ASCOCOTYLE (A) NUNEZAE N-SP (DIGENEA, HETEROPHYIDAE) FROM YUCATAN, MEXICO

A new heterophyid species, Ascocotyle (Ascocotyle) nunezae n. sp., is described from adults found in the intestine of naturally infected her on, Casmerodius albus (type host), from the coastal lagoon of Celestun , Yucatan, Mexico, and a domestic chick (Gallus gallus), experimentall y infected with metacercariae from Cichlasoma octofasciatum. The new s pecies is characterized mainly by the number (32-37) and arrangement o f circumoral spines, which form 1 complete row of 25-27 circumoral spi nes and 6-10 accessory spines on the dorsal side, and by the morpholog y of the ventrogenital sac with a large gonotyl, consisting of 2 indis tinctly separated lobes of vesicular tissue. Ascocotyle (A.) nunezae i s placed into the nominotypical subgenus Ascocotyle because of the pre sence of uterine loops at the pharyngeal region and position of vitell ine follicles. However, it differs distinctly from other members of th is subgenus by the presence of long intestinal ceca reaching posterior to the ventral sucker. Cichlids of the genus Cichlasoma from cenotes, lakes, and the river Rio Hondo in the Yucatan Peninsula were natural second intermediate hosts of A. (A.) nunezae, with metacercariae encys ted on their gills. Cichlasoma meeki (Brind) was the most heavily infe cted fish host (total prevalence 75%; mean intensity 11 +/- 9).