Ultrastructure of the primary gill lamellae of Scomber australasicus infected by a didymozoid parasite

Abstract

Didymozoid parasites occupy the space between the basal lamina of the primary epithelium and the efferent artery of the primary gill lamellae. The response of the host, slimy mackerel, consists mainly in the formation of (1) a capsule around the worms; (2) a layer of columnar epithelia1 cells; (3) electron-dense filamentous bands around the nucleus of the ep~thelial cells of the capsule; and (4) additional chloride cells in the capsule. Additionally, subepithelial cells degenerate and amoeboid cells occur in the lumen of the capsule in response to didymozoan infection.