Diphyllidean cestodes of the Gulf of California, Mexico with descriptions of two new species of Echinobothrium (Cestoda : Diphyllidea)

As part of a survey of parasites of elasmobranchs in the Gulf of California , a second and final report of the diphyllidean cestodes resulting from the survey is presented. Of 43 species of elasmobranchs examined for parasites , 7 (Rhinobatos productus, Rhinobatos leucorhynchus, Myliobatis californicu s, Myliobatis longirostris, Urobatis halleri, Urobatis maculatus, and Rhino ptera steindachneri) were found to host diphyllidean cestodes, all belongin g to Echinobothrium. No species of either of the other 2 diphyllidean gener a, Ditrachybothridium or Macrobothridium, were discovered. A greater divers ity of diphyllideans was found in 1996 than in 1993. Two new species, Echin obothrium hoffmanorum n. sp. and Echinobothrium rayallemangi n. sp. are des cribed from the spiral intestines of U. maculatus and R. leucorhynchus, res pectively. Echinobothrium hoffmanorum is unique in its possession of the fo llowing combination of characters: 19-21 apical hooks in each dorsoventral group, 12-22 lateral hooklets in each group, 10-17 cephalic peduncle spines per column, 4-8 testes, 4-10 segments and eggs with a single filament. Ech inobothrium rayallemangi is unique in its possession of the following combi nation of characters: 23 apical hooks in each dorsoventral group, 20-23 lat eral hooklets in each group, 2-5 cephalic peduncle spines per column, 4-6 t estes, and 4-6 segments. These 2 new species, together with Echinobothrium mexicanum and Echinobothrium fautleyae, brings the total number of diphylli deans known from the Gulf of California to 4. The survey of diphyllidean ce stodes of the Gulf of California has resulted in a new host record for Echi nobothrium for each of the host species mentioned above, with Rhinobatos an d Urobatis representing new host genera and Urolophidae a new host family f or Echinobothrium.