Abstracts - Deutsche Zoologische Gesellschaft

172 Neurobiology PostersP NB.3 - ENQuick and easy: active and passive unfolding of adhesive pads in antsThomas Endlein, Walter FederleDepartment of Zoology, University of Cambridge, UKAdhesive pads of ants can be unfolded both actively by the contraction of the claw flexor and passivelyby a pull of the leg towards the body. In severed legs of weaver ants (Oecophylla smaragdina),we investigated both mechanisms by pulling on the claw flexor tendon or by pulling on the leg. Inboth experiments, we simultaneously measured the force required to fully unfold the pad, usingforce transducers. Both the active and the passive unfolding can be explained by an elastic springmechanism deploying the pad gradually depending on the applied force. Force and pulling amplituderequired for unfolding were similar for active and passive mechanisms. During the passiveunfolding, faster pulls toward the body were required when the initial pad contact area was smaller.The passive unfolding may be essential during rapid perturbations. We tested this hypothesis byperforming rapid displacements of the surface. Pad contact area in weaver ants doubled in less than1 ms, demonstrating that this attachment reaction is a passive “preflex”. This was followed by a responseof the claw flexor with a delay of ca. 10 ms. We compared the forces required for unfoldingbetween arboreal weaver ants and ground-living carpenter ants (Camponotus rufipes). Even thoughweaver ants possess much larger pads, they required less force to unfold than those of carpenter ants.The easier unfolding of weaver ant pads may represent an adaptation to their arboreal habitat.P NB.4 - ENGanglion cell distribution, morphology and central projections in a weakly electric fishJacob Engelmann 1 , Roland Pusch 1 , Gerhard von der Emde 1 , Björn Karpestam 2 , Hans-JoachimWagner 21Institut für Zoologie, Abteilung Neuroethologie, Universität Bonn; 2 Anatomisches Institut,Graduate School of Neural and Behavioural Sciences, International Max Planck Research School,Universität TübingenAfrican weakly electric fish detect and distinguish objects through active electrolocation in completedarkness. In accordance to their nocturnal lifestyle the retina of G. petersii is highly specialized withhundreds of rods and tens of cones grouped in bundles. These “macro receptors” extend over roughly50 mikrons and are arranged in a regular hexagonal pattern and each bundle is optically isolatedfrom the others. Our earlier data show that the information from each bundle is transferred with astrong convergence to a few neurons of the inner retina, i.e. bipolar cells and horizontal cells, and toonly three or four ganglion cells. With their wide spacing, the macro-receptors suggest a very lowspatial resolution of the system. Here we report on the characterization of the ganglion cells based onanterograde labeling. Perikarya are located in the ganglion cell layer, and some are displaced to theinner nuclear layer. The density of photoreceptor bundles and ganglion cells is highest in the dorsalpart of the retina. Thus, the region of the visual field with the highest spatial resolution in G. petersiiis directed towards the bottom. Regarding the dendritic tree morphologies several different subtypesof ganglion cells are discernible, indicating that narrow-field and wide-field ganglion cells may bedistinguished. We will discuss the role of the retinal circuits and the bundle structure in contrastand/or movement detection.