Symposien Donnerstag

Änderungen im Programmablauf vorbehalten.

Raum Paris 16:15 - 17:45 01.10.2015
Symposium Do27
Sehen Tiere besser als Menschen? Do animals see better than humans?
Vorsitzende/r: Frank Schaeffel (Tübingen), Karl Ulrich Bartz-Schmidt (Tübingen)

The symposium compares visual performance in various animals with the one in humans and explains when and why animals may be superior. It includes analyses of physical limits of vision. Humans appear as generalists with surprisingly optimized visual function. Das Symposium vergleicht die Sehleistungen verschiedener Tiere mit denen des Menschen und erklärt, wann und warum Tiere überlegen sein können. Dabei werden auch die von der Physik vorgegebenen Grenzen analysiert. Der Mensch erscheint als Generalist mit erstaunlich vielseitig optimierter Sehfunktion.
Referent/in: Henrik Mouritsen (Oldenburg)
The magnetic compass of migratory birds is based on a light-dependent, radical-pair-based, chemical compass mechanism. Most likely, a cryptochrome is the primary sensory molecule. Neuroanatomical data show that a specific part of the birds visual system is involved in processing magnetic compass information. This raises the question whether birds actually "see" the magnetic field.
Referent/in: Frank Schaeffel (Tübingen)
The light sensitivity of the dark-adapted human retina reaches the physical limits: also human rods can respond to a single photon. To improve light sensitivity further, the following options exist (1) increasing the aperture and reducing the focal length of the optics of the eye which causes brighter retinal images, (2) lowering body temperature to reduce thermal noise, (3) adding a reflective layer behind the photoreceptors, (4) elongating rod outer segments. Animals make use of all of them.
Referent/in: Almut Kelber (Lund)
Normal human photopic vision, based on three types of cones, allows us to see millions of colours. Most mammals, however, have dichromatic colour vision based on only two cones, types, many marine and some nocturnal mammals are even cone monochromats and completely colour-blind. In contrast, fish, reptiles and birds are tetrachromats able to see a larger spectrum of light, and colours unseen by humans, and similar is true for some insects such as butterflies and dragonflies. Even more surprising, some animals can see colours in very dim light, at night. The seminar summarizes our present knowledge on animal colour vision abilities using selected examples.
Referent/in: Frank Schaeffel (Tübingen)
When animals move while they hunt, motion parallax is a perfect cue to determine the distance to the prey; it also works monocular. If animals attack from an imobile position, like a chameleon or a preying mantis, other cues are used - accommodation, triangulation, or stereopsis. Traces of some of these depth cues are found in human visual behavior, although convergence and accommodation are poor distance cues in humans.
Referent/in: Wolf Harmening (Bonn)
The eyes of some nocturnal animals have excellent optics. Yet in specific cases, the animal’s behavioral resolution capacities fall behind, by an order of magnitude in the barn owl, as will be presented. These and results from other species stand as a clear counterexample against an intuitive rule of thumb that optical and behavioral visual performance form a congruent pair.