This paper comprises a systematic survey of larval nematodes collected from fishes from cenotes (= sinkholes) of the Peninsula of Yucatan, southern Mexico, in 1993-1994. Larvae of the following nine species were recorded: Physocephalus sexa-lalus, Acuariidae gen. sp., Spiroxys sp., Falcausira sp., Hysterothylacium cenotae, Contracaecum sp. Type 1, Contracaecum sp. Type 2, Goezia sp., and Eustrongylides sp. Larvae of P. sexalatus are recorded from fishes (Rhamdia guatemalensis) for the first time. The larvae are briefly described and illustrated and problems concerning their morphology, taxonomy, hosts and geographical distribution are discussed. Adults of these larvae are parasitic in piscivorous fishes, reptiles, birds and mammals (definitive hosts). Fishes harbouring the larvae of these parasites serve as paratenic hosts, being mostly an important source of infection for the definitive hosts.
The present paper comprises a systematic survey of adult nematodes collected from fishes from cenotes (= sinkholes) of the Peninsula of Yucatan, southeastern Mexico, in 1993-1994. Examinations of a total of 533 fishes (17 species) originating from 39 cenotes from the Mexican states of Yucatan and Quintana Roo revealed the presence of the following nine nematode species: Rhabdochona (Rhabdochona) kidderi, Procamallanus (Spirocamallanus) rebecae, P. (S.) neacaballeroi, Philome-trnides caudata, Hysterothylacium cenotae, Pseudocapillaria yucatanensis, Paracapillaria rhamdiae, P. teixerafreitasi and Capillostrongyloides sp. (only females). Four species (R. kidderi, P. rebecae, P. neacaballeroi and Capillostrongyloides sp.) are briefly described and illustrated and some problems concerning their morphology, taxonomy, hosts and geographical distribution are discussed. Taxonomic changes include Procamallanus (Spirocamallanus) neacaballeroi (Caballero-Deloya, 1977) comb. n. and Procamallanus (Spirocamallanus) rebecae (Andrade-Salas, Pineda-López ct Garcfa-Magana, 1994) comb. n. The nematode fauna of fishes in cenotes of the Yucatan Peninsula shows its appurtenance to the Neotropical fauna with close affinities with that of fish nematodes from South America, but with a considerable degree of endemism.