Selective binocular vision loss in two subterranean caviomorph rodents: Spalacopus cyanus and Ctenomys talarum.
To what extent can the mammalian visual system be shaped by visual behavior? Here we analyze the shape of the visual fields, the densities and distribution of cells in the retinal ganglion-cell layer and the organization of the visual projections in two species of facultative non-strictly subterranean rodents, Spalacopus cyanus and Ctenomys talarum, aiming to compare these traits with those of phylogenetically closely related species possessing contrasting diurnal/nocturnal visual habits. S. cyanus shows a definite zone of frontal binocular overlap and a corresponding area centralis, but a highly reduced amount of ipsilateral retinal projections. The situation in C. talarum is more extreme as it lacks of a fronto-ventral area of binocular superposition, has no recognizable area centralis and shows no ipsilateral retinal projections except to the suprachiasmatic nucleus. In both species, the extension of the monocular visual field and of the dorsal region of binocular overlap as well as the whole set of contralateral visual projections, appear well-developed. We conclude that these subterranean rodents exhibit, paradoxically, diurnal instead of nocturnal visual specializations, but at the same time suffer a specific regression of the anatomical substrate for stereopsis. We discuss these findings in light of the visual ecology of subterranean lifestyles.
Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, de Chile.|Lehrstuhl für Zoologie, Technische Universität München, Freising-Weihenstephan, Germany.
T
T
Vega-Zuniga
Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, de Chile.
F S
FS
Medina
Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, de Chile.|Facultad de Medicina, Universidad Finis Terrae, Santiago, Chile.
G
G
Marín
Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, de Chile.
J C
JC
Letelier
Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.
A G
AG
Palacios
Department of Zoology, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
P
P
Němec
Laboratorio de Ecofisiología, Instituto de Investigaciones Marinas y Costeras, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina.
C E
CE
Schleich
Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, de Chile.
J
J
Mpodozis
D000818:Animals; D001766:Blindness / Q000175:diagnosis* / Q000209:etiology*; D005260:Female; D008297:Male; D009929:Organ Size; D012160:Retina / Q000378:metabolism / Q000473:pathology; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000473:pathology; D012377:Rodentia; D013477:Superior Colliculi / Q000378:metabolism / Q000473:pathology; D014786:Vision Disorders / Q000175:diagnosis / Q000209:etiology; D015348:Vision, Binocular; D014794:Visual Fields