Morphological abnormalities in anurans from central Mexico: a case study (anura: Ranidae, hylidae)

Abstract

high rates of morphological abnormalities (malformations) in amphibians are attributed to parasites, chemical pollution, uv radiation and selective predation. the objectives of this study were to quantify and qualify the external, gross-morphological abnormalities in anurans of the sierra nanchititla natural Reserve (Mexico) and to identify possible causes. six specimens (6.23 %) out of 95 Lithobates forreri (BoulengeR, 1883), as well as two “bycatch“ specimens of Lithobates zweifeli (hIllIs, FRost & WeBB, 1984), and Hyla arenicolor CoPe, 1866, showed a total of eight types of morphological abnormalities. the observed abnormality rate thus slightly exceeded the assumed background rate of five percent in a population. among macroparasites, nematoda (Ozwaldocruzia sp. and Rhabdias savagei) and trematoda (Haematoloechus sp. and Gorgoderina tarascae) were present in internal organs, and chigger mites (Hannemania sp.) on the skin. In the muscle samples, lead (Pb) and copper (Cu) were not detected nor quantified, whereas low (physiological) concentrations of zinc (Zn) were found. In the water samples, Pb was not detected and Zn and Cu was within the level for rivers as accepted in Mexico. the authors reject as possible causes for the observed, increased rate of abnormalities: (1) the effect of macroparasites, due to the absence of trematoda of the genus Riberoia that are known to develop anatomical abnormalities; and, (2) chemical pollution by Pb, Cu and Zn. Possible causes are discussed.