2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

specialization that can be found in the adaptive radiations of cichlid fish. The ?left
(L)? morph opens its mouth towards the left and a ?right (R)? morph towards the
right. These fish display handed (lateralized) foraging behavior, where the L morph
preferentially feeds on the scales of the right side of its victim fish and the R morph
bites the scales of the left side. We studied the degree of handedness and individual
variation of laterality of foraging behavior in relationship to morphological mouth
laterality in P. microlepis. In wild-caught adult fish mouth laterality is, as expected, a
very strong predictor of preferred attack orientation. Also laboratory-reared juveniles
exhibited a strong laterality in behavioral preference when feeding on scales, even at
an early age, although the initial level of mouth asymmetry appeared to be small.
This suggests that pronounced mouth asymmetry is not a prerequisite for handed
behavior in juvenile scale-eating cichlid fish and might suggest that behavioral
preference to attack a particular side of the prey might play a role in facilitating
morphological asymmetry.
����88 Gerlind U.C. Lehmann
Manipulating experiments on the role of internal genitalia in a bushcricket
(Orthoptera: Tettigoniidae): anchors or stimulatory devices?
Authors: Gerlind U.C. Lehmann 1 , Nadja C. Wulff 1
Affiliations: 1 Humboldt-Universität zu Berlin, Department of Biology, Behavioural
Physiology
Among most species male genitalia as well as secondary sexual organs are more
diverging compared to other body parts; hence they are one of the key properties in
species identification. In contrast to the broad knowledge about their morphological
form, the evolutionary selection forces affecting the shape and often even the
function of certain structures, which seem not to be directly involved in sperm
transfer, remains unclear.
In Tettigoniidae males of certain taxa possess sclerotisized internal genital structures,
called titillators. These titillators consist of paired structures that are covered inside
the male. During copulation, they are inserted rhythmically into the female?s genital
chamber. Their function for spermatophore transfer is unknown. Based on
comparative data (Vahed et al. 2011) it has been suggested, that they may act either
as anchors or stimulatory devices for female acceptance of the courtship and/or the
male's spermatophore. In this study, we tried to elucidate the function of the
titillators in Metrioptera roeselii. Therefore, two series of experiments were carried
out: (i) We removed the titillators in one group of males. During copulation we
counted the rhythmical titillator movement between unmanipulated males and those
with titillators cut off. Manipulated males showed a significant decrease of
rhythmical movements. Furthermore, males without titillators had a significant
number of failed spermatophore transfers, underlining the importance of the
titillators for the male reproductive success.
(ii) We deep froze couples in liquid nitrogen during copulation to examine the
positioning of the titillators inserted into the female?s genital chamber. The involved
anatomical structures of mating pairs were analyzed by high-resolution X-ray CT.
Visualizing the contact sides of the male titillators inside the female revealed no
anatomical counter structures in the females.
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