Ecology of hydromedusae from Bombay Harbour - Thana and Bassein Creek estuarine complex

Abstract

Species composition, abundance, seasonal variation and distribution of Hydromedusae were carried out during October 1985 to September 1986. Thirty four species belonging to twenty two genera were recorded from this region. Blackfordia virginica and Phialidium brunescens were found from all stations at least during certain period. The present study shows a general decrease in species diversity in the interior stations which receive large quantities of sewage and industrial effluents and this signifies the sensitive nature of these species. Density of dominant species such as Blackfordia virginica, Eirene ceylonensis, Phialidium brunescens and Eutima commensalis occurring in swarms at times constitute high standing stock. Maximum density was observed at st. 4 which is interior and closer to the industrial estates of Thana District. Abnormalities like occurrence of specimens having 3,5, and 6 radial canals instead of its usual 4 radial canals were observed in Blackfordia virginica and Eutima commensalis were found to be crumbled, distorted and brownish in colour. This indicates the adaptation of these hardy species to the prevailing water quality. Station 5 was found to be very poor in density as well as in species diversity of hydromedusae. This suggestive of the fact that some environmental factor or combination of several factors inhibit the growth and activity of these animals of this area. Ostroumovia inkermanica is a new record to Arbian Sea.