FEEDING, TENTACLE AND GUT MORPHOLOGY IN 5 SPECIES OF SOUTHERN AFRICANINTERTIDAL HOLOTHUROIDS (ECHINODERMATA)

Light, scanning and transmission electron microscopy were used to comp are the structure of the tentacles and digestive tracts of four specie s of intertidal dendrochirote (Roweia stephensoni, Pseudocnella sykion , Aslia spyridophora, R. frauenfeldi frauenfeld), and one species of a spidochirote holothuroid (Neostichopus grammatus). In addition, gut le ngths and contents of the five species were compared. Gut contents wer e sieved to determine the size of the particulate matter ingested. Row eia stephensoni, P. sykion and A. spyridophora were found to be suspen sion feeders using dendritic tentacles to capture and ingest food part icles mostly <53 pm in size. Roweia f. frauenfeldi was also a suspensi on feeder but, had atypical (reduced) dendritic tentacles which captur ed food particles between 250 mu m-1.18 mm in size. Neostichopus gramm atus was a deposit feeder, ingesting sediments mostly between 106-500 mu m using tentacles which are peltate with ramified processes. The gu t lengths of the four suspension-feeding species were found to be sign ificantly (p <0.001) longer than that of the deposit feeder. The diges tive tract of all species was composed of four tissue layers, with the digestive epithelial layer of the anterior and posterior ends of the intestine of suspension feeders being significantly thicker (52 to 57 mu m) than that of the deposit feeder (about 19 to 29 mu m). In additi on, the epithelial layer of the intestine of suspension feeders contai ned more highly vesicular enterocytes than that of the deposit feeder.