A new study, conducted by the University of Cincinnati (UC) biology professors Michal Polak and Joshua Benoit, suggests that a father's nutrition could play a similar role to the mother’s nutrition in his offspring’s health. Researchers from the University of Sydney's Charles Perkins Centre and the University of Western Australia also collaborated on the study.
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Researchers controlled the diet of male fruit flies and noticed a strong association between poor survivorship and poor diet among their offspring. Prof. Polak stated that it was a real surprise to determine an association between paternal nutrition and offspring.
In this study, researchers isolated males and females of the fruit fly species Drosophila melanogaster, which is known for its high reproductive capacity and giant red eyes. A single fruit fly can lay 50 eggs a day or as many as 2,000 eggs in her short lifespan of two months.
The same diet was fed to all the females by researchers but 30 different diets of sugars and yeasts were fed to males. The flies could consume everything they required from the agar mixture in the bottom part of their glass beaker habitats, but food quality varied intensely from low to high concentrations of calories, carbohydrates, and proteins.
Notably, none of the flies passed away due to starvation. This confirmed that the study did not unconsciously weed out the least-robust and weakest males, Polak affirmed.
After 17 days of stringent diet, the males were allowed to mate consecutively and individually with two females, which all consumed the same yeasted cornmeal diet. Researchers attempted to limit maternal condition variations of the study by governing the age and diet of the mated female.
Researchers wanted to study the role of diet in altering the male's ejaculate and the impact of male mating order, by allowing the males to mate consecutively.
The male fly was mated with a second female after 15 minutes following the first mate. Then the females were accommodated in isolated breeding vials that are filled with grape agar appropriate for laying eggs, their eggs were counted by the researchers after 24 hours.
After the incubation period of 24 hours, the eggs were investigated under a microscope to find the number of contained or hatched viable embryos. Unfertilized eggs were not considered for the study. Researchers waited additional 24 hours to give possibly unviable eggs time to hatch or develop but none did.
Researchers identified that embryos that were obtained from the second mating were more probable to survive, as their fathers' diets enriched in nutrition. These impacts were less evident in the first mating. Similarly, males that fed on a low-protein, high-carbohydrate diet were found to have offspring possessing highest embryo mortality.
Male's body condition was found to be associated with the mortality of his offspring. Males with lesser energy reserves (evaluated in whole-body glucose, protein, and fatty acids) were more probable to have fewer surviving offspring.
Females laid an approximately equal number of eggs irrespective of the male's mating frequency or diet. But the study revealed that something significant in the male's ejaculate was lost between the first and second mating.
Polak indicated that the impacts of diet actually became stronger during second mating. Weak males in poor body condition produced embryos that had high mortality rate, but only in the second mating.
The study also identified a slightly greater occurrence of embryo mortality related to male flies in the first copulation, which were fed with highest-calorie diet.
Researchers are now interested in investigating the epigenetic and genetic responses of parasitic-mite stressed fruit flies. The researchers also are involved in studying whether parasitic infection could alter the male seminal plasma quality, probably exerting impacts on the embryo as they witnessed in the diet study.