The first known example of photo-cellular symbiosis involving the cells of a fully grown vertebrate animal. Photo courtesy of Gizmodo

George Dvorsky writes in that, in a scientific first, researchers have discovered a bizarre inter-species relationship in which salamanders and algae cozy up together to share cells. Scientists aren’t entirely sure why these two very different organisms have adopted such an intimate arrangement, but the discovery could represent a completely new form of symbiotic relationship.

Cell-within-cell arrangements between species are common in nature, but up until this point it’s only been seen in creatures like coral, clams, and insects. New research published in the science journal eLife describes the first known example of photo-cellular symbiosis involving the cells of a fully grown vertebrate animal, that is, an animal with a spinal column or backbone.

As a collaborative research team from the American Museum of Natural History and Gettysburg College revealed, the green alga Oophila amblystomatis makes its home inside of cells located across the body of the spotted salamander Ambystoma maculatum. The salamander doesn’t appear to be negatively affected by its microbial roommates, and in fact the amphibian may even be benefitting from this arrangement. The normally photosynthetic green algae, on the other hand, are completely stressed out, forced to rely on an alternative means of energy production.

The finding is so strange and so unexpected that the scientists involved in the study aren’t sure why this relationship evolved in the first place, or how each creature might be benefitting.

To investigate this unusual relationship, John Burns from the AMNH’s Museum’s Division of Invertebrate Zoology sought to uncover what happens when the salamander cells and green algae cells are together. Using a technique called RNA-Seq, the researchers sequenced the RNA (a single-stranded copy of DNA that helps cells make proteins) of both organisms, and then used those sequences to learn how the algae and salamanders changed their patterns of gene expression while interacting.

As the data revealed, salamander cells containing green algae recognized the algae as foreign, but the salamanders showed no signs of distress. “The salamander really doesn’t seem too bothered by this [arrangement],” Dr. Burns told Gizmodo. “In fact, there are tantalizing hints that the salamander is actually responding in a way that dampens its immune response to this alga. Some genes related to slowing down a potent immune response were highly expressed by the salamander in this association.”

“We are very interested in doing more research imaging the algal cells as they enter the salamander tissues and cells,” study co-author Ryan Kerney told Gizmodo. “New advances in microscopy could give us additional insights into the dynamics of tissue entry, and even the exchange of molecules between symbiont and host.”

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