Habits and morphological adaptations of mytilids (Mollusca: Bivalvia) from coastal and reefal environments in southwest Malagasia (Indian Ocean)
Arnaud, P.M.; Thomassin, B.A. (1990). Habits and morphological adaptations of mytilids (Mollusca: Bivalvia) from coastal and reefal environments in southwest Malagasia (Indian Ocean), in: Morton, B. (Ed.) The Bivalvia: Proceedings of a Memorial Symposium in honour of Sir Charles Maurice Yonge (1899-1986) at the 9th International Malacological Congress, 1986, Edinburgh, Scotland, UK. pp. 333-344
In: Morton, B. (Ed.) (1990). The Bivalvia: Proceedings of a Memorial Symposium in honour of Sir Charles Maurice Yonge (1899-1986) at the 9th International Malacological Congress, 1986, Edinburgh, Scotland, UK. Hong Kong University Press: Hong Kong. ISBN 962-209-273-X. 355 pp., more
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| Authors | | Top |
- Arnaud, P.M.
- Thomassin, B.A.
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| Abstract |
The Tulear reef complex was chosen as a model for this work because of its high biotope diversity, its mytilid richness, and more generally because of the large background knowledge about its faunistic assemblages and environments. Distribution through the reef complex, habits, shell shape and ornamentation of 13 representative species are analysed on the basis of data obtained during an ecological survey. Five types of substrate relationships, linked to characteristic shell features, are identified: A. Epifaunal (or epibyssate) on hard substrates, i.e., either 1, exposed or 2, cryptic species with large or medium modiolid or mytilid shells, smooth in the former and radially ribbed in the latter; B. Infaunal (or endobyssate) in hard substrates, i.e., either 3, borers or 4, nestlers with elongate smooth shells in the former and modiolid shells with radial striae in the latter; C. Infaunal (or endobyssate) in soft substrates, i.e., 5, nestlers with thin glossy modiolid shells. The exposed epibyssate mussels, Modiolus auriculatus and M. elongatus, and borers of the genera Lithophaga and Botula are generally dominant, except in deeper waters where endobyssate mussels predominate. Almost all habitats are colonized, with few niche overlaps. The development of Modiolus beds in the lower intertidal appears linked to peculiar hydrological (laminar currents) and trophic conditions, and not predation. |
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