In this study, the metazoan parasites of three species of freshwater turtles (the spiny softshell, Apalone spinifera, the common snapping turtle, Chelydra serpentina, and the red-eared slider, Trachemys scripta elegans) were surveyed at 16 sites across the state of Texas. A total of 42 species of metazoan parasites were recovered from 15 A. spinifera, nine C. serpentina, and 55 T. s. elegans, representing 16 new host-parasite associations and 17 new locality records. The synonymy of Acanthostomum nuevoleonensis by Brooks (1980) is refuted and the species is redescribed. Two new species of monogenean worms in the genus Neopolystoma are reported, one from C. serpentina and A. spinifera and another from T. s. elegans. Through non-metric multidimensional scaling and analysis of similarities, A. spinifera was found to contain a significantly distinct parasite community from C. serpentina and T. s. elegans. A range of water parameters (ammonia, carbon dioxide, chloride, dissolved oxygen, hardness, nitrite, nitrate, pH, salinity, temperature, and turbidity) were recorded on each sampling trip and compared to parasite abundance and diversity. Ammonia levels were positively correlated with abundance of acanthocephalans. Carbon dioxide levels were negatively correlated with parasite diversity and monogenean abundance. Chloride levels were negatively correlated with parasite diversity. Dissolved oxygen levels were positively correlated with parasite diversity and monogenean abundance. Turbidity was positively correlated with parasite abundance, acanthocephalan abundance, and digenean abundance, and negatively correlated with parasite diversity. Parasite abundance was significantly lower in west Texas and western river basins, and lower in rivers than ponds. Acanthocephalan abundance was significantly lower in rivers than ponds. Leech abundance was highest in the Trinity river basin. Turbidity had the strongest correlations in this study. As water clarity increased, diversity increased and abundance of certain taxa decreased, indicating clearer water may have greater food web diversity and healthier hosts. This study adds valuable data on host-parasite associations, parasite distributions, and parasite ecology of turtles in the state of Texas. Many of these findings are likely transferable to other host taxa and should be studied in greater depth. Parasite diversity is not well known, even in common species, highlighting the need for more diversity surveys.
