Aquaculture ELSEVIER Aquaculture 153 (I 997) 291-300 Assimilation of gelatin-acacia microencapsulated lipid by Pacific oyster ( Crassostrea gigas) spat Jens Knauer *, Paul C. Southgate Deprtment of Zoology, James Cook l/nil,ersir?; of North Queensland, TowsrYlle. Qld. 481 I, Austrtrlicr Accepted 18 December 1996 Abstract Gelatin-acacia microcapsules (GAM) are commonly used as a delivery vehicle for lipids in nutritional studies with bivalves. In this study the efficiency with which lipid contained in GAM was assimilated by Pacific oyster (Crassostrea gi~ns) spat was determined. The marine diatom Ckaeroceros muelleri was cultured in the presence of “C-sodium bicarbonate for 24 h. The 14C-lipid fraction was extracted, mixed with corn oil and microencapsulated in GAM. Spat assimilated ‘“C-lipids from a mixed diet of the marine flagellate Dunalielln tertiolecta (80%) and GAM (20%) with an efficiency of 79.9 + 2.9%, while spat fed a 100% GAM diet assimilated “C-lipids at a rate of 57.1 + 5.2%. Addition of 100 mg 1-l of the antibiotic Thimerosal to both a mixed diet and GAM only significantly reduced bacterial degradation of GAM over 24 h. The high assimilation efficiencies underline the potential of GAM as carrier of lipids in nutritional studies with bivalves. 0 1997 Elsevier Science B.V. Kewvrds: Assimilation: Microcapsule: Nutrition; Lipid; Oyster; Crassostwu gigas 1. Introduction Microalgal diets have been used in many studies as tools to assess the nutritional requirements of bivalves (for review see Webb and Chu, 1983; Brown et al., 1989). However, it is probably impossible to offer either a number of microalgal species which differ in the level of one component only or, alternatively, to feed one species of microalgae and alter the quantity of a particular nutrient without affecting the levels of * Corresponding author: Tel: +61-77-815547; fax: +61-77.251570; e-mail: Jens.Knauer@jcu.edu.au. 0044-8486/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved. PII SOO44-8486(97)00038-O