Dietary Exposure to Low Levels of Crude Oil Affects Physiological and Morphological Phenotype in Adults and Their Eggs and Hatchlings of the King Quail (Coturnix chinensis)

Abstract

Despite the current knowledge of the devastating effects of external exposure to crude oil on animal mortality, the study of developmental, transgenerational effects of such exposure has received little attention. We used the king quail as an animal model to determine if chronic dietary exposure to crude oil in a parental population would affect morpho-physiological phenotypic variables in their immediate offspring generation. Adult quail were separated into three groups: (1) Control, and two experimental groups dietarily exposed for at least 3 weeks to (2) Low (800 PAH ng/g food), or (3) High (2,400 PAH ng/g food) levels of crude oil. To determine the parental influence on their offspring, we measured metabolic and respiratory physiology in exposed parents and in their non-exposed eggs and hatchlings. Body mass and numerous metabolic (e.g., O₂ consumption, CO₂ production) and respiratory (e.g., ventilation frequency and volume) variables did not vary between control and oil exposed parental groups. In contrast, blood PO₂, PCO₂, and SO₂ varied among parental groups. Notably, water loss though the eggshell was increased in eggs from High oil level exposed parents. Respiratory variables of hatchlings did not vary between populations, but hatchlings obtained from High oil-exposed parents exhibited lower capacities to maintain body temperature while exposed to a cooling protocol in comparison to hatchlings from Low- and Control-derived parents. The present study demonstrates that parental exposure to crude oil via diet impacts some aspects of physiological performance of the subsequent first (F ₁ ) generation.

Keywords: Transgenerational Inheritance; bird; crude oil; development; epigenetics; oxygen consumption; parental effects; physiology.

FIGURE 1

Experimental protocol for dietary crude oil exposure and breeding in the king quail (Coturnix chinensis). (A) A parental population of adult birds was divided into three groups (5 female and 5 male per group) and exposed to crude oil via diet for at least 21 days. (B) Adult quail were maintained as female and male couples (monogamous species) and allowed to breed daily. (C) The eggs obtained from each parental group were divided into three subgroups as follows: (1) eggs used to determine egg metrics and water loss, (2) eggs raised to 7–8 day old hatchlings used to measure respirometry variables, and (3) eggs raised to 7–8 days old hatchlings and used to measure blood chemistry, hematology, and organ masses. Eggs used for respirometry and hematological/organ analysis were collected from the third week of exposure toward the end of the experimental time.

FIGURE 2

Metabolic variables during experimentation in female (squares), and male (circles) groups of parental populations of king quail dietarily exposed to Low (1%HEWAF, light yellow symbols), High (10% HEWAF, red symbols), and Control (white symbols). (A) Oxygen consumption ($\dot{\text{V}}$O₂), (B) Carbon dioxide production ($\dot{\text{V}}$CO₂), and (C) Respiratory exchange ratio (RER). Data are expressed as mean ± 1 standard error of the mean. Statistical significance was considered to be α = 0.05. n = 3–5 per data point.

FIGURE 3

Ventilation variables during experimentation in adult female (squares), and adult male (circles) groups of parental populations of king quail dietarily exposed to Low (1%HEWAF, yellow symbols), High (10% HEWAF, red symbols), and Control (white symbols). (A) Minute ventilation ($\dot{\text{V}}$_E). (B) Breathing frequency (f), (C) Tidal volume (V_T). (D) Air convection requirement ($\dot{\text{V}}$_E/$\dot{\text{V}}$O₂). Data are expressed as mean ± 1 standard error of the mean. Statistical significance was considered to be α = 0.05. n = 3–5 per data point.

FIGURE 4

Metrics and water loss in F₁ eggs obtained from of king quail. (A) Egg mass (g), (B) Egg length (cm), (C) Egg width (cm), and (D) Water loss. Data is expressed as mean ± 1 standard error of the mean. Statistical significance was considered with α = 0.05. Different letters indicate statistical differences between weeks. “*” Indicate statistically significant differences between groups at the specific experimental weeks. n = 6–29 per data point.

FIGURE 5

Body temperature (T_b) as a function of declining ambient temperature in 7–8 day old king quail hatchlings (F₁) derived from parents (P₀) exposed to Control conditions or Low or High oil exposure through diet. Line of equality representing the decrease in temperature by the cooling protocol is shown as a gray dotted line. Data are expressed as mean ± 1 standard error of the mean. Different letters indicate statistical differences between temperatures. “*” indicate statistically significant differences between groups at the specific temperature. n = 4–8 per data point.

FIGURE 6

Metabolic variables as a function of declining ambient temperature in 7–8 day old king quail hatchlings (F₁) derived from parents (P₀) exposed to control conditions or Low or High oil exposure through diet. (A) Oxygen consumption $\dot{\text{V}}$CO₂, (B) carbon dioxide production ($\dot{\text{V}}$CO₂), and (C) respiratory exchange ratio (RER). Data are expressed as mean ± 1 standard error of the mean. Different letters indicate statistical differences of mean temperature values at specified ambient temperatures in comparison to the 37 temperature values. n = 4–8 per data point.

FIGURE 7

Ventilatory variables as a function of declining ambient temperature in 7–8 day old king quail hatchlings (F₁) derived from parents (P₀) exposed to control conditions or low or medium oil exposure through diet. (A) Breathing frequency (f). (B) Tidal volume (V_T). (C) Minute ventilation ($\dot{\text{V}}$_E). (D) Air convection requirement ($\dot{\text{V}}$_E/$\dot{\text{V}}$O₂). Data are expressed as mean ± 1 standard error of the mean. Different letters indicate statistically significant differences between temperatures. “*” indicate statistical differences between the groups at the specified temperature. n = 4–8 per data point.