Hatchling Phenotype Of Lake Whitefish Incubated At Increased Temperature During Critical Windows Of Development
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abstract
Phenotypic plasticity is the ability of an animal to modify its phenotype in response to the environment. Embryos may have critical windows during development when they are particularly plastic or susceptible to the environment. We examined whether there are critical windows during Lake whitefish (Coregonus clupeaformis) embryonic development when temperature has an especially strong effect on phenotype. Lake whitefish are a cold‐water fish species that inhabits the North American Great Lakes. This species lays eggs that develop over winter when lake temperatures are near freezing. With 2°C as the overall control temperature, embryos were incubated at either 5°C, 8°C or 11°C for all of embryonic development or only during one of four distinct windows of development: gastrulation, organogenesis, fin development, and late growth. Survival was monitored throughout development. Hatching characteristics, including time to hatch, mass at hatch, and hatchling oxygen consumption rate, were measured to examine if warmer temperatures during the four windows of development altered hatchling phenotype. No embryos survived to hatch when incubated constantly at 11°C, and survival was reduced at constant 8°C. Survival was also reduced when embryos were incubated at 11°C during the windows of gastrulation, organogenesis and fin development, but not during the late growth window. Time to 50% hatch decreased with an increase in constant incubation temperature, and only during the late growth window did an increase in temperature decrease time to hatch. Increased incubation temperature during the late growth window resulted in smaller hatchlings and reduced yolk conversion efficiency compared to embryos incubated constantly at 2°C or embryos incubated in warmer temperatures during earlier windows of development. Incubation at 11°C during organogenesis, fin development and the late growth window also reduced yolk conversion efficiency. Mass‐specific oxygen consumption rate increased with an increase in constant incubation temperature, but incubation at either 5°C, 8°C or 11°C during gastrulation, organogenesis, fin development or the growth window did not have substantial effects on metabolism at hatch. Overall, critical windows for survival in response to increased temperature were present during gastrulation, organogenesis and fin development. However, hatchling size was most influenced by incubation at warm temperatures during the late growth window prior to hatch, due to increased temperature inducing early hatching.Support or Funding InformationC.A.M. and J.E. were supported by a MITACS Accelerate grant to D.R.B. and J.Y.W. Funding was provided by Bruce Power® and a Collaborative Research and Development Grant from the Natural Sciences and Engineering Research Council of Canada to J.Y.W., R.G.M., and C.M.S.
