The biology, ecology and functional aspects of the organs of feeding and digestion of the S.E. Asian mangrove bivalve, Enigmonia aenigmatica (Mollusca: Anomiacea)

Enigmonia aenigmatica (Holten 1803) is an anomiid bivalved mollusc highly adapted for life attached to the trunks, projecting prop roots and leaves of mangrove trees. It is a characteristic member of the S.E. Asian mangrove community. It exists in four growth forms, or morphs determined by the nature of the surface on which settlement takes place. It is also orientated and positioned on the tree trunks of Avicennia and the prop roots of Rhizophora , in relation to the long axis of the tree and the direction of the current. Further aspects of the biology and ecology of Enigmonia are discussed. Enigmonia is monomyarian and lies on its right shell valve. This has resulted in an asymmetry which is of especial significance with regard to an understanding of the functional morphology of the organs of feeding and digestion in particular. The eccentricities seen in Enigmonia have been compared with the adaptations found in other anomiids in particular and other bivalves in general. The feeding and digestive cycle of Enigmonia has been described and found to be correlated with the rhythm of the tide; it is essentially similar to that described for some other littoral bivalves. The adaptations and specializations of Enigmonia are discussed in relation to its life in the mangal.