Plants have the remarkable ability to fuel themselves through the process of photosynthesis. This is occurs within the plants little energy factories or organelles called chloroplasts. Plants absorb the simple required chemicals from the external environment, carbon dioxide and water, convert them using light energyto oxygen and carbohydrates. Would be great if we as humans could photosynthesize, could solve a lot of problems, but sadly we cannot. But you know who can? A sea slug can. What the heck?
Researchers from the Rutgers University-New Brunswick discovered a solar-powered mollusk. The eastern emerald elysia (Elysia chlorotica) is found in the intertidal zone along North America’s east coast between Nova Scotia and Martha’s Vineyard, Massachusetts, and Florida as well, the researchers report. Resembling a nudibranch, another clade of fascinating sea slugs (google nudibranchs too see some really beautiful creatures), E. chlorotica is from the clade Sacoglossa, the sap-sucking sea slugs.The team’s work was recently published in Molecular Biology and Evolution. The senior author of the study, Debashish Bhattacharya, states “It’s a remarkable feat because it’s highly unusual for an animal to behave like a plant and survive solely on photosynthesis,”
As juveniles the slugs feed on filamentous green algae called Vaucheria litoria. Using its radula, a band of chitinous teeth, it pierces the algal filament and sucks the contents out. In a process that is yet to be understood, the algae’s photosynthetic chloroplasts are not digested, but somehow retained in the gut cells lining the branched digestive tract. Their branched digestive tract extends throughout the slug’s life-like body providing a greater surface area for the chloroplasts to absorb light.
It gets crazier still. Eventually the juvenile slugs eat enough algae to ceases feeding externally all together and rely solely on photosynthesis. The chloroplasts make glucose, which the slug’s body absorbs, and the researchers discovered these slugs can live this way without eating for a long as nine months.
The research team used RNA sequencing to see how the slug responds to the ingested chloroplasts. They found that the sea slug’s body actively responded to the important organelles, protecting them from digestion and activating genes to the use the photosynthetic products.
Many questions still remain however. While sucking up the contents of the algae, the nuclei do not survive. In the absence of nuclei, who do the chloroplast know how to do their jobs? “The existing paradigm is that to make green energy, we need the plant or alga to run the photosynthetic organelle, but the slug shows us that this does not have to be the case” Bhattacharya said.
“The broader implication is in the field of artificial photosynthesis. That is, if we can figure out how the slug maintains stolen, isolated plastids to fix carbon without the plant nucleus, then maybe we can also harness isolated plastids for eternity as green machines to create bioproducts or energy.” - Bhattacharya
For this fascinating work see the full text article:
https://academic.oup.com/mbe/advance-article-abstract/doi/10.1093/molbev/msy061/4962174?redirectedFrom=fulltext
Chan CX, Vaysberg P, Price DC, Pelletreau KN, Rumpho ME, Bhattacharya D. (2018) Active host response to algal symbionts in the sea slug Elysia chlorotica. Molecular Biology and Evolution. msy061, https://doi.org/10.1093/molbev/msy061
