Short Term in vitro Culture of Cryptocaryon irritans, a Protozoan Parasite of Marine Fishes

Abstract

Attempts were made to cultivate Cryptocaryon irritans in vitro at 23-25°C. Attachment of theronts and subsequent enlargement into trophonts were achieved in two experiments using strips of trypticase soy agar (TSA, supplemented with 3% NaCl) as an attachment substrate in filtered seawater. In the third experiment, transformation of theronts into trophonts was achieved in an enriched liquid medium composed of 50% filtered seawater, 30% Leibovitz L-15 and 20% fetal calf serum without attachment onto the TSA. Sizes (mean ±SD) of the trophonts, 114.6 ± 57.9 μm to 295.9 ± 130 μm, were from a recorded size range (50 to 700μm) of the parasite in vivo. Although only limited numbers of theronts (0.28-1.71%) transformed into trophonts, these results showed that the in vitro culture of C. irritans is potentially feasible as evidenced by the enlargement of the trophonts within the in vivo size range using either a solid medium as an attachment substrate or a liquid medium without attachment. There is a need, however, to determine essential factors that influence the transformation of the trophonts into viable tomonts capable of producing theronts.