Meeting Abstract

P3-146   -   Spiky, soccer balls of the sea - Ontogeny, morphology, and function of abrasion resistant armor in the Spiny Lumpsucker Woodruff, EC*; Huie, JM; Summers, AP; Cohen, KE; Carleton College, Northfield MN; The George Washington University, Washington DC; Friday Harbor Laboratories, Friday Harbor WA; Friday Harbor Laboratories, Friday Harbor WA eleanorcwoodruff@gmail.com

Fishes are armored against both biotic and abiotic assault. Predation and combat are important selective stressors, but so are the slings and arrows of an abrasive and high impact environment. The Pacific spiny lumpsucker ( Eumicrotremus orbis ) is an armored fish found in the rocky intertidal. Its rotund body is covered with epidermal, cone-shaped, enamel scales. We used micro-CT and SEM to reveal the morphology and ontogeny of the armor, and to quantify the amount of mineralization relative to the endoskeleton. Non-overlapping denticles are organized into eight rows - six rows on the body, one row surrounding the eye, and one row underneath the chin. Denticles start as a single, hooked cone; and they grow by the addition of cusps that accrete into a circular, toothed surface reminiscent of a Fibonacci spiral in 3D. The investment in armor compared to skeleton increases over ontogeny. Damage to the armor occurs both through passive abrasion and breakage from impact; and there is no evidence of replacement, or repair of damaged scales. We take the thin enamel armor, with gaps between scales, to be proof against abrasion rather than puncture. The lumpsucker is a poor swimmer in the wave swept rocky intertidal, and this armor may be a lightweight solution to the problem of collisions with abiotic obstacles.