Meeting Abstract
In the weakly electric group of African fishes, Mormyridae, there is diversity in the head shape and snout length among the c. 221 species; however, the evolutionary and allometric patterns within this diversity are largely unstudied. Similarly, the group of weakly electric fishes from the Amazon, Gymnotiformes, require further study on the allometric growth patterns during development in the c.245 species. In both groups, some species have elongate tubular snouts with a small terminal mouth used for benthic feeding, while others use brachycephalic snouts to feed throughout the pelagic zone. This research analyzed patterns in snout elongation and head shape diversity in four species, two gymotiform species and two mormyridae species, using two-dimensional geometric morphometrics. Species included in this study have varying snout lengths, and include Brienomyrus brachyistius (n=29), Mormyrops anguilloides (n=14), Porotergus duende (n=27) and Sternarchorhamphus muelleri (n=15). Homologous landmarks were placed to capture the head shape, angle of snout depression, and snout length of the specimens. Through the Geomorph program, Principal Component Analyses of statistically significant variables were generated to perform multivariate regressions between the measurements of head shape diversity. Further, evolutionary allometry was analyzed to determine the covariation between shape and allometric growth among these species. These results showed significant covariation between head shape, snout length, and angle of snout depression among the adult specimens of the four species. This preliminary study provides further opportunities to evaluate the underlying the diversity of head shape among additional electric fish species and examine the covariation between snout elongation and ontogenetic patterns of diversification.
