|Line 1:||Line 1:|
<span style="font-size: large">Doctoral
<span style="font-size: large">Doctoral </span><br>
Revision as of 16:31, 7 May 2009
Office: BioPharmacy 410
Voice: (860) 486-4158
75 N. Eagleville Road, U-3043
Storrs, CT 06269
I am currently a PhD candidate in the Ecology & Evolutionary Biology department at the University of Connecticut, Storrs.
Co-advisors Drs. Kurt Schwenk & Carl Schlichting head my committee– which also includes Drs. Elizabeth Jockusch and Kentwood Wells.
For more information, here's my CV
"Evolutionary-developmental-functional-eco-morphology" was the joke term I coined with my friend Manny. In a nutshell, it's about unraveling the mobius strip of how organisms perform their behaviors, how sources of variation affect that performance, and how that performance affects evolution. Raising related species under a set of different environments can reveal whether the develppmental response to the environment has evolved. Together with an understanding of the animals' natural environments and the results of a variety of performance tests, functional variation can be used to interpret evolution.
The goal of my dissertation work is to study how ontogenetic and ecological sources of variation contribute to species level diversity. Salamanders of all types incorporate larval features into the adult forms. Gills and tail fins are two of the main structures that vary across adult salamanders of different species. I am exploring salamander larvae for the developmental and environmental sources of variation generating the big picture, macroevolutionary pattern.
Salamander larvae vary consistently along one ecological axis: those that live in ponds typically have large gills and tail fins while those that live in streams have small gills and tail fins. I raised salamanders in high or low oxygen to see how the these respiratory organs respond to dissolved oxygen levels. Not surprisingly, the ones raised in low oxygen developed larger gills and tail fins. This type of investment could incur a cost– investment in metabolically active gill and tail tissues could retard growth or development. Surprisingly however, the low-oxygen animals that invested extra energy in respiratory organs also metamorphosed early. Low oxygen probably indicates poor water quality and pond drying. Larvae experiencing such conditions in the wild would probably be well served by getting out of the pond before they turn into the proverbial "meadow raisin"...
Egg size is another feature that varies dramatically among amphibians living in different environments. Stream breeders typically have large eggs while pond breeders have relatively small eggs. This difference has important evolutionary consequences because females are resource limited and cannot both have large eggs and many of them. This trade-off and correlation with habitat strongly suggests that stream environments require large eggs because of the high quality offspring they produce.
My approach to this question is experimental. By surgically removing small quantities of yolk from developing embryos, maternal investment can be artificially manipulated. The strategy is to compare siblings who have had yolk removed to the sham operated group– those who were "poked" but no yolk actually removed. Differences in growth and development between the two groups are interpreted as due to the amount of yolk they had. Tiny quantities of yolk can affect development from hatching all the way through metamorphosis.
Other salamander projects
During my tenure here at UConn, I've engaged in a number of other fruitful projects. They are just for fun and as such are all collaborative efforts.
Predator induced plasticity
One of the best-studied forms of adaptive plasticity in amphibians is their response to predators. Early hatching in response to egg predators is practically ubiquitous among amphibians, but what are the long term costs of leaving the egg early? How do predators that specialize on different life stages interact? Since metamorphosis is thought to be a particularly vulnerable life stage, is it responsive to the presence of predators? Has metamorphosis been selected to be as rapid as possible? Is it constrained physiologically by the demands of transformation?
Leah Brown-Wilusz's honors thesis (under Carl Schlichting's supervision),was designed to address some of these questions in our local spotted salamander (Ambystoma maculatum). We raised embryos with and without egg predators (trichopteran larvae) and larval predators (marbled salamander larvae:Ambystoma opacum) to see if the early hatching response to one predator affected a future the response to larval predators. Presence of the egg predator caused early hatching regardless of the presence of the larval predator indicating that the immediate threat outweighs any future potential threat. Salamander embryos exposed to larval predators grew larger tail fins and survived longer with the predators but early hatching incurred a measurable cost. The effect of early hatching even extended to the adult life stage indicating that hatching early in response to an egg predator can make individuals smaller at metamorphosis. The early hatching response therefore looks to be maintained as a plastic strategy by costs in the larval period in terms of larval predator avoidance as well as potential fitness costs at metamorphosis.
Laurel Dwyer's honors thesis was designed to address several questions about the mysterious process of metamorphosis. We employed centrarchid sunfish (green sunfish: Lepomis cyanellus and bluegill sunfish: L. macrochirus) to see if spotted salamander larvae Ambystoma maculatum) can adaptively reduce their predation risk by either reducing the amount of time they spend in the vulnerable process of metamorphosis or behaviorally increasing their survival time with lethal predators. The predator exposed salamanders died in large numbers. The fish couldn't eat them, so they may have been scared to death. Behavioral trials indicated that predator exposed animals ate and weighed less. Metamorphosis is ongoing, but this experiment should conclude in the fall of 2008.
With undergraduate Shawn Binns, and professor Louise Lewis, I am investigating algae-salamander mutualisms. Ambystomatid salamander eggs deposited in vernal ponds often develop a green hue. This is not just a coating of pond scum, but rather an alga that lives inside the egg capsule. Poetically named, Oophila means egg-lover. Research has previously shown that the salamander benefits from increased oxygen levels produced by the algae while the algae gets nitrogenous waste products from the embryos. Everybody wins!
Who are these little green invaders? Do all the eggs have the same strain or species of algae. Does this vary from year to year? The algae inside of Louisiana spotted salamanders looks morphologically different from Connecticut algae. Is it plasticity or the same species? We also noticed that Kentucky algae growing on a different species (Ambystoma texanum) grows in the jelly matrix rather than inside the egg capsule. They look similar to the Connecticut algae but bigger. It's fun to think of salamander embryos as a source of food for plants.
Breathing & locomotionElizabeth Brainerd and Jeff Mailhot at the University of Massachusetts at Amherst, I studied turtle breathing and locomotion. Turtles can breathe using the limbs at rest... can they breathe during locomotion? Work done by Dr. Don Jackson and colleagues showed that nesting green sea turtles (Chelonia mydas) don't breathe at all during terrestrial locomotion. Box turtles and red eared sliders do however. Surprisingly, there is no relationship between limb movement and when breaths occur. So they can't be using the limbs for breathing during locomotion. Both species appear to use specialized abdominal muscles for breathing during locomotion, but there is one difference. There was no measurable effect of locomotion on breathing in the box turtle, Terrapene carolina- a species that has numerous adaptations for terrestriality. The red-eared slider, Trachemys scripta is much more typically semi-aquatic. When sliders pause between bouts of locomotion, they double the size of each breath indicating that locomotion interferes with breathing– by reducing the size of each breath. And the adult green sea turtle, of course, who has many highly derived features for aquatic locomotion, doesn't breathe during terrestrial locomotion. Three species–– three different life styles and three different patterns of interaction between breathing & locomotion. Makes you wonder...
Snapping turtle ecologyOur Piece of the Pie, Riverfront Recapture, Connecticut Water Company as well as the National Geographic Society, I am working with high school students on a snapping turtle ecology. The goal is expose teenagers in Hartford, CT to nature, science and career options they might not otherwise see – and learn a thing or two about snappers.
Click the video below to see Shenipsit Lake, Connecticut from the shell of a 24 pound snapper!
Learn more about the snapping turtle research team
Landberg T., J. D. Mailhot and E. L. Brainerd (2008). Lung ventilation during treadmill locomotion in a semi-aquatic turtle, Trachemys scripta. J. Exp. Zool. 309A. In press.
Azizi, E., T. Landberg and R. J. Wassersug (2007) Vertebral function during tadpole locomotion. Zoology 110:290-297.
Landberg, T., J. Mailhot and E.L. Brainerd (2003) Lung ventilation during treadmill locomotion in a terrestrial turtle, Terrapene carolina. Journal of Experimental Biology 206:3391-3404.
Azizi, E., and T. Landberg (2002) Effects of metamorphosis on the aquatic escape response of the two-lined salamander (Eurycea bislineata). Journal of Experimental Biology 205:841-849.
The Biology Club is for anyone interested in undergraduate research in Biology at UConn.
My YouTube account has lots more videos
My Facebook account has lots more photos