Nachweis der epitokie als fortpflanzungsmodus des polychaeten Eunice siciliensis (Polychaeta: Annelida)

Eunice siciliensis (Grube)¹ is a sedentary polychaete with separate sexes; its germ cells develop only in the posterior part of the body. In March and April, females with whitish or even dark-green oocytes, males with only few spermatogonia, and individuals with no germ cells at all were discovered in the “coralligène” of the Banyuls region (European Mediterranean Sea). In august, besides immature and sexually non-differentiated worms, mature individuals of both sexes were captured: females with dark bluish-green oocytes of diameters up to 250μm, and males with milky genital segments containing spermatozoa. Soon after isolation from the substrate, these individuals performed characteristic movements with their posterior body parts, which then autotomized, and released ova and spermatozoa. Evidence is given that the anterior, atokous body parts survive in their tubes in the “coralligène” after separation from the epitokous portions, and regenerate new genetal segments. The development of gametes observed in these regenerated segments indicates the ability of E. siciliensis to reproduce more than once during its lifetime. Not only caudal, but also prostomial regeneration was observed; the formation of a (morphologically different) secondary prostomium appears to be essential for any development of germ cells in worm fragments. E. siciliensis exhibits surprising similarities in habits and in formation of an epitokous form with Eunice viridis (Gray), the “palolo” worm of the South Pacific Ocean, but nevertheless, lacks the prominent criteria of this famous species: the ventral eye spots on each genital segment in males and females, and the paired areas with brown pigmentation on the ventral side of each epitokous segment in the males.     

Carbon metabolism and strobilation in Cassiopea andromedea (Cnidaria: Scyphozoa): Significance of endosymbiotic dinoflagellates

Scyphopolyps and scyphomedusae of Cassiopea andromeda Forskål (Cnidaria, Scyphozoa) containing dinoflagellate endosymbionts (zooxanthellae) were investigated for rates and pathways of carbon fixation. Photosynthesis by the algae, accounting for 80 and 15 mol C h^-1 on a dry weight basis in medusae and polyps, respectively, by far exceeds dark incorporation of inorganic carbon by the intact association. Photosynthetic carbon fixation is operated via C₃ pathway of carbon reduction. DCMU-treatment (1×10^-6 M and 1×10^-5 M) completely inhibits light-dependent carbon assimilation. Major photosynthates presumably involved in a metabolite flow from algal symbionts to animal tissue are glycerol and glucose. A total of 5–10% net algal photosynthate appears to be seleased in vivo to the host. This is probably less than the energy supply ultimately required for the nutrition of the polyps and medusae. The presence of zooxanthellae proved to be indispensable for strobilation in the scyphopolyps. However, photosynthesis by algal symbionts as well as photosynthate release is obviously not essential for the initiation of ephyrae as is shown by DCMU-treatment, culture in continous darkness, and aposymbiotic controls. It is therefore concluded that strobilation is supported, but not triggered by algal photosynthetic activity. The induction of strobilation thus seems to depend on a more complex system of regulation.     

How <Emphasis Type="Italic">Doratomyces stemonitis</Emphasis> copes with Benzoxazolin-2(3<Emphasis Type="Italic">H</Emphasis>)-one (BOA), its derivatives and detoxification products

Summary. Doratomyces stemonitis (Hyphomycetales, Dematiaceae) is a saprotrophic fungus belonging to the mycobiota of the cereal rhizosphere. The fungus is able to metabolize benzoxazolin-2-(3H)-one and a variety of its derivatives including higher plant detoxification products, microbial degradation products and the chemically rather stable 2-amino-(3H)-phenoxazin-3-one. D. stemonitis can use all of these compounds as sole C-sources but their utilization, especially that of microbial degradation products and 2-amino-(3H)-phenoxazin-3-one, seems to be highly energy consuming, resulting in slow mycelium growth and a change of colony morphology. Benzoxazolin-2-(3H)-one derived compounds induce the synthesis of different isoforms of a glycosylated protein with sequence homologies to the endo-1,3-β-glucanase Asp f2, an allergen from Aspergillus fumigatus and other Asp f2-like proteins e.g., from Verticillium dahliae or PRA1 antigen from Candida albicans. The induction of the protein is regarded as a stress response.