Spotted salamanders lay eggs in early April in temporary vernal pools. A species of single cell green algae named “Oophilia” colonize salamander egg masses. Biologists describe a symbiotic relationship where embryonic salamanders release wastes used as fertilizer by algae. The photosynthesizing algae provide oxygen-rich water to developing salamander eggs while a whip-like “flagellum” on algal cells stirs water within the salamander egg mass to circulate oxygen.
You can readily find green salamander egg masses in local vernal pools. Each egg mass starts as a clear, tennis ball-size gelatinous greenhouse that protects both algae and embryos from hungry foraging invertebrates.
This is really cool: research now reveals it’s hard to discern where the salamanders end and the algae begin! Close examination of salamander eggs reveals algae living inside the tissues of the developing salamanders. Studies using carbon-14 showed how algae play a key role, using carbon dioxide from the water to produce glucose that fuels development of salamander eggs - unless they’re kept in compete darkness. The salamanders are essentially photosynthesizing!
The idea of salamander eggs as photosynthetic through association with an alga has scientists investigating if other aquatic animals employ a similar strategy.