Morphology, (Mollusca: Gastropoda Pulmonata)
BASTERIA, 52: 77-100, 1988 On morphology, function and taxonomic importance of the shell ribs in Clausiliidae (Mollusca: Gastropoda Pulmonata), with special reference to those in Albinaria Th.C.M. Kemperman & E. Gittenberger Systematic Zoology Section, Leiden University, c/o Rijksmuseum van Natuurlijke Historic, P.O. Box 9517, NL 2300 RA Leiden, The Netherlands In and other the shell hollow Clausiliidae, Urocoptidae a few groups ribs are not solid, but and and provided with complicated structures inside. These structures are described il- lustrated. Their be correlated with certain least within presence may a habitat, at a poly- Several of ribs and morphic species. physical consequences are suggested some are ex- perimentally tested. Especially shell weight and strength, surface water adhesion, shell permeabilityand warming up after insolation are dealt with. The possible adaptive value is discussed. Key words: Gastropoda Pulmonata, Clausiliidae, Albinaria, shell ribs, shell structure, shell formation, adaptation, taxonomy. Contents 1. Introduction 77 2. Material 78 2.1. Specieswith shells with hollow ribs 80 2.2. Species with shells with massive ribs 81 3. Morphologyofthe hollow ribs 81 3.1. The generalstructure 81 3.2. The septal particles 84 3.3. Chemical compositionofthe crystals 89 of 4. Development the ribs 89 5. Hollowribs and phylogeny 90 6. Hollowribs and habitat 91 7. and relevance ofshell ribs Physical consequences biological 94 7.1. Shell weight and strength 94 7.2. Surface water adhesion 95 7.3. Evaporationand shell permeability 97 7.4. Ribs and insolation 97 8. Acknowledgements 98 9. References 98 10. Samenvatting 99 1. Introduction Gastropod shells are often provided with ribs (costae), which are transverse eleva- on surface, different from the remains of former tions the shell e.g.
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