Abstracts - Deutsche Zoologische Gesellschaft

68 Morphology SymposiumO MO.7 (Mo) - ENJaw-closing mechanics in caecilians: a biomechanical modeling approachThomas KleinteichBiozentrum Grindel und Zoologisches Museum, Universität HamburgThe caecilian (Lissamphibia: Gymnophiona) skull is characterized by numerous specializations to afossorial lifestyle. The skull is compact and heavily ossified, the jaw closing muscles (mm. levatoresmandibulae) are covered laterally by bone (the squamosal). A hyobranchial muscle, the m. interhyoideusposterior, acts as an additional second jaw closing system in caecilians. The recruitment ofthe m. interhyoideus posterior to the jaw closing apparatus is suggested to support the mm. levatoresmandibulae those space is restricted by the squamosal. I will present a biomechanical model thatpredicts bite force over gape angles for the two jaw closing systems. Every muscle in the caecilianjaw closing apparatus has a critical gape angle above that the muscle will act against bite force. Theintegration of the two jaw closing systems, however, results in almost constant bite forces over awide range of gape angles. Skull morphology has a direct impact on the relative contribution of theseparate jaw closing systems to total bite force. In species with a fenestrate temporal region (zygokrotaphy)the mm. levatores mandibulae contribute more to total bite force than in species with aroofed temporal region (stegokrotaphy). The action of the m. interhyoideus posterior on the ventralside of the lower jaw, caudal to the jaw joint, correlates with an unusual jaw joint in which the fossais a deep groove which has an oblique orientation.O MO.8 (Mo) - DELooking deep into your eyes – a morphological multi-method approach to learn aboutvertebrate visionMartin HeßBiozentrum Ludwig-Maximilians-Universität München, Planegg-MartinsriedThe fully differentiated vertebrate eye is a complex 3D-structure on the organ-, tissue-, cell- andsubcellular level – a comparison of developmental stages and related species creates additional dimensions.Various morphological characters in different scales and coordinate systems, like eyepositioning within the head, internal eye geometry, retina layering and topography, architecture ofphotoreceptors and pigment epithelium cells, as well as the neuroanatomy and synaptic wiring of theinner retina all have to be recorded in 3D. This was done exemplarily with the eyes of selected teleostspecies using tomography (µMRT, µCT, TEM), mechanical sectioning (light microscopy, TEM) andoptical sectioning (CLSM, 2-photon microscopy), followed by computer aided segmentation, surfacerendering, volumetry, cell counting and topographic mapping and supplemented by REM andRaman measurements. This way complex structure data were obtained for a description, comparisonand interpretation of some lower vertebrate eyes in terms of probable visual functions, adaptationsto habitats and habits and evolutionary aspects, e.g. eye migration in flatfishes, polarization visionin anchovies, duplex eel retinas with banked rods and the development of the eyes and supportingstructures in different teleost species.