Since the early 1970s, many artificial reefs (ARs) have been deployed in Japanese coastal waters to create fisheries grounds. Recently, researchers began to use environmental DNA (eDNA) methods for biodiversity monitoring of aquatic species. A metabarcoding approach using internal standard DNAs [i.e., quantitative MiSeq sequencing (qMiSeq)] makes it possible to monitor eDNA concentrations of multiple species simultaneously. This method can improve the efficiency of monitoring AR effects on fishes. Our study investigated distributions of marine fishes at ARs and surrounding stations in the open oceanographic environment of Tateyama Bay, central Japan, using qMiSeq and echo sounder survey. Using the qMiSeq with 12S primers, we found higher quantities of fish eDNAs at the ARs than at surrounding stations and different fish species compositions between them. Comparisons with echo sounder survey also showed positive correlations between fish eDNA concentration and echo intensity, which indicated a highly localized signal of eDNA at each sampling station. These results suggest that qMiSeq is a promising technique to complement conventional methods to monitor distributions of multiple fish species.

p. 748, caption for Fig. 1; "Fig. 1. Current systems in the upper layer of Japanese and its neighboring waters (from Kawai, 1991), with notes on geographical distributions of ..." should be read as "Fig. 1. Current system in the western North Pacific in summer (Aug., 1933), originally prepared by Uda (1935), and adapted from Kawai (1972, Fig. 3.2, Forklike currents without confluence), with notes on geographical distributions of ...

No abstract

For pearl culture, the pearl oyster is forced open and a nucleus is implanted into the gonad with a mantle graft. The outer mantle epithelial cells of the implanted mantle graft elongate and surrounding the nucleus a pearl sac is formed. Shell matrix proteins secreted by the pearl sac play an important role in the regulation of pearl formation. Recently, seven shell matrix proteins were identified from the pearl oyster Pinctada fucata. However, there is a paucity of information on the function of these proteins and their gene expression patterns. Our study aims to elucidate the relationship between pearl type, quality, and gene expression patterns of six shell matrix proteins (msi60, n16, nacrein, msi31, prismalin-14, and aspein) in the pearl sac based on real-time PCR analysis. After culturing for about 2 months, the pearl sac tissues were collected from 22 individuals: 12 with high quality (HP), nine with low quality (LP), and one with organic (ORG) pearl formation. The surface of each of the 12 HP pearls was composed only of a nacreous layer; in contrast, that of the nine LP pearls was composed of nacreous and prismatic layers. The six target gene expressions were detected in all individuals. However, delta threshold cycle (ΔC(T)) for msi31 was significantly higher in the HP than in the LP individuals (Mann-Whitney's U test, p=0.02). This means that the relative expression level of msi31, which constitutes the framework of the prismatic layer, was higher in the LP than in the HP individuals.

The present study was undertaken in waters south of the Kuroshio Subgyre to examine and/or test Sekiguchi’s (1985, 1997) hypothesis about the larval recruitment processes of Panulirus japonicus by which the benthic populations of the species are maintained in Japanese waters. A total of 61 Panulirus phyllosoma larvae were collected in early summer; 56 belonged to P. japonicus, of which 30 were in the final stage, 24 in the subfinal stage, and 2 were too heavily damaged to permit identification of the stage. Most of the final-stage phyllosoma larvae were found in the northern part of the waters east of the Ryukyu Archipelago, whereas the larvae in the subfinal stage were found in the southern part. The present study supports Sekiguchi’s hypothesis that late-stage P. japonicus phyllosoma larvae are transported by the Kuroshio Countercurrent into waters east of the archipelago and then again enter the Kuroshio Current.