Meeting Abstract
Weakly electric fishes provide an opportunity to examine multiple instances of morphological convergence across continents. Gymnotiformes and Mormyridae use weak electric signals for prey detection, predator avoidance, and social communication. Species within each lineage inhabit deep river channels, shallow streams, and flooded plains, but it is unclear how these habitat types influence morphology. Snout length and shape are affected by prey type and availability, both of which are strongly influenced by a habitat’s water velocity and habitat complexity. Two families of electric fishes, Apteronotidae (Gymnotiformes) and Mormyridae (Osteoglossiformes), exhibit particularly high range of head shape disparity. A few studies have examined the similarities between the external morphologies of species in these two lineages, but we have yet to quantify the morphologies of internal head structures. Individuals from Apteronotidae (14 species, n=40 specimens) and Mormyridae (6 species, n=30 specimens) were analyzed using 3D geometric morphometrics with 22 homologous landmarks. Specimens were CT-scanned and analyzed using the programs 3D-Slicer and Geomorph. Procrustes ANOVA and multivariate regressions were used to analyze morphological similarities, which were then traced on phylogenetic trees. Results indicate multiple instances of significantly convergent morphologies, both within and between the families. Several species are more morphologically similar to those in another family than to species within a family. These results invite further study into the roles of natural selection and developmental constraints in the production of convergent phenotypes.
