Watchariya Purivirojkul and Prapaisiri Sirikanchana

pp. 745 - 751

Abstract

Two species of bucephalids were found in intestine of Mekong giant catfish (Pangasianodon gigas Chevey) collected from Mekong River, Chiang Khong district, Chiangrai Province. Prosorhynchoides sp.1 is characterised by a rhynchus without tentacle. The tegument covered with spines. The mouth opening is located posteriorly third of body, opening into sac-like intestine. Ovary is pretesticular. Testis is slightly larger than ovary. Prosorhynchoides sp.2 is different from Prosorhynchoides sp.1 in not having spine on the tegument and the presence of two groups of spines adjacent to both sides of the rhynchus; the size of the ovary and testes is almost equal.