Utilization of algal cell fractions by the marine herbivore the luderick, Girella tricuspidata (Quoy and Gaimard)

Absorption of 14C from the marine alga Enteromorpha by an herbivorous marine fish, the luderick, Girella tricuspidata, was used to demonstrate the capability of this species to utilize an herbivorous diet. Absorption of 14C from protoplasts and cell walls clearly demonstrated a capability of the luderick to utilize cell walls. Two patterns of absorption of algal fractions were seen, but in all cases isotope absorption by the fish was highest from protoplasts over a 16‐h digestion period. The first pattern, demonstrated by the absorptive tissues of the gut, showed greater absorption of the radioactive label from cell walls over 5 days than over 16 h. The second, occurring in the anterior regions of the gut and in the liver and spleen, showed greater absorption of 14C from cell walls over 16 h than over 5 days. It is suggested that the marker found in this second group of tissues derives from absorption in the pyloric caeca, the only absorptive region showing significant absorption of carbon label from cell walls over 16 h. Absorption of 14C from cell walls is greater over 5 days than over 16 h.