Population Biology And Internal Structure Of The Unionicola In A.woodiana Woodiana

Population dynamics of the water mite U. ypsilophora and U. arcuata was investigated in freshwater bivalve A.woodiana woodiana during the period from August 2006 to July 2007 in Nanchang. A pattern of seasonal variation was observed, with prevalence and abundance of U. ypsilophora and U. arcuata peaked in May and Jun, respectively. The number of mites in individual host was significantly correlated with the size, but not with the sex, of bivalves. The U. ypsilophora and U. arcuata have a site preference for mantles and gill of the host, respectively. Analysis for interspecific association indicated that it was obviously negative association between U. ypsilophora and U. arcuata; it was possible that they were parasitic on different positions or the ecological niches isolated.The phototactic behavior of U. ypsilophora, U. arcuata and U. penicillatus were studied by artificial equipment. The phototactic index, which had been detected under the conditions of different light intensity and varied colour light, was considered as an important performance in phototactic behavior research .The result indicated that there was significant difference in all of three species mites (P<0.05). In all light intensity excluded 700 Lux, there were extremely significant difference (P<0.01). For U. ypsilophora, with the increase of light intensity, the phototactic index increased; U. penicillatus the phototactic index reached the max value on the 1000 Lux; while U. arcuata performanced differently with the former two species, which showed positive phototactic on 700Lux while performanced negative phototactic under otherelse ones. However, U. arcuata showed positive phototaxis in red, blue and yellow light, which become more sensitive under red light than blue and yellow. U. penicillatus holded positive phototaxis only, while under other colour light becomes negative phototaxis. U. ypsilophora performanced positive phototaxis under red light only.The digestive system and gonad of adult U. arcuata are described from serial paraffin sections. The alimentary canal consists of pharynx, stomach, mesenteron, colon and rectum. There were no obvious wall cells in alimentary tract. The gonad of female U. arcuata contains outer membrane and inner epithelium; the gonad of male U. arcuata abounds with spermatophores which were surrounded by hemocytes.