Insulin Switches Off Praying Mantis's Urge to Hunt When Full

INSIDE JEB

Insulin switches off praying mantis’s urge to hunt when full

interest in the more distant nymphs, with only the closest cockroaches catching their attention. In short, they switched from actively pursuing prey to simply waiting for a snack to saunter within range as they became fuller. But what was driving the change?

‘Insulin is a hugely important hormone in animals ranging from C. elegans nematode worms to humans’,says Bertsch, explaining that the hormone is released when blood is flooded with glucose after feeding. Could the hormone be responsible for triggering the change in the mantis’s behaviour? This time, Bertsch injected ravenous praying mantises with the hormone and filmed their reactions to A praying mantis (Tenodera sinensis). Photo credit: David Bertsch. a mini-intrusion of cockroaches. Initially, the famished insects were keen to focus There is something eerie about the gently had to be housed individually for their on any cockroach, no matter how distant. swaying motion of a praying mantis own safety. ‘Cockroaches are infinitely However, as the insulin took hold over a poised in wait for a tasty snack to saunter easier to raise’, he chuckles. Next, Bertsch matter of minutes, the mantises’ interest past. ‘The praying mantis is an incredibly filmed the ravenous insects’ actions when waned until they were only interested motivated organism when hungry’, they were offered four lively cockroach in cockroaches that scuttled right past. says David Bertsch from Case Western nymphs – relieving the successful female The hormone could drive the switch Reserve University, USA, describing how hunters of their trophies to keep them from active predator to couch potato, the famished predators are even partial to on their toes in order to film further suggesting that it might be a key driver picking off members of their own species. encounters – before eventually allowing in the insects’ behavioural change as However, when his colleague Josh Martin the starving animals to dine. Then, he their appetites became more satisfied: noticed that the voracious insects might filmed their next encounters – on a ‘Something that we as humans can relate begin to lose interest in pouncing on partially full stomach – repeating the to’,smilesBertsch. food when their appetites are satisfied, process until the mantises had eaten all coworkers Gavin Svenson and Roy four of their cockroach snacks. So, praying mantises change their Ritzmann began wondering why the full behaviour depending on how well fed they insects lose motivation. Intriguingly, the mantises’ strike style are and insulin is one hormone that seems never varied over the course of each to drive the behavioural switch. Bertsch ‘We know that metabolism is critical to an filming session; each mantis fixed a adds that he is keen to find out how the animal’s daily life, but how metabolism nymph in its gaze until the tasty treat was hormone alters the insects’ behaviour. affects animal behaviour is not well within 1–2 cm range, when it lunged understood’, says Bertsch, who needed a forward, grabbing the unsuspecting 10.1242/jeb.207191 year-round supply of motivated mantises cockroach youngster with its forelimbs. to find out how their hunger affects their However, the mantises’ attention range Bertsch, D. J., Martin, J. P., Svenson, G. J. and Ritzmann, R. E. (2019). Predatory behavior hunting style. ‘[But] living in Cleveland, shifted depending on how well fed they changes with satiety or increased insulin levels Ohio, we only had access to wild mantises were. The hungriest animals seemed to be in the praying mantis (Tenodera sinensis). J. Exp. during the warmer months’, explains interested in victims that were as far as Biol. 222, jeb197673. doi:10.1242/jeb.197673 Bertsch, who became guardian to a 20 cm away. However, as the mantises Kathryn Knight colony of the aggressive insects, which consumed more cockroaches, they lost [email protected]

Inside JEB highlights the key developments in Journal of Experimental Biology. Written by science journalists, each short report gives the inside view of the science in JEB. Journal of Experimental Biology