Ophiotaenia gilberti sp. n. (Eucestoda: proteocephalidea), a parasite of Thamnodynastes pallidus (Serpentes: Colubridae) from Paraguay

Ophiotaenia gilberti sp.n. (Eucestoda: Proteocephalidea), a parasite of Thamnodynastes pallidus (Serpentes: Colubridae) from Paraguay.-Ophiotaenia gilberti sp.n. is described from the intestine of the colubrid snake, Thamnodynastes pallidus (Linnaeus, 1758) (Serpentes: Xenodontinae), from Paraguay.The new species differs from most species of New World members of Ophiotaenia in possessing an apical organ.It differs from the six species possessing an apical organ by a smaller scolex diameter (140-145 versus more than 480) and by a smaller number of testes (57-91 versus more than 107).In all Ophiotaenia with two separate testes fields parasites of New World snakes, the ovary is small, occupying a surface five times smaller (in relation to the proglottis surface) than in most Proteocephalus parasites of Palaearctic fishes.This new character may become important in Proteocephalidea systematics.Because of the presence of two separate testicular field, preformed uterus and smaller ovary surface/proglottis surface ratio, we transfer the following Proteocephalus species parasite of snakes to Ophiotaenia: Proteocephalus arandasi Santos & Rolas, 1973 becomes Ophiotaenia arandasi new combination; P. azevedoi de Chambrier & Vaucher, 1992 becomes O. azevedoi new combination; P catzeflisi de Chambrier & Vaucher, 1992 becomes O. catzeflisi new combination; P. euzeti de Chambrier & Vaucher, 1992 becomes O. euzeti new combination; P. joanae de Chambrier & Paulino, 1997 becomes O. joanae new combination; P. micruricola Shoop & Corkum, 1982 becomes O. micruricola new combination and P. variabilis Brooks, 1978 becomes O. variabilis new combination.