Abstract

The feeding habits and growth relationships of the keyhole limpet ("lapa") Fissurella picta were analyzed in the field and under laboratory conditions. This species is of significant commercial value and considerable ecological importance in southern Chile. F. picta is not strictly a herbivore, although it prefers algae; the quantity of vegetable items consumed compared with animal items did not vary seasonally. The items most commonly found in the stomach of F. picta were the algae Ulva sp, Polysophonia sp and Gelidium sp. The abundance pattern of the principal items did not vary seasonally. However, there was greater diversity in the summer. The relative abundance of items in the diet was closely associated with their relative abundance in the environment. Under laboratory conditions, adults showed a higher consumption rate for the alga Gracilaria chilensis (artificial diet) than for Ulva sp (natural diet). The preferred alga is not usually found in the natural habitat of F. picta and has a lower caloric value than that of Ulva sp. G. chilensis proved to be the best source of energy available for growth in juveniles. Keyhole limpets feeding on the chlorophyte alga Ulva sp show a negative energy balance. Specimens maintained in suspended systems and fed with the artificial diet (G. chilensis) reached the average commercial size of 53 mm in ?3 y; the average survival rate was 90%. The results suggest that keyhole limpets prefer food with a high energetic scope for growth, although in field conditions they consume food with a lower energetic content but high in abundance. Factors such as morphology or palatability of food are more important than caloric value or presence in the natural habitats of keyhole limpets. This information is important for the culture of the keyhole limpet.