Study On Endoparasite Perkinsns Sp. In The Manila Clams Ruditapes Philippinarum In China

Abstract: Perkinsus is one of the most harmful protozoan parasites for mollusk in the world. The Manila clam Ruditapes philippinarum is a very commercially cultured bivalve at the coast in China, and its endoparasite Perkinsus sp had been researched following. (1) Mass morality of the clams in the coast of northern Yellow sea in China happened on July to November 2000, number of Perkinsus were isolated from the infected clams, and they were confirmed to be responsible for the disease by infected experiment at laboratory; (2) Perkinsus trophozoites predominantly focused in the clam connective tissue, and frequently found in gill, mantle and digested gland, less in adductor muscle and efferent siphon, no found in podium. The epithelium was shrunk, necrotic and decomposed in heavily infected clam tissue; (3) Perkinsus sp. was detected in clams at 21 sites investigated along the coast of Bohai sea, Yellow sea and East sea in China from 2000 to 2003, and the results indicated the mostly clams were heavily infected by Perkinsus sp.(4) Seasonal changes in the infection intensity of Perkinsus were investigated in the clams colleted from Donggang, Shichengdao and Lingsuiqiao on the coast of northern Yellow sea in China from Oct 2000 to Oct 2001, the seasonal variations of Perkinsus prevalence and infected intensity in the three localities were not quite obvious, but a slightly tendency was found that was heavily infection in the autumn and spring, but less heavily in the winter and summer;(5)The Perkinsus sp. infected clams experiment of warm water over nature temperature at laboratory were conducted, the results indicated that the clams' Perkinsus sp prevalence in all of warm water was significant higher than nature, and could resulted in high mortality following summer with the obvious warm winter effect, the temperature at 20℃and salinity from 20 to 24 were proved to be optimum for Perkinsus sp prevalence in the clams;(6) Perkinsus sp infection of the clamcould increase the clam energy expenditure and decrease energy income level;(7)The Perkinsus sp was proved to be the species of P. olseni(P.atlanticus) by rRNA genes sequence measured and analysis;(8)Commercial medium 1:2DME:Ham's F12 adapted well to propagation in vitro of Perkinsus sp in the clams;(9) An indirect enzyme-linked immunosorbent assay (iELISA) for rapid diagnosis of Perkinsus sp in the clams had been developed, and could sharply shorten time detected the mass samples. This study firstly reported the disease of endoparasites Perkinsus in the Manila clams at the coast in China, the results of the pathogen epidemic, detection and host-parasite interaction and so on, were also useful to research the other pathogens of mollusk on the coast in China.