Digestive physiology and metabolism of green abalone Haliotis fulgens from postlarvae to juvenile, fed three different diatoms

Abstract

Growth, survival, digestive enzymes, ingestion rates, digestibility, fatty acid profile and energy budget were used to assess the nutritional quality of three diatoms as food for the first 3 months of age: Navicula incerta (NAV), Amphiprora paludosa (AMP), Nitzschia thermalis (NIT) and a combination of all three species (MIX). The highest growth was observed for postlarvae fed the MIX (51.37 mu m day(-1) and 0.578 +/- 0.1 mg day(-1)), but was not significantly different from the NAV treatments (46.60 +/- 3.4 gm day(-1) and 0.550 +/- 0.1 mg day(-1)). Abalone larvae, which are lecithotrophic organisms, seem to utilize proteins as a preferred energy substrate up to metamorphosis, since the relative lipid content increased from 15 to 30% from days 0 to 10. Thereafter, lipids are rapidly utilized and decreased to a level of 2% of the dry matter in the postlarvae whole soft tissue. Tissue fatty acid analysis indicated a similar trend among treatments, where relative fatty acid levels increased during the endogenous feeding period and started to decrease concomitant with the start of the exogenous feeding. Polyunsaturated fatty acids, reported on abalone tissue showed a similar trend, among treatments. Based on the results reported here, it can be concluded that the type of diatom is an important factor for growth, where a high lipid and low ash content could be important to improve the performance in terms of growth and survival, in combination to stimulate protease activity and therefore better digestibility. Last but not the least important, the use of monoculture with NAV will be of importance when culturing abalone postlarvae. The estimated energy budget, back calculated from the digestibility figures, indicates that abalone requires from 25 to 38 cal day(-1) g abalone(-1) for adequate growth. (C) 2007 Elsevier B.V. All rights reserved.