Sticky, stickier and stickiest – a comparison of adhesive performance in clingfish, lumpsuckers and snailfish

Abstract

The coastal waters of the North Pacific are home to the Northern clingfish (Gobiesox maeandricus), Pacific spiny lumpsucker (Eumicrotremus orbis), and marbled snailfish (Liparis dennyi) – three fishes that have evolved ventral adhesive discs. Clingfish adhesive performance has been studied extensively, but relatively little is known about the performance of other sticky fishes. Here, we compared the peak adhesive forces and work to detachment of clingfish, lumpsuckers, and snailfish on surfaces of varying roughness and over ontogeny. We also investigated the morphology of their adhesive discs through micro-CT scanning and scanning electron microscopy. We found evidence that adhesive performance is tied to the intensity and variability of flow regimes in the fishes’ habitats. The Northern clingfish generates the highest adhesive forces and lives in the rocky intertidal where it must resist exposure to crashing waves. Lumpsuckers and snailfish both generate only a fraction of the clingfish's adhesive force, but live more subtidal where currents are slower and less variable. However, lumpsuckers generate more adhesive force relative to their body weight than snailfish, which we attribute to their higher-drag body shape and frequent bouts into the intertidal. Even so, the performance and morphology data suggest that snailfish adhesive discs are stiffer and built more efficiently than lumpsucker discs. Future studies should focus on sampling additional diversity and designing more ecologically relevant experiments when investigating differences in adhesive performance.

Stickiness in shear: stiffness, shape, and sealing in bioinspired suction cups affect shear performance on diverse surfaces

“…The functional morphology of these adhesive discs has been well-documented, with some studies also evaluating the performance of the organisms on diverse surfaces. One prominent example, the Northern clingfish (Gobiesox maeandricus), can adhere strongly to surfaces with an average roughness of up to 1000 µm [12][13][14]. This exceptional performance is attributed to the hierarchically structured papillae around the edge of disc margin, which interlock with rough asperities and seal the disc as it is pulled [4,13,15].…”

“…Despite the great interest in the adhesive capabilities of these organisms, there are still avenues of research that remain largely unexplored. For example, it is primarily understood that bony elements within the disc provide rigidity, derived from modified structures such as paired pelvic and pectoral girdles (clingfish) [14,15], pelvic fin rays (gobies) [5,21], and dorsal fins (remoras) [17,22]. However, less is known about how the morphological diversity of such structures affects adhesion.…”

“…However, less is known about how the morphological diversity of such structures affects adhesion. Huie, et al [14] compared the adhesion performance of the Northern clingfish against the marbled snailfish (Liparis dennyi) and the Pacific spiny lumpsucker (Eumicrotremus orbis). When tested by pulling the fish in the normal direction away from the substrate, the clingfish displayed the greatest adhesion force across a range of rough surfaces.…”

“…stiffness, shape) may affect adhesive performance. However, comparative studies focusing on these requirements within aquatic adhesion has been somewhat limited, with only more recent studies exploring performance across multiple species [5,14,16].…”

“…To achieve variable stiffness, we fabricated elliptical cups, which resulted in shorter walls along the minor axis. This produced higher taper angles along the sides of the cup [14,21], and the lower aspect ratio of the shorter walls would create regions of higher stiffness. Based on recent studies of skeletal structures within adhesive discs [14,21], we hypothesized these regions of stiffness would provide the cup with additional structural integrity needed to maintain the suction chamber under load, namely, a cup which was stiffer on the minor axis would have a higher resistance to shear applied on the major axis.…”