Echinobothrium notoguidoi n. sp. (Cestoda: Diphyllidea) from Mustelus schmitti (Chondrichthyes: Carcharhiniformes) in the Argentine Sea.

A new cestode, Echinobothrium notoguidoi n. sp., is described from the spiral intestine of the shark Mustelus schmitti, from coastal waters off Mar del Plata, Argentina. This species is distinguished from all others in the genus by a rostellar armature consisting of 2 apical groups of 31 large hooks each, arranged in 2 rows (16 anterior, 15 posterior) with 13 hooklets per side, a wide corona of 8-11 rows of spines posterior to the rostellum, 8 rows of 24-26 spines on the cephalic peduncle, and 11-15 testes per proglottid. The new species most closely resembles 2 congeners that also parasitize sharks, Echinobothrium musteli and Echinobothrium scoliodoni, on the basis of the armature of the rostellum and cephalic peduncle and the presence of a corona of small spines. Echinobothrium notoguidoi can be differentiated from E. musteli by the number of hooklets (3) and testes (22), and from E. scoliodoni by the number of large hooks (10-13), spines on the cephalic peduncle (> 100), and segments (40-50). Echinobothrium notoguidoi is clearly distinguished from Echinobothrium pigmentatum described previously from Zapteryx brevirostris in Argentine waters by the following combination of characters: corona of hooks lacking, possession of fewer apical hooks (20), hooklets in a continuous row instead of separate groups, fewer spines in the cephalic peduncle (9-13 per row), and fewer testes (5-7) per proglottid.