FUNCTIONAL MORPHOLOGY OF THE DIGESTIVE SYSTEM OF THE NUDIBRANCH MOLLUSC ACANTHODORIS PILOSA

¹ Marine Science Institute, Northeastern University, East Point, Nahant, Massachusetts

This investigation has demonstrated that functional anatomy of the digestive system of Acanthodoris pilosa reflects the following modifications for manipulation of semi-liquid food:

1. The anterior buccal mass is enlarged forming a muscular buccal pump which is utilized to suck the contents of the ectoproct into the buccal cavity once the radula has rasped a hole in the zooecium.

2. A spined buccal lip at the entrance of the buccal cavity probably functions to anchor the muscular buccal mass during pumping and/or scraping activities.

3. An enlargement of the antero-dorsal wall of the esophagus forms a thin-walled crop capable of distension and functioning for storage of semi-liquid food.

4. The digestive gland epithelium consists of two cell types, pyramidal-shaped crypt cells and more numerous tubule cells with their variants A and B. The rhythmic nature of the digestive epithelium involves: (1) a period of ingestion of food particles by fragmentation phagocytes and the tips of the tubule cells, (2) a concentration of undigested materials in the tubule cells, and (3) extrusion of these waste materials into the lumina of the digestive gland.

5. There is a reduced cecal evagination of the dorsal stomach which probably functions to form small fecal pellets.