Browsing by Author "Palacios, AG"

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    An "enactive" approach to integrative and comparative biology: Thoughts on the table
    (2003) Palacios, AG; Bozinovic, F
    We discuss the concept of Enaction as originally proposed by Varela. We attempt to exemplify through two specific topics, sensory ecology and behavior, as well as physiological and behavioral ecology, on which the enactive approach is based. We argue that sensory physiology allows us to explore the biological and cognitive meaning of animal 'private' sensory channels, beyond the scope of our own sensory capacity. Furthermore, after analyzing the interplay between factors that may impose limits upon an animal's use of time and energy, we call for a program of research in integrative and comparative biology that simultaneously considers evolutionary ecology (including physiological and behavioral ecology) and neurobiology (including cognitive mechanisms as well structural design). We believe that this approach represents a shift in scientific attitude among biologists concerning the place of biological and ecological topics in studies of integrative and comparative biology and biological diversity and vice versa.
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    Eye and vision in the subterranean rodent cururo (Spalacopus cyanus, Octodontidae)
    (2005) Peichl, L; Chavez, AE; Ocampo, A; Mena, W; Bozinovic, F; Palacios, AG
    Subterranean mammals are generally considered to have reduced eyes and apparent blindness as a convergent adaptation to their lightless microhabitat. However, there are substantial interspecific differences. We have studied the prospect of vision in the Chilean subterranean rodent cururo (Spalacopus cyanus, Octodontidae) by analyzing the optical properties of the eye, the presence and distribution of rod and cone photoreceptors, and their spectral sensitivities. Cururo eye size is normal for rodents of similar body size, the cornea and lens are transparent from red to near-U-V light, and the retina is well-structured. Electroretinography reveals three spectral mechanisms: a rod with peak sensitivity at about 500nm, a cone with lambda(max) at about 505 nm (green-sensitive L-cone), and a cone with lambda(max), near 365 nm (UV-sensitive S-cone). This suggests dichromatic color vision. Immunocytochemistry with opsin-specific antibodies confirms the presence of rods, L-cones, and S-cones. Cururo rod density is much lower than that of nocturnal surface-dwelling rodents, and the cones form an unexpectedly high 10% proportion of the photoreceptors. Of these, S-cones constitute a regionally varying proportion from 2% in dorsal to 20% in ventral retina. The high cone proportion suggests adaptation to visual demands during the sporadic short phases of diurnal surface activity, rather than to the lightless subterranean environment. Our measurements on fresh cururo urine reveal a high UV reflectance, suggesting that scent marks may be visible to the UV-sensitive cones. The present results challenge the general view of convergent adaptive eye reduction and blindness in subterranean mammals. (c) 2005 Wiley-Liss, Inc.
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    Retinal spectral sensitivity, fur coloration, and urine reflectance in the genus Octodon (Rodentia)
    (2003) Chávez, AE; Bozinovic, F; Peichl, L; Palacios, AG
    PURPOSE. To determine the eye's spectral sensitivity in three species of the genus Octodon (order Rodentia; infraorder Caviomorpha), O. degus, O. bridgesi, and O. lunatus, as well as the spectral properties of the animals' fur and urine and of objects in their habitat. The genus is endemic in Chile and contains species with different habitats and circadian patterns (diurnal versus nocturnal).