Bioinspired remora adhesive disc offers insight into evolution

Abstract

Remoras are a family of fishes that can attach to other swimming organisms via an adhesive disc evolved from dorsal fin elements. However, the factors driving the evolution of remora disc morphology are poorly understood. It is not possible to link selective pressure for attachment to a specific host surface because all known hosts evolved before remoras themselves. Fortunately, the fundamental physics of suction and friction are mechanically conserved. Therefore, a morphologically relevant bioinspired model can be used to examine performance of hypothetical evolutionary intermediates. Using a bioinspired remora disc, we experimentally investigated the performance of increased lamellar number on shear adhesion. Herein, we translated fundamental biological principles into engineering design rules and show that a passive model system can autonomously achieve adhesive forces measured in live remoras in any environment. Our experimental results show that an increase in lamellar number resulted in an increase in shear adhesive performance, supporting the phylogenetic trend observed in extant remoras. The greatest pull-off forces measured for our model were on surface roughness on the order of shark skin and exceeded those measured for live remoras attached to shark skin by almost 60%. Overall, relative to fossil remoras and their closest ancestor, extant remoras exhibit a morphology indicative of selection for enhanced shear adhesive performance.

Knowing when to stick: touch receptors found in the remora adhesive disc

“…Remoras (family Echeneidae) are well known for their hitch-hiking behaviour; these fishes attach to other organisms such as sharks, whales, billfish and turtles [1][2][3] to take advantage of greater locomotor efficiency, increased probability of meeting mates, reduced predation and access to food such as parasites living on the host. The remora adhesive disc is capable of attaching to surfaces of varying roughness and stiffness and remaining attached under high shear conditions, where drag forces impart pressure strain-inducing sliding relative to the host [4,5]. Derived from dorsal fin elements [6,7], the adhesive disc is comprised of a central series of flat pectinated, or comb-like, lamellae surrounded by a fleshy lip (figure 1).…”

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

“…Remora fish use suction pads—highly modified dorsal fin spines—to attach to sharks, whales, and manta rays ( Beckert et al, 2015 ; Fulcher and Motta, 2006 ). Recent studies on the functional morphology of remora suction pads have greatly expanded our understanding on the mechanisms underlying their impressive performance ( Beckert et al, 2015 ; Wang et al, 2017 ; Gamel et al, 2019 ). A remora suction pad comprises a soft fleshy outer rim and rows of lamellae topped with spinules.…”

Toward understanding the communication in sperm whales

“…A critical current limitation of tags is onboard energy storage and memory as well as the effectiveness of their adhesion mechanisms. Bioinspired suction-based adhesion mechanisms inspired by carangiform fish ( Gamel et al., 2019 ; Wang et al., 2017 ) and cephalopod tentacles hold the promise of achieving working times on the order of several days and potentially to weeks. Fused with the sensor array data, the recordings from tags also allow the identification of whales in multi-party discourses and when associating behavior patterns with background recordings of the hydrophone/static sensor arrays.…”