Month: March 2021

Other Symbiots

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Sea slugs (marine gastropods) are one of my all-time favorite creatures. A nice surprise this morning was learning that some of them are similar to lichens, another of my favorite Kin. How could a sea slug be similar to a terrestrial based lichen? Both can photosynthesize! Humans wonder at lichens’ unique status as a combination of two (or more) very different life forms that join to make a completely different life form. The fungus uses the energy produced by the bacteria or algae partner. Some sea slugs incorporate chloroplasts into their bodies from algae they eat. The chloroplasts produce sugars that the sea slug uses for energy.

Elysia marginata

There are some lucky people who spend their lives studying sea slugs. They are a quiet bunch of scientists and naturalists, probably because staring at sea slugs is mesmerizing. Sea slugs seem to be as varied as lichens in shapes and colors, and are one of the small beings that do much to keep the Web of Life woven together, as lichens do.

Elysia atroviridis
Peltigera sp.

Lichen and sea slug shapes are similar too, for some species.The similarity between Elysia sp. and Peltiger sp. is especially striking.

Humans have known about sea slugs using algae photosynthesis after eating the algae for many decades, but recently sea slugs were in the news because a Japanese scientist noticed one of them had lost her head. The body and head were separated, and the head was acting quite unconcerned and quite alive. Within a short time, the separated head had regrown a complete new body. Humans are guessing that is done to avoid parasites. The decapitated-sea-slugs also were ones that incorporated algae photobionts, so that information came to my attention while being amazed about the rearrangement of body parts.

All this strangeness, to us, opens many paths to new understanding about the world we are a part of but often so separate from. Each ‘fact’ we ‘know’ is one small piece of the endlessly intricate world that comes to our attention, but is never the whole story. Now when I visit Peltigera at Site 4 on our Kickapoo Valley Reserve Lichen Trail (the Wintergreen Trail) they will remind me of their distant Kin, far away in a shallow sea, with wavy green, brown and yellow bodies full of algae, so similar to the lichens here on a rock in the middle of the continent.

Onchidella celtica
Lichen-unknown species, on soil in Sonoran desert

Thanks for sharing the exploration. Please share this blog with others, to make more friends with lichens.