First known case of vertebrate endosymbiosis

Researchers led by Ryan Kerney of Dalhousie University have confirmed a unique case of endosymbiosis within a vertebrate embryo. They found evidence that algal cells (Oophila amblystomatis) were not only growing in association with spotted salamander (Ambystoma maculatum) embryos, but were within the salamander cells themselves.

Salamander embryos grow inside egg capsules that are covered with and usually infiltrated by a type of green algae.

Credit: Courtesy of Roger Hangarter

Endosymbiosis, like other types of symbiosis, involves a close relationship between two different species. The twist here is that one of the organisms resides within the very cells of the other. Although this kind of relationship is not uncommon among simpler organisms, this is a first for vertebrates, whose immune systems usually fight off any such invasion.

The relationship between O. amblystomatis and spotted salamanders has been observed for more than a century. Each organism grows more slowly in the absence of the other. It wasn’t until the modern techniques of using gene specific probes and fluorescence microscopy became available that scientists could see that the algae were actually inside the cells of the salamander embryos.

The salamanders appear to lose their algae once they hatch from their egg capsules. Presumably, the benefit gained by maintaining the endosymbiants is diminished once the animals are able to gather their own food.

Caption: Spotted salamanders are the first known vertebrate to have an endosymbiont. The salamanders are found throughout eastern North America.

Credit: Courtesy of Roger Hangarter

Roger Hangarter of Indiana University makes this observation about the spotted salamander, which is a common backyard occupant in many parts of North America:

I think it is important for people to realize that you do not need to go to exotic locations to make interesting scientific discoveries.