Data from: incubation as a driver of maternal effects: temperature influences levels of yolk maternally derived 5α-dihydrotestosterone
Abstract
In birds, maternal hormones deposited into eggs in response to environmental stimuli can impact offspring phenotype. Although less studied, environmental conditions can also influence females’ incubation behavior, which might play a role in regulating embryo exposure to maternal hormones through changes in incubation temperature that affect the activity of the enzymes responsible for converting testosterone (T) to 5α-dihydrotestosterone (DHT) or estradiol. Here, we tested the hypothesis that the initial T content of the yolk and incubation temperature determine exposure to T metabolites during early embryo development. In the Japanese quail (Coturnix japonica), we experimentally manipulated yolk T and incubation temperature (38° C versus 36° C) and analyzed DHT and estradiol titers on day four of incubation. We found that eggs with experimentally increased T and those incubated at 36° C showed higher DHT concentration in egg yolk (with no synergistic effect of the two treatments). Estradiol titers were not affected by T manipulation or incubation temperature. Our study suggests that incubation temperature influences DHT titers and may act as an understudied source of maternal influence on offspring phenotype.
https://doi.org/10.5061/dryad.5mkkwh7cv
Description of the data and file structure
| Column | Variable type | Value | Unit | Explanatation |
|---|---|---|---|---|
| egg_id | Numerical | Sample egg identity | ||
| biopsy_id | Numerical | Identity of biopsy sample taken at 4 days of incubation | ||
| inc_temp | Factor | 36/38 | degree Celsius (° C) | Incubation temperature |
| t_treat | Factor | Increased-T/Control | Yolk testosterone manipulation | |
| female_id | Numerical | Identity of female that laid each egg | ||
| log_horm | Numerical | pg hormone/mL yolk | Hormone concentration in yolk transformed to logarithm | |
| laying_date | Numerical | Julian days | Laying date | |
| egg_mass | Numerical | grams | Egg mass | |
| embryo | Binomial | 1/0 | Presence/absence | Presence or absence of developing embryo through observation of egg vascularization or the beating heart at 4 days of incubation or examining the egg 3 days after estimated hatching date |
| inc_batch | Factor | 1-3 | Incubation batch |
T= Testosterone
E= Estradiol
DHT= 5α-Dihydrotestosterone
Missing data code: NA
Data were collected under an experimental setting in captivitity conditions. Eggs from 29 Japanise quail females were individually marked and weighed with a digital balance (± 0.1 g). Same clutch eggs were randomly assigned to treatments, in a full factorial 2 × 2 design: increased-T eggs incubated at 38° C (n = 40 eggs from 20 clutches), increased-T eggs incubated at 36° C (n = 42 eggs from 26 clutches), control eggs incubated at 38° C (n = 39 eggs from 21 clutches), and control eggs incubated at 36° C (n = 40 eggs from 21 clutches). During the first day of incubation 82 eggs were injected with 25 ng of T (increased-T eggs) diluted in 10 μL sesame oil. The amount of testosterone injected was within the natural range of variation reported for this species (4-30 ng/g of yolk). Seventy-nine eggs were injected with only 10 μL sesame oil. The injection site was sealed with surgical glue.
On day four of incubation, a yolk biopsy of 80 μL (< 5% of total yolk volume) was taken from all eggs to quantify hormone concentration (testosterone, estradiol and DHT). Yolk samples were diluted in 100 μL deionized water and frozen at -80° C until hormone analyses. After biopsy, eggs continued with the assigned incubation treatment until hatching.