Functional consequences of carapace shape diversity in boxfishes

Meeting Abstract

P3.97  Sunday, Jan. 6  Functional consequences of carapace shape diversity in boxfishes MARCROFT, TA*; MODLIN, J; SLATER, G; VAN WASSENBERGH, S; SANTINI, F; ALFARO, ME; Univ. of California, Los Angeles; Univ. of California, Los Angeles; Smithsonian Institution; University of Antwerp; University of Torino; Univ. of California, Los Angeles

The carapace is a hard structure, similar to that of a turtle, which encases boxfishes and comes in a variety of shapes. Boxfish are composed of two families: the aracanids, which primarily consist of disk and tube-like shapes, and the ostraciids, which consist of prism, box, and bell-like shapes. This diversity in shape might be explained by its multiple functions, i.e. its hydrodynamic abilities and its ability to distribute stress. The carapace’s many keels are implicated in creating stabilizing forces via vortices shed posteriorly. We suggest that the boxfish carapace may have initially served as a defensive structure, but recently its function was altered for hydrodynamic stability and/or maneuverability, reflected in the aracanid-ostraciid split. We hypothesized that these two functions trade-off, i.e. stabilizing well means being less able to distribute stress and vice versa. We actually found that the association between the two functions and their morphologies is more complex. We found strong correlation between lift, lift/drag and morphology, suggesting maneuverability rather than stability explains some of the variation. While we did find a trade-off in function between two major carapace shapes, we also found that some shapes minimize performance in multiple orientations, but not as strongly as in extreme cases.

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