The present paper comprises a systematic survey of helminths from 202 red groupers, Epinephelus morio (Valenciennes) (Pisces: Serranidae), the most important commercial marine fish in the region, collected from ten localities off the Yucatan Peninsula in the Gulf of Mexico during 1994-1996; two more helminth species were recorded from E. morio earlier. Thirty species of helminths were found: Monogenea 1, Cestoda 3, Trematoda 17, Nematoda 8, Acanthocephala 1. Of them, 15 species were adults, whereas 15 species were larval stages parasitizing piscivorous elasmobranch and teleostean fishes, birds and marine mammals as adults. A new didymozoid trematode, Allonematohnlhrium yucatanense sp. n., is described from the fins of this host. Most findings represent new host- and geographical records. Philometra margolisi, a nematode parasitizing the gonads, is undoubtedly the most important parasite affecting the reproduction of the host, endangering E. morio in aquaculture. Larval anisakid nematodes (Anisakis, Pseudoterranova, Hysterothylacium) recorded from the red grouper in the region of the southern Gulf of Mexico are important from the viewpoint of public health.
A new monogcncan species, Pseudorhabdosynochus capurroi sp. n., is described from the gills of the black grouper, Mycteroperca bonaci (Poey) (Serranidae), from the Yucatan Peninsula, Mexico. The new species can be differentiated from all other known species of Pseudorhabdosynochus Yamaguti, 1958 by being the largest one recorded until now (1162-1535 pm body length). Moreover, the vagina of P. capurroi has a small funnel-shaped opening with a non sclerotized vesicle from which a fine sclerotized duct leads proximally to a sclerotized seminal receptacle, and the testis is bilobate. The squamodiscs have 14 to 16 rows of rods, of which 3 to 5 rows are closed.
Pseudarhahdttsynachus yucatanensis sp. n. (Diplectanidae) is described from the gills of the red grouper, Epinephelus maria (Valenciennes, 1824) (Serranidae), from the coast of the Yucatan Peninsula, Mexico. This new species is characterized by having both the ventral and the dorsal squamodiscs composed of 10-12 rows of rods, with 0-1 innermost row forming a closed circle. Furthermore, the vagina of P. yucatanensis has a non-sclerotized ampulla with a fine, sclerotized duct leading to a sclerot-ized seminal receptacle. Prevalence (percentage of infected fish) and abundance (mean number of worms per examined fish) were estimated for P. yucatanensis from 8 localities along the coast of Yucatan. Prevalence varies from 38% to 100%, while abundance was between 1.2 ± 0.6 and 43.2 ± 17.8 worms per ftsh. The lack of linear relationship between the host length and the number of monogcneans per fish (regression F, = 0.56. p = 0.45) was probably due to the fact that the sample was restricted to juvenile hosts.
Sciadicleithrum meekii sp. n. is described from the gills of the cichlid fish Cichlasoma meeki (Brind) from cenotes (= sinkholes) of the Yucatan Peninsula, Mcxico.The new species differs from congeners by having a dorsal hamuli with a prominent superficial root articulated with a straight shaft and curved point, and a vagina with a coiled tube comprised of one ring.