Articles avec #amphibiens
Among vertebrates, comparable spatial learning abilities have been found in birds, mammals, turtles and fishes, but virtually nothing is known about such abilities in amphibians. Overall, amphibians are the most sedentary vertebrates, but poison frogs (Dendrobatidae) routinely shuttle tadpoles from terrestrial territories to dispersed aquatic deposition sites. We hypothesize that dendrobatid frogs rely on learning for flexible navigation. We tested the role of experience with the local cues for poison frog way-finding by (i) experimentally displacing territorial males of Allobates femoralis over several hundred metres, (ii) using a harmonic direction finder with miniature transponders to track these small frogs, and (iii) using a natural river barrier to separate the translocated frogs from any familiar landmarks. We found that homeward orientation was disrupted by the translocation to the unfamiliar area but frogs translocated over similar distances in their local area showed significant homeward orientation and returned to their territories via a direct path. We suggest that poison frogs rely on spatial learning for way-finding in their local area.
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Nature Neuroscience 8, 1087 - 1095 (2005)
Abstract: Synchronized oscillatory activity is generated among visual neurons in a manner that depends on certain key features of visual stimulation. Although this activity may be important for perceptual integration, its functional significance has yet to be explained. Here we find a very strong correlation between synchronized oscillatory activity in a class of frog retinal ganglion cells (dimming detectors) and a well-known escape response, as shown by behavioral tests and multi-electrode recordings from isolated retinas. Escape behavior elicited by an expanding dark spot was suppressed and potentiated by intraocular injection of GABAA receptor and GABAC receptor antagonists, respectively. Changes in escape behavior correlated with antagonist-evoked changes in synchronized oscillatory activity but not with changes in the discharge rate of dimming detectors. These antagonists did not affect the expanding dark spot–induced responses in retinal ganglion cells other than dimming detectors. Thus, synchronized oscillations in the retina are likely to encode escape-related information in frogs.
Thaddeus D. Matula followed conservation biologist, amphibian specialist, and nature photographer Robin Moore into the heart of the Costa Rican rain forest on the Osa Peninsula. The Osa is a mecca for biologists as it is home to 2.5% of all the world's unique species. Robin sets out to document some of its smallest four-legged inhabitants.
A la sortie de l'hiver, aux premiers rayons du Soleil, crapauds et grenouilles regagnent la gravière. C'est la saison des amours !
Prix du meilleur film écologique au "GreenScreen - internationales Naturfilmfestival" à Eckerförde (Allemagne).