The Field Guide to Super Powers #1: The Parasite and Elysia chlorotica

Super powers seem to fall into two broad categories: those that emulate what other organisms do naturally (like scaling a shear wall or breathing under water) and those that do not (such as shooting beams of energy out of your eyes or becoming intangible). The power to steal someone else’s powers, as Superman’s nemesis The Parasite can do, always seemed to fit squarely in the latter category. A recent discover in sea slugs, however, suggests that power stealing may have a natural analog.

cartoon (c) Jay Hosler 2010

In the comics, the Parasite can absorb the super powers of any hero he touches. Tap the Flash on the shoulder and he gets super speed. Shake Superman’s hand, and he’s able to leap tall buildings in a single bound. Nudibanch sea slugs appear to have a surprising similar ability.  Researchers have identified a species of sea slug, Elysia chlorotica , that steals chloroplast from algae and then starts photosynthesizing. The nudibranch takes a single meal of algae early in life, extracts the chloroplasts from its prey and inserts them into its cells.

This ability to harvest the cellular apparatus of another species seems to be something nudibranchs do very well. Several species of nudibranchs have been identified that can extract the stinging organelles (or cnidocytes) of jellyfish and coral and insert them into their own tissues for protection (although, how they extract the sensitive cnidocytes without triggering them is a still a mystery).  But, just like the Parasite, this ability doesn’t last forever.  Once the nudibranch has fired its purloined cnidocytes, it must replenish them by eating more jellyfish or coral.

What makes the discovery of Elysia chlorotica so exciting is that, unlike the Parasite or its cnidocyte-stealing nudibranch brethren, once E. chlorotica has the ability to photosynthesize it never loses it. And it never eats algae again. This is surprising because the stolen chloroplasts require a constant supply of chlorophyll to catch the light necessary for photosynthesis. But if the sea slug isn’t eating algae then it can’t replenish the chlorophyll that way. It would have to make its own, and we know of no animal on the planet that can do that. Until now.

E. chlorotica has the genetic hardware to make it’s own chlorophyll and keep its stolen chloroplast running. Where did it get the genes to do this? Probably stolen from some algae a long time ago.

The research was published in the Nov 18, 2008 issue of Proceedings of the National Academy of Sciences