Algae invasion

Algae and salamander relationship is mutually beneficial

- April 5, 2011

Salamander embryos. (Roger Hangarter / University of Indiana)
Salamander embryos. (Roger Hangarter / University of Indiana)

It’s around this time of the year that Ambystoma maculatum—the yellow spotted salamander—emerges from hibernation, deep underground, to breed. The male salamander does an elaborate courtship dance to attract the female, which then lays its eggs in puddles and pools.

And that’s where Ryan Kerney comes in, dressed in hip waders and carrying a bucket to collect the bright green egg clutches that appear as fist-sized blobs of jelly attached to pond plants or sticks.

Blue with yellow polka dots

“It’s a real sign of spring,” says Dr. Kerney, postdoctoral fellow at Dalhousie. He’s collected some of his best samples of salamander dalliances in the heart-shaped pond in Halifax’s Hemlock Ravine Park, and less romantically, in the puddles formed by ATV tracks. Colored cobalt blue with yellow polka dots, the salamanders have a range that extends along eastern North America from southern Quebec to Georgia.

“The (egg) clutches are so common in Nova Scotia that in the next few weeks you’ll see them with minimal effort.”

Research on the eggs and the developing salamander embryos inside has turned up something surprising: the bright green colour of the eggs is due to algae. Using long-exposure imaging, the team of researchers (from the Departments of Biology and Biochemistry and Molecular Biololgy at Dalhousie with partners from Indiana University and St. Francis Xavier University) detected algal fluorescence inside the developing salamander.

It’s the first documented case of a plant living in symbiosis with a vertebrate.

The findings have just been published in the April edition of the Proceedings of the National Academy of Science.

“The algae invades the vertebrate tissue,” explains Dr. Kerney, the lead researcher. “It’s a mutually beneficial arrangement. The salamander’s egg capsule becomes a home for the algae and the algae increases the amount of dissolved oxygen available for the salamander embryo, helping it to grow.”

New questions

Scientists have known the algae lived with the eggs, but not inside them. “Our work shows the algae actually invades the embryonic tissues and cells,” says Dr. Kerney, who has a PhD from Harvard. He came to Dalhousie to work with professor emeritus Brian Hall, a pioneer in the field of evolution development.

The findings raise all kinds of other questions, which the team will turn its attention to next. Namely, is the algae persisting from one generation of salamanders to the next? Or is it absorbed from the environment?

LINK: Proceedings of the National Academy of Science

SEE PAPER: Intracellular invasion of green algae in a salamander host


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