Luis García-Prieto

Study of the ethiological agent of gnathostomosis in Nayarit, Mexico.

In order to clarify the specific identity of the etiological agent of human gnathostomosis in Nayarit State, Mexico, morphological and molecular studies were conducted on advanced third stage larvae obtained from human and fish tissue. Cathorops fuerthii from Agua Brava lagoons complex, was the only fish species found to be infected among four species surveyed. Morphological variability does not allow specific identification of the larvae. Internal transcribed spacer 2 of the ribosomal DNA was sequenced for six larvae (five from fish, one from human tissue). Low divergence in the sequences of Nayarit larvae and Gnathostoma binucleatum (0.24% or less) indicate that the larvae examined belong to this species.

HELMINTH INFRACOMMUNITIES OF RANA VAILLANTI BROCCHI (ANURA: RANIDAE) IN LOS TUXTLAS, VERACRUZ, MEXICO

A total of 76 adult individuals of Rana vaillanti were collected in Laguna Escondida, Los Tuxtlas, Veracruz, Mexico, and their helminth infracommunity structure was determined. Among the 21 helminth taxa collected (10 digeneans, 8 nematodes, and 3 acanthocephalans), the digenean Langeronia macrocirra reached the highest prevalence (64.4%), mean abundance (6.6), and mean intensity (10.4), as well as the highest total number of individuals (499). Only 2 frogs were uninfected, the remainder harbored between 1 and 7 helminth species and 1–102 individuals; mean species richness and abundance were 3.49 ± 0.22 and 16.1 ± 16.3, respectively. Langeronia macrocirra dominated in 50.6% of the infracommunities, with relatively low Berger– Parker index values (0.56); for this reason, the evenness was high (0.70 ± 0.31), and consequently, diversity values are the highest recorded to date in species of Rana. However, patterns of helminth infracommunity richness and diversity were similar to those previously observed in amphibians. This structure is attributed to the feeding habits (between 66.7 and 81% of helminth species parasitizing R. vaillanti enter using the food web dynamics) and low vagility (the remainder species infect by host penetration).

Checklist of Helminth Parasites of the Cane Toad Bufo marinus (Anura: Bufonidae) From Mexico

Thirty-four adult cane toads Bufo marinus L. (12 males and 22 females) collected from 2 localities in Mexico (Cerro de Oro and Temascal Dams, Oaxaca) in September 2003 were examined for helminth parasites. In total, 14,749 helminths belonging to 14 taxa were collected. Included were 2 adult digeneans (Choledocystus hepaticus, Mesocoelium monas); 1 larval cestode (an unidentified pseudophyllidean); and 11 nematodes, including 3 species of larvae (Contracaecum sp., Physaloptera sp., Physocephalus sexalatus) and 8 species of adults (Aplectana itzocanensis, Cosmocerca sp., Cruzia morleyi, Ochoterenella digiticauda, Oswaldocruzia sp., Raillietnema sp., Rhabdias americanus, and Rhabdiasfuelleborni). Higher species richness was recorded in B. marinus from Cerro de Oro (12 taxa versus 9 in those from Temascal); hosts from both localities shared 7 taxa. There were 25 new locality records, and 2 taxa were registered in Mexico for the first time. To date, 112 helminth species have been recorded parasitizing B. marinus along its native and introduced range of distribution, with 40.5% of them reported from Mexico.

NESTEDNESS IN COLONIZATION-DOMINATED SYSTEMS: HELMINTH INFRACOMMUNITIES OF RANA VAILLANTI BROCCHI (ANURA: RANIDAE) IN LOS TUXTLAS, VERACRUZ, MEXICO

Colonization probabilities of parasite species often are determined by the habitat preference and vagility of host individuals. Although extinction-based interpretations have been investigated for nested subset patterns of parasite infracommunities, the low relative frequency of nestedness in colonization-dominated systems makes the determination and interpretation of nested infracommunities of broad ecological importance. In these systems, ontogenetic shifts in habitat preference or diet of the host have the potential to produce nested subset patterns of parasite infracommunities. Helminth infracommunity structure was investigated for 76 Rana vaillanti individuals collected from Laguna Escondida, Los Tuxtlas, Veracruz, Mexico, in 1998. Pooled helminth infracommunities were significantly nested, as were penetrating and ingested helminth infracommunities when considered separately. Richness, diversity, and evenness of the helminth infracommunities were not correlated with host size, and did not differ between host sexes, suggesting that the structure of infracommunities simply is a product of the interaction between host individuals and their landscape mediated by individual differences in vagility. It is hypothesized that individual differences in recruitment can produce nested subset infracommunity patterns when the habitats or habitat preferences of hosts are themselves nested.

Helminth parasites of freshwater fishes, Nazas River basin, northern Mexico

This paper represents the first study of the helminth parasites of freshwater fishes from the Nazas River basin in northern Mexico. Between July 2005 and December 2008, 906 individual fish were collected and examined for helminth parasites in 23 localities along the river basin. Twenty-three species of fish were examined as a part of this inventory work. In total, 41 helminth species were identified: 19 monogeneans, 10 digeneans, seven cestodes, one acanthocephalan, and four nematodes. The biogeographical implications of our findings are briefly discussed.

A NEW SPECIES OF GNATHOSTOMA (NEMATODA: GNATHOSTOMATIDAE) IN PROCYON LOTOR HERNANDEZII FROM MEXICO

Gnathostoma lamothei n. sp., inhabiting the stomach of Procyon lotor hernandezii Wagler, 1831, in Tlacotalpan, Veracruz State, and Río Sapo, Oaxaca, Mexico, is described. This new species differs from all other congeners by having the posterior half of the body surface covered by rows of tiny round bosses instead of spines, or lacking ornamentations. Sequences of the ITS2 of the ribosomal DNA of G. lamothei n. sp. are compared with sequences of other species of the genus recorded in Mexico; they show a wide divergence (<50%) with Gnathostoma binucleatum Almeyda-Artigas, 1991, and Gnathostoma turgidum Stossich, 1902, and high similarity with Gnathostoma sp. I sequence (99.2%). On the basis of morphometric traits and sequences, previous records of Gnathostoma sp. I (=Gnathostoma procyonis of Almeyda-Artigas et al., 1994, not Chandler, 1942, and Gnathostoma neoprocyonis nomen nudem) in Mexico are referred to as the new species.

Morphological and molecular differentiation of Parastrigea (Trematoda: Strigeidae) from Mexico, with the description of a new species

Parastrigea plataleae n. sp. (Digenea: Strigeidae) is described from the intestine of the roseate spoonbill Platalea ajaja (Threskiornithidae) from four localities on the Pacific coast of Mexico. The new species is mainly distinguished from the other 18 described species of Parastrigea based on the ratio of its hindbody length to forebody length. A principal component analysis (PCA) of 16 morphometric traits for 15 specimens of P. plataleae n. sp., five of Parastrigea cincta and 11 of Parastrigea diovadena previously recorded in Mexico, clearly shows three clusters, which correspond to the three species. DNA sequences of the internal transcribed spacers (ITSs) of ribosomal DNA and the mitochondrial gene cytochrome c oxidase subunit I (cox 1) were used to corroborate this morphological distinction. The genetic divergence estimated among P. plataleae n. sp., P. cincta and P. diovadena ranged from 0.5 to 1.48% for ITSs and from 9.31 to 11.47% for cox 1. Maximum parsimony (MP) and maximum likelihood (ML) analyses were performed on the combined datasets (ITSs+cox 1) and on each dataset alone. All of the phylogenetic analyses indicated that the specimens from the roseate spoonbill represent a clade with strong bootstrap support. The morphological evidence and the genetic divergence in combination with the reciprocal monophyly in all of the phylogenetic trees support the hypothesis that the digeneans found in the intestines of roseate spoonbills represent a new species.

Describing Parasite Biodiversity: The Case of the Helminth Fauna of Wildlife Vertebrates in Mexico

Parasites are extremely abundant and diverse in nature, representing a substantial portion of global biodiversity. At least 50% of the species living on earth are parasites of some form, considering all viruses and some bacteria, and the eukaryotic species most commonly associated with parasitology, including agents of diseases affecting not only humans, but also livestock, crops, and wildlife (Brooks & Hoberg, 2006). Interestingly, only a small fraction of the existing species are of medical or veterinary importance (Price, 1980; Poulin & Morand, 2004). There are many reasons to include parasites in any biodiversity survey, and indeed to study parasite diversity on its own. For example, parasites have been mentioned several times as elegant and sophisticated biological markers and as contemporary probes of biodiversity (Gardner & Campbell, 1992). Additionally, parasite diversity provides insights into the history and biogeography of other organisms, into the structure of ecosystems, and into the processes behind the diversification of life (Brooks & Hoberg, 2000; Poulin & Morand, 2000, 2004). In this context, parasites have, according to Brooks & Hoberg (2006), a dual and conflicting significance because they may regulate host populations, playing a central role in maintenance of genetic diversity and structuring host communities and, at the same time, they represent treats to human health, agriculture, natural systems, conservation practices, and the global economy (see Horwitz & Wilcox, 2005). For a comprehensive overview of the role that parasites play in research programs on biodiversity, the reader should refer to Brooks and Hoberg (2000) and to Poulin and Morand (2000, 2004). On the other hand, even though parasites have been proposed as indicators of ecosystem stress (e.g., Marcogliese & Cone, 1997), more recently, based on new methodological approaches, some authors have emphasized the role of parasites as indicators of environmental changes, probably as a result of a renewed interest in the impacts of climate change on earth. For instance, Vidal-Martinez et al., (2010) reviewed the usefulness of parasites as bioindicators of environmental impact, and their meta-analysis showed significant effects and interactions between parasite levels and the presence and concentration of various pollulants and/or environmental stressors. Meanwhile, Palm et al. (2011) demonstrated that fish parasites are

A NEW SPECIES OF OOCHORISTICA (EUCESTODA: CYCLOPHYLLIDEA) PARASITE OF CTENOSAURA PECTINATA (REPTILIA: IGUANIDAE) FROM OAXACA, MEXICO

During January 2002, 3 specimens of an undescribed species of Oochoristica Lühe, 1898, were collected in Ctenosaura pectinata (Wiegmann, 1834) from Santa María Mixtequilla, Oaxaca, Mexico. Oochoristica leonregagnonae n. sp. differs from 71 of 82 species of the genus by its large number of testes (78–112 [95] vs. less than 65 per proglottid, respectively). In addition, the numerous ovarian lobes (31–79 [51]) possessed by the new species distinguish it from the other 10, with a maximum of 20 ovarian lobes. The new species differs from Oochoristica acapulcoensis Brooks, Pérez-Ponce de León and García-Prieto, 1999, which also infects C. pectinata in Mexico, by the presence of numerous staining granules throughout the parenchyma of the scolex in the latter species; likewise, testes in O. acapulcoensis reach and even overpass the excretory canals, whereas in the new species they are limited to the central region between these tubules.

HELMINTH INFRACOMMUNITY STRUCTURE OF THE SYMPATRIC GARTER SNAKES THAMNOPHIS EQUES AND THAMNOPHIS MELANOGASTER FROM THE MESA CENTRAL OF MEXICO

Seventy-two Mexican garter snakes (Thamnophis eques) and 126 black-bellied garter snakes (T. melanogaster) were collected from 4 localities of the Mesa Central of Mexico between July 1996 and February 1998 and examined for helminths. Both species of garter snakes occurred sympatrically in every locality except in Lake Cuitzeo. Both species of snakes shared 9 helminth species, and in general, T. melanogaster hosted a larger number of species than T. eques. In each locality, a different helminth species showed the highest levels of prevalence and abundance (Spiroxys susanae in Ciénaga de Lerma, Telorchis corti in Lago de Pátzcuaro, Proteocephalus variabilis in Lago de Cuitzeo, and Contracaecum sp. in Lago de Chapala). Helminth communities in garter snakes of the Mesa Central are depauperate and dominated by a single parasite species. In those localities where the snakes occurred in sympatry, helminth communities were, in general, more diverse and species-rich in T. melanogaster. Differences in the ecology and physiology of these species of garter snakes may explain this pattern because black-bellied garter snakes (T. melanogaster) are more aquatic than Mexican garter snakes (T. eques) and primarily eat aquatic prey, potentially exposing themselves to a larger number of helminths transmitted by predator–prey infection. The helminth infracommunities of garter snakes in the Mesa Central of Mexico show a strong Nearctic influence because most of the species infecting these hosts have been recorded in other Nearctic colubrid snakes. However, the helminth infracommunities of these garter snakes are less species-rich and less diverse than those in colubrid snakes in more temperate latitudes. The widespread ecological perturbation of sampling sites in the Mesa Central because of human activity, and geographic differences in foraging ecology of the hosts and, thus, exposure to parasites transmitted by intermediate hosts may help to explain these patterns.