Stick tight: suction adhesion on irregular surfaces in the northern clingfish

Abstract

The northern clingfish, Gobiesox maeandricus, is able to adhere to slippery, fouled and irregular surfaces in the marine intertidal environment. We have found that the fish can adhere equally well to surfaces with a broad range of surface roughness, from the finest sandpaper (R a ¼ 15 mm) to textures suitable for removing finish from flooring (R a ¼ 269 mm). The fishes outperform manmade suction cups, which only adhere to the smoothest surfaces. The adhesive forces of clingfish correspond to pressures 0.2-0.5 atm below ambient and are 80-230 times the body weight of the fish. The tenacity appears related to hierarchically structured microvilli around the edges of the adhesive disc that are similar in size and aspect ratio to the setae found on the feet of geckoes, spiders and insects. This points to a possible biomimetic solution to the problem of reversibly adhering to irregular, submerged surfaces.

Attachment to challenging substrates – fouling, roughness and limits of adhesion in the northern clingfish (Gobiesox maeandricus)

“…The substrates that clingfish adhere to have a variety of surface topographies, from nearly smooth to very rough, and G. maeandricus sticks so well that it can launch predatory attacks on the archetypal attached marine invertebrate -the limpet. In fact, clingfish are able to stick better to rough surfaces than to smooth ones (Wainwright et al, 2013). This is counter to our expectations for suction cups, which adhere only to smooth surfaces (Pennisi, 2012).…”

“…On rough, unfouled surfaces, clingfish can use their elastic disc margin covered with hierarchical papillae made of microvilli to adapt to surface irregularities. These structures probably increase the friction when pulled in a horizontal direction and thereby delay inward slipping and failure of the disc to cling (Wainwright et al, 2013). In contrast, a fish attached to a fouled substrate makes no direct contact with the primary substrate, but instead contacts the fouling organisms.…”

“…This ability to stick to rough surfaces seems to be connected with a specialized epithelial microstructure on the ventral surface of the clingfish adhesive disc (Fig. 1B) (Wainwright et al, 2013). Epidermal papillae made of tiny hairlike rods, which are subdivided at the tips into tiny filaments, cover the margin of the disc and we expect they play a role in adhering to rough surfaces (Arita, 1962;Green and Barber, 1988).…”

Remora attachment is enhanced by spinule friction

“…Among known suction-based attachment mechanisms in fishes (Gibson, 1969;Green and Barber, 1988;Maie et al, 2012;Wainwright et al, 2013), the remoras (family Echeneidae) are the only group to have derived their suction apparatus from dorsal fin elements. The suction pad of remoras is homologous to the dorsal fin common to other bony fish species (Britz and Johnson, 2012).…”

Unveiling the morphology of the acetabulum in octopus suckers and its role in attachment

“…It has been further supported by the recent discovery of hair-like structures covering the entire surface of the acetabular roof [15]. Hair structures have been recognized as fundamental to attachment under wet conditions in other animals, such as clingfish and abalone molluscs [27,28]. This natural solution should prevent sliding between the acetabular protuberance and the orifice [29,30] and help to seal region P i from region P a .…”