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The spotted salamander (Ambystoma maculatum)
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Embryos of the spotted salamander (
Ambystoma maculatum) are green. This green color is derived from the alga
Oophila amblystomatis. This has long been understood as a mutualistic symbiosis between the salamander embryo and algae living outside it, namely, the embryo produces nitrogen-rich waste that is useful to algae, and the algae increase the oxygen content of the water around the respiring embryos (Gilbert, 1942, 1944: Hutchison & Hammen, 1958). It has recently been discovered, however, that these algae are, in fact, commonly located INSIDE cells all over the salamander's body. Moreover, it is likely that intracellular algae are directly providing the products of photosynthesis (i.e., oxygen and carbohydrate) to the salamander cells. It was also discovered that algae are present in the oviducts of adult female salamanders. This means symbiotic algae may be transmitted from mother to offspring. Because vertebrate cells have a highly-sophisticated adaptive immune system, it was thought to be impossible for a symbiont to live stably inside vertebrate cells. Such a close coexistence with a photosynthetic organism has previously been found in invertebrates, such as corals, but never in a vertebrate.
This finding was reported by Ryan Kerney of Dalhousie University in Halifax, Nova Scotia, Canada, at the Ninth International Congress of Vertebrate Morphology, which was held in Punta del Este, Uruguay, and was subsequently highlighted in NatureNews.
References
- Petherick A (2010) News: Salamander’s egg surprise. Nature 466: 675. [link]
- Gilbert PW (1942) Observations on the eggs of Ambystonia maculatum with especial reference to the green algae found within the egg envelopes. Ecology 23: 215-227.
- Gilbert PW (1944) The alga-egg relationship in Ambystoma maculatum, a case of symbiosis. Ecology 25: 366-369.
- Hutchison VH & Hammen CS (1958) Oxygen Utilization in the Symbiosis of Embryos of the Salamander, Ambystoma maculatum and the Alga, Oophila amblystomatis. Biological Bulletin 115: 483-489.
