Abstract
Alterations in fish developmental trajectories occur in response to genetic and environmental changes, especially during sensitive periods of development (critical windows). Embryos and larvae of Atractosteus tropicus were used as a model to study fish survival, growth, and development as a function of temperature (28 °C control, 33 °C, and 36 °C), salinity (0.0 ppt control, 4.0 ppt, and 6.0 ppt), and air saturation (control ~95% air saturation, hypoxia ~30% air saturation, and hyperoxia ~117% air saturation) during three developmental periods: (1) fertilization to hatch, (2) day 1 to day 6 post hatch (dph), and (3) 7 to 12 dph. Elevated temperature, hypoxia, and hyperoxia decreased survival during incubation, and salinity at 2 and 3 dph. Growth increased in embryos incubated at elevated temperature, at higher salinity, and in hyperoxia but decreased in hypoxia. Changes in development occurred as alterations in the timing of hatching, yolk depletion, acceptance of exogenous feeding, free swimming, and snout shape change, especially at high temperature and hypoxia. Our results suggest identifiable critical windows of development in the early ontogeny of A. tropicus and contribute to the knowledge of fish larval ecology and the interactions of individuals × stressors × time of exposure.
Highlights
Introduction published maps and institutional affilDevelopmental phenotypic plasticity is the ability of an organism in its early stages to modify its phenotype as a function of intrinsic or extrinsic factors [1,2,3]
The highest survival rates at the end of the experimental period occurred in the control group (84%), followed by larvae from experimental groups Period 2 (P2)-33 ◦ C, Period 3 (P3)-33 ◦ C, P2-36 ◦ C, and P3-36 ◦ C (76–81%; p < 0.001)
A similar growth pattern to A. tropicus occurred in A. tristoechus [51], A. spatula [42], Lepisosteus osseus [69], and L. oculatus [70], suggesting that this pattern is conserved among Lepisosteid species. These findings suggest that the period of transition from lecithotrophy to exotrophy could represent a critical window not just for growth and for survival, especially when the young larvae must cope with the changing environment and the development of feeding strategies [71]
Summary
Developmental phenotypic plasticity is the ability of an organism in its early stages to modify its phenotype as a function of intrinsic (genetic) or extrinsic (environmental) factors [1,2,3]. Alterations in certain characteristics of developing organisms occur during specific periods of time known as critical windows, which are sensitive periods during development when phenotype is responsive to intrinsic or extrinsic factors [1,7,8,9]. Most studies analyzing critical windows have focused on the effect of one factor (stressor) at different times in development [10,11,12,13]. An experimental design for critical windows that is multifactorial (e.g., multiple factors varying simultaneously) offers a more realistic set of circumstances that affords the opportunity to understand and visualize the interaction of development, stressor dose, and the response on phenotypic iations.
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