between the frequency of abnormal molting and the relative chela length to carapace length in the fourth zoeal stage showed a signiˆcant positive correlation. Thus, it was revealed that the morphologically advanced fourth stage zoeas were unable to undergo normal metamorphosis to megalops and larval mass mortality occurred.