GYRODACTYLUS GEMINI N-SP (MONOGENEA, GYRODACTYLIDAE), A PARASITE OF SEMAPROCHILODUS-TAENIURUS (STEINDACHNER) FROM THE VENEZUELAN AMAZON

Gyrodactylus gemini n. sp. (Monogenea, Gyrodactylidae) is described fr om the surface of the body and fins of the fish Semaprochilodus taeniu rus (Steindachner) imported into Britain from the Venezuelan Amazon. T he new species differs from other species of the genus, including thos e described from South and Central America, by having: (i) stout hamul i with straight shafts and diverging roots; (ii) marginal hooks with t he sickle length larger than the width; (iii) a dorsal bar without a m edial constriction; (iv) a rectangular ventral bar with short processe s; (v) a triangular ventral bar membrane; and, most obviously, (vi) at least two generations which can develop two embryos simultaneously. T his is the first known species of the genus Gyrodactylus from the Vene zuelan Amazon and the first record of the subgenus Gyrodactylus (Gyrod actylus) from South America.