Features
The Skeleton in the Skin
Studying skin bones may unlock secrets of how animals grow for dinosaur hunter turned U of G prof
BY ANDREW VOWLES
 |
| Prof. Matt Vickaryous, Biomedical Sciences, has joined U of G to study the dermal skeleton, work that may help us understand how creatures like this leopard gecko can regrow their tails. Photo by Martin Schwalbe |
He's all skin and bones. Studying the dermal skeleton in fish, reptiles, birds, amphibians and mammals including ourselves is the research passion of anatomist and biomedical sciences professor Matt Vickaryous.
Wait a minute. A skeleton in the skin? Question the apparent paradox and he smiles indulgently across the desk in his OVC office.
It's one of my favourite topics, says Vickaryous, a former dinosaur hunter in his native Alberta who came to Guelph this spring.
He's fascinated by creatures that wear their bones not only inside but outside as well. Examples range from the obvious consider the body armour of alligators or armadillos to the surprising.
Take that frog preserved in liquid in a glass bottle on his desk. The specimen, a South American tree frog, contains tiny bones in the skin of its back. Vickaryous says skin bones have been found in only a handful of frog species, but there may be more examples.
No one knows why frogs have skin-deep back bones. But he thinks these may have something in common with other creatures that carry bone or other skeletal tissues on their outsides.
Bits and pieces of bone wedged in the skin of modern animals may be vestiges of outer skeletons that were more common among their ancestors hundreds of millions of years ago. Whether they're bony remnants or full-blown plates, he says, these structures may tell us how body tissues have evolved, how structures develop in the embryo and even how damaged or missing body parts might be coaxed to regenerate.
We've all heard about lizards whose tails snap off and grow back as effortlessly as new shoots sprouting from a clipped shrub. Look more closely, as Vickaryous has, and you learn that the mystery of regeneration involves bone as well as every other tissue.
He palms two more liquid-filled specimen bottles onto his desk. Each contains an ivory-coloured fleshy object the tail of a leopard gecko, a pet-store staple. It's the tail or tails from a single animal, says Vickaryous.
A light pinch between his thumb and forefinger was all it needed for this particular lizard to drop its tail, an apparently painless trick that allows the animal to escape predators. (A broken tail causes all of the animal's hind tissues to respond, including small blood vessels that immediately clamp off.) That tail is the stub now swimming in that first bottle on his desk.
Flicking through slides on his computer monitor, he shows how the tail regenerated. Within 10 days there was a sprout. By a month, it had grown into a recognizable tail. By about 70 days, the tail had become the fat-swollen stub in Vickaryous's second bottle.
On one slide, he highlights the vertical fissure running through the middle of one tail vertebra. That enables the limb to break cleanly, like perforations on a sheet of paper. Similar fracture planes exist in the other vertebrae, explaining how the lizard can throw more or less of its tail away.
What's intriguing is that the new tail contains not bone as in the original but cartilage. In any animal embryo, bone either develops from scratch or grows on a cartilage scaffold, says Vickaryous. Studying how a lizard makes or remakes its tail may help him learn more about tissue development and evolution, not to mention the obvious biomedical implications.
There's a connection back to dermal bones. Look again at those slides, this time at skin samples from a wall gecko. All those red-stained dots indicate calcium in thousands of bits of real bone studding the animal's skin. That shows that bone may be regenerated, at least in these lizards.
Vickaryous says the dermal skeleton poses numerous puzzles in various creatures.
For instance, we've all seen alligator armour-plating and probably learned that it's a protective device. But that doesn't explain why dermal bones are lacking in vulnerable hatchlings. Maybe the bones' main purpose, says Vickaryous, is to serve as anchors for muscles that enable the reptiles' signature side-to-side movement.
Or consider the bony bits in birds' eyeballs. It sounds extraordinary but almost all birds have bones in their eyes. So do most lizards and fish, but not snakes or crocodiles. Why? Another black box, he says.
Look in the mirror, not at your eyes but at the superficial bones of your face and skull. You're looking at dermal bones whose origin can be traced back to the earliest vertebrates.
Vickaryous studied anatomy at the University of Calgary and at Dalhousie University. For his master's degree at Calgary, he studied a group of armoured dinosaurs called ankylosaurs.
He'd done his share of digs here in Canada, including boyhood camping trips to the Badlands. Part of that master's degree involved digging with famed Canadian paleontologist Phil Currie, mostly in southern Alberta but also in Argentina.
Here in Guelph, he's got plenty of preserved animal specimens and skeletons to investigate around the Ontario Veterinary College and in the wildlife museum in the Department of Integrative Biology.
And if he still needs an ice- breaker in his anatomy course this fall, he can always tell his students about his house pets: a corn snake, a carpet python, a fire skink and a water dragon. Oh, and two greyhounds.
I'm interested in watching animals in their environment, he says.
For some people, he concedes, his reptilian menagerie sounds a bit creepy. But for some students, it's an interesting gateway to get into topics like developmental and evolutionary biology.
Vickaryous will give a talk on his research Sept. 30 at 3:30 p.m. in Room 2315 of the science complex as part of the Department of Integrative Biology seminar series.