Guillermo Salgado-Maldonado

The Asian Fish Tapeworm Bothriocephalus acheilognathi: a Potential Threat to Native Freshwater Fish Species in Mexico

Introduction of the parasite Bothriocephalus acheilognathi Yamaguti, 1934 with the herbivorous carp Ctenopharyngodon idellus, and other cyprinids, has been documented in almost every continent, except Antarctica. This study presents the current geographical distribution of this cestode in the freshwater fish of Mexico, highlighting infections in autochthonous and endemic species. It compiles existing information and presents original data. B. acheilognathi is widely dispersed among the freshwater fish of Mexico, being recorded to date in 49 fish species from 26 genera, 7 families and 5 orders. B. acheilognathi is reported from Mexico for the first time in Dionda ipni, Notropis celayensis, Yuriria alta, Gambusia vittata, Poecilia butleri, P. mexicana, Poeciliopsis baenschi, Poeciliopsis sp., Cichlasoma cyanoguttatum and C. labridens. The new hosts identified in this study bring the total number of known host species to 102 in 14 families and 7 orders of freshwater fishes around the world. Given its wide distribution among Mexican freshwater fish species, the abundance of the parasite and its high pathogenicity, parasitological data for B. acheilognathi should be considered as an important factor in native fish conservation policies. Biological changes in the freshwater habitats in Mexico caused by the introduction of exotic fish species and their parasites are virtually ubiquitous and extremely difficult to eradicate once established. As such, they should be considered as one of the most serious threats to native fish conservation.

The Introduction and Dispersal of Centrocestus formosanus (Nishigori, 1924) (Digenea: Heterophyidae) in Mexico: A Review

Abstract The taxonomy, distributional history, present occurrence, life cycle, morphology of developmental stages and epizootiology of the heterophyid trematode Centrocestus formosanus (Nishigori, 1924) in Mexico are reviewed. This parasite was most likely introduced to Mexico with the importation of the first intermediate host, the thiarid snail Melanoides tuberculata, from Asia in 1979. Centrocestus formosanus was first recorded in 1985 as metacercariae in fry of the first generation of black carp Mylopharyngodon piceus imported from China and subsequently in other fish from a farm in central Mexico. Since that time the trematode has spread rapidly over a wide area which includes central Mexico and both the Atlantic and Pacific coasts. This rapid spread has apparently been enabled by previous propagation of M. tuberculata in Mexico. Metacercariae of C. formosanus occur encysted on the gills of fish. They have been found in 39 species of fish of the families Atherinidae, Characidae, Cichlidae, Cyprinidae, Eleotridae, Gobiidae, Goodeidae, Ictaluridae, Mugilidae and Poeciliidae from 11 Mexican states (Colima, Guanajuato, Hidalgo, Jalisco, Michoacán, Morelos, San Luis Potosí, Sonora, Tabasco, Tamaulipas and Veracruz). The heron Butorides striatus is the only known natural definitive host in Mexico. Further research towards better understanding of all aspects of the life cycle, transmission, host-parasite relationships and the effective control of C. formosanus in Mexico is necessary. It should also include monitoring of the present distribution of M. tuberculata and its infection with larval stages of C. formosanus. Much more emphasis should be given to histopathological studies to assess actual impact of the parasite on fish of different species and age classes. The spectrum of natural definitive hosts and their epizootiological importance in the transmission and maintenance of the parasite in Mexico should also be better documented. Adequate preventive and control measures should be applied in aquaculture, with emphasis given to prevention of movement of infected fish stocks.

Trematodes of the family Heterophyidae (Digenea) in Mexico: a review of species and new host and geographical records

A review of heterophyid trematodes found in Mexico, both as metacercariae encysted in fish and adults in fish-eating birds and mammals, is presented, including numerous new geographical and host records. Data on the morphology, spectrum of intermediate and definitive hosts, site of infection of metacercariae, distribution in Mexico and biology of the following species are provided (species first reported from Mexico marked with an asterisk): *Ascocotyle (Ascocotyle) gemina Font, Overstreet and Heard, 1984; A. (A.) leighi Burton, 1956; A. (A.) tenuicollis Price, 1935; A. (Leighia) chandleri Lumsden, 1963; *A. (L.) mcintoshi Price, 1936; A. (L.) megalocephala Price, 1932; A. (L.) nunezae Scholz, Vargas-Vazquez, Vidal-Martínez and Aguirre-Macedo, 1997; Ascocotyle (Leighia) sp.; *A. (Phagicola) ampullacea Miller and Harkema, 1962; A. (P.) diminuta Stunkard and Haviland, 1924; A. (P.) macrostoma (Robinson, 1956); *A. (P.) longa Ransom, 1920; A. (P.) nana Ransom, 1920; Centrocestus formosanus (Nishigori, 1924); *Euhaplorchis californiensis Martin, 1950; Galactosomum puffini Yamaguti, 1941; *Haplorchis pumilio (Looss, 1896); Heterophyidae gen. sp. (= Haplorchoides sp. of Scholz and Vargas-Vázquez, 1998); *Phocitremoides ovale Martin, 1950; and *Pygidiopsis pindoramensis (Travassos, 1929). Two of the above-listed species, C. formosanus and H. pumilio, have been introduced recently to Mexico, most probably from Asia with the imported thiarid snail Melanoides tuberculata (Müller). Metacercariae of heterophyid trematodes are among the most frequent and abundant parasites offish in Mexico, in particular in its southeastern part.

Helminth parasites in freshwater fish from the Papaloapan river basin, Mexico

A checklist based on previously published records and original data is presented for the helminth parasites reported in 35 fish species from nine families from the Río Papaloapan basin, east Mexico. The checklist contains 85 taxa from 39 helminth families. Trematodes and nematodes were the most abundant taxonomic groups. The helminth fauna in the fish of the Papaloapan River basin predominantly consists of Neotropical species that are largely autogenic. The introduced species Centrocestus formosanus was the most widely distributed helminth, infecting 16 host species. Ten of the recorded helminth species have only been found in fish from the Papaloapan. This inventory contributes 157 new host records, and reports the presence of 30 helminth species in the Papaloapan for the first time . This inventory shows the richness of helminth parasite species in the fish of the Papaloapan River basin in comparison with the other hydrological basins in Mexico. It also demonstrates that this fauna is typically Neotropical and quite similar to that from the neighboring basins of the Grijalva–Usumacinta system and the Yucatan Peninsula. The data also suggest highly effective transmission between environments within the same basin and that the regional parasite fauna is strongly influenced by fish community composition.

Helminth Parasites of Freshwater Fishes of the Pánuco River Basin, East Central Mexico

Abstract This study presents results from a survey of helminth parasites of fishes in the Pánuco River basin, in the states of San Luis Potosí, Hidalgo, Querétaro and Guanajuato, all in east central Mexico. Seventeen freshwater fish species (n = 1,019) were examined for helminths between May 1997 and September 1998. Thirty-one helminth species were collected: 11 allogenic species, mostly Nearctic in origin, and 20 autogenic species. Two anthropogenically introduced species were recorded. The most prevalent and widespread helminth taxon was Posthodiplostomum minimum (metacercariae). The helminth fauna of fishes of the Pánuco River is dominated by trematodes (12 species) and nematodes (11 species) accompanied by a few monogenean (4 species), cestode (3 species), and acanthocephalan (1 species) taxa. Most of the helminth taxa reported have been reported from other regions of Mexico. Thus, the helminth parasite fauna of fishes of the Pánuco River basin are not exclusive, including a primordially autogenic Neotropical species component mixed with a mainly allogenic, globally distributed Nearctic species component. The regional freshwater fish helminth fauna is associated with the ichthyofaunanal composition of the basin. The nematode family Rhabdochonidae displays high species richness in this hydrological basin of Mexico.

Helminth Parasites of Freshwater Fishes of the Ayuquila River, Sierra de Manantlán Biosphere Reserve, West Central Mexico

Abstract This study presents results from the first survey of the helminth parasites of fishes in the Ayuquila River, Sierra de Manantlán Biosphere Reserve, in the states of Jalisco and Colima, west central Mexico. Twenty-eight helminth species were collected from 14 freshwater fish species in July 2000 and February 2001. No helminth species collected is exclusive to the Ayuquila River: 11 are allogenic species, mostly Nearctic in origin, and 17 are autogenics. Three introduced species were recovered. Saccocoelioides sogandaresi (Trematoda) was the most prevalent and widespread helminth recovered. The fish helminth fauna of the Ayuquila River is dominated by trematode and nematode species with only a few monogenean and acanthocephalan species. The fauna exhibits considerable overlap with that reported for other freshwater basins in Mexico, and all helminths recovered have been reported previously from Mexico.

A new species of Philometra (Nematoda, Philometridae) from the gonads of the rock hind Epinephelus adscensionis (Osteichthyes) from the southern Gulf of Mexico

A new species of parasitic nematode, Philometra mexicana sp. nov. (Philometridae), is described based on males and females parasitizing the gonads of the marine perciform fish (rock hind) Epinephelus adscensionis (Osbeck) (Serranidae) off the coast of the southern Gulf of Mexico (reefs of the Enmedio Island, Veracruz), Mexico, collected on 10 April 1990. The new species is characterized mainly by very small males (body length 1.63–1.86 mm) with equally long, needle-like spicules (length 90–120 μm) and the gubernaculum (57–66 μm) without the usual dorsal barb on the distal end, the body length of gravid females (178–230 mm), the presence of a well-developed anterior bulbous inflation on the female oesophagus, and by the length of the first-stage larvae (420–435 μm). A comparison with other congeners parasitizing the gonads of marine fishes is provided. The cephalic end of the gravid female of Philometra margolisi Moravec, Vidal-Martínez et Aguirre-Macedo, 1995, another related species from the gonads of Epinephelus [E. morio (Valenciennes)] in Mexico, has been studied by SEM for the first time; it confirms the arrangement of the cephalic papillae as reported in the original species description. Philometra mexicana is the fifth species of Philometra reported from the gonads of marine fishes in the West Atlantic region.

Helminth Parasites of Chapalichthys encaustus (Pisces: Goodeidae), an Endemic Freshwater Fish From Lake Chapala, Jalisco, Mexico

A total of 6 helminth species were recorded during helminthological examination of 50 Chapalichthys encaustus from Lake Chapala, Jalisco, Mexico. Helminth species identified included: Salsuginus sp. (an undescribed monogenea); Posthodiplostomum minimum (metacercariae); Cyclustera ralli (metacestode); Polymorphus brevis (cystacanth); Contracaecum sp. (nematode larvae); and Rhabdochona lichtenfelsi (adult nematode). Of these, 2 (Salsuginus sp. and R. lichtenfelsi) are specialist species. The observed species richness, individual parasite abundance, and diversity were low. Data suggest that host specificity is an important factor contributing to observed community composition and richness. Host feeding habits and helminth species availability seem to determine the characteristics of these helminth assemblages.

TWO NEW SPECIES OF RHABDOCHONIDS (NEMATODA: RHABDOCHONIDAE) FROM FRESHWATER FISHES IN MEXICO, WITH A DESCRIPTION OF A NEW GENUS

Two new nematode species, Beaninema nayaritense n. gen., n. sp. and Rhabdochona xiphophori n. sp., are described on the basis of the specimens recovered from the gall bladder and intestine of 2 fishes, Cichlasoma beani (Jordan) (Cichlidae, Perciformes) and Xiphophorus sp. (Poeciliidae, Cyprinodontiformes), respectively, from Mexico. The monotypic genus Beaninema differs from other rhabdochonid genera mainly in the presence of large conical teeth in the middle of the prostom. Rhabdochona xiphophori is characterized mainly by a unique structure of the prostom (presence of 6 anterior teeth; dorsal and ventral teeth unusually broad, with 2 lateral horns) and the shape of the deirids (bifurcated, with markedly long base).

Digeneans (Plathelminthes: Trematoda) of seven sympatric species of anurans from Los Tuxtlas, Veracruz, Mexico

Digeneans of sympatric Bufo marinus, B. valliceps, Hyla picta, H. ebraccata, Smilisca baudini, Rana berlandieri, and R. vaillanti from Los Tuxtlas, Veracruz, Mexico, are reported. A total of 7 adult trematode species and 3 unidentified metacercariae was found in the different host species examined: Gorgoderina attenuata, G. parvicava, Cephalogonimus americanus, Haematoloechus medioplexus, Glypthelmins californiensis, Mesocoelium monas and Langeronia macrocirrus. Prevalence, mean intensity and abundance of the trematodes in each host species are given.