ヤムシ研究会ワークショップ論文集
日本東方海域における浮遊性ヤムシ類の動物相と分布生態に関するレビュー
2012 年 59 巻 2 号 p. 98-101
詳細
2012 年 59 巻 2 号 p. 98-101
The fauna and the distributional ecology of pelagic chaetognaths in the eastern seas of Japan (Oyashio, Kuroshio regions and Transitional domain) were reviewed. Chaetognaths composed ca. 10％ of the mesozooplankton biomass, and 29 species with 1 form belonging to 14 genera were reported from this region. Species number was lesser in the Oyashio region and neritic Otsuchi Bay (5–9 species), while it was higher in the Kuroshio region and warm core rings (18–22 species). Seasonal changes of dominant species were reported in the Oyashio region, which might be caused by the seasonal fluctuation in intensity of the Oyashio Current. While the chaetognath fauna showed clear geographical changes in the upper 1000 m, fauna below 1000 m was dominated by Eukrohnia fowleri throughout the three regions. The epipelagic species Parasagitta elegans underwent diel vertical migration (DVM) characterized by a nocturnal ascent, while meso- and bathypelagic species had no DVM. For Eukrohnia species, vertical segregation within the genus was evident. The life cycle of P. elegans in the Oyashio region was characterized by distinct seasonality in reproduction and growth, which might be caused by the large seasonal changes of environmental conditions (i.e. temperature and food organism availability) in the Oyashio region. For future studies, three topics should be addressed: firstly; the functional role of chaetognaths in marine ecosystems, secondary; the life cycle of mesopelagic E. hamata/bathypelagica, thirdly; application of the Visual Plankton Recorder (VPR) for evaluation of feeding of by chaetognaths.
