No abstract

In order to evaluate genetic differentiation among three color variants (red, green and black) of Japanese sea cucumber, Stichopus japonicus, 11 isozyme loci were used as genetic markers for 448 individuals collected from four localities around Japan. Significant differences of allele frequencies were observed between all pairs of color types sympatrically. Average genetic distances at seven loci between the three sympatric color types were 0.0173 between the red and the other color types, and 0.0015 between the green and the black types. A dendrogram drawn from genetic distances among the three color types across all four localities showed two distinct clusters comprising all the red types and all the green and the black types, respectively. These results indicated that the red type showed definite genetic differentiation from the other color types.

The genetic relationship among the three color variants (Red, Green, and Black) of the Japanese sea cucumber, S. japonicus, was investigated using 11 microsatellite markers. Genetic differentiation testing among the three sympatric color types showed the strong heterogeneity of Red (p<0.001), while no significant difference was observed between Green and Black (p=0.301 to 0.961). UPGMA trees constructed from 10 sample lots from 5 localities showed two distinct clusters, one from the Red types and the other from the Green and Black types. In addition, the sympatric Green and Black formed one subcluster with strong bootstrap support at each locality. These results indicate the separate species status of Red and the other color types, and also support the population identity of sympatric Green and Black.

We examined the phylogeography of the common Japanese intertidal goby Chaenogobius annularis using the mitochondrial cytochrome b gene, the NADH dehydrogenase subunit 2 gene, and the surrounding transfer RNA from 195 specimens collected in 27 localities around the Japanese Archipelago and the Korean Peninsula, and reconstructed the historical processes of its current distribution. In total, 169 unique haplotypes were obtained, and phylogenetic trees showed 2 genetically distinct lineages: the Pacific Ocean and the Sea of Japan lineages, whose divergence was estimated to have occurred in the early Pleistocene, related to the paleoenvironmental history of the Sea of Japan. After the divergence, the Sea of Japan lineage rapidly attained its current distribution, whereas the present-day distribution of the Pacific Ocean lineage was formed as a result of vicariance and dispersal.

The present study was undertaken to determine scallop vitellogenin (Vtg) cDNA sequence, to identify Vtg synthesizing cell, and to analyze the regulation of Vtg mRNA expression. Clones containing partial cDNA sequence of Vtg were isolated from cDNA library of the scallop ovary by immunoscreening with the anti-scallop vitellin (Vn) serum. The deduced amino acid sequence of the clone containing the longest cDNA insert (1,689 bp) was identified as a member of the lipid transport protein family and exhibited about 20-35% identity with Vtgs of other oviparous animals. Northern blot analysis identified a single transcript longer than 10 kb in the ovary. Dot blot analysis of the ovary showed a high amount of Vtg mRNA during the growing stage and the level was retained until spawning stage. In situ hybridization demonstrated the expression of Vtg mRNA in the auxiliary cells closely associated with growing oocytes, suggesting that the synthesis of a major yolk protein in the scallop occurs through hetero-synthetic pathway without mediation through the blood flow but occurs de novo in the ovary. The content of Vtg mRNA in the ovarian tissue cultured in vitro with vitellogenesis promoting factor (VPF), which strongly promotes Vtg protein synthesis, from the cerebral plus pedal ganglion (CPG) showed no change. The transcription of Vtg mRNA appeared to be promoted by estradiol-17beta (E2) not by VPF although VPF may enhance the translation of Vtg mRNA.