COMPARATIVE-STUDIES ON THE NUTRITION OF 2 SPECIES OF ABALONE, HALIOTIS-TUBERCULATA L AND HALIOTIS-DISCUS HANNNI-INO .5. THE ROLE OF POLYUNSATURATED FATTY-ACIDS OF MACROALGAE IN ABALONE NUTRITION

This study was undertaken to evaluate the nutritional role of polyunsa turated fatty acids (PUFA) in dietary macroalgae for the abalone, Hali otis tuberculata and Haliotis discus hannai. The effects of five speci es of macroalgae (Alaria esculenta, Laminaria digitata, Laminaria sacc harina, Palmaria palmata and Ulva lactuca) on specific growth rates (S GR) of the abalone and, the relationship between abalone SGR and fatty acid profiles in the algae were investigated. The current study confi rmed our previous findings. Based on SGR the dietary values of these m acroalgae can be listed in a decreasing order as follows: P. palmata, A. esculenta, U. lactuca, L. digitata and L. saccharina for H. tubercu lata and, A. esculenta, P. palmata, L. digitata, L. saccharina and LI. lactuca for H. discus hannai. Fatty acid analysis revealed that C-18 and C-20 PUFA, such as 18:4n-3, 18:3n-3, 20:4n-6 and 20:5n-3, were dom inant in the brown algae, A. esculenta, L. digitata and L. saccharina. The red alga, P. palmata, was characterised by the highest proportion of 20:5n-3 among the selected algae. In the green alga, Li. lactuca, however, the dominant PUFA were C-16 and C-18 fatty acids, while C-20 fatty acids were minimal. All the selected algae consistently containe d very low levels of C-22 fatty acids. Statistical analyses demonstrat ed that (a) 20:5n-3 played a prominent role in the nutrition of both a balone species; (b) 18:3n-3 as well as other n-3 PUFA, and 18:2n-6 tog ether with other n-3,6 long-chained PUFA also contributed to the faste r growth of H. tuberculata and H. discus hannai, respectively. The res ults suggest that the PUFA of both n-3 and n-6 families seem to be ess ential for growth of H. discus hannai; for H. tuberculata, however, gr owth enhancement appeared to depend largely on n-3 PUFA.