Abstract
The construction of dams causes major impacts on fauna by changing or eliminating irreversibly their habitats. The resulting changes lead to deep potential modifications on reproductive biology and population structure of lizards, snakes and amphisbaenas. The reservoir in the Multiple Use Area of Manso (APM-Manso) is located near to Chapada dos Guimaraes National Park, in Mato Grosso State. We analyzed comparatively the male gonads of Anolis meridionalis, Colobosaura modesta, Cercosaura ocellata, Cnemidophorus ocellifer, Hoplocercus spinosus, Bachia bresslaui, Mabuya frenata, Micrablepharus atticolus and Tropidurus oreadicus, from APM-Manso, aiming to verify possible changes in the reproductive success according to environmental changes. Before the impoundment A. meridionalis, Colobosaura modesta, Cercosaura ocellata, M. atticolus and T. oreadicus showed up reproductive. However, during the impoundment period they presented changes in seminiferous tubules, evidenced by the absence of spermatids and spermatozoids. B. bresslaui and M. frenata had no differences in the seminiferous tubules before and after the impoundment, being reproductive in both moments. The damming and the formation of the lake of Manso reservoir may have interfered on the reproduction of some lizards species, especially if the reproductive cycle is regulated by the rainfall of the habitat.
Highlights
The process of dam construction in many Brazilian rivers has caused large impacts on the fauna by changing or eliminating their habitats irreversibly (RODRIGUES, 1999, 2005)
Two main hypotheses have been raised to explain the seasonal reproduction: (1) deterioration of niches for eggs laying during the rainy season, and (2) the decrease in the availability of food for adults and/or juveniles during the rainy season
Recent research indicates that the reproductive cycles of tropical lizards present great variability and these cycles are not always linked to rainfall patterns (VITT, 1986)
Summary
The process of dam construction in many Brazilian rivers has caused large impacts on the fauna by changing or eliminating their habitats irreversibly (RODRIGUES, 1999, 2005). The reservoirs are semi-natural ecosystems and intermediate between rivers and lakes (TUNDISI, 1993). The impoundment of rivers causes the transformation of the original ecosystem, resulting in great changes physical, chemical, limnological and. For shallow rivers with large floodplains and distinct cycles of flood, the ecosystem changes may be highly significant. The impacts resulting from changes in river flow and the natural cycle of flooding by modifying the deposition of sediments, the nutrients supply and succession of vegetation, have a deep potential impact on reproductive biology and population structure of lizards, snakes
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