Four new species of Acanthobothrium (Cestoda : Tetraphyllidea) from the whiptail stingray Dasyatis brevis in the Gulf of California, Mexico

Examination of the spiral intestines of 29 whiptail stingrays, Dasyatis bre vis, from 6 sites in the Gulf of California, Mexico in 1993 and 1996 result ed in the discovery of 4 new species of Acanthobothrium: Acanthobothrium bu llardi, Acanthobothrium dasi, Acanthobothrium rajivi, and Acanthobothrium s oberoni. This brings the total number of species of Acanthobothrium known f rom the eastern Pacific Ocean to 34. With 22 additional species reported fr om elasmobranchs from the western Atlantic Ocean, and over 100 species glob ally, the number of interspecific comparisons required to justify the desig nation of a new species is rather unwieldy. To facilitate these and future comparisons, and in the absence of a phylogenetic hypothesis for this genus , the 56 species of Acanthobothrium from these 2 geographic regions were ca tegorized for 4 characters: total length (less than or equal to or >15 mm), number of segments (less than or equal to or >50 segments), number of test es (less than or equal to or >80), and symmetry of poral and aporal ovarian lobes. These 56 taxa and their categories are presented in tabular form. B ased on these characters, A. bullardi, A. dasi, and A. rajivi are category 2 species (they are relatively small, possess few segments, relatively few testes, and exhibit asymmetrical ovaries): A. soberoni is a category 6 spec ies tit is a relatively longer worm with a larger number of segments, but w ith fewer testes and an asymmetrical ovary). All 4 species differ from 1 an other and from species in other geographic regions in further subtleties of these 4 characters as well as hook size and relative length of hook prongs , cirrus sac size, genital pore position, number of columns of testes anter ior to the cirrus sac, and number of postvaginal testes. Five specimens tha t appear to represent a new species of Acanthobothroides were also collecte d. This species is figured and some details of the morphology are described , but the material was considered to be insufficient to allow for formal de scription of this species at this time. This is the first record of either of these genera of onchobothriid tapeworms from the Gulf of California.