Abstract

In view of the necessity to conserve threatened species like the Queen Conch Strombus gigas, the development of techniques for its cultivation arises. In order to contribute to this development, this study presents the effect of diet on feeding behavior of S. gigas veliger larvae. This effect was studied by means of the direct observation of ingestion and digestion, using the epifluorescence microscopy. Five microalgal diets were tested: Tetraselmis suecica, Tetraselmis chuii, I. aff. galbana, Chlamydomonas coccoides and Thalassiosira fluviatilis. Temperature was 32ºC; food concentration was 10,000 cells/ml, and larval density was 400 larvas*/L. To detect ingestion, larvae were fed for two hours, and observed under the epifluorescence microscopy each hour. To observe digestion, larvae were sieved and placed in new containers with filtered seawater without food. Ingestion and digestion were observed each hour, during eight hours, and at 24 hours after feeding. All observations were made on live larvae. To compare feeding behavior between different diets and temperatures, the absolute ingestion index (AII) and absolute digestion index (ADI) were used. A qualitative estimation of the stomach filling (GR), according to diet was also done. Although the AII was high with the five diets (90 - 77%), the highest GR (75 a 100%) were observed with T. suecica, T. chuii, I. aff. galbana and C. coccoides. A 100% of larvae fed T. fluviatilis had an RG ? 25%. Respect the AID, the lowest value is observed with T. fluviatilis (66%); while the other diets resulted in an index was between 80 and 86%.

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