CRYPTOCARYON IRRITANS (CILIOPHORA) - PRIMARY INFECTION IN THICK-LIPPED MULLET, CHELON LABROSUS (RISSO)

Cryptocaryon irritans (Ciliophora), isolated from the reef fish, Gramm istes sexlineatus Thumberg, was established as primary infections in m ullet, Chelon labrosus (Risso). Only a small percentage (<22%) of expo sed theronts established infection under controlled conditions. This i s discussed in relation to the probability of host parasite contact an d susceptibility. There was no evidence of density-dependent or intra- specific competition in trophont establishment, a strong linear relati onship being found between the levels of exposure and infection. Infec tion intensity was assessed in relation to host survival, indicating a 90% probability of host death following levels of >200 trophonts per gram of host. A close temporal association between host death and trop hont exit was found, possibly as a result of epidermal disruption lead ing to dysfunction of osmoregulatory and respiratory systems.