Long-chain PUFA enrichment in microalgae and metabolic dynamics inTapes philippinarumlarvae

Abstract

The possibility of increasing n-3 and n-6 long-chain polyunsaturated fatty acids (PUFA) content in microalgal mixtures used to feed Tapes philippinarum larvae was explored by lowering culture temperature from 26 to 14°C. Although fatty acid composition of different microalgal species has a genetic basis, the algal cultures grown at 14°C significantly increased the content of long-chain n-3 PUFA in Isocrysis galbana and in Thalassiosira pseudonana, while in Tetraselmis tetrathelo, the PUFA increase only involved shorter chain PUFA, namely 16:4n-3 and 18:4n-3. However, larvae fed on the PUFA enriched microalgal mixture did not show improvements in growth and survival performances with respect to the control group fed the microalgal mixture grown at 26°C. From a biochemical perspective, two key aspects emerged from the results: (i) clam larvae have adequate biotransformation and selection skills to adjust fatty acid profile to their requirements as they can even modulate the incorporation of essential long-chain PUFA as 20:5n-3 and 22:6n-3 when the dietary supply exceeds the physiological requirements; (ii) bivalve can biosynthesize non-methylene-interrupted dienoic (NMID) fatty acids as confirmed by the constancy of relative proportion with larvae growth in spite of the NMID fatty acid absence in the diet.

Fatty acid composition of female and male clams (Ruditapes philippinarum): energy intake and temperature reliance

“…The initial FA profile of R. philippinarum was comparable to that described previously for early life stages (larvae, spat) of the same species (Caers et al 1999;Fern andez-Reiriz et al 2006;Ventrella et al 2015).…”

“…In these treatments, clams also presented significant differences in FA composition (6% difference, SIMPER). The 18°C H clams showed higher levels of 18:3x3 and 18:3x6 than those conditioned at 22°C H. Short-chained PUFA could provide a more efficient and prompt energy reservoir with respect to that provided by long-chained PUFA (Ventrella et al 2015). As bivalves have a limited capacity to desaturate 18:3x3 to produce EPA or DHA, these FAs are preferentially retained irrespective of the diet composition (Soudant et al 1996;Caers et al 1999).…”