Two new species of Yorkeria (Tetraphyllidea: Onchobothriidae) from Chiloscyllium punctatum (Elasmobranchii: Hemiscylliidae) in Thailand.

Two new species of the tapeworm genus Yorkeria are described from the spiral intestine of a specimen of the Brownbanded bambooshark, Chiloscyllium punctatum, collected from a fish market in Bangsarai, Thailand in 1996. The larger of the 2 new tapeworm species, Y. hilli, possesses fewer proglottids, fewer testes, and is smaller than most of its congeners. The smaller of the 2 new species, Y. kelleyae, conspicuously differs from all of its congeners in its possession of medial hooks that are only slightly larger than the lateral hooks (rather than conspicuously larger). Scanning electron microscopy shows both species to possess elongate filitriches on their distal prehook locular surfaces and elongate filitrichs and spinitrichs on their proximal bothridial, distal posthook locular surfaces, pedicels, and cephalic peduncles. In both species, the spinitrichs on the proximal bothridial surfaces, pedicels, and peduncles are very large and readily visible with light microscopy. Whereas the spinitrichs on these 4 surfaces are bluntly rounded in Y. hilli, they are pointed in Y. kelleyae. Examination of specimens identified as Y. parva, collected by several previous workers from a diversity of hosts and localities, calls into question the conspecificity of at least some of this material. The unusual scolex form suggests that the configuration of the cerebral ganglionic mass in species of Yorkeria may differ from that seen in most other tetraphyllidean taxa.