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Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, PO Box 11.461, CEP 05422-970, São Paulo, Brazil
(e-mail: sonialop{at}uol.com.br)
Studies on the digestive system of the Teredinidae are useful for a better understanding of the evolution of these bivalves in relation to the xylophagous habit. Neoteredo reynei and Psiloteredo healdi, two common species in Brazilian mangroves, have evolved differently in their methods to use wood as food, despite the similarities in the anatomy and functioning of their globular type II stomachs. N. reynei is predominantly xylophagous throughout its life, while P. healdi, despite its predominant suspension-feeding habit, uses wood more efficiently as the animal grows older. The outstanding differences that allow these conclusions are the large size of the appendix and anal canal in N. reynei, always conspicuous and packed with wood, and the small appendix of P. healdi, which increases in size with age. Based on anatomical data and revision of the literature, it is suggested that in both species the appendix, and also the anal canal in N. reynei, is of primary importance in the digestion of wood and absorption of nutrients, counterbalancing the reduced specialized digestive diverticula.
