Mothers use sex pheromones to veil eggs, preventing cannibalism

January 10, 2019, Public Library of Science
The image illustrates how altered pheromone composition in the wax layer makes a D. melanogaster egg leak, consequently unmasking its identity and making it vulnerable to cannibal larvae. Credit: Roshan K. Vijendravarma

Species that lay eggs but don't actively keep watch over them often protect their precious eggs from predators by laying them in communal groups or by fortifying them with toxins. However, protecting these eggs from being devoured by their own kind is a completely different game; the catch is that any anti-cannibalistic strategy needs to be an effective deterrent while remaining nontoxic to the cannibals. In a new study published in the open-access journal PLOS Biology on January 10, Sunitha Narasimha, Roshan Vijendravarma and colleagues report how fruit flies (Drosophila melanogaster), which lay eggs communally, use chemical deception to protect their eggs from being cannibalized by their own larvae.

Using a , Dr. Roshan Vijendravarma from the Department of Ecology and Evolution, University of Lausanne, Switzerland (currently at Institut Curie, Paris, France) and his team of international collaborators teased apart the chemical, sensory, genetic and mechanistic basis of deception using the Drosophila model system.

The team was intrigued by the observation that fruit fly , despite their predatory nature, seldom attacked in their vicinity even when deprived of food. While testing for various plausible defense mechanisms, the researchers found that the extremely thin wax layer within the egg shell acts as a protective barrier that prevents cannibalism.

Using high-resolution mass spectrometry to identify the specific molecules involved, the team discovered that the wax layer is composed of a bouquet of sex pheromones originating from both parents, and then nailed the protective effect on a female chemical called 7,11-heptacosadiene (7,11-HD); this pheromone, normally used to spice up the adult flies' mating, was incorporated into the egg's wax layer by the mother.

It was already known that the adults need a gene called ppk23 for detecting the 7,11-HD pheromone during mating, so the authors looked to see whether the ppk23 gene played an analogous role in the larvae. They found that the gene was indeed involved in detection of this pheromone in larvae "a different developmental life-stage" but modulates an entirely different behavioral outcome.

Finally, this nontoxic pheromone had an interesting property whereby a coating of 7,11-HD could mask the identity of underlying substances from larvae—even yeast, normally irresistible to fly larvae. In the egg, these maternal hydrocarbons incorporated within the wax layer leak-proofed the egg to prevent desiccation, and by doing so additionally serve as a mask that conceals the egg's identity from cannibal larvae.

Deception as a defense strategy against predation has evolved independently in diverse species. However, partly owing to our human bias for , studies on deception have largely focused on vision-based strategies and less on those that dupe the other senses. The team's findings suggest that chemical deception might be common across the tree of life, especially when predators rely on chemical cues to forage. Furthermore, since studies on animal deception have rarely used powerful model systems like the fruit fly, this study demonstrates how doing so potentially opens the way for research on the sensory, neural, genetic, and mechanistic basis of deception. The in-depth understanding of such strategies is crucial, especially to the fields of conservation, epidemiology, and pest management.

Explore further: Enemy odors help flies protect their offspring

More information: Narasimha S, Nagornov KO, Menin L, Mucciolo A, Rohwedder A, Humbel BM, et al. (2019) Drosophila melanogaster cloak their eggs with pheromones, which prevents cannibalism. PLoS Biol 17(1): e2006012. doi.org/10.1371/journal.pbio.2006012

Related Stories

Study shows how beetle larvae adapt to different bee hosts

September 11, 2018

A team of researchers at the University of California has discovered adaptations made by a species of beetle to survive in different geographic locations. In their paper published in Proceedings of the National Academy of ...

Fruit fly species can learn each other's dialects

July 19, 2018

Fruit flies from different species can warn each other when parasitic wasps are near. But according to a new study led by Balint Z. Kacsoh of Geisel School of Medicine at Dartmouth, published July 19th in PLOS Genetics, they ...

Fruit flies fear lion feces

May 30, 2018

A new doctoral thesis from Lund University in Sweden shows how fruit flies use their sense of smell and humidity to find food, avoid dehydration and discover the best place to lay their eggs—in overripe marula fruits. Faeces ...

Fruit flies medicate their larvae with alcohol

February 22, 2013

(Phys.org)—A new study in the U.S. shows that fruit flies lay their eggs on a food source with a high alcohol content if they see parasitic wasps in the area, instead of a non-alcohol food.

Recommended for you

How our cellular antennas are formed

January 17, 2019

Most of our cells contain an immobile primary cilium, an antenna used to transfer information from the surrounding environment. Some cells also have many mobile cilia that are used to generate movement. The 'skeleton' of ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.