Different mechanics of snap-trapping in the two closely related carnivorous plants Dionaea muscipula and Aldrovanda vesiculosa

TL;DR

This paper compares the distinct snap-trap mechanisms of the aquatic Aldrovanda and terrestrial Dionaea plants, revealing different biomechanical processes underlying their rapid closure.

Contribution

It presents the first detailed mechanical models explaining the different snap-trap mechanisms based on thin solid membrane theory.

Findings

Aldrovanda's snapping involves midrib deformation and kinematic amplification.

Dionaea's snapping relies on buckling instability of the lobes.

Different mechanical principles underlie similar trap functions.

Abstract

The carnivorous aquatic Waterwheel Plant (Aldrovanda vesiculosa L.) and the closely related terrestrial Venus Flytrap (Dionaea muscipula SOL. EX J. ELLIS) both feature elaborate snap-traps, which shut after reception of an external mechanical stimulus by prey animals. Traditionally, Aldrovanda is considered as a miniature, aquatic Dionaea, an assumption which was already established by Charles Darwin. However, videos of snapping traps from both species suggest completely different closure mechanisms. Indeed, the well-described snapping mechanism in Dionaea comprises abrupt curvature inversion of the two trap lobes, while the closing movement in Aldrovanda involves deformation of the trap midrib but not of the lobes, which do not change curvature. In this paper, we present the first detailed mechanical models for these plants, which are based on the theory of thin solid membranes and explain this difference by showing that the fast snapping of Aldrovanda is due to kinematic amplification of the bending deformation of the midrib, while that of Dionaea unambiguously relies on the buckling instability that affects the two lobes.