Abstracts - Deutsche Zoologische Gesellschaft

82 Physiology SymposiumO PH.3 (Sa) - ENDigestive physiology of the cricket, Gryllus bimaculatus (Ensifera, Gryllidae)Matthias W. Lorenz 1,2 , Joseph Woodring 21Lehrstuhl Tierphysiologie, Universität Bayreuth; 2 Lehrstuhl Tierökologie I, Universität BayreuthAdult female crickets voraciously feed for the first 3 d of adult life. Within 2 d after adult moult, fatbody energy stores are filled to a maximum and thereafter decline because fuel is provided for eggproduction. We investigated the source, activity, and flow of digestive enzymes, the nutrient flow,and the morphology of the gut tract to better understand the mechanisms that allow female cricketsto process such high amounts of food within a very short time. On d 0, proteases and amylases flowfrom the midgut caeca, the primary site for secretion of digestive enzymes, through the proventriculusinto the empty crop to allow some digestion of carbohydrate and protein as soon as food ispresent. The partially digested food is then ground in the proventriculus, partly squeezed throughfilter-like folds into the caecal lumen and mixed with digestive enzymes. Then, the food mush comingfrom the proventriculus and from the caeca is mixed and forced into the lumen of the peritrophicmembrane, leaving no exoperitrophic space. In the ileum, however, the dorsal wall bulges out toform a large exoperitrophic pouch into which finger-like invaginations project, giving rise to highlybranched setae, which effectively hold symbiotic bacteria in place. These bacteria are thought to assistin the digestion of complex carbohydrates and probably provide the main building blocks for thesynthesis of fatty acids in the fat body. Supported by the DFG (Lo 697/4-3 and 4-4)O PH.4 (Sa) - DELipoprotein mediated lipid uptake in oocytes of Platynereis dumerilii (Polychaeta)Ulrich Hoeger, Björn Felber, Sven SchenkInstitut für Zoologie, Abt. I, Johannes Gutenberg-Universität, MainzOocytes of polychaetes store large amounts of lipids which can be supplied either by exogenousuptake or autosynthesis. We have investigated the role of a recently described non sex specific discoidallipoprotein (LP) in the lipid supply for the growing gametes in Nereis virens and Platynereisdumerilii. Fluorescence labeled LP was readily incorporated into oocytes via endocytotic vesicles.After uptake, LP containing endocytotic vesicles fused with the yolk granules of the oocyte indicatingthese organelles as the primary lipid storage site. The large intracellular lipid droplets did notshow any LP related fluorescence. Western blots of oocytes using a LP specific antibody did notreveal intact LP apoproteins but only peptide fragments indicating that the LP is degraded inside thecell. Our observations suggest the importance of the LP-mediated lipid uptake in oocytes of Nereididpolychaetes in addition to the uptake of another well known lipoprotein, the yolk precursor proteinvitellogenin and demonstrate for the first time the LP mediated lipid uptake in male germ cells andeleocytes, coelomic cells with specific functions in reproduction. Supported by the Deutsche Forschungsgemeinschaft(Ho 889/7-1)