Sharks of Onslow County
Have you ever wondered why, if you touch a shark from head to fin, it feels smooth—but from fin to head, it’s skin is rough like sandpaper? Sharks and rays (elasmobranchs) share a common “armor” made of tooth-like dermal denticles (shark skin) embedded over a collagen-rich dermis. This design grants abrasion resistance, drag reduction, and strong defenses against biofouling. And they heal fast!
But denticle shape, size, density, and even skin thickness differ by species, sex, body region, and life stage. Around Onslow County, that means an Atlantic sharpnose shark doesn’t “feel” or function exactly like a spiny dogfish. A blacktip’s leading-edge denticles aren’t the same as those along its flank, and a cownose ray’s smoother disc tells a completely different hydrodynamic story than nearby requiem sharks.
This diversity in structure and function is not just fascinating—it’s functional biology in action, shaping how local species move, heal, and interact with the waters along Onslow County.
Dermal denticles (placoid scales)
Sharks and rays share an external armor of dermal denticles—tiny tooth-like structures that reduce drag, resist abrasion, and deter fouling (Domel et al., 2018; Feld et al., 2019). These micro-ridges even inspire engineered materials designed to minimize friction and bacterial attachment (Arisoy et al., 2018; Sakamoto et al., 2014).
A collagen-rich dermis
Beneath those denticles lies a collagen-dense dermis that anchors and supports them, distributing stress and contributing to flexibility and toughness (Hagood et al., 2023, 2025).
Rapid wound healing
Many sharks heal rapidly—re-epithelializing within days and closing large injuries in weeks to months (Womersley et al., 2021).
Species differences.
Denticle shape, ridge count, and spacing vary by ecology. Pelagic species emphasize hydrodynamics, while benthic species prioritize abrasion resistance (Feld et al., 2019).
Body-region mosaics.
Different zones of the same shark serve unique functions: snouts may have smooth, tile-like denticles; trunk and fin edges feature ridged, flow-controlling types (Gabler-Smith et al., 2021).
Sexual dimorphism and mechanical variation.
Hagood et al. (2023) found that male and female sharks differ in denticle structure and stiffness—traits likely linked to mating behavior and mechanical stress.
Ontogenetic and ecomorphological changes.
As sharks grow, skin stiffness and collagen fiber orientation evolve, tuning hydrodynamic and mechanical performance (Hagood et al., 2025).
Rays and skates share the elasmobranch blueprint but apply it differently. Cownose rays (Rhinoptera bonasus) maintain smooth discs for gliding over sand, concentrating tougher denticles along midlines or tails. Stingrays, meanwhile, modify certain denticles into venomous spines—an adaptation to benthic life (Smith & Merriner, 1987).
Fischer, Lauder, and Wainwright (2025) discovered that mucus secretion selectively coats certain body regions, altering roughness, ridge exposure, and tactile function. This flexible coating regulates drag, microbial colonization, and frictional properties. Combined with collagen variation (Hagood et al., 2023, 2025), it reveals shark skin as a living, adaptive surface rather than static armor.
Feld et al. (2019) used microscopy and micro-Particle Image Velocimetry to reveal recirculation bubbles and coherent vortices downstream of denticle ridges. Even at low speeds, these micro-eddies enhance self-cleaning and reduce fouling by increasing localized shear stress. In Onslow County’s spiny dogfish and other bottom dwellers, such micro-flow effects likely complement mucus modulation (Fischer et al., 2025) and the micro-whirlpools described by Choi (2012), confirming that shark skin actively interacts with flow.
Gabler-Smith et al. (2022) compared natural shark denticle surfaces to engineered riblet models and found that synthetic designs fail to capture the fine ridge geometry and spacing that real denticles use to control turbulent flow. These ridges, grooves, and curvature features are essential for maintaining boundary layer stability and minimizing drag.
Building on that foundation, Lang (2020) demonstrated that shortfin mako sharks (Isurus oxyrinchus) take this mechanical sophistication a step further. Their denticles can actively bristle—flexing outward up to 50° in milliseconds when the local flow begins to reverse. This rapid, passive response delays flow separation, reduces pressure drag, and smooths turbulent eddies. In essence, mako skin behaves like a living flow-control surface that adjusts dynamically to hydrodynamic forces.
Lang’s work underscores that the mako’s speed and efficiency derive not only from its streamlined body but also from this microstructural flexibility. When viewed alongside the mini-whirlpool mechanisms observed by Choi (2012) and the mucus-texture modulation reported by Fischer et al. (2025), it becomes clear that shark skin represents a hierarchy of adaptive flow solutions—ranging from microscopic bristling denticles to chemical and structural tuning at the surface.
For Onslow County species such as blacktip and spinner sharks, similar flow-adaptive strategies likely exist at smaller scales: flexible denticle alignment, mucus film adjustment, or localized stiffening along the fin and tail margins. Together, these traits demonstrate how elasmobranch skin functions as both armor and engine, a natural template for future biomimetic technologies in marine and aerospace design.
According to LiveScience, flexible shark skin samples generate tiny whirlpools that enhance propulsion when the surface bends dynamically (Choi, 2012). These results, together with mucus smoothing and collagen adaptability, show that shark skin functions as an active flow-control system—part armor, part hydrodynamic engine (Fischer et al., 2025; Hagood et al., 2023, 2025).
Fish gills actively metabolize dissolved substances. Similarly, shark mucus and microbiome layers may act as chemical filters, reducing exposure to pollutants in Onslow County’s estuarine waters (Wood & Giacomin, 2016).
Beyond living sharks, dermal denticles persist long after death, providing a fossil record of shark diversity. Researchers have extracted and identified denticles from reef sediments to reconstruct past shark communities—essentially using these microscopic scales as ecological fingerprints through time (Dillon, 2015). Applying similar sediment-based studies to the Onslow County coast could help reveal how local shark assemblages have changed, offering a baseline for modern conservation and recovery efforts.
| Function | Biological Basis | Example in Onslow County Species |
| Drag reduction & flow control | Denticle ridges, mucus overlays, and flexible flow (Domel et al., 2018; Fischer et al., 2025; Choi, 2012) | Blacktip & sharpnose sharks |
| Mechanical resilience | Collagen and denticle variation (Hagood et al., 2023, 2025) | Juvenile vs. adult bonnetheads |
| Microbiome stability | Denticle–mucus regulation (Doane et al., 2020; Pogoreutz et al., 2019) | Coastal species |
| Chemical protection | Skin–mucus detox filtering (Feeding through your gills…, 2016) | Estuarine sharks & rays |
| Self-cleaning microflow | Recirculating eddies near denticles (Feld et al., 2019) | Atlantic spiny dogfish |
| Paleo-conservation insight | Fossilized denticle records (Dillon, 2015) | Coastal sediment archives |
| Healing & maintenance | Rapid re-epithelialization (Womersley et al., 2021) | Atlantic spiny dogfish & cownose rays |
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Choi, C. Q. (2012, February 21). Sharks’ scales create tiny whirlpools for speedy swimming. LiveScience. https://www.livescience.com/18385-shark-skin-mini-whirlpools.html
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Smith, J. W., & Merriner, J. V. (1987). Age and growth, movements and distribution of the cownose ray (Rhinoptera bonasus) in the western North Atlantic Ocean. Environmental Biology of Fishes, 20, 233–242. https://doi.org/10.1007/BF00004913
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