Meeting Abstract

31.1  Jan. 5  Ontogeny of the cortisol stress response and expression of CYP11B in larval red drum APPLEBAUM, Scott*; WILSON, Alex; NUNEZ, Scott; The University of Texas at Austin scotta@utmsi.utexas.edu

In addition to their crucial role in stress and osmoregulatory function corticosteroids play an important role in teleost development. Corticosteroids may influence larval development directly, or through interactions with the thyroid system which is responsible for the larval to juvenile transformation. Nonetheless, the development of adrenocortical function in teleosts is poorly understood. Due to the potential impact on development, it is valuable to determine the ontogenetic onset of corticosteroid production and when an integrated corticosteroid stress response is first evident. In this study, we describe the ontogeny the corticosteroid stress response and the expression of a key corticosteroidogenic enzyme, CYP11B, in larval red drum (Sciaenops occelatus). Stress experiments were conducted between 1 and 33 days post-hatch (DPH). Groups of larvae were subjected to an acute handling stress and sampled at 0.5, 1, and 3h post-stress for cortisol analysis. Larvae sampled prior to stress were used to establish basal cortisol levels. Basal cortisol was first detected at 3 DPH, increased to a maximum of 4.9 ng/g at 13 DPH, and declined to 1-2 ng/g for the remainder of the study. Cortisol did not increase in response to stress prior to 6 DPH. After 6 DPH, stress caused significant increases (9 to 153 fold) in larval cortisol content. Stress-induced cortisol increases in 6 to 11 DPH larvae was highest after 3h. In larvae older than 11 DPH cortisol levels peaked at 0.5h and declined to near basal levels by 3h post-stress. Eggs and larvae collected between 0 and 33 DPH were analyzed for the expression of CYP11B mRNA and preliminary results indicate that CYP11B is expressed beginning 1 DPH.