Red drum Sciaenops ocellatus (Sciaenidae), a recent introduction to Mediterranean mariculture, is susceptible to Myxidium leei (Myxosporea)

Red drum Sciaenops ocellatus is a new fish species farmed in Mediterranean and Red Sea mariculture facilities in Israel. The success of this introduced species in Israel will undoubtedly encourage expansion of red drum farming also to other Mediterranean countries. In the present study, red drum was shown to be susceptible to myxidiosis, a serious disease of cultured sparids. The responsible agent, Myxidium leei, has been causing increasing economical losses to cultured sea bream Sparus aurata throughout the Mediterranean basin. Red drum of mean weight 69.7 g (range 23-117 g) were cohabited with infected sea bream or exposed to water effluent discharged from the same fish. Forty three days after initial exposure, trophozoites, sporoblasts and spores identified as M. leei were found developing in the posterior gut of 45.8% and 35.0% of the test fish in the respective treatments. The early stages of infection and parasite development in the gut mucosa epithelium of red drum were similar to those previously observed in sea bream. M. leei has a low degree of host specificity and should be regarded a potential threat not only to members of the Sparidae, but also to other warmwater cultured fish species in the Mediterranean. Although fish stocks from Mediterranean waters have been introduced into the Caribbean, M. leei has hitherto not been reported from North America. It is advisable to exercise extreme caution with future Mediterranean introductions so as to prevent accidental transemination of this myxosporean into the US Gulf Coast states, in which red drum is a commonly farmed species, as there is presently no available treatment for myxidiosis.