Pelagic tunicates in the China Seas

Abstract

The biogeography of pelagic tunicates belonging to the two taxonomic classes Larvacea and Thaliacea was analysed using seven sampling stations along the coastal regions of Taiwan which contribute to all the China Seas surrounding Taiwan. The collected data were then compared with the information in the available literature about pelagic tunicate species diversity in the China Seas (Bohai Sea, North Yellow Sea, East China Sea and South China Sea) and previous studies on these organisms in Taiwan waters to get a better understanding of their biodiversity, abundance and distribution. A total of 19 species of pelagic tunicates were observed and identified to the speciel level: five species belonging to the class Larvacea, in the two families Oikopleuriidae and Fritillariidae; 14 species belonging to the class Thaliacea, in the families Salpidae and Doliolidae. We summarised morphological characteristics of the recorded species which were found to be useful for identification, and we provided further information about their global distribution and ecological preferences. Our results revealed that pelagic tunicates occurred in the China Seas with high species richness throughout the year. This is the first account on the class Larvacea from Taiwan. Comparing our results with available records from all China Seas, Taiwan proved to be a species diversity hotspot for pelagic tunicates, especially for the family Salpidae. The waters of southern Taiwan showed a higher species richness compared to the northern counterpart. The doliolid Doliolum denticulatum can be designated as an indicator of the low-temperature China Coastal Current species.