Abstract
Investigations on some biological aspects of the two species of sanguinicolid trematodes, viz. Paradeontacylix grandispinus and P. kampachi, infecting the vascular system of cultured amberjack, Seriola dumerili were conducted. In a survey of 50 naturally infected fish, P. grandispinus was the dominant of the two species. P. grandispinus mostly infected the afferent branchial arteries, while nearly half of P. kampachi infected the sinus venosus and heart. Eggs were first found in the gill filaments in November, about four 'months after introduction of amberjack seedlings to culture site. Egg numbers tended to increase until March (average egg number per gill filament : 452), and decreased toward July. Cercarial invasion to amberjack, determined by transferring fish from an endemic area to an infection-free site at different times of year, started sometime in September, suggesting that the two species of blood flukes matured about two months after invasion to fish.
