Redescription of Houssayela sudobim (Woodland, 1935) (Cestoda: Proteocephalidea), a parasite of Pseudoplatystoma fasciatum (Pisces: Siluriformes) from the River Amazon

The proteocephalidean cestode Houssayela sudobim (Woodland, 1935), the type and only species of Houssayela Rego, 1987, is redescribed on the basis of re-examination of its type-specimens and freshly collected material found in the intestine of the barred sudobim Pseudoplatystoma fasciatum (Siluriformes: Pimelodidae) from the River Amazon in Peru. The validity of the genus is confirmed, but its diagnosis is amended because suckers possess four pairs of cone-shaped (papilla-like) projections on their anterior margins (rather than 16, as reported in the original description), the actual number of testes is more than 400 in a proglottis (not 150 as given by Woodland, 1935) and the vitelline follicles form one dorsolateral medullary band and one lateral cortical band on both sides of proglottides. In addition, the distal (terminal) portion of the vagina has a double sphincter and the cirrus-sac has very thick walls; neither of these characteristics was mentioned in the original description. The specimen collected in Peru represents the first record of the species since its original description in 1935.