Digesting your prey
Venus flytraps are one of the speediest plants around. You can read here in an earlier post how they manage to catch their prey that quickly. But have you ever wondered what happens after a fly or cricket is trapped between those two big trap-leaves? This new study called “Venus flytraps’ metabolome analysis discloses the metabolic fate of prey animal foodstock” shows what happens next.
For Venus to be able to feed on the trapped fly or cricket it needs to digest it. But it doesn’t just automatically release its digestive fluids after closing its trap. First it performs a kind of confirmation test: are those trigger-hairs still being touched in quick succession? Only if this question is answered with a ‘yes’ does Venus is seals its trap close. In that regard it is useless to feed your Venus flytrap dead flies.
Those same signals that tells Venus that it has secured its next meal, activate the secretion of digested fluids. A thick sugary fluid with ions and lytic enzymes. These slowly degrade the exoskeleton and internal tissues of the insect.
Digestion fluids come at a cost
To find out in more detail what happens next, the researchers compared the metabolites of four traps and petioles that hold up those traps. A control non-fed trap. A trap that after closing received mechanical stimulation as if to say: there is a fly here that wants to get out. A trap that closed on tissue paper that was sprayed with an analogue of jasmonic acid as if it say: start secreting those digestive fluids now. And of course, a trap with an actual living prey inside.
The researchers found that a trap with an actual living prey contained already after 24 hours much more amino acids and sugars than the others. The one which tricked the trap into believing that it needed digestive fluids actual contained less amino acids and sugars. Suggesting that providing those digestive fluids is costly.
Where those digested metabolites go
Subsequently, the researchers looked into which genes were activated after capture of a prey. Interestingly, it seems as if the plant activated genes that most other plants use to defend themselves against herbivory insects for prey digestion. The researchers also found genes, that normally are active in the roots for nutrient uptake, were activated for nutrient uptake, transport and absorption in the closed trap-leaves.
This all suggest that closed trap-leaves that are digesting pray are actively taking up and transporting those nutrients to the rest of the plant. This is also what the researchers found when they looked at the metabolites in the petioles. Just as the metabolites in the closed trap-leaves, those in the petioles had increased amino acid levels. But only when they contained an actual prey, and not when one of the other stimulations took place.
Venus flytraps are thus only putting effort into digesting a prey when there is an actual prey. Mostly because digesting is costly. It therefore wouldn’t do to secrete digestive fluids when there is no prey to handsomely compensate for the cost.
Literature
Kreuzer, I., Scossa, F., Tohge, T., Fernie, A.R. and Hedrich, R. (2025), Venus flytraps’ metabolome analysis discloses the metabolic fate of prey animal foodstock. Plant J, 123: e70391. https://doi.org/10.1111/tpj.70391
Plant en Zo 