2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

�85 Michael Heethoff A 702 / 15:00
Functional morphology and bite performance of raptorial chelicerae of camel
spiders (Solifugae).
Authors: Michael Heethoff 1 , Franz Langer 1 , Arie van der Meijden 2
Affiliation: 1 Institute for Evolution and Ecology, University of Tübingen; 2 CIBIO, Centro
de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de
Vairão, Portugal
Solifugae are an understudied group of relatively large arachnids. These highly active
predators utilize their large chelicerae for feeding, defense, burrowing and mating.
We investigated the differences in cheliceral morphology and performance of two
ecologically divergent species from North-Africa; the cursorial Galeodes sp. and the
burrowing Rhagodes melanus. Bite force measurements show Rhagodes to be a
much stronger biter than Galeodes, both in absolute maximum force (Rhagodes 5,63
N, Galeodes 2,12 N) and relative to cheliceral size. Synchrotron-µ-tomographies of
one specimen for each species reveal large differences in physiological cross sectional
area (PCSA) and estimated muscle stress, resulting in a higher muscle stress in
Rhagodes. Relative bite forces of both species were in the range of pedipalpal pinch
forces of scorpions, but lower that pinch forces of crabs.
�86 Stefan Blazek A 702 / 15:15
Impact of UV-radiation on the bending resistance of barn owl and pigeon feathers
Authors: Stefan Blazek 1 , Hermann Wagner 1
Affiliation: 1 RWTH Aachen University, Institute for Biology II
The wings of the barn owl (Tyto alba) are constantly subjected to wearing. Feathers
are exposed to stress like turbulences in air, UV-radiation, degradation by bacteria
and collision with obstacles.
It was shown that most individuals of species with body weights below 0.5 kg replace
their feathers every year. The barn owl has a body weight of 400-500g. However, the
barn owl has an untypical moulting cycle extending over 2-3 years. Feathers are
replaced one by one sequentially.
The keratin of feathers is rich in cysteine. This amino acid includes sulfur and is able
to build disulfide bonds which underlie the high stability of the protein. It has a peak
in the absorption spectrum for wave lengths ranging from 280 to 310nm. An
exposure of UV-B radiation may destroy the disulfide-bonds and leads to a lower
stability of the protein.
With this study we aim to investigate the impact of UV-B radiation on the bending
resistance of barn owl feathers. Further we want determine whether the duration of
the moulting cycle is related to the change of the bending resistance induced by UV
exposure. For comparison we included the domestic pigeon (Columba livia), which
has an annual moulting cycle, in our study. The bending resistance is determined by a
2 point bending test. It was performed before and after the exposure to a UV-B
radiation dosage corresponding UV-B exposition in Germany for 2.5 years.
We will present data on the influence of UV-radiation on the bending resistance of
the feathers of both species.
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