Nutritional potentialities of Chlamydomonas coccoides and Thalassiosira fluviatilis, as measured by their ingestion and digestion rates by the Queen Conch larvae (Strombus gigas)

Epifluorescence microscopy and ingestion and digestion indices were used to study the nutritional potentialities of two algae cells, Chlamydomonas coccoides and Thalassiosira fluviatilis, as a function of their ingestibility and digestibility by the Queen conch (Strombus gigas) larvae. The ingestibility and digestibility of both algae, which have been seldom used in conch hatcheries, were evaluated at four larval ages: 1, 10, 18 and 30 days after hatching. Veligers were reared at 100 larvae l(-1) and the temperature was kept at 28 +/- 1 degrees C. Ingestion and digestion rates were observed continuously for 8 h in 1920 larvae. The ingestion rate for those larvae fed T. fluviatilis were lower than the ingestion rate for those fed C. coccoides. It was also observed that larvae digested C. coccoides better than T. fluviatilis. Ingestion and digestion kinetics, as well as stomach filling of S. gigas larvae showed that the feeding behaviour of young larvae and those close to metamorphosis differed considerably. The ingestion and digestion levels indicate that C. coccoides is a food source recommended for S. gigas larvae. (C) 1997 Elsevier Science B.V.