Anatomy and Morphology

Elasmobranch fishes are characterized by a diverse suite of morphologies among often closely related species. We employ geometric morphometrics, clearing and staining, traditional dissection, and behavioral assays to determine the evolutionary function of various morphological features. Although the research is primarily focused upon sensory systems, the principles can be applied to other biological characters.

We have investigated how the specialized morphology of the pelvic fins of skates enables them to ‘punt’ along the seafloor much more effectively than other benthic batoids. Various stingray species have less robust pelvic girdles and lack the specialized crura of skates but still exhibit punting locomotion to a greater or lesser extent. For example, electric rays, in which the body disc is largely comprised of the electric organ, cannot undulate their pectoral fins and thus rely on axial undulation and punting for locomotion.

The lesser electric ray, Narcine bancroftii, is unique in that it possesses two pairs of electric organs - the main electric organs and the smaller accessory electric organs. The main electric organs emit strong discharges (up to 60 V) which deter predators and the accessory electric organs emit weak discharges (1 V) which are likely used to communicate with other individuals via their electrosensory system.

The distribution and arrangement of sensory systems on the body of various species is also an area of active research. Staining is often employed to facilitate visualization of the glycoprotein-filled subdermal electrosensory tubules. This enables us to more easily quantify and map the arrangement of sensors over the surface of the body.

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