SYSTEMIC INFECTION OF FRESH-WATER CRAYFISH CHERAX-QUADRICARINATUS BY HYMENOSTOME CILIATES OF THE TETRAHYMENA-PYRIFORMIS COMPLEX

A survey of cultured freshwater crayfish Cherax quadricarinatus in nor th Queensland revealed systemic infections by hymenostome ciliates in moribund crayfish from one location. The ciliates were identified foll owing protargol impregnation as belonging to the Tetrahymena pyriformi s species complex on the basis of their somatic and oral ciliature and morphometric characteristics. Live ciliates were observed in the haem al sinuses of the gills browsing on tissue fragments. Histological exa mination revealed the ciliates to have invaded most organs and tissues , causing extensive necrosis particularly in the hepatopancreas and an tennal gland. Lipid reserves were not depleted in the hepatopancreas, suggesting the rapid development of acute disease. This is the first r ecord of systemic ciliate infections in freshwater decapods.