Difference between revisions of "Tobias Landberg"

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In collaboration with Elizabeth Brainerd and Jeff Mailhot while we were at the University of Massachusetts at Amherst, I studied turtle breathing and locomotion. We started out wanting to see if turtles could buccal pump- that is to force air into the lungs using positive pressure created by throat muscles. They didn't– even when we convinced them to run on a treadmill. Then we started to wonder how they breathed so much during locomotion. Did they use the limbs? SInce the turtle shell is essentially a rigid box surrounding the lungs and other viscera, turtles were known to be able to breathe by simply moving their limbs in and out of the shell. But that was when they weren't locomoting. Turns out that there is no relationship between limb movement and when breaths occur. So they can't use the limbs for breathing during locomotion. In fact, there was no measurable effect of locomotion on breathing in the North American box turtle, ''Terrapene carolina''. That species has numerous adaptations for terrestriality, so we looked at the red-eared slider, ''Trachemys scripta''. This species is much more typical in that it is semi-aquatic. And sure enough, this species also breathes rapidly during treadmill locomotion, but also without any effect of the stride cycle. So both species appear to use specialized abdominal muscles for breathing during locomotion, but there is one difference. When sliders pause between bout of locomotion, they approximately double the size of each breath. This indicates that locomotion may interfere with breathing– not enough to stop it completely, but enough to reduce each breath. Interestingly, work done previously by Dr. Don Jackson and colleagues showed that green sea turtles don't breathe at all during terrestrial locomotion. And they, of course, have many highly derived features for aquatic locomotion. Three species, three different life styles and three different patterns of interaction between breathing & locomotion. Makes you wonder what else is going on out there in the other ~300 species!<br>
 
In collaboration with Elizabeth Brainerd and Jeff Mailhot while we were at the University of Massachusetts at Amherst, I studied turtle breathing and locomotion. We started out wanting to see if turtles could buccal pump- that is to force air into the lungs using positive pressure created by throat muscles. They didn't– even when we convinced them to run on a treadmill. Then we started to wonder how they breathed so much during locomotion. Did they use the limbs? SInce the turtle shell is essentially a rigid box surrounding the lungs and other viscera, turtles were known to be able to breathe by simply moving their limbs in and out of the shell. But that was when they weren't locomoting. Turns out that there is no relationship between limb movement and when breaths occur. So they can't use the limbs for breathing during locomotion. In fact, there was no measurable effect of locomotion on breathing in the North American box turtle, ''Terrapene carolina''. That species has numerous adaptations for terrestriality, so we looked at the red-eared slider, ''Trachemys scripta''. This species is much more typical in that it is semi-aquatic. And sure enough, this species also breathes rapidly during treadmill locomotion, but also without any effect of the stride cycle. So both species appear to use specialized abdominal muscles for breathing during locomotion, but there is one difference. When sliders pause between bout of locomotion, they approximately double the size of each breath. This indicates that locomotion may interfere with breathing– not enough to stop it completely, but enough to reduce each breath. Interestingly, work done previously by Dr. Don Jackson and colleagues showed that green sea turtles don't breathe at all during terrestrial locomotion. And they, of course, have many highly derived features for aquatic locomotion. Three species, three different life styles and three different patterns of interaction between breathing & locomotion. Makes you wonder what else is going on out there in the other ~300 species!<br>
  

Revision as of 20:02, 6 July 2008

Doctoral Student


Office: BioPharmacy 410
Voice: (860) 486-4158
E-mail: tobias.landberg@uconn.edu
Mailing address:
75 N. Eagleville Road, U-3043
Storrs, CT 06269

Barbouribaby.jpg

About:

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.

Research philosophy:

Ontogeny.jpg
Hellbender from Lycoming Creek, PA

"Evolutionary-developmental-functional-eco-morphology" was the joke term I coined with my good friend Manny Azizi to cover our interests. 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. The three main sources of variation in nature are ontogenetic (or developmental), ecological (or environmental) and phylogenetic (or evolutionary or genetic). Raising one species of animal under different conditions can reveal whether developmental variation is affected by that environment. Raising related species under the same set of different environments can reveal whether their response to the environment has evolved. Together with detailed knowledge of the animals' environments and the results of a variety of performance tests, the adaptive nature of all this variation can be used to interpret evolution.




Dissertation research:

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‎As the above statement shows, my research interests are broad. The goal of my dissertation work is to study how ontogenetic and ecological sources of variation contribute to species level diversity. If we look at salamanders generally, we see that one of the repeated patterns is to incorporate larval features into the adult forms. The general term for this is paedomorphosis. To understand the processes underlying this macroevolutionary pattern, I have turned to the source: salamander larvae. Salamander larvae are surprisingly uniform, at least compared to frog larvae. However, they do vary consistently along one ecological axis. Salamander larvae that live in ponds characteristically have large gills and tail fins while those that live in streams have small gills and tail fins. Not coincidentally, these are some of the same structures that vary across paedomorphic adult salamanders.
Streamvspond.jpg


Oxygen plasticity:

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Gills and tail fins are respiratory organs in amphibians and they are responsive to dissolved oxygen levels. To see how the environment affects these organs, I raised spotted salamanders in high or low oxygen. Not surprisingly, the ones raised in low oxygen developed larger gills and tail fins. Plasticity often comes at a cost– investment in metabolically active tissues could retard growth or development. Surprisingly, those same animals that invested extra energy in respiratory organs also metamorphosed early. In retrospect it looks like this was an adaptive response. That is, 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".


Maternal investment:

Spotted salamander larvae: can you guess which one had yolk removed? Photo by Tobias Landberg
Spottedlarvadorsal.jpg

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 was 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.

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Predator induced plasticity:

One of the best-studied forms of adaptive plasticity in amphibians is their response to predators. Most of this work has been done on frogs but there are still many unanswered questions. 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 transforming practically all the systems and organs?

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I mentored Leah Brown-Wilusz's honors thesis (under Carl Schlichting's supervision),and together we designed an experiment 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 early hatching affected the response to larval predators. It didn't affect hatching. 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. Next we looked at morphology and escape performance with lethal fish predators. Salamander embryos exposed to larval predators grew larger tail fins and survived longer with the predators but early hatching incurred a cost– smaller tails and shorter survival times. The effect of early hatching even extended to the adult life stage. Those animals that hatched early in response to the egg predator were 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 addresses several questions about the mysterious process of metamorphosis. We are using centrarchid sunfish (green sunfish: Lepomis cyanellus and bluegill sunfish: L. macrochirus) to see if salamander larvae (our local workhorse, the spotted salamander: Ambystoma maculatum) can adaptively reduce their predation risk by either reducing the amount of time they spend in the presumably vulnerable process of metamorphosis or somehow increase their survival time with lethal predators. This project will conclude in the early fall of 2008.

Algae–salamander symbiosis:

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Along with undergraduate, Shawn Binns, and professor Louise Lewis, we are investigating one of the coolest mutualisms known to science. 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. Yum. Everybody wins!

The first question we are asking is, who are these little green invaders? We want to know if all the eggs have the same strain or species of algae. Does this vary from year to year? We discovered that 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 not inside the egg capsule but in the jelly matrix. They look similar to the Connecticut algae but bigger. Hmm. What's going on here. We performed a pilot study with freshly deposited Connecticut eggs to see what would happen if we inoculated them with equal quantities of Connecticut and Louisiana algae. The controls developed lots of algal growth complicating the experiment, but we are working on the morphology and molecular analysis...

Turtle research:

Breathing & locomotion:

BojanusXVIII.jpg
Babywoodflipsmall.gif

In collaboration with Elizabeth Brainerd and Jeff Mailhot while we were at the University of Massachusetts at Amherst, I studied turtle breathing and locomotion. We started out wanting to see if turtles could buccal pump- that is to force air into the lungs using positive pressure created by throat muscles. They didn't– even when we convinced them to run on a treadmill. Then we started to wonder how they breathed so much during locomotion. Did they use the limbs? SInce the turtle shell is essentially a rigid box surrounding the lungs and other viscera, turtles were known to be able to breathe by simply moving their limbs in and out of the shell. But that was when they weren't locomoting. Turns out that there is no relationship between limb movement and when breaths occur. So they can't use the limbs for breathing during locomotion. In fact, there was no measurable effect of locomotion on breathing in the North American box turtle, Terrapene carolina. That species has numerous adaptations for terrestriality, so we looked at the red-eared slider, Trachemys scripta. This species is much more typical in that it is semi-aquatic. And sure enough, this species also breathes rapidly during treadmill locomotion, but also without any effect of the stride cycle. So both species appear to use specialized abdominal muscles for breathing during locomotion, but there is one difference. When sliders pause between bout of locomotion, they approximately double the size of each breath. This indicates that locomotion may interfere with breathing– not enough to stop it completely, but enough to reduce each breath. Interestingly, work done previously by Dr. Don Jackson and colleagues showed that green sea turtles don't breathe at all during terrestrial locomotion. And they, of course, have many highly derived features for aquatic locomotion. Three species, three different life styles and three different patterns of interaction between breathing & locomotion. Makes you wonder what else is going on out there in the other ~300 species!


Snapping turtle ecology:

Snapperdesignsmall.jpg

In conjunction with many generous private volunteers, several local Connecticut organizations including Our Piece of the Pie and Riverfront Recapture as well as the National Geographic Society, I am working with about a dozen high school students on a snapping turtle ecology project. The primary goal is to allow these young teenagers growing up in urban Hartford, CT access to nature, science and career options they might not otherwise be exposed to. The first phase of the project includes a study of nest protector devices that is designed to keep out large mammalian predators. The second phase involves trapping snappers and outfitting them with National Geographic's CritterCam. We are currently trying to figure out how to attach a $14000 camera to a turtle notorious for burrowing through weed-choked muck and underwater log jams. These kids are getting their money's worth!

Misc:

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