Thrombocytes of diploid and triploid rainbow trouts assessed by flow cytometry and aggregation assay

Thrombocytes are blood cells that protect fish by aggregation to hinder hemorrhages and play a role on pathogen phagocytosis. Moreover, there is a lack of information regarding to the population of thrombocytes and its relationship with fish ploidy. The goal of this work was to determine the thrombocyte numbers and its aggregation capacity in adult diploid and triploid rainbow trouts Oncorhynchus mykiss by flow cytometry screening using monoclonal antibody and magnetic separation. As expected, thrombocytes were in similar proportions between ploidies with 15.26 ± 6.77% in diploid and 13.11 ± 6.37% in triploid blood samples; however, with thrombocytes of triploid trouts showing less aggregation activity when exposed to collagen (85.59 ± 3.36% vs. 95.51 ± 1.25%). In conclusion, triploid thrombocytes have lower aggregation capacity than the diploid ones. This response is possibly related to the deficiency of receptors on the surface of thrombocytes of triploid trouts, which requires further studies for confirmation.