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Photoreceptors properties in strictly subterranean African mole-rats
Krejčová, Tereza ; Němec, Pavel (advisor) ; Kott, Ondřej (referee)
4 Photoreceptor properties and distribution in strictly subterranean African mole-rats (Rodentia, Bathyergidae) The visual system of subterranean rodents is assumed to be regressed in response to their lightless ecotope. According to the prevailing doctrine, negative or non-selective processes have driven evolutionary regression of the visual system in many unrelated groups of rodents that has adopted strictly subterranean mode of life. Among rodents this has been exemplified by detailed studies of the blind mole-rat Spalax ehrenbergi. However, recent studies involving a larger spectrum of subterranean rodent species demonstrated unexpected diversity of retinal properties and visual system designs among subterranean rodent species and thus challenged the widely held view that the visual system has undergone extensive convergent evolution in subterranean mammals. This paper examines the presence, the distribution, and photoreceptor properties in the African mole-rats (Bathyergidae, Rodentia). It describes rodopsin, S- and L-opsin expression patterns, photoreceptor densities and rod/cones proportions in five species of bathyergid mole-rats, namely Bathyergus suillus, Georychus capensis, Fukomys damarensis, Cryptomys natalensis and Heliophobius argenteocinereus. Spectral cone types and rods were assessed...
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Visual capabilities in subterranean rodents
KOTT, Ondřej
This Ph.D. thesis focuses on the visual capabilities of subterranean African mole-rats (family Bathyegidae) and a potential role of their residual vision. We described basic visual capability of light/dark discrimination and capacity to perceive short to medium-wavelength light in the photopic range of intensities. Our behavioural findings revealed severe visual deficits, implying visually guided spatial orientation in molerats improbable. Our field study demostrated no light-correlated daily activitivy pattern of mole-rats in the natural habitat. We described very effective propagation of long wavelength light in breached burrows that can be detected by mole-rats for long distances, in contary to short wavelengths with very low propagation. Thus, an unique primary blue light perception, described only in African mole-rats among all mammalian species so far, has most probably no adaptive value and might be only a result of arrested cone development. Mole-rats effectively localized and plugged with soil illuminated sites under laboratory conditions, supporting the hypothesis that low acuity residual vision play an indispensable role in bathyergid anti-predatory behaviour and tunnel maintanance but not in spatial orientation.
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Light perception in two mole-rat species, the silvery mole-rat \kur{(Heliophobius argenteocinereus)} and the giant mole-rat \kur{(Fukomys mechowii)}.
KOTT, Ondřej
Sight in subterranean mammals living in a dark ecotope has generally been assumed as not needed and therefore greatly diminished in its function. Recent neuroanatomical studies demonstrate unexpected preservation of the visual system of several African mole-rats (Bathyergidae, Rodentia). Only a few behavioural studies, testing visual abilities and discussing their adaptive significance in these rodents, have been published to date. A spontaneous preference to light stimuli of two mole-rat species, the silvery mole-rat (Heliophobius argenteocinereus) and the giant mole-rat (Fukomys mechowii), was tested in this study. Assessed results showed convincingly that both species are able to perceive light. The following experiments provided the first behavioural support to the perception of short-wavelengths in this intensively studied group of subterranean rodents.
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