Systemic infection of freshwater crayfish Cherax quadricarinatus by hymenostome ciliates of the Tetrahymena pyriformis complex

Abstract

A survey of cultured freshwater crayfish Cherax quadricarinatus in north Queensland revealed systemic infections by hymenostome ciliates in moribund crayfish from one location. The ciliates were identified following protargol impregnation as belonging to the Tetrahymena pyriformis species complex on the basis of their somatic and oral ciliature and morphometric characteristics. Live ciliates were observed in the haemal sinuses of the gills browsing on tissue fragments. Histological examination revealed the ciliates to have invaded most organs and tissues, causing extensive necrosis particularly in the hepatopancreas and antennal gland. Lipid reserves were not depleted in the hepatopancreas, suggesting the rapid development of acute disease. This is the first record of systemic ciliate infections in freshwater decapods.