Past research

Integration between locomotion and 

feeding in Centrarchids

Bluegill, Lepomis macrochirus, capturing a
live fish (frames taken from high speed video)

Integration refers to the ability of systems to work together to reach a common goal, for example, the locomotor and feeding systems must be highly coordinated to successfully capture mobile prey.  My work with sculpins made me realize that there are large gaps in our understanding of integrated systems during prey capture in animals. I realized that a better understanding of how to quantify integration, the sources of variation in integration such as flexibility and stereotypy, and the relevance of integration to prey capture success in a predator are necessary if we want to understand how predators successfully attack prey, and the significance of divergent predatory modes.  

For my PhD, I am using 3D video (setup shown in photo) of prey capture on both evasive and non-evasive prey types for 3 species of centrarchid fishes to understand the causes and consequences of integrated functional traits. I am applying a multivatiate technique used to quantify morphological integration to this idea of functional integration.  I will then quantify integration across several centrarchid predators to determine the sources of variation in integration.  I have also developed a model to predict the shape of the ingested volume of water (IVW) in 3D, that can be used to estimate accuracy during unconstrained predatory behaviors.  This estimate of accuracy directly relates to prey capture success.  The final step will be to link integration, accuracy, and success to understand why some predators are more successful than others.   From this work, I hope to demonstrate that the emergent level of integration between two systems adds insight into predator strategies that can help us understand why some predators are better than others on certain prey types.

Filming setup

Evolutionary transitions and locomotor

specialization in sculpins

Photo by Sandy Kawano
This is a continuation of the work I did at Bamfield Marine Sciences Centre.  I knew that sculpins have high morphological diversity, and I was interested in finding a pattern that could describe the diversity.  My work with feeding in sculpins, and reading about sculpin phylogeny, led me to an idea that the locomotor system becomes more specialized for behaviors that prevent sculpins from getting swept away in high flow environments (and that this might be influencing what I observed during feeding).  To test this idea, I collected 9 species from several habitats and took morphological measurements of the body and pectoral fins. I analyzed similarities by using cluster analysis to determine how morphology grouped among the species, and then discriminant function analysis to determine the morphological characters that defined each group.

I found that there are indeed differences that indicate evolutionary specialization to high flow habitats.  The morphology of species that typically occur in lower flow demand habitats is likely used for gripping, whereas species that occur in tidepools and higher flow demand habitats rely on both gripping and negative lift generation to maintain position in flow.  Interestingly, there was another more pelagic species that only showed traits for positive lift generation.  This paper indicates the importance of the pectoral fins to the divergence of sculpins across habitats and generates important hypotheses about diversification and specialization.

Integration of locomotion and feeding in sculpins

This is my recent work that I started while up at Bamfield Marine Sciences Centre in summer 2010. I became interested in sculpins because of their morphological and ecological diversity, despite their specialization for living on the benthos. Sculpins vary along a continuum of morphology and prey ecology, such that species with a small mouth feed on non-evasive prey using suction.  However, I was curious how variation in locomotor strategy, as sculpins swim toward prey, might be integrated with prey capture behaviors, and might affect the strategy sculpins use to capture prey.  Silver-spotted sculpins (top) are unlike most sculpins since they do not rest on the bottom, but live in kelp canopies and eelgrass beds where they swim more constantly.  Alternatively, tidepool sculpins (bottom) represent more typical sculpins, living on the bottom and using their pectoral fins to grasp the substrate and maintain position in flowing water.  Therefore, although these species should be similar in feeding behaviors, they should differ in locomotor performance and locomotor integration with feeding as a result of their differing ecology. 

This was exactly the case--these two species did not differ from each other in attack velocity (ram) or feeding morphology, but silver-spotted sculpins showed greater acceleration that occurred near the time of peak gape.  In contrast, tidepool sculpins accelerated earlier and to a lesser extent, and were actually decelerating as prey was captured.  These differences in locomotor strategy enabled silver-spotted sculpins to more tightly integrate locomotion with feeding performance.  We then hypothesized that in more specialized species like Tidepool sculpins, ecological differences, such as demands for station-holding in high flow habitats, might supercede demands for integration.

Comparative feeding kinematics and

performance of Odontocetes

Putting high contrast marks (sunscreen) on a
pilot whale at SeaWorld San Diego

This is the work I did for my Master’s thesis. I was interested in studying feeding biomechanics in toothed whales (odontocetes) because, unlike fishes, they have secondarily adapted to living in the water, and are constrained to feeding with a mammalian jaw. This means that suction feeding is not expected.  However, pygmy and dwarf sperm whales use suction to capture prey, and anecdotal accounts of belugas and pilot whales indicated that they also use suction, but it had never been quantified.  We suspected that suction was more widespread than what was originally thought, so we also included pacific white-sided dolphins as a species that was presumed to overtake prey using ram.  I filmed several individuals of each species and analyzed the videos to determine if feeding kinematics and feeding mode differed among belugas, pilot whales, and pacific white-sided dolphins.  I also used a small pressure transducer to measure the amount of suction generated while capturing prey to determine suction performance in each species.

Circular mouth shapes of a beluga, Delphinapterus leucas,
and a Sacramento perch, Archoplites interruptus

Belugas were in fact able to generate -126 kPa of suction, which is similar to walrus that are known for sucking clams out of their shells.  Belugas were also able to form a small circular mouth opening, which you can see in the picture, that is similar to the small opening observed in fishes during suction feeding.  Pilot whales also used suction during prey capture, but were not able to generate strong suction pressures.  The suction generated by Pacific white-sided dolphins was small and was probably used to manipulate prey in their jaws or to compensate for the bow wave generated by swimming toward the prey.  Since a variety of feeding behaviors were used in these three odontocetes, this indicates that odontocetes display a wider diversity of feeding behaviors than previously thought, and that feeding in toothed whales is convergent with feeding modes that are used by fishes and other aquatic vertebrates.

Billfish reproductive staging

Dissecting otoliths and gonads from a marlin

This is a project that Chris and I started as a collaboration between our lab and Dr. Jay Rooker’s Fisheries Ecology Lab.  I was in charge of going to offshore fishing tournaments along the coasts of TX and LA to collect samples from marlin that were brought back to the dock to be weighed.  The objective of the study was to sex and stage the gonads, and use the tiny ear bones (otoliths) to determine the age of the individual.  Our lab was responsible for preserving, sectioning and staining the gonads, and looking at them under a microscope to determine whether the fish was male or female, and what stage the gametes were, to determine if marlin were likely breeding in the Gulf of Mexico.  Dr. Rooker’s lab then took the otolith and counted the growth layers like rings of a tree.  By working on this project, I not only learned histology techniques, but also gained experience with fish anatomy, and I really enjoyed the chance to help with something I would not have experienced otherwise!

Field herpetology with Dr. Brad Moon

Yes, that's me with a Sceloperus lizard (and short hair)!

When I was finishing my Master’s, I had ideas to work with salamanders for my Ph.D., however, I was inexperienced with where and how to find salamanders in the field.  Dr. Brad Moon was kind enough to let me tag along with his field herpetology class during an overnight camping trip in Kisatchie Forest in northern LA.  This was a great opportunity for me, and I really appreciate having the chance to join Brad in the field.  We not only found salamanders, but also snakes, lizards, birds, frogs, and even alligators! 

Green sea turtle bite force

Collecting bite force data from a green sea turtle, Chelonia mydas

Chris collaborated with a research team from the University of Hawaii and Aquatic Adventures, who were interested in testing methods for deterring sea turtles from fishing nets, and let us join them for a field trial.  The advantage for us was that we could collect bite force data from turtles that were caught in the experimental nets, before they were released.  The trip involved driving to a small fishing village in southern Baja California and camping on the beach so we would have access to the small bay where we set the nets.  The picture above shows me encouraging a large turtle to bite a set of metal plates that are connected to a force transducer to measure bite force.  The turtles were placed on tires to keep them restrained while we were measuring and collecting data on them.

Striped bass age and growth

Measuring fish

After I graduated with my Bachelor’s degree, I refused to work in retail anymore, and relentlessly searched for a summer job where I could be a marine biologist.  I was fortunate to get a lab technician position with Dr. Tom Miller and his graduate student Adam Peer at the Chesapeake Biological Laboratory.  This is the marine campus of  the University of Maryland located on Solomon’s Island on the Chesapeake Bay.  I was responsible for helping Adam collect larval striped bass using beach seines along the Patuxent River.  In the picture above, I am sorting, counting, and measuring fish that we brought back from one of our sampling trips.  I also helped him take care of larvae that he was housing in the lab for an age and growth study.  While I was at CBL, I was also able to join the CHESFIMS team on a trawling trip from Baltimore to the Bay Bridge along the Chesapeake to sample fish species of the Bay.  

Xenobalanus occurrence on eastern
tropical Pacific cetaceans

That's the Scripps pier behind me!

After I had done internships in animals care, I realized that I wanted to start on a research project that I could call my own, while traveling somewhere new and meeting new scientists and learning about what they do.  I ended up in La Jolla, CA at the Southwest Fisheries Science Center, a NOAA lab, working with Dr. Tim Gerrodette and Paula Olson.  I had no idea what I would be working on, and in fact didn’t even have a place to live for the first 2-3 days, but I knew I wanted to see what I could do.  

Tim and Paula had ideas of using Xenobalanus, a barnacle that lives only on the fins and flukes of whales and dolphins, as a biological tag for the cetaceans of the Eastern Tropical Pacific, and it was my job to design a project to determine if that was possible.  First I had to determine where the barnacle occurred, and on what species.  I looked at over 10,000 photos that had been taken on the yearly research cruises for about 10 years, to count the occurrence of the barnacle in the ETP.

I found that the barnacle appeared on 22 species of cetaceans, 4 of which were newly documented hosts.  It was also the first time that anyone had reported the barnacle appearing in pelagic waters, as it is most common close to land where small cetaceans are common.  I also noticed that Xenobalanus appeared to be concentrated in a few areas of the ETP where upwelling is prevalent, but I couldn’t determine if this was due to more cetaceans taking advantage of the productive areas, or better nutrient uptake and reproduction of barnacles.  Unfortunately, the barnacle was too common to be used as a biological tag, however, if we can learn more about the biology of Xenobalanus, it might be useful to cetacean researchers in other contexts.

Me and Diego
This work resulted in my first publications, a NOAA administrative report, and later, a publication in Fishery Bulletin.  It also allowed me to attend and give my first oral presentation at the European Association of Aquatic Mammals in Riccione, Italy.  I really consider this work the beginning of my academic career, and I attribute this success to the reason I was accepted into a Master’s program.  To commemorate my time and work in San Diego, when I adopted my dog the first semester I was at Texas A&M, I named him Diego.

Captive manatee care and research

My second internship was at Mote Marine Laboratory in Sarasota, FL with Joe Gaspard and Dr. Debbie Colbert.  I worked with Hugh and Buffet, the two captive manatees that have been trained to perform in research experiments.  At the time, they were interested in determining how well manatees can localize sound, and Hugh and Buffet were trained to swim towards one of several speakers that played a sound at different frequencies.  For more information on this experiment, check out their recent paper in the Journal of Experimental Biology!

Me and Buffett (yes, named after Jimmy Buffett)

My job as an intern was to take care of the animals, including feeding and cleaning their tank, as well as help during the training sessions by holding the manatee that wasn’t being tested in a separate pool.  In addition to animal husbandry, we were also doing research, and I thought this was a unique way to combine husbandry, which I was still leaning towards, and research, which I was beginning to get more interested in.

Mote has a fantastic internship program, and I was also responsible for conducting a small independent research project on the manatees during my time there.  Behavioral studies, which were common for captive animals, weren’t good enough for me, and I wanted to do something more quantitative. I had heard that when a manatee swims past, you almost don’t even feel it.  Retrospectively, I can also attest that in the wild manatees are incredibly difficult to find even in shallow calm waters, and sometimes don’t even leave ripples on the surface.  I was inspired by Dr. Frank Fish and his work on hydrodynamics of marine mammals, to quantify the amount of drag induced by a swimming manatee.

This was my first experience with kinematic analysis, and I didn’t know at the time that it was a premonition of what was to come for me.  I set up a camera above their tank and recorded them as they swam back and forth to quantify swim speed.  I had Joe and Debbie help me take measurements of both animals so I could calculate their volume and estimate their frontal area as they swam through the water.

Marine mammal rescue and rehabilitation

Weighing a sea turtle

As a sophomore in college, I desperately wanted to start getting involved in internships, and at the time, I was interested in marine mammals, but wasn’t completely sure why.  Given that the Riverhead Foundation for Marine Research and Preservation, an organization that rescues and rehabilitates marine mammals and turtles, was within a 30 minute drive from campus, I thought this would be a good start.  I was able to help with care for gray seals, harp seals, hooded seals, harbor seals, green and kemp’s ridley sea turtles, and even a risso’s dolphin!  I was also able to go on a few stranding calls for cetaceans and turtles that had washed up dead on local beaches.  Although I liked watching the animals and getting an up-close experience with them, I learned that I was more interested in what the animals were doing and how they did it than learning veterinary care and husbandry techniques.  This was a valuable experience for me and taught me that I was more inquisitive, and wouldn’t be satisfied unless I was able to ask questions and figure out a way to answer them.

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