Penaeus indicus (Decapoda: Crustacea)

A survey was carried out on the prevalence of bacteria and ciliate protozoan of Pellaells indiclls obtained from Ennore estuary, Chennai (Madras), India from November 1989 to July 1992. The study r~vealed the occurrence of Vibrio parahaemolyticus, V. VUlllijiCUS, V. harvey;, V. allguillarum, V. damsela, Pseudomollas sp., P. aemgillo.\'{/ and a tilamentous bacterium Leucothrix sp. This study also revealed the occurrence of three different peritrichous ciliates viz .. Zoothall/llillll/ sp., Epistylis sp. and Vorticella sp. and a loricate ciliate Lagenophrys sp. ZoothamlliulI1 sp ., Epistylis sp. and Vorticella sp. were recorded on the body surface. gills. appendages and pleopods. Trophonts of ZoothallllliulIl sp. occurred as hranched colonies with contractile stalk with myoneme. Epistylis sp. also consisted of branched colonies but was lacking myoneme. In contrast the Vorticella sp. occurred as individual trophonts with a contractile stalk. Scanning electron microscopy of Epistylis sp. revealed the surface topography, convoluteC: ridges over the trophont surface and stalk. Both Pselldo/llOl1{lS spp. and Vibrio spp. caused darkening of cuticle, loss of appendage setae and their hairs in the pleopods and uropods. blister in the gills and accumulation of hemocytes at the infected sites. Minimum inhibitory concentration of acritlavin . ampicillin, furazolidone, kanamycin and prefuran required to control the growth of Vibrio spp. and Pseudomollas spp. were found to he higher than the recommended limits. Intramuscular inoculation of bacterial cells of Vibrio spp. and PseudoIlUlna.\· spp. into P. indicus caused mortalities from 30% to 80% but drug treatment with neomycin sulphate (20 ~g mr l of culture tank)/ streptomycin (10 ~g mrl of culture tank) reduced the mortality (0% 30%). Drug therapy of P. indiclls infected with peritrichous ciliates revealed that formalin and a tlavonoid tlavone effectively killed the ciliates whereas methylene hili(: was ineffective. The present study revealed that the populations of the prawn P. illdicus suffer from bacterial and epibiont protozoan diseases retlecting the quality of the environment which is polluted with industri al eftluent s and sewage discharge.