Feeding Ecology of an Abalone, Haliotis discus hannai, in Their Early Life Stages
Recent studies on the feeding ecology of abalone, Haliotis discus hannai, during the early life stages were reviewed in this article. The feeding habits of H. discus hannai changed with growth, and three major changes in the feeding were identified. The first change occurred at the time of the metamorphosis of 0.28 mm in shell length (SL), namely a shift from lecithotrophy (yolk absorption) to exogenous feeding. The energy source of abalone is gradually transferred from yolk to particulate food after metamorphosis by the size of 0.3-0.4 mm SL. Several days of food limitation after metamorphosis leads to a failure to shift to exogenous feeding. In the second change, when the SL reached values of about 0.6-0.8 mm, post-larvae were able to digest diatom diet. They grew more rapidly, feeding on efficiently digested diatoms, whereas those fed poor diatom diet will generally grow slowly. The differences in the dietary value of diatoms for abalone were controlled mainly by the digestibility of diatoms. The final change consisted of a shift from a biofilm-dominated diet to a macroalgal dominated diet. Abalone (>1.8 mm SL) were able to utilize juvenile macro algae efficiently. Juvenile macroalgae provide a much higher biomass per unit area than small-volume, two dimensional diatom films. The energetics of diatom ingestion became insufficient to support rapid growth. These changes in feeding habits were closely related to ontogenetic changes in the digestive enzyme activities and the development of the radula morphology. The activity of macroalgal polysaccharide-degrading enzymes showed marked increase at 2 mm SL. The morphological development in the radula occurred mostly in abalone less than 4 mm SL, to complete adult radula which is suitable to graze macroalgae.
Abalone, feeding, growth, Haliotis discus hannai nutrition, survival
Tohoku National Fisheries Research Institute
Proceedings from an undisclosed conference; NOAA Central Library.
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