Abstract
Climate change challenges coral reefs. As sea temperature increases, dissolved oxygen decreases. During embryonic development, a large increase in oxygen consumption occurs primarily due to muscle tissue expansion. Exposure to chronic hypoxia during this time may induce phenotypic change that could affect larval performance and the fish's final form. To determine effects of environmental hypoxia on survival rate, morphological growth, and histological patterning during embryonic development, Amphiprion (Premnas) biaculeatus embryos were exposed to dissolved oxygen treatments of 8.0 mg/L ‘control, 4.0 mg/L ‘Low DO’, 2.5 mg/L ‘Hypoxia’, or 12hr:12hr 8.0/4.0 ‘cycle’ from day 1 to 6 of development. Greater proportions of ‘control’ embryos survived to day 6. ‘Low DO’ and ‘cycle’ treatments had significantly slower heart rates than ‘control’. Notochord length and eye diameter were found to be significantly smaller in ‘low DO’ and ‘hypoxia’ treatments, while yolk area was larger. These results coupled with significantly decreased myotome width indicate reduced metabolism. Histological measurements of ‘low DO’ and ‘cycle’ within the brain, eyes, heart, and gill arches maintained the same level of differentiation as the ‘control’. This indicates development may place a greater emphasis on the differentiation of sensory, neural, and organ systems than that of physical growth and size. Changes to survival, morphology, and performance seen during development may lead to new evolutionary patterns of diversity that are important to understand with the changing environment.