Functional Groups of Metazoan Parasites of the Dusky Flounder (Syacium papillosum) as Bioindicators of Environmental Health of the Yucatan Shelf.

We aimed to compare the percentage of explained variance given by the relationship of species and functional groups of metazoan parasites of the dusky flounder Syacium papillosum and environmental variables from water and sediments in the Yucatan shelf (YS). Parasite data were obtained from 127 S. papillosum specimens collected from 17 of 67 stations. At each station, 46 environmental variables were measured, including hydrocarbons, heavy metals, and physicochemical variables from water and sediments. Fifteen functional groups were defined based on biological characteristics of 48 parasite species. Our multivariate statistical analyses showed that species and functional groups produced similar explained variance values (47.3% and 50% respectively). However, using functional groups the time and financial resources were minimal compared with those used for morphological and molecular identification to produce the species composition matrix. Thus, functional groups are the best choice from the point of view of saving time and money.

Metazoan Parasite Infracommunities of the Tomtate Grunt (Haemulon aurolineatum) as Potential Bioindicators of Environmental Conditions in the Yucatan Continental Shelf, Mexico.

Metazoan parasites and their hosts experience the environmental influence of the seasonal presence of Western and Eastern subzones with different oceanographic conditions on the Yucatan continental shelf (YS). In addition, natural seeps and oil transport in the area lead to the presence of hydrocarbons. We hypothesized that the parasite infrapopulations and infracommunities of Haemulon aurolineatum will respond to environmental variability related with ongoing oceanographic subzone conditions of the YS. Spatial and multivariate statistical analyses were used to test this hypothesis. For 17 sampling sites along the YS, 55 parasite morphospecies were recovered from 146 fishes. There were significant differences in the number of parasite species between Western and Eastern subzones, but not in the number of parasite individuals. Spatial autocorrelation on environmental variables as a consequence of the Yucatan current was found. Overall, the parasite metrics suggested a region with a good ecosystem health condition naturally influenced by oceanographic processes.

New morphological and molecular data for Xystretrum solidum (Gorgoderidae, Gorgoderinae) from Sphoeroides testudineus (Tetraodontiformes, Tetraodontidae) in Mexican waters.

Adults of trematodes in the genus Xystretrum Linton, 1910 (Gorgoderidae, Gorgoderinae) are parasites found exclusively in the urinary bladders of tetraodontiform fishes. However, limited and unclear morphological data were used to describe the type species, X. solidum Linton, 1910. Here, we present the first detailed morphological information for a member of Xystretrum. Morphological characters were described using light and scanning electron microscopy (SEM) of Xystretrum specimens from Sphoeroides testudineus (Linnaeus) (Tetraodontiformes, Tetraodontidae), collected at six localities off the northern Yucatan Peninsula coast of the Gulf of Mexico. We also compared sequence fragments of the 28S (region D1-D3) ribosomal DNA and mitochondrial Cytochrome c oxidase subunit 1 (COI) gene with those available for other gorgoderine taxa. We assigned these Xystretrum specimens to X. solidum, despite the incompleteness of published descriptions. The data provide a foundation for future work to validate the identities of X. solidum, X. papillosum Linton, 1910 and X. pulchrum (Travassos, 1920) with new collections from the type localities and hosts. Comparisons of 28S and COI regions described here also provide an opportunity to evaluate the monophyletic status of Xystretrum.