Can Artemia franciscana produce essential fatty acids? Unveiling the capacity of brine shrimp to biosynthesise long-chain polyunsaturated fatty acids

Artemia nauplii are widely used as live preys for feeding early life-cycle stages of marine finfish and shrimp. However, a major drawback associated to using Artemia is their deficient nutritional value for marine larvae that is primarily linked to suboptimal levels of long-chain polyunsaturated fatty acids (LC-PUFA), essential nutrients that guarantee normal growth and development of animals. While common marine hatchery procedures involve enrichment processes to address such nutritional deficiencies, the specific drivers accounting for the naturally occurring variability in LC-PUFA of Artemia are largely unknown. Biosynthesis, along diet, is one of the main factors determining the LC-PUFA profiles in animals and it depends upon the repertoire and function of fatty acyl elongases and desaturases existing in a particular species. The aim of this study was the molecular and functional characterisation of all elongase and desaturase enzymes involved in the LC-PUFA biosynthesis from Artemia franciscana, arguably the most commonly used Artemia species. Seven out of eight elongases (termed Elo1-8) found in A. franciscana had distinctive features of LC-PUFA biosynthesising elongases. Consistently, functional assays showed these elongases were able to elongate multiple substrates and thus enabling A. franciscana to perform all elongation reactions of the LC-PUFA biosynthetic pathways. While all seven functionally characterised elongases from A. franciscana showed activity towards multiple substrates including C18 to C22 polyunsaturated fatty acids, particularly high activity was detected for the Elovl8 orthologue (termed herein as Elo7). Additionally, A. franciscana was found to have three genes of the so-called first desaturases (Des1-3), and lack other key LC-PUFA biosynthesising desaturases such as methyl-end and front-end desaturases. Two desaturases have the expected Delta 9 desaturase activity, whereas a third one showed Delta 12 activity. Neither methylend nor front-end desaturases were found in A. franciscana. In conclusion, this study demonstrated that A. franciscana has high elongation capacity but its overall LC-PUFA biosynthesis can be regarded as limited due to the lack of an adequate complement of fatty acyl desaturases in its genome.

Automated summary

The study demonstrates that Artemia franciscana has a high elongation capacity but limited overall LC-PUFA biosynthesis due to the lack of an adequate complement of fatty acyl desaturases in its genome.