Underwater attachment using hairs: the functioning of spatula and sucker setae from male diving beetles

Abstract

Males of Dytiscinae beetles use specialized adhesive setae to adhere to female elytra during underwater courtship. This coevolution of male setae and female elytra has attracted much attention since Darwin. However, there has been little examination of their biomechanical functioning despite increasing knowledge on biofibrillar adhesion. Here, we report and compare, for the first time, the mechanisms of underwater attachment using two hair types, the primitive spatula and derived 'passive' sucker, found in male diving beetles. Results from interspecific scaling of protarsal palettes and adhesion by single seta suggest better performance in the later-evolved circular (sucker) setae. Spatula setae with a modified shallow sucker and channels use the combined mechanisms of suction and viscous resistance for adhesion. Velocity-dependent adhesion provides sufficient control for resisting the female's erratic movements while also detaching easily through slow peeling. Direction-dependent shear resistance helps reorient setae surfaces into a preferred direction for effective adhesion. Seta deformation using different mechanisms for circular and spatula setae reduces the force that is transmitted to the contact interface. A softer spring in spatula setae explains their adhesion at lower preloads and assists in complete substrate contact. Attachment mechanisms revealed in adhesive setae with modified spatula and passive suckers provide insights for bioinspired designs of underwater attachment devices.

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

“…(3) there are no known mechanisms for rapid detachment in dytiscid circular setae [33][34][35]. As male dytiscid beetles use their suction organs to attach to the smooth sections of the female's pronotum and elytra, their attachment works best on smooth surfaces and their performance declines strongly on rough surfaces [34].…”

A Review of the State of Dry Adhesives: Biomimetic Structures and the Alternative Designs They Inspire

“…Animals with hairy, or “fibrillar”, adhesive organs include flies [ 97 ], beetles ( Figure 6 B) [ 94 , 98 ], spiders ( Figure 6 C) [ 99 , 100 ], skinks [ 8 , 101 ], anoles, and geckos ( Figure 6 D) [ 5 , 102 , 103 ]. Evidence indicates that fibrillar adhesive organs evolved independently for many of the animals that possess them, including lizard species of skinks, anoles, and geckos [ 8 ].…”

“…It is however a fundamental concern for the development of a truly robust and practical dry adhesive, and thus some researchers have given the issue special attention. Generally, the hydrophobicity of the surface is cited as an important factor in whether a surface is proficient in the shedding of particles in either wet or dry conditions [ 25 , 98 , 99 ]. Hydrophobic surfaces are generally made of low-surface energy materials and may be made superhydrophobic through careful use of nanoscale structuring.…”

Morphology and adhesion mechanisms of newt <italic>Cynops orientalis</italic>’ foot pads

“…[5,8] . 类似地, 东方蝾螈幼体足垫 表面的凸起边界围绕表皮细胞形成的浅边小杯在黏液 和纳米柱阵列的援助下, 可能在更小的尺度范围内发 挥吸附作用, 甚至可能适应水下黏附和摩擦 [14,16,17] .…”