Beetles that receive less care from their parents spend more time caring for their own offspring.
Roundneck sexton beetles (Nicrophorus orbicollis), a kind of burying beetle, bury the bodies of small animals and feed their larvae by releasing flesh-digesting enzymes into the carcass. They can also regurgitate digested meat directly into the mouths of their young.
at the University of Georgia and his colleagues wanted to know whether the parental care these beetles receive as larvae affects how they feed their offspring as adults. 鈥淚f you receive poor parenting yourself, are you destined to be a poor parent?鈥� he says.
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The researchers gave 10 unrelated larvae to each of 36 female N. orbicollis beetles in the presence of a mouse carcass 鈥� these beetles readily adopt unrelated larvae as their own. The team allowed half of the beetles to fully care for their larvae for a week. The others were separated from their larvae after 6 hours.
When they became adult beetles, the larvae that had full parenting weighed roughly 500 milligrams on average, while those with reduced care weighed just 373 milligrams on average.
These adult beetles reared in the first part of the experiment were then introduced to a separate group of beetles to have their own offspring around a mouse carcass. A day after the larvae entered the carcass, the team observed parenting behaviour for 15 minutes.
All of the beetles spent the same amount of time indirectly feeding their offspring by releasing enzymes, but those that had received less parental care spent more than 10 per cent longer directly regurgitating digested meat into the mouths of their larvae.
鈥淚f the beetle chews up the meat and digests it before regurgitating it out, that direct feeding is probably breaking down the carcass more effectively than just spitting out some enzymes onto the carcass,鈥� says Cunningham.
鈥淚 would think that direct feeding releases more amino acids and sugars for the larvae to use compared to indirect feeding, so poorly parented beetles seem to become better parents,鈥� he says.
However, all the larvae in this part of the research weighed the same, so the study can鈥檛 determine whether direct feeding is better in terms of larval growth, says Cunningham. 鈥淏ut we can say that bad parenting does not always pass down from one generation to the next.鈥�
Further work is needed to establish whether the same effects occur in the wild, where there are predators, and whether these findings apply to other species, says Cunningham. If so, we could potentially find ways to improve breeding success for animals that have had a rough childhood, he speculates.
鈥淯nderstanding the genetic pathways underpinning this shift in parenting behaviour could eventually reveal ways to manipulate those pathways using drugs,鈥� he says.
bioRxiv
