I study several different species of squamate reptiles. Squamates are what we classically think of as lizards and snakes. I study the tongue morphology, as well as the feeding kinematics, of the blue-tounged skink (Tiliqua scincoides) and several lizards from the clade Iguania, including the bearded dragon (Pogona vitticeps) and the emerald swift (Sceloporus malachiticus). I study these species because they all use their tongue to capture prey, but T. scincoides evolved the ability to do so independent of iguanians. By comparing the way lingual prey capture is accomplished kinematically, and determining whether there are morphological correlates of the behavior across these multiple evolutions, we can learn about what traits are required for lingual prey capture and what traits are unique to certain lineages.
The word "morphology" is synonymous with the words "body form" or "body shape." A scientist that studies morphology studies the variation in body form in a certain group of organisms. I study lingual (tongue) morphology via methods such as dissection and histology. These methods allow me to see and measure the relative sizes, as well as the shapes, of different muscle groups and microscopic tongue features across species.
Images: Left-Paraffin histology through the tongue of the blue-tongue skink, Tiliqua scincoides (transverse section). Right-Paraffin histology through the tongue of the prehensile-tailed skink, Corucia zebrata (transverse section).
"Kinematics" refers to the sequence of events, and duration of those events, within a large motion or cycle. When I study kinematics in the context of lizard feeding, I first establish the sequence of events in a single feeding cycle, then I determine the timing of each event. I do this using fast-motion videography.
Images: Left - lingual prey capture in the blue-tongued skink, Tiliqua scincoides. Right- lingual prey capture in the bearded dragon, Pogona vitticeps.
I am interested in feeding morphology and kinematics as it relates to the evolution integrated suites of traits. Integration and functional complexity are inherent to biological systems, just think about how many muscles have to work with or against one another to make your arm move. How does that trait integration influence morphological evolution? How do the relationships between morphology and function shape that evolution?
In conjunction with other members of the Schwenk Lab, I study breathing cycles in tadpoles. The tadpoles we study are those of the gray tree frog (Hyla versicolor), the African clawed frog (Xenopus laevis), the wood frog (Rana sylvatica) and the green frog (Rana clamitans). I specifically work on analyzing the breathing cycles of the gray tree frog and African clawed frog.
Image: Tadpoles of the gray tree frog, Hyla versicolor, in a filming chamber.
To begin the process of kinematic analysis, we use fast-motion videography to record the tadpoles while they breath. I then analyze the steps of each breathing cycle using ImageJ software. Once the steps of each cycle are analyzed, we can make comparisons about the structure of the cycles between species.
Tadpoles are a widely understudied phase in the amphibian life cycle. Analyzing and comparing the breathing cycles in these tadpole species allows us to fill major gaps in our scientific understanding about amphibian development.
Title Image: Sceloporus occidentalis; Photo Credit: Jackson Phillips