College Honors Program

Scaling of red sea urchin (Mesocentrotus fransiscanus) spines

Date of Creation

5-17-2024

Document Type

Campus Access Only

Department

Biology

First Advisor

Stephanie Crofts

Abstract

As the size and shape of an animal changes over ontogeny, so too will its interactions with the surrounding environment. Sometimes the environment shapes how animals change over ontogeny. In the case of the red sea urchin (Mesocentrotus fransicanus), spines are critically important to both defense, stabilization, and movement, though the importance of each may change over time. In this study, I examine the changes in urchin spine size, shape, and function over a range of body sizes to detect potential functional trade-offs over ontogeny. Urchins included here range from a body diameter of 22.2 mm to large individuals body diameters around 150 mm. For each urchin I quantified representative spine size, 2nd moment of area (a geometrical measure of resistance to bending), and puncture ability. Spine lengths grew in proportion to tests, though widths didn’t always, indicating that spines of some regions change shape while others stay the same shape. 2nd moment of area changed inconsistently over ontogeny, displaying a test diameter threshold after which spine ability to resist bending plateaus. Puncture ability overall grew slower than test diameter, indicating less spine tip deformation over time. Differences in spine dimensions and performance across ontogeny, and between regions of the body, suggest that selective pressures on sea urchin spines change as urchins grow.

Comments

Reader: Justin McAlister

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