Plantimals 2: the solar-mander
In the previous post, I introduced a sea slug that uses chloroplasts for energy production. This is intended as a companion post about plant-animal hybrids, and will focus on a photosynthetic salamander.
For several years I’ve nursed a fascination with the idea of plant-animal hybrids. I ask myself what life would be like as a person able to eat sunlight, and find the answers in my imagination encouraging. While the slug mentioned in my previous post, as a mollusk, is a far cry from my vision of harnessing photosynthesis for myself, the discovery of solar salamanders is downright exciting. Salamanders, as vertebrates, are more closely related to humans and one step closer to the human branch on the taxonomic tree.
Some argue it is unlikely humans could become photosynthetic in this way, as our digestive tract chews up what we eat, including chloroplasts and DNA from plants. However, a similar argument could be made about salamanders, yet the inner workings 0f one salamander in particular has an ingenious work-around.
The spotted salamander (Ambystoma maculatum) is a secretive amphibian common to hardwood forests in the Eastern US and Canada. A nocturnal fellow, A. maculatum forages at night and hides during the day under logs, rocks, damp earth and moss on the forest floor. Our salamander possesses skills a ninja would envy: perfect camouflage, glands to secrete poison from it’s skin and the ability to regenerate lost and damaged body parts.
Now photosynthesis can be added to the salamander’s skill set.
A. maculatum eggs are laid and develop in water. Within each egg, the developing salamander embryo often forms an association with the alga Oophilia amblystomatis (literally “loves salamander eggs” in Latin). The relationship — in which the Oophilia photosynthesizes and produces oxygen for the egg while the developing salamander metabolizes the oxygen, producing carbon dioxide for the alga to consume — was first categorized as symbiosis in 1958.
Research reported in July 2010 indicates the relationship between our two symbionts is more complicated than previously thought. Not only does O. amblystomatis provide oxygen for the salamander egg, the single-celled alga is commonly located inside cells within the developing salamander’s body. Ooxygen produced by algal photosynthesis may be directly provided to the salamander cells that contain them.
This is the first time such a close co-existence with a photosynthetic organism has been shown in a vertebrate. The mechanism for this symbiosis is unknown. The salamander cells may have turned off their internal immune system, allowing the “non-self” photosynthetic machinery to function stably inside vertebrate cells.
Such a cunning developmental adaptation would not be a complete surprise, given the spotted salamander’s ability to regrow limbs as an adult. The metabolic acrobatics our salamander is capable of as an adult may begin with an early symbiotic dalliance in the egg.