384 University of California Publications in Zoology [Vol. 



INTRODUCTION 



Ever since the classical investigations of Teredo by Sellius in 

 1733, it has been debated periodically whether or not the destructive 

 boring mollusks of this group derive any nutriment from the wood 

 which they so effectively perforate. Sellius himself discussed the 

 question (p. 108) without arriving at a definite conclusion. Reimarus 

 (1773, pp. 55 ff.) expressed a negative opinion, which was shared by 

 Home (1814, p. 373), who examined wood particles removed from the 

 bodies of the animals and thought them to be unchanged by the 

 digestive fluids. Baumhauer (1866, p. 19) states unreservedly that 

 Teredo bores in wood, not for nutriment, but solely to secure a pro- 

 tected dwelling. Most recent writers, such as Sigerfoos (1908, p. 218), 

 Moll (1914, p. 257), and Caiman (1919, p. 12), although considering 

 plankton the principal food of the organisms, admit the possibility 

 that some nourishment may be derived from the wood. Bartsch, 

 however, in a recent monograph (1922) inclines to the earlier view 

 of non-utilization of the wood particles as food, suggesting (p. 4) 

 witli apparent seriousness that "the shipworm may simply indulge 

 in a partial meal of this kind to have the comfortable feeling of a 

 copious repast." 



BIOLOGICAL CONSIDERATIONS 



The arguments against utilization of the wood as food are several 

 and varied. Certain near relatives of Teredo (Pholas, Zirphaea, and 

 Saxicava) bore for protection only, in such substances as sandstone, 

 limestone, shale, marl, and gneiss — materials which cannot be sup- 

 posed to yield them any nourishment; these indigestible borings may 

 even be found in considerable quantities in the digestive tract of the 

 rock borers (Caiman, 1919, p. 12), so that the presence of wood 

 borings in the digestive tract of Teredo is of itself no proof of 

 utilization of wood as food. The principal constituents of wood, 

 cellulose and lignin, are notoriously resistant to digestive action, so 

 that they pass through the digestive tract of many animals entirely 

 unchanged by the enzymes there present. Teredo is equipped to 

 take its food from the water as do other lamellibranchs ; also, the 

 inner end of a teredo's burrow is often closed off by the forma- 

 tion of a shelly cross-partition, and the animal may live for an 



