Exploring the attachment of the Mediterranean medicinal leech (Hirudo verbana) to porous substrates

Abstract

Haematophagous ectoparasites must ensure a reliable hold to their host during blood meals and, therefore, have evolved a broad spectrum of versatile and effective attachment mechanisms. The Mediterranean medicinal leech ( Hirudo verbana ), for example, uses suction on both smooth and textured air-tight substrates. However, preliminary studies showed that H. verbana is also capable of attaching itself to air-permeable substrates, where suction does not work. Using high-speed videography and mechanical tests, we comparatively investigated the attachment of H. verbana on both smooth and textured air-tight as well as on porous artificial substrates, also considering the influence of mucus on sucker surfaces. In general, the leech-specific locomotion cycle did not differ between the tested surfaces, and the leeches were able to reliably attach to both air-tight and porous substrates. From our results, we conclude that suction is presumably the primary attachment mechanism of H. verbana . However, secondary mechanisms such as mechanical interlocking with surface asperities and pores or capillary forces occurring at the interface between the mucus-covered suckers and the substratum are also employed. In any case, the rich repertoire of applicable attachment principles renders the organs of H. verbana functionally highly resilient.

3D printed leech-inspired origami dry electrodes for electrophysiology sensing robots

“…Among complex mechanisms of leech's adhesive feature, it has an expandable posterior sucker and body 32 . Its organs expand and shrink appropriately to maintain better adhesion to the victim 33,34 . This adhering mechanism can be considered as the simultaneous motion of non 35 and auxetic 36 structures.…”

The effects of substrate porosity, mechanical substrate properties and loading conditions on the attachment performance of the Mediterranean medicinal leech (Hirudo verbana)

“…Similarly, the suction devices of the Mediterranean medicinal leech ( Hirudo verbana ) are also very versatile. They function both under water and air, as well as on substrates with varying surface textures, thereby relying on multiple physical mechanisms such as suction, wet adhesion as well as various mechanical interlocking techniques [19,20]. This is important since, in their natural habitats, leeches are confronted with a wide variety of substrates (e.g.…”

“…during vertical climbing or avoidance behaviour of their hosts). In case of H. verbana , the attachment performance to date has exclusively been analysed under normal loading conditions [19,20]. Therefore, the aim of this study was to investigate the influences of the loading conditions (normal versus shear loading) and of the mechanical substrate properties on the attachment performance of H. verbana .…”

Extreme suction attachment performance from specialised insects living in mountain streams (Diptera: Blephariceridae)

“…This is in remarkable contrast to artificial suction devices widely used in technical applications, which allow only slow control and are limited to clean and smooth surfaces. Despite their potential for bio-inspiration, there are only a few well-studied animals (namely, remora fish, clingfish, octopus, and leeches), for which the function of specific structures in biological suction attachments has been experimentally demonstrated ( Beckert et al, 2015 ; Fulcher and Motta, 2006 ; Arita, 1967 ; Wainwright et al, 2013 ; Kampowski et al, 2016 ; Kampowski et al, 2020 ; Ditsche et al, 2014c ; Kier and Smith, 1990 ; Kier and Smith, 2002 ; Smith, 1996 ). To date, mechanistic studies on biological adhesion have focused primarily on terrestrial climbing animals such as geckos, tree frogs, insects, and spiders ( Lengerer and Ladurner, 2018 ; Federle and Labonte, 2019 ), and have greatly expanded our knowledge on how to achieve and control adhesion in air.…”