Salamander Has Algae Living Inside Its Cells

In a symbiotic union more complete than any previously found in vertebrates, the common spotted salamander lives with algae inside its cells.

Such a degree of cross-species fusion was long thought to exist only among invertebrates, whose immune systems are not primed to destroy invaders. But algae live inside the salamanders from before birth, possibly passed down from parent to offspring.

That spotted salamanders and algae live in symbiosis was first noted in the 19th century, and in the 20th century researchers worked out the relationship’s mutual benefits. Salamander eggs provide a nitrogen-rich environment for algae to grow; algae oxygenate the embryos, which develop deformities without them.

But algae were believed to float outside the embryo itself, in the egg’s nutrient broth.  Now scientists have noted that algae’s distinctive green glow didn’t just emanate from eggs, but from inside embryos.

Algae invade spotted salamander embryos early in their development, when individuals are just beginning to take shape inside their eggs, as the brain folds up and tissue layers-to-be first organize themselves. As an embryo develops, algae suffuses its body, but most becomes concentrated along its gut and alimentary canal.

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