Beetle mothers use 'anti-aphrodisiac' pheromone to put the kids first

A study published on Tuesday in the science journal Nature Communications proves once again that bugs might just be wiser than we think. When it is time to focus on the children, female burying beetles (Nicrophorus vespilloides) can send discouraging chemical signals to warn off their eager mates.

The group of German scientists who conducted the study found that, although burying beetles are known to engage in co-parenting behavior, sometimes female beetles are forced to use pheromones to discourage attention at crucial points.

Biologists studied 400 pairs of burying beetles to better understand the resource trade off and signaling patterns that allow the species to make the best reproductive choices possible. The results, they say, were fascinating.

"It is kind of intriguing that such mechanisms exist in animals and that animal parents synchronize their mating and parental-care behavior for their own benefit and that of the children," one of the study’s authors, biologist Sandra Steiger, a professor at the Institute for Evolutionary Ecology and Conservation Genomics at Ulm University, told Reuters.

Burying beetles are not usually adverse to mating. These two-centimeter, black-and-orange insects get their name from a bizarre courtship ritual that includes fighting over small animal carcasses and burying them. Researchers left mouse carcasses in the woods by their university to attract the first generation of beetles, and then recreated the process in the laboratory. 

Burying beetles are smart family planners. Only after the beetles have secured a carcass and lathered it with anti-microbial secretions to keep the food fresh for their future young do they mate and produce offspring. The female alternates between mating with the male and laying eggs for 20 hours before finally throwing in the towel. 

Around 60 hours after the beetles mate and the female beetle produces larvae, she begins to produce a pheromone that discourages her mate. The hormone, called the juvenile hormone, can temporarily inhibit the reproductive capability of the female when released in high doses. Females release this hormone for three days while their young are in the tender larval stage, which leaves them dependent on their parents.

The biologists who conducted this study refer to the pheromone as an “anti-aphrodisiac” for the way it “turns off” the male beetles and discourages their interest in mating.

This makes the burying beetles special, because not only do they work together to parent their children, but the chemical signals released by the female parent help maintain the parental relationship.

"Parents of many species cooperate to rear offspring, but nevertheless there can be intense conflicts between males and females over mating rate or how much each sex should invest in raising the young," reads the text of the study.

Other animal and insects also struggle to balance the urge to produce more offspring and the urge to care for the ones they already have. According to the study, it makes more evolutionary sense to care for an existing set of offspring. 

According to Dr. Steiger, this study is important for understanding chemical communication amongst animals, including insects like beetles, and their impact on evolution.

"This is important to answer questions about chemical ecology and animal physiology,” said Dr. Steiger in a University at Ulm press release. “It helps us to understand how animals communicate with each other and how, for example, chemical communication patterns have worked in the path of evolution to change or stabilize."