Performance and scaling of a novel locomotor structure: adhesive capacity of climbing gobiid fishes

Abstract

SUMMARYMany species of gobiid fishes adhere to surfaces using a sucker formed from fusion of the pelvic fins. Juveniles of many amphidromous species use this pelvic sucker to scale waterfalls during migrations to upstream habitats after an oceanic larval phase. However, adults may still use suckers to re-scale waterfalls if displaced. If attachment force is proportional to sucker area and if growth of the sucker is isometric, then increases in the forces that climbing fish must resist might outpace adhesive capacity, causing climbing performance to decline through ontogeny. To test for such trends, we measured pressure differentials and adhesive suction forces generated by the pelvic sucker across wide size ranges in six goby species, including climbing and non-climbing taxa. Suction was achieved via two distinct growth strategies: (1) small suckers with isometric (or negatively allometric) scaling among climbing gobies and (2) large suckers with positively allometric growth in non-climbing gobies. Species using the first strategy show a high baseline of adhesive capacity that may aid climbing performance throughout ontogeny, with pressure differentials and suction forces much greater than expected if adhesion were a passive function of sucker area. In contrast, large suckers possessed by non-climbing species may help compensate for reduced pressure differentials, thereby producing suction sufficient to support body weight. Climbing Sicyopterus species also use oral suckers during climbing waterfalls, and these exhibited scaling patterns similar to those for pelvic suckers. However, oral suction force was considerably lower than that for pelvic suckers, reducing the ability for these fish to attach to substrates by the oral sucker alone.

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).…”

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

“…For example, many clingfishes (Gobiesocidae) have a suction disc that allows them to adhere to intertidal rocks with sufficient strength to resist dislodgement amidst crashing waves. The high-speed flows in stream environments have presumably shaped the attachment organs of gobies, balitorid loaches and loricariid catfishes (Gerstner, 2007;Maie et al, 2012;Roberts, 1998). Suction attachment has also allowed fishes to exploit entirely new habitats; for example, shark suckers (Echiniidae) attach themselves to larger fishes and live off the leavings of their host (Fulcher and Motta, 2006).…”

Understanding Surface Adhesion in Nature: A Peeling Model

“…Some creatures utilize suction forces to adhere to substrates such as octopus suckers57, 58 and climbing fish oral suckers 59. There is dispute within suction forces.…”