Abstracts - Deutsche Zoologische Gesellschaft

Neurobiology Posters 183P NB.26 - ENPolarization-sensitive descending neurons in the nervous system of the locustSchistocerca gregariaUlrike Träger, Uwe HombergFachbereich Biologie – Neurobiologie/Ethologie, Universität MarburgMany insects rely on a sun compass for spatial orientation. In addition to direct sunlight, they canalso use the polarization pattern of the blue sky as a reference to determine navigational directions.The polarization pattern is perceived by a specialized dorsal rim area of the compound eye. Studiesin locusts have demonstrated a compass-like map of E-vector orientations in the central complex(Heinze and Homberg, 2007, Science 315:995) and suggest that this brain areas act as an internalsky compass. In order to understand how polarized light information affects flight motor circuits,we have analyzed polarization sensitivity in neurons descending from the locust brain to thoracicganglia. Responses of descending neurons to visual stimuli including polarized light were recordedintracellularly from the neck connectives. Most descending neurons investigated so far exhibitedbackground spiking activities in the dark ranging from a few spikes up to 20 spikes per second.Many neurons showed phasic excitations to lights-on and/or lights-off. In response to polarizedlight, neurons showed excitations and inhibitions at orthogonal E-vector orientations, characteristicfor polarization-opponent interneurons (POL neurons). Current experiments are aimed at tracingthe arborizations of descending POL neurons in the brain and thoracic ganglia. Supported by DFGGrant HO 950/18-1.P NB.27 - ENOrientation to jetflow and particulars of the flow field in Northern KrillMeganyctiphanes norvegica (M.Sars 1857)Konrad Wiese 1 , Mufti P. Patria 21Tierphysiologie, Universität Hamburg; 2 Department of Biology, University of IndonesiaSwimming in formation rests on a mechanosensory analysis of the flow field generated by locomotingkrill. The flow field is generated by metachronally beating swimmerets arranged at the ventralside of the pleon. The flow field is characterized by the jetflow of circular crossection, by the 6 Hzmodulationof the jetflow in the rhythm of the pleopod-beat, and by a ringvortex which developsaround the jetflow at approximately 10-12 cm behind the pleopods of tetheredly swimming shrimps.Our hypothesis is, that the energetically favourable position ontop of the ring vortex is the firstlandmark for the follower-shrimp, a second landmark could be the limit of extension of the 6 Hzmodulationof the flow. As a third component a rheotaxis orientation towards an incoming jetflowis likely to help maintain the energetically favorable spot in the flow field. In the line of our experimentswe measured modulation in the flowjet by CTA-anemometry, constructed a piston type pumpwith walves as a technical analog of the swimmeret pump and observed and recorded components ofbehavior in response to periodically diverted flow direction. Additionally we tested the large antennasas potential tools to hold on to a ringvortex. Equipment provided by DFG Wi-363 Travel grantby DAAD to M.P.P