Aspects of the biology of Cryptocaryon irritans, and hyposalinity as a control measure in cultured gilthead sea bream Sparus aurata

Abstract

The life cycle and halotolerance of Cryptocaryon im-tans were studied. Trophontscompleted their growth phase on the host in 3 to 7 d. The reproductive process of the tomonts yieldedtomites as early as 3 and as late as 28 d. Tomite life span was 24 to 48 h. Trophonts embedded in the fishskin withstood 18 h exposure of the host to fresh water. Tomonts withstood salinities ranging from 20 to70 %O for 48 h without losing viability. Tomites were seen emerging only from tomonts kept in constantsalinities ranging from 25 to 50 %o. All tomonts degenerated when immersed in 0 to 10 %O for 3 h.Eradication of the parasite based on these findings was achieved. Four consecutive treatments of 3 heach in 10 %O salinity 3 d apart destroyed all tomonts before tomites could excyst and were welltolerated by the fish. C. imitans life cycle was similarly interrupted by 4 consecutive transfers of fishinto clean tanks at 3 d intervals. A certain degree of resistance to C. irritans invasion was observed infish that had survived several infections.