Karl-Heinz Tomaschko

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Chitin is usually found in stiff extracellular coatings typified by the arthropod exoskeleton, and is not associated with the soft, flexible mollusc skin. Here, we show, however, that chitin in nudibranch gastropods (Opisthobranchia, Mollusca) occurs as intracellular granules that fill the epidermal cells of the skin and the epithelial cells of the stomach.(More)
Chemical communication is virtually universal among terrestrial and aquatic organisms. Chemical signals control the interactions of cells and organs (hormones) as well as the intra- (pheromones) and interspecific (allelochemicals) relationships between animals. The review considers three examples for chemical communication in insects and other arthropods on(More)
Parapodia of the sacoglossan slug Elysia timida were preserved by high-pressure cryofixation during feeding experiments and investigated with transmission electron microscopy. This slug has been known for its long-term retention of active chloroplasts and photosynthesis. We observed different stages of phagocytosis of chloroplast components from ingested(More)
Cross-linked and uncross-linked acrylamide polymers were used to alleviate technical difficulties in cryosectioning and autoradiographic processing of marine arthropods (Pycnogonum litorale), larval insect tissues (Sarcophaga bullata), and amphibian (Xenopus laevis) oocytes. Rapidly polymerized cross-linked acrylamide was used to prepare sections from an(More)
In defense against attack by predators, cnidosacs in the tips of cerata (dorsal appendages) of aeolidacean nudibranchs discharge masses of mature nematocysts that are derived from cnidarian food. Cnidosac-related structures in various nudibranchs may provide a reconstruction of potential steps in the evolution of cnidosacs. Such structures in the cerata of(More)
Pycnogonum litorale (Ström) is unpalatable to the common shore crabCarcinus maenas, a generalist predator in the pycnogonid's habitat. A feeding bioassay reveals that the crabs are deterred by ecdysteroids that occur in high levels in all developmental stages ofP. litorale. The total ecdysteroids in the pycnogonids reach 5.9×10(-4) M. The 20-hydroxyecdysone(More)
Molting in pycnogonid larvae, Pycnogonum litorale, is accelerated by exposing the animals to 20-hydroxyecdysone at concentrations of 10 to 1000 ppm during Days 5 to 9 after the first ecdysis. Hormone application at the beginning or at the end of the molt cycle, as well as treatment all through the molt cycle, delays or even inhibits the molt by upsetting(More)
In embryos, larvae, and juveniles of Pycnogonum litorale, unusual ecdysteroids have been found at excessively high levels. Concentrations and dynamics of the following eight ecdysteroids were determined by HPLC: 20-hydroxyecdysone, 20-hydroxyecdysone 22-glycolate, (25R) and (25S) isomers of 20,26-dihydroxyecdysone 22-acetate,(More)
Six species of sacoglossan sea slugs engulf and store chloroplasts from their algal food (kleptoplasts) in digestive gland cells for weeks. The question is unresolved as to why kleptoplasts are retained only in certain species, while in most others they are digested. We recently showed phagocytosis of algal chloroplasts by digestive cells in the long-term(More)
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