Vertebral morphology in partially sympatric dolphin species: a 3D approach

MARIA CONSTANZA MARCHESI; ROLANDO GONZÁLEZ-JOSÉ; MATÍAS S. MORA; SILVANA DANS

Barcelona

Conferencia; World Marine Mammal Conference; 2019

Society for Marine Mammalogy y European Cetacean Society

In cetaceans, body flexibility is associated with swimming speed and foraging behavior. Greater flexibility is associated with increased maneuverability. One factor affecting flexibility is the structure and interference of the vertebrae. We studied vertebral morphology in four closely related and partially sympatric dolphin species from the Southern Hemisphere: Commerson?s dolphin (Cephalorhynchus commersonii), Peale?s dolphin (Lagenorhynchus australis), dusky dolphin (Lagenorhynchus obscurus) and hourglass dolphin (Lagenorhynchus cruciger). The former two, are usually referred to as coastal. They are associated with complex habitats and foraging strategies that require greater maneuverability, showing plasticity in their prey preference. The latter two are cooperative feeders on pelagic prey with long distance displacements according to prey availability. We employed 3D geometric morphometrics to analyze differences in vertebral morphology and relate them with the preferred habitats and habits. We used a Microscribe G2X to obtain five original landmark configurations with 28 to 41 landmarks, depending on the functional region under analysis. We performed multivariate analyses for comparisons (PCA and CVA). Inferences about the biomechanical significance of the particular morphologies allowed us to establish links between morphology and behavioral patterns. PCA showed there is great differentiation among species along the vertebral column. This was especially evident in the mid area, except for the dusky and hourglass dolphin; that showed no difference in the mid-column. PCA results were confirmed by CVA. Features associated with greater flexibility were observed in species with complex habitats/behaviors whilst cooperative feeder species had features associated with greater stability. In these latter species, mid-column morphologies suggested mechanical advantage of the swimming muscles. Even though these species are closely related, vertebral morphology is distinctive and it is related with each species foraging strategy and habitat. This reflects a high plasticity and highlights the importance of habitat and behavioral complexity in the development of particular adaptations.