Thursday, August 5, 2010

Solar salamander

An amazing discovery has been made by Ryan Kerney, a postdoctoral researcher in the Biology Department at Dalhousie University in Halifax, Nova Scotia. While looking closely at a clutch of spotted salamander (Ambystoma maculatum) embryos (1st image), he noticed that their bright green color comes from within the embryos themselves, as well as from the jelly capsule that encases them. This viridescence is caused by the single-celled alga Oophila amblystomatis, which has long been known to enjoy symbiosis with the spotted salamander (2nd image). But this mutually beneficial relationship was believed to occur in the water, where the salamander lays its eggs, not within the eggs themselves. At a conference in Uruguay last month, Kerney reported that these algae are located inside cells all over the spotted salamander's body, and that it may be directly providing the products of photosynthesis — oxygen and carbohydrate — to the salamander cells that encapsulate them.

This unprecedented finding between a vertebrate and a photosynthetic organism requires that the salamander embryos shut off their immune system, or that the algae find a way around it. Kearney is now trying to find out how the algae enters the salamander cells, and has so far discovered its presence in the oviducts of adult female spotted salamanders, where the embryo-encompassing jelly sacs form, which points to the possibility that the algae are passed from mother to the offspring's jelly sacs during reproduction. A key factor may be the way self-recognition is learned by salamander cells, which retain pluripotency (the ability to divide and change into other cell types) into adulthood - which is what allows the animal to regrow its limbs.

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