A NEW SPECIES OF ACANTHOBOTHRIUM VANBENEDEN, 1849 (EUCESTODA, TETRAPHYLLIDEA, ONCHOBOTHRIIDAE) IN DASYATIS-LONGUS GARMAN (CHONDRICHTHYES, MYLIOBATIFORMES, DASYATIDIDAE) FROM CHAMELA-BAY, JALISCO, MEXICO

A new species of Acanthobothrium in Dasyatis longus from Chamela Bay, Jalisco, Mexico, is a member of a presumed clade of species diagnosed by being anapolytic or nearly so, having more than 100 testes per prog lottis, with immature and mature proglottides wider than long to squar e, aspinose scolex, muscular bothridia fused to the scolex at their po sterior ends, H- to V-shaped ovaries, relatively short symmetrical to asymmetrical ovarian arms that extend anteriorly to, or nearly to, the cirrus sac, and vitellaria arranged in fields rather than a single ro w of follicles. The new species most closely resembles Acanthobothrium terezae from the freshwater stingray Potamotrygon motoro in the follo wing characters: bothridial hooks longer than 200 mu m with inner hook s having bent asymmetrical prongs, an average of 130-140 testes per pr oglottis, and shallow genital atria located posterior to midline of pr oglottis. The new species differs from A. terezae by having outer hook s approximately the same size and shape as the inner hooks, inner hook s averaging 230 mu m rather than 313 mu m in total length, and cirrus sacs averaging 255 mu m rather than 450 mu m in length. The new specie s is unique among all described species of Acanthobothrium by having a cleft in the posterior margin of each apical bothridial pad. The appa rent close relationship of the new species to one inhabiting a Neotrop ical freshwater stingray provides support for the hypothesized Pacific marine ancestry of Neotropical freshwater stingrays and raises the po ssibility that the Neotropical freshwater stingrays may not be monophy letic.