Joaquín Vargas-Vázquez

Species of Ascocotyle Looss, 1899 (Digenea: Heterophyidae) of the Yucatan Peninsula, Mexico, and notes on their life-cycles.

Heterophyid trematodes of the genus Ascocotyle Looss, 1899, metacercariae of which were found in fish from freshwater (cenotes [sinkholes], lakes and the Río Hondo River) and brackish coastal lagoons of the Peninsula of Yucatan, Mexico, are reviewed. The following species were found: Ascocotyle (Ascocotyle) tenuicollis Price, 1935; A. (A.) nunezae Scholz, Vargas-Vázquez, Vidal-Martínez & Aguirre-Macedo, 1996; A. (A.) chandleri Lumsden, 1963; A. (Phagicola) nana Ransom, 1920; A. (P.) diminuta Stunkard & Haviland, 1924; A. (P.) macrostoma (Robinson, 1956); and A. (Leighia) megalocephala Price, 1932. Descriptions of metacercariae and adults from naturally and experimentally infected hosts are provided. Considerable variation was found in the number (18–22) and arrangement of circumoral spines of A. (P.) nana: most specimens (70%) had 20 spines arranged in one complete row of 16 spines and four additional spines dorsally, which differs from the arrangement of circumoral spines in the type-series of this species. In contrast, spination patterns of A. (A.) tenuicollis (16 + 16 spines in two rows) and A. (P.) diminuta (16 + 2) were constant. The validity of A. (P.) diminuta and A. (P.) nana, species recently resurrected from synonymy with A. (P.) angrense Travassos, 1916, was confirmed. Except for A. (A.) tenuicollis, all species are reported from Mexico for the first time. The heron Casmerodius albus represents a new definitive host of adults of all the above-mentioned species excluding A. (A.) chandleri. A key to the identification of Ascocotyle metacercariae occurring in fishes of the Yucatan Peninsula is also provided.

First description of the male and redescription of the female of Paratrichosomarecurvum (Nematoda: Capillariidae), a skin-invading parasite of crocodiles in Mexico

Abstract The first description of the male and a redescription of the female of the nematode Paratrichosomarecurvum (Solger, 1877), a parasite of the abdominal skin of crocodiles, are presented on the basis of specimens collected from Crocodilusmoreletii Duméril et Bibron from the Lagoon of Celestún, Yucatán, Mexico. The morphology of P. recurvum proved to be very similar to that of the only other congeneric species, P.␣crocodylus Ashford et Muller, 1978, but the former differed from the latter in having distinctly protruding polar plugs on eggs, reduced mesenchymal cells at the esophagointestinal junction, and a smooth spicular surface as well as in geographic distribution. The finding of P. recurvum in C. moreletii represents a new host record. Paratrichosoma spp. appear to be widely distributed in tropical countries of different continents and may be of economic importance for crocodile farms.

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 heron, Casmerodius albus (type host), from the coastal lagoon of Celestún. Yucatan, Mexico, and a domestic chick (Gallus gallus), experimentally infected with metacercariae from Cichlasoma octofasciatum. The new species is characterized mainly by the number (32-37) and arrangement of circumoral spines, which form I complete row of 25-27 circumoral spines and 6-10 accessory spines on the dorsal side, and by the morphology of the ventrogenital sac with a large gonotyl, consisting of 2 indistinctly separated lobes of vesicular tissue. Ascocotyle (A.) nunezae is placed into the nominotypical subgenus Ascocotyle because of the presence of uterine loops at the pharyngeal region and position of vitelline follicles. However, it differs distinctly from other members of this 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 Río Hondo in the Yucatan Peninsula were natural second intermediate hosts of A. (A.) nunezae, with metacercariae encysted on their gills. Cichlasoma meeki (Brind) was the most heavily infected fish host (total prevalence 75%; mean intensity 11 +/- 9).

Life-cycle ofEchinochasmus macrocaudatus n. sp. (Trematoda: Echinostomatidae)

The life-cycle ofEchinochasmus macrocaudatus n. sp., from mother-sporocyst to adult, was studied under natural and experimental conditions. The aquatic snailsPyrgophorus coronatus (Prosobranchia: Hydrobiidae) from cenotes (sinkholes) of the Yucatan Peninsula, Mexico, served as the first intermediate host of this parasite, liberating cercariae possessing an extremely large tail (zygocercous cercaria). Metacercariae of the fluke were encysted on the gills of the characid fishAstyanax fasciatus (natural infection); the poeciliidsXiphophorus variatus andPoecilia velifera were suitable experimental hosts. Feeding experiments withE. macrocaudatus metacercariae resulted in finding adult trematodes, possessing 22 collar spines (with 2 angle spines on each side), in the intestine of chicks and ducks.E. macrocaudatus differs from the most closely related species,E. schwartzi Price, 1931, by its larger oral sucker (138−170×118−176 μm) and by the position of the acetabulum which is situated at two-fifths of the body length.

Systematic status and first description of male of Dujardinia cenotae Pearse, 1936 (= Hysterothylacium cenotae (Pearse, 1936) Moravec et al., 1995) (Nematoda: Anisakidae)

A new collection of adult anisakid nematodes from the intestine of the catfish Rhamdia guatemalensis from two cenotes (= sinkholes) and a cave in the Yucatan Peninsula, southeastern Mexico, has shown that they are conspecific with those inadequately described as Dujardinia cenotae Pearse, 1936. The female is redescribed and the male is described for the first time. The morphology of this species shows that it belongs to the genus Hysterothylacium. This is the only Hysterothylacium species recorded from freshwater fishes in Mexico and it may well be endemic to cenotes and caves of the Yucatan Peninsula.

Echinochasmus leopoldinae n. sp. (Trematoda: Echinostomatidae) and data on its life-cycle

The echinostomatid trematodeEchinochasmus leopoldinae n. sp. is described on the basis of adults found in the intestine of chicks and mice experimentally infected with metacercariae from the gills of the cichlid fishesCichlasoma urophthalmus andC. synspilum from the Peninsula of Yucatan.E. leopoldinae, which had previously been misidentified asE. zubedakhaname Nasir & Díaz, 1968, is characterised by the presence of 20 collar spines with one angular spine on each side and vitelline follicles confluent in the posterior part of the body. A differential diagnosis ofEchinochasmus species possessing 20 collar spines is provided, and the developmental stages (redia, cercaria, metacercaria and adult) ofE. leopoldinae are described.

Paracapillaria epinepheli n. sp. (Nematoda: Capillariidae) from the red grouper Epinephelus morio (Pisces) from Mexico

A new nematode species, Paracapillaria epinepheli, is described from the stomach of the marine fish Epinephelus morio (Valenciennes), the red grouper, (Serranidae, Perciformes) from coastal waters of the Gulf of Mexico in Yucatan, southeastern Mexico. It is characterised mainly by its small body (body length of male and female 2.73–3.22 mm and 5.94–6.35 mm, respectively), number (31–36) and structure of the stichocytes, length of the spicule (0.180–0.195 mm), structure of the male caudal bursa (considerably reduced), structure and size of the eggs (size 0.057–0.063 × 0.027–0.030 mm), and by their site within the host. It is the second Paracapillaria species known to occur in the marine and estuarine fishes of the Gulf of Mexico.