The periganglionic sheath regulating nervous system homeostasis in snails living in terrestrial or aquatic habitats: A histochemical approach

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Terrestrial and freshwater snails are very sensitive to water balance influencing habitat colonization. The homeostasis of the central nervous system is maintained by the periganglionic connective tissue sheath (PCTS), although the molecular composition responsible for water retention is yet to be clarified. In this chapter we investigated the type and location of these proteins and carbohydrates which are potentially functioning as water-binding molecules. The acid/base and red/ox characteristics of the PCTS of a terrestrial Helix pomatia and a freshwater Lymnaea stagnalis were visualized by histochemistry. Based on the different binding affinity of silver ions to protein macromolecules, reticular fibers were found abundant in the basement lamina, while collagen was found mainly in the central matrix of the PCTS. The interstitial space was impregnated by mucin which was also found in acini as revealed by periodic acid - Schiff (PAS) reaction. A part of this material had both weakly and heavily acidic (sulfated) glucosaminoglycan side chains visualized by cationic dyes such as acridine orange and alcian blue (pH 2.5), respectively. In several areas of the H. pomatia PCTS highly reducing molecules were detected. Although the chemical composition of the PCTS was proved to be similar in both species, H. pomatia had a markedly thicker sheath than L. stagnalis, which was rich of carbohydrates implying a higher capacity for energy storage, cryoprotection, and water-binding. In further investigations the functional groups of glycoproteins were determined using carbohydrate side chain-specific lectin probes. The majority of the lectin-labeled molecules were bound to the PCTS. Galactose (Gal) - N-acetyl galactosamine (GalNac) oligomers, detected by jacalin, showed a uniform distribution in the PCTS. In H. pomatia a single, but extensively glycosylated protein (~200 kDa) was found, in contrast to L. stagnalis, in which a number of proteins showed only weak jacalin signals. N-acetyl glusosamine (GlcNac) oligomers, labeled by Lycopersicon esculentum lectin or wheat germ agglutinin, were also detected more frequently in L. stagnalis, whereas in the PCTS of H. pomatia a single protein (~11 kDa) displayed extensive glycosylation. Mannose was found to bind multiple proteins in both species. Lectin labeling revealed that the basement lamina contains a significant amount of carbohydrates. Among them the terminal Gal bound to Ricinus communis agglutinin was characteristic for H. pomatia, whereas the terminal GalNac detected by the Vicia villosa agglutinin was observed only in L. stagnalis. Our results indicate a complex molecular structure of the snail PCTS, playing a role under different humidity conditions, hence influencing the habitat of the animals.

Original languageEnglish
Title of host publicationGastropods
Subtitle of host publicationDiversity, Habitat and Genetics
PublisherNova Science Publishers, Inc.
Number of pages16
ISBN (Print)9781613246955
Publication statusPublished - Dec 1 2011


ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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