BOTHRIOCEPHALUS-PEARSEI N-SP (CESTODA, PSEUDOPHYLLIDEA) FROM CENOTE FISHES OF THE YUCATAN PENINSULA, MEXICO

The cestode Bothriocephalus pearsei n. sp. is described from the intes tine of the cichlid Cichlasoma urophthalmus (Gunther) from cenote (=si nkhole) Zaci near Valladolid, Yucatan, Mexico. The pimelodid catfish R hamdia guatemalensis Gunther, which also harbored conspecific cestodes , seems to represent accidental or postcyclic host of B. pearsei. The new species differs from congeners mainly by the morphology of the sco lex, which is clavate, with the maximum width in its middle part, has a distinct but weakly muscular apical disc, 2 short and wide bothria d istinctly demarcated in their anterior part, becoming indistinct poste riorly in the middle part of the scolex, and 2 elongate, lateral groov es. In addition to the scolex morphology, the new species can be diffe rentiated from Bothriocephalus species parasitizing North American fre shwater fishes as follows: B. claviceps (Goeze, 1782), a specific para site of eels in the Holarctic, B. cuspidatus Cooper, 1917, occurring m ostly in perciform fishes in North America, B. musculosus Baer, 1937 f ound in the cichlid Cichlasoma biocellata (Regan) (=C. octofasciatum ( Regan)), and B. texomensis Self, 1954, described from Hiodon alosoides (Rafinesque), are much larger, with strobilae consisting of relativel y short and very wide proglottids versus small-sized strobila (length 26-32 mm) composed of about 70 proglottids, which are only slightly wi der than they are long (ratio 1:1-3), rectangular, or even longer than wide in the last proglottids in B. pearsei. Bothriocephalus formosus Mueller and Van Cleave, 1932, described from Percopsis omiscomaycus (W albaum) in the USA, can be distinguished from B. pearsei, besides the different shape of the scolex, by the distribution of vitelline follic les, which are not separated into 2 lateral fields and are present alo ng the midline of proglottids in the former species. Bothriocephalus a cheilognathi, a widely distributed parasite of fishes of many families , in particular of cyprinids, distinctly differs from B. pearsei by it s arrow- or heart-shaped scolex, larger strobila, and vitelline follic les scattered along the midline of proglottids in the former taxon. Bo thriocephalus pearsei is also typified by its fish hosts, which are bo th of Neotropical origin, and by its geographical distribution limited to isolated deep-lying cenotes of inferior Yucatan.