Lovesick flies

THEY say the way to a man’s heart is through his stomach – but for one fruit fly species, it’s more of a round trip. In a courtship ritual that’s equal parts romantic and revolting, male Drosophila subobscura regurgitate their food and present it to females as a gift during courtship. Nothing says “I fancy you” like a partially digested dinner.

Meanwhile, their cousin Drosophila melanogaster has spent the last 30–35 million years wooing mates with wing vibrations – rhythmic “courtship songs” that are more Barry White than bodily fluids. But thanks to researchers in Japan, these flies are now shelving the sexy soundtrack and embracing the puke.

By turning on a single gene in insulin-producing neurons, the team successfully made the male Drosophila melanogaster perform a gift-giving ritual it had never done before. The study, published in the journal Science, represents the first example of manipulating a single gene to create new neural connections and transfer behaviour between species. Both have a gene called “fruitless” or “fru” that controls courtship behaviour in males, but they use different strategies: in gift-giving flies, insulin-producing neurons are connected to the courtship control centre in the brain, while in singing flies these cells remain disconnected.

“When we activated the fru gene in insulin-producing neurons of singing flies to produce FruM proteins, the cells grew long neural projections and connected to the courtship centre in the brain, creating new brain circuits that produce gift-giving behaviour in Drosophila melanogaster for the first time,” explained Ryoya Tanaka, co-lead author and lecturer at Nagoya University’s Graduate School of Science.

The researchers inserted DNA into Drosophila subobscura embryos to create flies with heat-activated proteins in specific brain cells. They used heat to activate groups of these cells and compared the brains of flies that did and did not regurgitate food. They identified 16–18 insulin-producing neurons that make the male-specific protein FruM, clustered in a part of the brain called the pars intercerebralis. And while it may sound like sci-fi matchmaking for fruit flies, its implications extend far beyond courtship rituals.

“Our findings indicate that the evolution of novel behaviours does not necessarily require the emergence of new neurons; instead, small-scale genetic rewiring in a few pre-existing neurons can lead to behavioural diversification and, ultimately, contribute to species differentiation,” noted Yusuke Hara, co-lead author from the National Institute of Information and Communications Technology (NICT).

Insects like bees, ants, and mosquitoes have well-mapped genomes and relatively simple brains, making them promising candidates for genetic tweaks to influence behaviours like foraging, mating, or aggression – with potential applications in pest control and pollination.

But the success seen in fruit flies hinged on conserved genes and shared brain architecture – a luxury not afforded by more complex species, like mammals for instance. So, the next time you’re out for a romantic meal and your date throws up, they’re after a glass of water, not your undying love.

Foie Gras without the aargh!

FOIE GRAS production is illegal in the UK on animal cruelty grounds – and it’s not hard to see why. The delicacy is made by force-feeding ducks or geese using a specialised feeding tube (gavage) to unnaturally enlarge their livers.

During this process, the birds endure extreme physical and psychological distress. Over the course of just a few weeks, their livers swell to as much as ten times their normal size – a transformation marked by pain and suffering.

Despite the UK ban on production, foie gras imports remain legal, with nearly 200 tonnes brought in annually, mainly from France.

However, a new alternative may soon offer the same flavour without the unethical aftertaste. Already available in Singapore, the Vow Group has received approval in Australia to use cell-cultured quail as food. The green light from the Food Standards Australia New Zealand (FSANZ) Board means foie gras made from cultured Japanese quail will now appear on select menus in Sydney and Melbourne. The ruling has established a clear regulatory framework, requiring cell-cultured foods to be labelled as “cell-cultured” or “cell-cultivated”.

The UK has already seen cell-cultivated meat appear on dogs’ menus courtesy of Meatly’s Chick Bites (see TCE 1,008) and is actively developing its own regulatory framework for human consumption. Vow is one of eight companies participating in a two-year programme to help shape UK regulations, alongside academic institutions and industry bodies. The success (or not) of its cultured foie gras – “all the decadence of the traditional version, minus the animal intervention” – could play a pivotal role in shaping the conversation.