Abstract
ABSTRACT The aim of this study was to establish normal baseline ERG values of 23 anesthetized deer belonging to 8 neotropical species (Mazama americana, Mazama nemorivaga, Mazama gouazoubira, Mazama nana, Mazama bororo, Ozotocerus bezoarticus, Odocoileus virginianus and Blastocerus dichotomus). Only right eyes were studied. Chemical restraint was performed using xylazine associated with ketamine, IM, for M. americana, M. gouazoubira, M. nemorivaga, M. nana, M. bororo, O. bezoarticus and O. virginianus. A combination of tiletamine/zolazepam diluted in xylazine 2% was used for B. dichotomus individuals. After 20min of dark adaptation, electroretinograms were obtained using a handheld electroretinography (ERG) machine using the QuickRetCheck Protocol at three different light intensities: 0.01cd.s/m2, 3cd.s/m2, and 10cd.s/m2. After light adaptation, photopic phase was recorded. A-wave amplitude recorded during pattern mixed rod/cone response in M. americana was significantly lower when compared to B. dichotomus. No other differences were observed between the species studied. ERG in Neotropical deer is applicable using a portable ERG system and did not show differences among species in relation to the retinal response at different light intensities. Therefore, the lifestyle of the species is more dictated by the selection pressure of the environment than by physiological factors.
Highlights
Cervids form a subclass of ruminant artiodactyles and play important roles in ecosystem health and sustainability (Duarte and Gonzalez, 2010)
A-wave amplitudes were significantly lower in M. americana (174μV) when compared to B
This study describes a feasible technique for performing ERG in different species of deer, enhancing collective knowledge of vision patterns, and leading to a better understanding of visual physiology in wild species and its relation to lifestyles, periods of activity, and the environment
Summary
Cervids form a subclass of ruminant artiodactyles and play important roles in ecosystem health and sustainability (Duarte and Gonzalez, 2010). There is little data on the ocular morphophysiology of the different deer species (Jacobs et al, 1994; Martins et al, 2007). Studies in this scope are important for evolutionary and environmental reasons, since the vision of each animal seems to adapt to its lifestyle (Osorio and Vorobvev, 2008; Nilsson, 2009). Several quali-quantitative ophthalmic parameters usually assessed for diagnosing and treating the ocular diseases are species-specific, and the extrapolation between species is not always appropriate (Balthazar da Silveira et al, 2017)
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