Coral Reef Project—Papers in Memory of Dr. Thomas F. Goreau. 13.

Further Studies on the Mucopolysaccharide Secreted by the Pedal Gland of the Marine Slug Tridachia Crispata (Opisthobranchia, Sacoglossa)

The reef-dwelling marine slug Tridachia crispata (Opisthobranchia, Sacoglossa) possesses endosymbiotic chloroplasts which contribute photosynthetically fixed carbon to the animal host. One of the predominant ways in which the slug utilizes chloroplast products is in the synthesis of mucopolysaccharide by the pedal gland.

Chemical analysis of the secreted mucopolysaccharide shows that it is acidic, sulphated, of large molecular weight (> 2 × 10⁶), and is composed of glucose, glucuronic acid, glucosamine, galactosamine, and traces of galactose. The protein moiety contains leucine, glutamic acid, aspartic acid, glycine, serine, valine, proline, and alanine. Many of these substances are derived from chloroplast photosynthesis.

The synthesis and secretion of photosynthetically derived materials by animals with autotrophic endosymbionts is widespread, and is viewed as an important aspect of the recycling of organic matter in coral-reef ecosystems.