Date of Award

Summer 8-22-2025

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Marine Biology

First Committee Advisor

Timothy J. Bowden

Second Committee Member

Ian R. Bricknell

Third Committee Member

Michael R. Pietrak

Abstract

Sea lice, namely Lepeophtheirus salmonis (Krøyer, 1837), are a significant threat to the financial and biological success of farmed Atlantic salmon and are one of the top contributors to economic losses in the industry. The use of lumpfish, Cyclopterus lumpus L., as cleaner fish in salmon net pens has increased recently in Europe and Atlantic Canada, due to their demonstrated efficacy in controlling sea lice. To mitigate associated threats to fish welfare and biosecurity, aquaculture operations producing lumpfish must closely monitor the fishes’ health and vaccinate them against harmful pathogens. An optimal vaccination regime has yet to be determined, as the understanding of lumpfish immune system development and adaptive immune response is still in its infancy. This project aims to identify and investigate the expression of genes directly related to the development of the lumpfish immune system and adaptive immune response, to establish when during development lumpfish become immunocompetent. Methodology includes gene expression analysis of immune genes: secretory immunoglobulin M (sIgM), T-cell receptor alpha (TCR a), and major histocompatibility complex II beta (MHCII b), and histological assessment of thymus development in lumpfish ranging from approximately -8 days post hatch (DPH) to 34 DPH. Gene expression results indicated significant differences in expression of sIgM between -8 DPH and all other sampled timepoints, and between 0 and 34 DPH. There was no significant difference of TCRa expression across sampled timepoints. Significant differences in expression of MHCII b were observed between 34 DPH and all other sampled timepoints, and between days 4-8 and days 19-31. Histopathology of the developing thymus indicated first instance of thymus presence at 4 DPH with potential zonation appearing at 23 and 29 DPH. These findings suggest the possibility of adaptive immunocompetence closely following 34 days post hatch, with significant expression of sIgM in the egg indicating potential evidence of maternal transfer. Significant upregulation of MHCII b at 34 DPH following thymus zonation could also indicate the beginning of lymphoid capabilities of the thymus and T-cell activity near or after this point of early development.

Download

Files over 10MB may be slow to open. For best results, right-click and select "save as..."

Share