Meeting Abstract
Doradid catfishes are weaponized with pectoral and dorsal fin spines with lateral rows of thorn-like barbs. These spines often reach 30% of body length and can be abducted and locked into place. The pectoral girdle, which supports the pectoral spines, has a broad ventral surface with an interdigitating median suture, in contrast to the slender ventral arms of the pectoral girdle in other teleosts. We used micro-CT scans, finite element analysis, mechanical testing, and phylogenetic comparative methods to study the morphology, function, and evolution of these defensive adaptations in doradids. The median suture is formed by a zipper-like series of projections, which differ in three-dimensional morphology from the well-documented interdigitating sutures of cranial bones. We predict this suture permits flexion under mediolateral compression. This is supported by the results of both static compression of a finite element model of a pectoral girdle and spines and by compression of the pectoral girdle using a mechanical testing system. We also tested for evolutionary integration between barb and girdle morphologies and found a strong phylogenetic signal in the morphometrics of the pectoral spines, girdle, and median suture. A phylogenetic partial least-squares regression indicated strong integration between barb and girdle morphologies overall; however, phylogenetic generalized least squares (PGLS) regressions on paired traits did not find strong relationships between suture interdigitation and either pectoral girdle or spine morphometrics. PGLS results did find strong integration between girdle width and barb cross-sectional area, suggesting that as spines get stiffer, the pectoral girdle gets broader.
