Examining growth in dusky kob (Argyrosomus japonicus) via differential transcriptomic analysis of gill tissue.

Joao, S. A.*, Rhode, C.

Dept Genetics, Stellenbosch University, Stellenbosch

Understanding the molecular mechanisms driving growth differentials in dusky kob (Argyrosomus japonicus), a commercially important finfish species, is crucial for advancing aquaculture practices. The gills play a pivotal role in growth, encompassing essential functions such as respiration, osmoregulation, nitrogen excretion, acid-base balance, and hormone metabolism. This study analysed gene expression profiles from the gill tissue of large (±550 g) and small (±250 g) dusky kob of the same age and spawning event. Transcriptomic data was then utilised to assemble an organ-specific gill transcriptome and to identify differences in the expression of growth-related genes between fast- and slow-growing individuals. Preliminary findings indicated that the smaller cohort exhibited elevated expression of genes linked to immune response and cell proliferation, whereas the larger cohort displayed increased expression of genes associated with gill health and gene regulation. Faster-growing fish likely prioritise energy allocation towards these genes to support their larger size and higher metabolic demands. In contrast, slower-growing fish may allocate more energy towards immune defence and compensatory growth. Further investigation will provide deeper insights into the molecular mechanisms underlying gill function and growth in dusky kob, providing valuable knowledge to optimise aquaculture efficiency through targeted genetic and environmental strategies in the future.