A small silver-spotted sculpin, Blepsias cirrhosus
During my PhD, I had the opportunity to work at Bamfield Marine Sciences Center on Vancouver Island in British Columbia. This experience jump-started my long-standing interest in marine sculpins! During the 6 week course taught by my PhD advisor, I collected enough data for 2 publications, and additional preliminary data that has kept sculpins in the back of my mind for 10 years!
Sculpins are (what some would call ugly) bottom-dwelling fishes that are common on the Pacific Coast of the US. They are found in habitats ranging from shallow rocky tidepools to deep ocean channels, which means they also deal with a variety of environmental demands. One such demand is maintaining their position on the bottom in the face of strong currents or waves. They have several traits that assist with this - they lack a swim bladder and are negatively buoyant, for example.
But one adaptation is particularly exceptional - they have enormous pectoral fins that that they use to generate negative lift (like an upside down bird wing) and that have reduced webbing on the bottom half that they can use to physically grab the substrate (like claws). I became interested in the variation in size and shape of these fins, and how this variation relates to prey capture and integration with locomotion.
Variation in shape of sculpin pectoral fins. A) a deepwater sculpin, Dasycottus setiger; B) an intertidal sculpin, Oligocottus maculosus. Figure from Kane and Higham, 2012.
Through morphological analyses of the shape of pectoral fins of several species, we showed that species clustered into groups that suggested differences in demand for positive lift (one species was an open water swimmer), negative lift without griping (deep water species), and negative lift with gripping (shallow water species) (see the paper here).
I then focused on two species, the one that swims in open water and one with the most extreme gripping fins, to examine how differences in ecological demand can affect prey capture and integration. We found that kinematics alone were not different, but that the swimming species showed integration across more traits (see the paper here). This result suggested that station-holding demands on the fins might restrict how these fins can be used during prey capture.
However, when we re-analyzed these data using a statistical test that can examine all variables at the same time, rather than individually, we found that differences in integration may more complicated. Specifically, there may be multiple ways the variables are integrated and depending on which is interpreted, the two species may be similar or the gripping species may have tighter integration (see the paper here). This demonstrates that we are only beginning to understand how traits work together, and that different species may rely on these relationships in different ways.
With the start of a new collaboration with Friday Harbor Laboratories, the lab is now making plans to return to work with marine sculpins. The questions we are interested in answering include:
How does variation in environmental demand for station-holding affect morphology and function of sculpins and their fins?
What is the role of ecological specialization on tradeoffs and integration of functions, both within and across species?
A sculpin, Dasycottus setiger; in a swim tunnel. A face only our lab can love.