Metamicrocotyla macracantha, a polyopisthocotylid gill parasite of the striped mullet, Mugil cephalus: population dynamics in South Carolina estuaries.

In the estuarine system of South Carolina (USA), the striped mullet, Mugil cephalus, was found to be parasitized by the polyopisthocotylid monogenean Metamicrocotyla macracantha among other gill parasites. Mullet of various ages were collected monthly for 1 year from oligohaline, mesohaline, polyhaline, and euryhaline localities. The population dynamics of M. macracantha was analyzed according to time of year, different salinity levels, and host age and sex. Out of the 770 mullet studied, 11.2% were infected (mean, two worms per host). Neither prevalence nor mean intensity was correlated with biotic factors. However, significant seasonal variation in prevalence was observed, and the worm was found more frequently in higher salinities. Mean intensity, however, did not change significantly with time of year or salinity. This is the first published report of M. macracantha in the South Carolina estuarine system and represents the northernmost record for this parasite. Furthermore, the lack of common egg-bearing individuals and juveniles indicated that this area is likely the northern limit of the geographical range of M. macracantha, whose life cycle seems restricted to more constant water temperatures than those found at the South Carolina latitudes.