THE POPULATION DYNAMICS OF MYXOSPOREAN PARASITES IN POND-REARED ALLOGYNOGENETIC GIBEL CARP, CARASSIUS GIBELIO

Myxosporean species are one of the major parasite pathogens that hinder the allogynogenetic gibel carp aquaculture. The epidemiologic survey of the myxosporean species in allogynogenetic gibel carp should help with the control of myxosporidiosis. We found 4 types of myxosporean species Henneguya doneci, Myxobolus hearti, M. ampullicapsulatus, and H. sp. during the investigation of the myxosporean-infected pond-reared allogynogenetic gibel carp in Honghu city of Hubei province. The infection rate of gill-infecting H. doneci varied significantly in different months (P 0.05). The plasmodia of H. doneci were absent from April to June. But its infection rate increased dramatically from July and reached to the peak in September, and then gradually decreased from October to March of the following year. The mean abundance of the plasmodia of H. doneci showed a similar trend and also varied remarkably in different months (P 0.05). The mean diameter of the plasmodia of H. doneci gradually increased from July to December, and then decreased in January of the following year. The differences in the mean diameter between months were statistically significant (P 0.05). Moreover, the mean infection intensity of the H. doneci plasmodia on the fourth gill bar was apparently higher than that on the other gill bars. The plasmodia of gill-infecting species, M. ampullicapsulatus, were present only from March to June, and its infection rate gradually increased to its peak value in June. The plasmodia of heart-infecting species, M. hearti, were present in the entire year, but its infection rate was not significantly different between months (P 0.05). Henneguya sp. was found to infect the urinary bladder of fish in the whole year except for August, and its infection rate was relatively higher from January to April.