AN EMPIRICAL TEST OF 3D PRINTED TURRITELLINE SHELLS: DOES DIFFERENTIAL DISTRIBUTION OF ORNAMENTATION INCREASE SHELL STRENGTH?

Gastropod shell shapes are subject to numerous ecological selective pressures. While past investigators have successfully related some aspects of shape to relevant selective pressures, in many taxa the role of shell ornamentation remains unclear. We studied the role of ornamentation on turritelline gastropods by experimentally analyzing the strength of differently sculptured shells in compression. Our experiments relied on the ability to mathematically model and 3D print shells with varying ornamentation. As a result, we were able to constrain the overall amount of material being dispensed by the printer, while changing the distribution of that material. We used this technique to model control (unornamented) shells, shells with a single rib, shells with two ribs, and shells which were thickened universally. All shells besides the control were constructed with the same amount of material, thus mimicking the same energetic cost to the organism. While it is possible to construct these complex shapes with relatively new resin 3D printers, the models must be carefully created during the preprocessing phase of printing and the shells must be tested with various curing conditions after printing for the desired brittle behavior. We used a compression apparatus with flat plates to simulate crushing predation. Peak load before failure was used as a proxy for adaptive value against crushing.