| Autor: |
Tyrrell LP; SUNY Plattsburgh, Department of Biological Sciences, 101 Broad Street, Plattsburgh, NY, 12901, USA. ltyrr002@plattsburgh.edu., Teixeira LBC; University of Wisconsin-Madison, Department of Pathobiological Sciences, School of Veterinary Medicine, 2015 Linden Drive, Madison, WI, 53706, USA., Dubielzig RR; University of Wisconsin-Madison, Department of Pathobiological Sciences, School of Veterinary Medicine, 2015 Linden Drive, Madison, WI, 53706, USA., Pita D; Purdue University, Department of Biological Sciences, 915 W State Street, West Lafayette, IN, 47904, USA., Baumhardt P; Purdue University, Department of Biological Sciences, 915 W State Street, West Lafayette, IN, 47904, USA., Moore BA; University of California-Davis, William R. Pritchard Veterinary Teaching Hospital, School of Veterinary Medicine, 1 Garrod Drive, Davis, CA, 95695, USA., Fernández-Juricic E; Purdue University, Department of Biological Sciences, 915 W State Street, West Lafayette, IN, 47904, USA. |
| Abstrakt: |
The keen visual systems of birds have been relatively well-studied. The foundations of avian vision rest on their cone and rod photoreceptors. Most birds use four cone photoreceptor types for color vision, a fifth cone for achromatic tasks, and a rod for dim-light vision. The cones, along with their oil droplets, and rods are conserved across birds - with the exception of a few shifts in spectral sensitivity - despite taxonomic, behavioral and ecological differences. Here, however, we describe a novel photoreceptor organelle in a group of New World flycatchers (Empidonax spp.) in which the traditional oil droplet is replaced with a complex of electron-dense megamitochondria surrounded by hundreds of small, orange oil droplets. The photoreceptors with this organelle were unevenly distributed across the retina, being present in the central region (including in the fovea), but absent from the retinal periphery and the area temporalis of these insectivorous birds. Of the many bird species with their photoreceptors characterized, only the two flycatchers described here (E. virescens and E. minimus) possess this unusual retinal structure. We discuss the potential functional significance of this unique sub-cellular structure, which might provide an additional visual channel for these small predatory songbirds. |
