Ectothermic f ish can be characterized by a certain degree of environmental plasticity and many of their traits related to behavior, stress response, and social skills can be influenced by early life experiences. These plastic responses provide different species with a coping mechanism to changing environmental conditions with epigenetic alterations in DNA seeming to play a major role. Ho wever, the mechanisms behind the induction of the adaptation process and environmental plasticity are not well understood . The main objective of this study was to use zebrafish (Danio rerio) as a model to determine if exposure to high temperatures at the larval stage can cause phenotypic plasticity, and how this could affect factors including growth, survival, and food conversion ratio (FCR) when exposed to similar conditions later in life.
Two treatments of zebrafish were randomly distributed into 6 (3L) tanks at 3 days post-hatch (dph), with 120 larvae per tank. This study initially included two treatment groups for the environmental programming : 1) an environmental control (EC) treatment, which remained at the control temperature of 26° C; and 2) an environmental programmed (EP) treatment which was raised to 32 °C for a 24hr period between 6-8dph, then returned to 26 °C. Both treatments continued with a grow-out period to 35 dph at 26°C . At 35pdh, the initial treatment groups were split in half and randomly distributed into four treatments with 11 fish per tank for the environmental challenge . The treatment groups were: 1) both EP and EC raised at 32°C from 35-57dph (EP-32 and EC-32) ; 2) EC and EP raised at optimal temperature of 26°C from 35-57dph (EP-26 and EC-26). All groups were fed at a restricted feeding rate during the challenge phase equal across all treatments.
During the environmental challenge, the numerical data indicated the EP-32 group tended to have higher individual weight gain compared to the EC-32. The EP-26 group also tended to have higher individual weight gain compared to the EC-26. In addition, t he EP-32 group tended to have the lowest FCR, particularly in comparison to EC-32 . These preliminary results potentially suggest that brief exposure to high water temperature induced at the larval stage may lead to improved feed utilization and growth in zebrafish when exposed to similar temperatures at a later stage. The statistical and gene expression analyses will be included in the oral presentation.