Larvacea

Franco, P., Dahms, H. - U., Lo, W. - T. & Hwang, J. - S., 2017, Pelagic tunicates in the China Seas, Journal of Natural History 51 (15 - 16), pp. 917-936 : 923

Class Larvacea

Representatives of the class Larvacea are eurythermal and euryhaline ( Alldredge 1976). Reproduction of larvaceans commonly increases with a rise in temperature ( Paffenhöfer 1976), and the two most abundant species are known to prefer surface waters for spawning ( Alldredge 1976). Franco et al. (2014) observed that high abundances of larvaceans in the northern Yellow Sea occurring mainly during summer in areas with high Chl-a concentrations, and confirmed that high food concentrations were not limiting for larvaceans which are able to substitute their feeding structure (house). Xu et al. (2006) stated that the variation of appendicularian abundance was closely linked to the ebb and flow of warm currents in the East China Sea. A perusal of literature reveals that the South China Sea is richer in larvacean species (17 species recorded), compared to the East China Sea (five species recorded) and the North Yellow Sea (three species recorded). Li et al. (2010) showed that appendicularian abundance in the north-western part of the South China Sea is affected by Chl- a availability in summer, and that monsoonal winds (a south-west monsoon during summer and a north-east monsoon during winter) play important roles in shaping the distribution of species richness of appendicularians in the same area. There is no previous record of larvaceans in Taiwan, and thus the present study deserves special attention. Four of the species we found ( O. dioica , O. (Coecaria) longicauda , O. (Vexillaria) rufescens and Fritillaria aberrans ) were present at all sampling stations. Oikopleura dioica was always the most abundant species. Two species ( Oikopleura intermedia and Oikopleura fusiformis ) were encountered exclusively in the south-west area, which belongs to the South China Sea. The sampling station in Taitung showed no thaliacean species. Here, larvaceans were present in high abundances. Larvaceans can replace their clogged feeding apparatus, called a ‘house’, when food particles are too dense ( Tiselius et al. 2003). Zeldis et al. showed that Thaliaceans are also filter feeders but their apparatus could be clogged and damaged because of abundant levels of particulate material ( Zeldis et al. 1995). The distribution of thaliaceans during the warm season could be influenced by high-density patches of larvaceans, since both taxa compete for food.