How the velvet worm squirts slime

ORAL

Abstract

The rapid squirt of a proteinaceous slime jet endows the ancient velvet worms (Onychophora) with a unique mechanism for defense from predators and for capturing prey by entangling them in a disordered web that immobilizes their target. However, to date neither qualitative nor quantitative descriptions have been provided for this unique adaptation. Here we investigate the fast oscillatory motion of the oral papillae and the exiting liquid jet that oscillates with frequencies $f\sim 30-60$ Hz. Using anatomical images, high speed videography, theoretical analysis and a physical simulacrum we show that this fast oscillatory motion is the result of an elastohydrodynamic instability driven by the interplay between the elasticity of oral papillae and the fast unsteady flow during squirting. Our results demonstrate how passive strategies can be cleverly harnessed by organisms, while suggesting future oscillating micro-fluidic devices as well as novel ways for micro and nano fiber production using bioinspired strategies.

Authors

  • Andres Concha

    Adolfo Iba\~{n}ez University, School of Engineering and Sciences, Adolfo Iba\~{nez} University, Santiago, Chile.

  • Paula Mellado

    Adolfo Iba\~{n}ez University

  • Bernal Morera-Brenes

    Universidad Nacional de Costa Rica

  • Cristiano Sampaio

    Universidade de Sao Paulo

  • L. Mahadevan

    Harvard School of Engineering and Applied Science, Harvard University, SEAS, Harvard University, Cambridge, MA, USA, Harvard, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138,USA., SEAS, Department of organismic and evolutionary biology, Harvard university, SEAS, Harvard University, Harvard Univ, School of Engineering and Applied Sciences, Wyss Institute, Harvard University

  • Juli\'{a}n Monge-N\'{a}jera

    Universidad de Costa Rica