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Infestation by chigger mites in two lizard species from a dune habitat of Northern Mexico.

Article Excerpt
Abstract. -- The occurrence and levels of infestation by larvae of the chigger mite Eutrombicula alfreddugesi on the desert lizards Uma exsul and Uta stejnegeri were studied on the sand dunes of Viesca, Coahuila, Mexico. Chiggers were observed on 68.1% of U. exsul males with an average of 7.81 [+ or -] 2.7 chiggers per lizard; chiggers occurred on 54.5% of the females and averaged 4.18 [+ or -] 1.5 mites per lizard. For U. stejnegeri males, chiggers were observed on 100% of the captured lizards and each lizard averaged 61.12 [+ or -] 6.8 chiggers; 86.8% of the females were parasitized and they averaged 38.05 [+ or -] 6.8 mites per lizard. Regression analyses were used to test the relationship between chigger infestation levels and lizard body size; however, no relationships were detected. All chiggers were found on the neck folds in both lizard species. Morphology (shallow neck folds), microhabitat selection (sandy and sunny), and burrowing behavior could influence the infestation pattern of U. exsul. Home range size (for males), deeper neck folds and selection for cooler and shaded microhabitats with higher relative humidity could account for the greater chigger infestation levels found on U. stejnegeri.

Resumen. -- Se estudio la prevalencia e intensidad de infestacion por larvas de Eutrombicula alfreddugesi en los saurios deserticos Uma exsul y Uta stejnegeri en las dunas de arena de Viesca, Coahuila, Mexico. En U. exsul la prevalencia e infestacion en los machos fue de 68.1% y 7.81 [+ or -] 2.7 acaros respectivamente, y en las hembras fue de 54.5% y 4.18 [+ or -] 1.5 acaros. En U. stejnegeri fue del 100% y 61.12 [+ or -] 6.8 acaros para los machos, y 86.8% y 38.05 [+ or -] 6.8 acaros para las hembras. Utilizando el analisis de regresion se determino que no hubo relacion entre la intensidad de infestacion y el tamano de los saurios. Todos los acaros se encontraron dentro de los pliegues del cuello en ambas especies. La morfologia (pliegues poco profundos en el cuello), la seleccion de microhabitat (arenoso y soleado) y la conducta de entierro son caracteristicas que pueden influenciar el patron de infestacion de U. exsul. El tamano del ambito hogareno (en los machos), los pliegues profundos en el cuello y una seleccion de microhabitats templados y sombreados con una mayor humedad relativa, pueden intervenir en el alto grado de infestacion de U. stejnegeri.

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Chigger mite occurrence and parasitism rates on lizards have been associated with host species' characteristics such as morphology, behavior, and gender. Size of the lizard, scale type, and the presence of folds or pockets, are morphological variables that affect chigger parasitism (Cunha-Barros & Rocha 2000; Salvador et al. 1999). The foraging mode and the activity patterns are examples of behavioral factors (Clopton & Gold 1993;...

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