Fatty acid bioconversion in harpacticoid copepods in a changing environment: a transcriptomic approach.

Area of Science:

• Marine biology
• Ecology
• Biochemistry

Background:

• Global warming threatens marine primary producers' synthesis of essential long-chain polyunsaturated fatty acids (LC-PUFAs).
• Marine food webs may be impacted by reduced LC-PUFA availability.
• Harpacticoid copepods, as primary consumers, could play a role in mitigating these effects through bioconversion.

Purpose of the Study:

• To generate a high-quality de novo transcriptome assembly for the copepod Platychelipus littoralis.
• To investigate the copepod's capacity for LC-PUFA bioconversion under simulated climate change conditions (increased temperature and altered dietary LC-PUFA availability).
• To identify and phylogenetically analyze genes involved in LC-PUFA synthesis (desaturases and elongases).

Main Methods:

• De novo transcriptome assembly of Platychelipus littoralis.
• Exposure of copepods to elevated temperature (+3°C) and a diet deficient in LC-PUFAs.
• Analysis of fatty acid concentrations and expression levels of key bioconversion enzyme transcripts (desaturases and elongases).
• Phylogenetic analysis of identified transcripts.

Main Results:

• A high-quality transcriptome assembly was generated.
• Temperature influenced overall fatty acid concentrations, but LC-PUFA levels in copepods were maintained even on a deficient diet.
• No differential expression was observed in putative LC-PUFA-bioconverting front-end desaturase or elongase transcripts under the experimental conditions.
• Phylogenetic analysis placed identified transcripts within crustacean taxa.

Conclusions:

• Platychelipus littoralis exhibits some plasticity in maintaining LC-PUFA levels, suggesting potential resilience in bioconversion capacity.
• Despite plasticity, the genetic machinery for LC-PUFA bioconversion did not show altered expression in response to the tested environmental changes.
• The generated transcriptome provides a valuable resource for future research on harpacticoid copepod ecophysiology and their role in marine food webs under climate change.