Temporal and spatial distribution of Thaliacea of the Urochordata around Hormuz Island, the Persian Gulf

Abstract

The class Thaliacea belongs to Urochordata which branched from phylum chordata. Thaliacea have three orders: Doliolida (Cyclomyaria), Pyrosomatida and Salpida (Desmomyaria) and all are considered marine plankton, holoplankton and microphages. These animals feed by filtering water through their body. The aim of this research was to identify and study the ecological processes of the tunicates in coastal waters of the Hormuz Island in the Persian Gulf. We sampled water in an annual basis, starting from July 2007 and terminating in May 2008. Periodic sampling (Every 40 days) was applied and the use of plankton net with mesh size 300µm made it possible to collect plankton samples from four localities (south, north, east, west) of the Island each having two stations, one in the vicinity of the coastal waters and another away at about 2.5 miles. We found 4 species of Thaliacea: Doliolum denticulatum, Doliolum nationalis, Thalia democratica, Salpa cylindrica. In addition, we observed a life stage of Doliolum. The highest frequency was observed in May and in the south station. There was significant correlation between abundance of Doliolum denticulatum and its late oozoid or old nurse; and between Thalia democratica and Doliolum denticulatum.