title: Critical windows in embryonic development: Shifting incubation temperatures alter heart rate and oxygen consumption of Lake Whitefish (Coregonus clupeaformis) embryos and hatchlings.
abstract: Critical windows are periods of developmental susceptibility when the phenotype of an embryonic, juvenile or adult animal may be vulnerable to environmental fluctuations. Temperature has pervasive effects on poikilotherm physiology, and embryos are especially vulnerable to temperature shifts. To identify critical windows, we incubated whitefish embryos at control temperatures of 2°C, 5°C, or 8°C, and shifted treatments among temperatures at the end of gastrulation or organogenesis. Heart rate (fH) and oxygen consumption ( [Formula: see text] ) were measured across embryonic development, and [Formula: see text] was measured in 1-day old hatchlings. Thermal shifts, up or down, from initial incubation temperatures caused persistent changes in fH and [Formula: see text] compared to control embryos measured at the same temperature (2°C, 5°C, or 8°C). Most prominently, when embryos were measured at organogenesis, shifting incubation temperature after gastrulation significantly lowered [Formula: see text] or fH. Incubation at 2°C or 5°C through gastrulation significantly lowered [Formula: see text] (42% decrease) and fH (20% decrease) at 8°C, incubation at 2°C significantly lowered [Formula: see text] (40% decrease) and fH (30% decrease) at 5°C, and incubation at 5°C and 8°C significantly lowered [Formula: see text] at 2°C (27% decrease). Through the latter half of development, [Formula: see text] and fH in embryos were not different from control values for thermally shifted treatments. However, in hatchlings measured at 2°C, [Formula: see text] was higher in groups incubated at 5°C or 8°C through organogenesis, compared to 2°C controls (43 or 65% increase, respectively). Collectively, these data suggest that embryonic development through organogenesis represents a critical window of embryonic and hatchling phenotypic plasticity. This study presents an experimental design that identified thermally sensitive periods for fish embryos.
authors.affiliation: Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON L8S 4K1, Canada. Electronic address: johneme23@gmail.com.
authors.forename: J
authors.initials: J
authors.lastname: Eme
authors.affiliation: Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON L8S 4K1, Canada. Electronic address: caseyamueller@gmail.com.
authors.forename: C A
authors.initials: CA
authors.lastname: Mueller
authors.affiliation: Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada. Electronic address: richard.manzon@uregina.ca.
authors.forename: R G
authors.initials: RG
authors.lastname: Manzon
authors.affiliation: Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada. Electronic address: chris.somers@uregina.ca.
authors.forename: C M
authors.initials: CM
authors.lastname: Somers
authors.affiliation: Medical Sciences, Northern Ontario School of Medicine, Laurentian University, 935 Ramsey Lake Road, Sudbury, ON P3E 2C6, Canada; Bruce Power, Tiverton, ON, Canada; Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, ON, Canada. Electronic address: boreham@nosm.ca.
authors.forename: D R
authors.initials: DR
authors.lastname: Boreham
authors.affiliation: Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON L8S 4K1, Canada. Electronic address: joanna.wilson@mcmaster.ca.
authors.forename: J Y
authors.initials: JY
authors.lastname: Wilson
mesh_terms: D058500:Animal Fins / Q000196:embryology; D000818:Animals; D004625:Embryo, Nonmammalian / Q000502:physiology*; D047108:Embryonic Development; D005260:Female; D005306:Fertilization; D005399:Fishes / Q000196:embryology*; D054262:Gastrulation; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D038081:Organogenesis; D010101:Oxygen Consumption / Q000502:physiology*; D013696:Temperature
keywords: Critical windows; Development; Developmental plasticity; Embryo; Fish; Heart rate; Oxygen consumption; Temperature