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Sea Slugs That Really Are What They Eat!

In some species, up to half the sugar produced by the captive chloroplasts is passed to the sea slug.

Ringed Sacoglossan sitting at ocean bottom

Photo: Ken-ichi (flickr)

Ringed sacoglossan off the coast of Hawaii

Ever wondered what it would be like if you could acquire the attributes of things you ate? Well, there actually are some animals that can harness the special powers of what they eat for their own benefit. For example, the sacoglossans is a type of shell-less marine snail, sometimes called “solar-powered sea slugs.”

Sacoglossans can extract whole, functional chloroplasts from the algae they eat. Chloroplasts are the parts of plant and algae cells that perform photosynthesis–using the sunlight to create sugars for energy. Rather than digesting the algae, sacoglossans have special branches off their digestive system that store the chloroplasts for up to two months. The slugs’ skin is transparent, so the chloroplasts still receive sunlight and produce sugars that the sea slugs use for energy.

In some species, up to half the sugar produced by the captive chloroplasts is passed to the sea slug. Sacoglossans are vegetarians, but some carnivores have also evolved “power stealing” abilities. Certain corals and different kinds of sea slugs called nudibranchs capture and store photosynthetic plankton to use the energy and nutrients for themselves.

And it’s not only photosynthetic powers that some animals steal from their prey. Certain nudibranchs feed on deadly stinging jellyfish, related to the Portuguese man-of-war. That’s a feat unto itself, but the nudibranchs then extract the stinging cells and use them to protect their own bodies. A nudibranch can become so well armed with stinging cells that they are even dangerous to humans!

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