BIOLOGY OF CRASSICUTIS-CICHLASOMAE, A PARASITE OF CICHLID FISHES IN MEXICO AND CENTRAL-AMERICA

Field study on the biology of Crassicutis cichlasomae Manter, 1936 (Di genea: Homalometridae) was carried out in a small swamp in a limestone factory near Merida, Yucatan, Mexico. Aquatic snails, Littorina (Litt oridinopsis) angulifera, harbouring C. cichlasomae rediae, cercariae a nd metacercariae, served both as the first and second intermediate hos ts. Feeding experiments confirmed the conspecificity of metacercariae from naturally infected snails with adults from naturally infected fis h. Gravid C. cichlasomae worms were obtained from experimentally infec ted fish 19 days post exposure at 22-24 degrees C. Examination of fish from the swamp in Mitza and other localities in the Yucatan Peninsula showed that the cichlids Cichlasoma urophthalmus and C, meeki were de finitive hosts of C. cichlasomae. There was no pronounced preference o f C. cichlasomae adults for the site of their location in the intestin e of the definitive host; a slightly higher proportion (41%) of worms was only found in the anterior third of the gut. The time of miracidiu m development varied from 18.5 to 27.5 days; different temperature (20 .1-35.7 degrees C) or light/darkness regimes influenced only slightly the rate of embryonic development, with shorter development times at h igher temperature (34.8-35.7 degrees C) and constant darkness and/or l ight. With the exception of the sporocyst, all developmental stages ar e described and figured.