Meeting Abstract

P2-107   -   The functional morphology of sea urchin spines as puncturing tools Akinrinade, AO*; Crofts, SB; University of Washington Bothell; College of the Holy Cross ayoakinrinade@gmail.com

Sea urchins use their spines for a variety of functions, such as burrowing, anchoring, and defense. As defensive tools, we know that some urchins have venomous spines and we know that some spines are capable of puncturing human skin. However, there remains much to explore in terms of urchin spine form and function. To understand the mechanisms underpinning puncture by urchin spines, we tested puncture performance across three species of urchin looking at the effects of tip and surface morphology. Because spine morphology varies across regions of the body and between species, it is likely that puncture performance will vary similarly, so we quantified regional differences in morphology and puncture ability in three species of the genus Strongylocentrotus: the green sea urchin (S. droebachiensis), pale sea urchin (S. pallidus), and purple sea urchin (S. purpuratus). As indicators of puncture performance, we measured force to initiate fracture, work to initiate fracture and work to propagate fracture. We found that purple sea urchin spines were significantly different from pale and green urchins in all three of these measurements. To quantify morphology, we measured included angle and radius of curvature at the tip, and ridge and furrow widths at the shaft. We found that radius of curvature was the only measure correlated with puncture performance. We also found that green urchins had serrations on the ridges of all of their spines, in contrast, only some oral spines from pale and purple sea urchins had serrations. The variation in spine puncture performance between species is likely due to differences in ecological demands; purple urchins reside in more open shore habitats with stronger wave action than the other species. This difference could indicate a trade-off between puncture and anchoring ability.