Current Research
Research Interests
The overall goal of my research is to test hypotheses about the relationships between morphology, function, and ecology in an evolutionary framework by adapting techniques from comparative functional morphology and biomechanics. My primary focus is on planktivorous fish that filter enormous volumes of water to retain food particles that are too small (~ 5 µm to 2 mm) to be sensed and engulfed individually.
These filter-feeding fishes (e.g., anchovies, menhaden, and tilapia) belong to twelve orders and compose more than 25% of the world fish catch. Although they have substantial impacts on plankton abundance and community structure, the mechanisms that they use to extract small food particles from the water have been unclear. By inserting a miniature fiberoptic endoscope and a thermistor flow probe into the mouths of freely-swimming fishes in the laboratory, we have visualized and measured flow near the gill rakers in distantly related filter-feeding fish species.
The unexpected flow patterns recorded by my laboratory indicate that the rakers can function as a crossflow filter rather than as a dead-end sieve. Although crossflow filtration is a multi-billion dollar industry for the manufacture of products that we use every day (e.g., dairy products, wine and beer, pharmaceuticals), this filtration mechanism had not been recognized previously in any vertebrate. The techniques that we use for flow visualization and measurement can be adapted to study the function of internal feeding structures in a diversity of animals, including filter-feeding birds and bivalves.
By incorporating computer-aided design (CAD) and 3D printing, novel filtration structures and mechanisms are being identified in my laboratory. Based on our discovery of vortical cross-step filtration, a patent for a bioinspired mass transfer device has been assigned to William & Mary. My research is expanding the application of additional approaches to address problems in bioengineering and bioinspired design.
cjfas_Edwards_Video_S1.movFollowing completion of experiments, juvenile goldfish in a laboratory aquarium learned to engulf globules in a film of canola oil on the water surface that had been released from the tip of a polyethylene cannula as the tip was removed from the water (240 frames·s-1; video by C.M. LaValley).
cjfas_Edwards_Video_S2.movIn outdoor ponds, suspension-feeding juvenile goldfish that had been introduced previously to liquid oil engulfed a thin layer of canola oil with interspersed oil globules at the surface (30 frames·s-1).