Work

Hepatic Expression of Growth Hormone Receptor (GHrec) and Insulin-like Growth Factor-I (IGF-I) Genes and Cellular Location of IGF-I mRNA in Diploid and Triploid Atlantic Salmon (Salmo salar) Undergoing Parr–Smolt Transformation

Year: 2026

Type: article

Abstract: The induction of triploidy, used to mitigate pre-harvest sexual maturation and as a genetic containment measure for escaped farmed Atlantic salmon, may pose challenges due to the distinct environmental and dietary requirements of sterile triploids. Smoltification is a crucial phase in Salmo salar, so understanding this transformation in triploids could be valuable for aquaculture. This study covered an investigation of hepatic expression of growth hormone receptor (GHrec) and insulin-like growth factor-I (IGF-I) genes, both involved in the regulation of osmoregulation and growth. Additionally, hepatic presence and location of IGF-I mRNA was examined using RNAscope®, an advanced in situ hybridization technique. Triplicate groups of juvenile diploid and triploid salmon were reared at low temperature (10°C) and fed either a standard diet or one enriched with hydrolysed fish proteins from start feeding onwards. Liver samples were collected from three fish per tank each month from October to December (2454-3044 degree-days post-start feeding), the period encompassing smoltification, and hepatic expression of IGF-I and GHrec genes was quantified by Real-Time PCR. The results indicated that neither ploidy nor diet significantly influenced IGF-I or GHrec gene expression, suggesting that, under our conditions, triploidy and diet did not adversely affect this molecular pathway linked to growth and osmoregulation. IGF-I gene expression exhibited significant temporal variation, correlating with the progression of smoltification, GHrec gene expression showed a similar, albeit non-significant, trend. Triploids exhibited IGF-I and GHrec gene expression patterns comparable to diploids, and these results were mirrored in the quantification of IGF-I mRNA within the liver cells.

Source: Animals

DOI: 10.3390/ani16030515