Background: Global aquaculture production of black tiger shrimp Penaeus monodon was valued at US$4.9 billion in 2016. Blood chemistry often mirrors health status in living organisms, but highly abundant proteins often preclude identification or measurement of important markers. In shrimp, haemolymph is a blood-like fluid that could be used to identify health markers, but the multimeric and multi-functional protein haemocyanin (Hc) comprises 95% of the total protein content. Hc was initially identified as a copper-based oxygen transport protein, but roles in immunity and as a growth performance indicator in shrimp aquaculture have been recently reported. A large number of Hc isoforms have been previously reported; however, functional analysis of specific Hc isoforms are non-existent. Methodology: Transcriptomics-informed proteomics was used to resolve the complexity of Hc isoforms. Multiple reaction monitoring mass spectrometry (MRM-MS) was used to assess the suitability of six Hc isoforms as health and performance markers in 5 µl of haemolymph plasma from shrimp fed specific diets, or unfed. Findings: A total of 21 Hc isoforms were identified using proteomics, wherein six isoforms bore unique tryptic peptides suitable for MRM-MS. Shrimp weight gain and haemolymph total protein concentration were significantly higher in fed shrimp. Principal component analysis of MRM-MS Hc abundance clearly discriminated between fed and unfed shrimp. The abundance of the gamma isoform PmoHcG7 was significantly higher in the unfed group whilst PmoHcG2 was significantly higher in shrimp fed diets containing 10% microbial biomass and a control basal diet. Conclusion: Hc is a protein involved in shrimp health and growth that warrants investigation as a potential marker of shrimp performance. The application of proteomics in aquaculture can enable feed companies to test functional diet formulations, and as a result, farmers will have the opportunity for better growth rates and optimised health in aquaculture shrimp whilst maintaining sustainability.
Keywords: Haemolymph, Haemocyanin, Shrimp, Aquaculture, proteomics