Transcription of defense related genes in Pacific white shrimp, Litopenaeus vannamei, kept in biofloc and in clear seawater and challenged with the white spot syndrome virus

Abstract

Shrimp farming in biofloc technology system (BFT) has been considered a sustainable alternative to conventional production, reducing environmental impacts due to zero water exchange. Besides increasing productivity, as microorganisms represent additional feed for shrimp, BTF may prevent diseases. White spot disease is the most devastating viral disease of farmed shrimp, causing large socio-economic impacts. Our aim was to compare survival rates and transcription profiles of target genes in different tissues of juvenile specimens of the Pacific white shrimp, Litopenaeus vannamei, reared either in BFT or in clear seawater (CSW), after challenging with white spot syndrome virus (WSSV). Shrimp survival rate was higher among animals kept in CSW, which also presented a lower viral load after 48 h post-infection (p.i.). We could also address possible individual patterns in the sole survivor at 72 h p.i. in biofloc, probably a less vulnerable shrimp to WSSV. There was no significant difference regarding the transcription profile of target genes between systems before WSSV infection; gene transcription was apparently modulated by WSSV infection. Changes in gene profile were more frequently observed in the hepatopancreas. Out of the eleven selected target genes, those coding for Calreticulin, β-tubulin, and Prophenoloxidase showed the most significant upregulation, followed by QM, SOD, and Ubiquitin. Although BFT is considered more biosecure, shrimp kept in this system are not immune to disease, especially against highly virulent pathogens, such as WSSV.