The influence of nutritional status and environmental factors on growth, feeding behaviour and appetite-related peptide transcript expression in Atlantic cod (Gadus morhua)

• Main Author: Tuziak, Sarah
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2016
• Subjects: atlantic cod; Gadus morhua
• Online Access: https://research.library.mun.ca/11963/; https://research.library.mun.ca/11963/1/thesis.pdf

Appetite regulation and energy homeostasis are critical processes for vertebrate survival that are regulated by neuroendocrine mechanisms. Understanding how appetiteregulating hormones are influenced by intrinsic and extrinsic cues is essential for the comprehension of how vertebrates maintain an appropriate energy balance. This thesis focuses on some important appetite regulators [melanin-concentrating hormone (MCH), orexin, neuropeptide Y (NPY), gonadotrophin-releasing hormone (GnRH) and cocaineand amphetamine-regulated transcript (CART)] in a commercially important fish species, Atlantic cod (Gadus morhua). To begin my analyses of these important appetiteregulating hormones in cod, I identified for the first time cDNA sequences for MCH and GnRH mRNAs, while orexin, NPY and CART transcripts were previously isolated in cod. MCH and GnRH hormones were shown to be expressed in regions of the brain and peripheral tissues (i.e. gastrointestinal tract) related to food intake regulation. MCH, but not GnRHs, transcript expression was higher in fed compared with fasted fish, indicating that MCH may play an important role in appetite regulation in cod. Then, I examined how diet (i.e. plant-based feed, Camelina sativa) and environment (i.e. background colour) influence feeding behaviour and appetite-related peptide transcript expression. Camelina meal-supplemented feed reduced food intake and growth, and increased orexigenic peptide mRNA expression (i.e. MCH, orexin and NPY), but did not affect CART expression, suggesting fish are still “hungry” and that MCH, orexin and NPY peptides could be involved in other feeding behaviours and metabolic processes, such as nutrient sensing and food searching behaviour. Finally, I addressed the effects of background colour and fasting on Atlantic cod feeding and swimming behaviour, as well as appetiterelated transcript expression. Atlantic cod subjected to fasting and different background colours displayed reduced locomotion. Furthermore, a decrease in MCH and orexin mRNA expressions ...