The development of endogenous cortisol production and chromaffin cells in larval Lake Sturgeon (Acipenser fulvescens)

Abstract

The development of the HPI axis has long lasting effects on behavior, fitness and ultimately survival in teleost fish. Endogenous cortisol production was measured in larval Lake Sturgeon in 2016 to determine the proper development of the hypothalamic-pituitary-interrenal axis. Following the results of 2016, in 2017 baseline cortisol levels were measured again along with stress-induced cortisol levels and metyrapone-treated fish. In 2016 the larvae had a significant increase (P-value=<0.0001) in baseline cortisol prior to exogenous feeding and during the transition from artemia to bloodworm. In 2017 larvae also had an increase (P-value=<0.0001) in baseline levels prior to feeding and metyrapone-treated larvae with lower cortisol never fully transitioned and had developmental abnormalities. These studies indicate a relationship between endogenous cortisol production and dietary shifts. Also in 2017, larvae were sampled for development of chromaffin cells through immunohistochemistry, specifically a tyrosine-hydroxylase (TH) antibody. The TH antibody was reactive at 13 DPF, five days following hatch. Both cortisol production and chromaffin cell proliferation showed a delay in development, only appearing after hatch, suggesting both these important endocrine components to stress undergo a hypo-responsive period during early development in the Lake Sturgeon.