CONTENT - International Society of Zoological Sciences

S25 ICZ2008 - Abstracts
Evolution of eyes and visual tasks
Dan-Eric Nilsson
The Lund Vision Group, Lund University, Dept. of Cell and
Organism Biology, Zoology Building, Helgonavagen 3, 22362 Lund,
Sweden
Vertebrates, cephalopods, and arthropods have prominent eyes
that are involved in most of the behaviours these animals display.
But it is not the eyes and brains themselves that provide the
selective advantage driving evolution of their visual systems.
Rather, it is the ability to perform visual tasks that drive the
evolution of vision. Naturally, early stages in the evolution of these
complex visual organs must have been simpler, and served fewer
visual tasks. Hence, eye evolution is driven by a consecutive
accumulation of visual tasks. Each task ads to the requirements on
eye structure, making it gradually more complex. For these
reasons, reconstructions of eye evolution should ideally be based
on an understanding of the sequential addition of visual tasks. In
particular, it is interesting to ask what the first visual tasks might
have been, and what requirements these would have placed on
the structure and function of early eyes. With this objective, we
have investigated vision in a group of simple and phylogenetically
basal animal, the box jellyfish. Behavioural experiments indicate
that these animals use vision primarily for positioning in the habitat,
and for negotiating obstacles. To serve these tasks, the eyes are
tuned for low spatial frequencies and are colour blind. The findings
indicate that low resolution is not just sufficient, but in fact
desirable in early stages of eye evolution. The lecture will analyse
early phases of eye evolution and identify visual tasks and neural
mechanisms that were involved in the first imaging visual systems.
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