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The Green Sea Slug is a Solar Powered Planimal

Though I have a college degree, I didn't pay all that much attention to what any of my teachers and professors said. Even as an elementary student, I realized they were all too often simply relaying information they garnered from books; books written by historians, often repeating politically correct myths rather than truths, and scientists brainwashed into believing outdated scientific doctrine based on man's need to reign supreme over all other life forms.

Many of our readers remember lectures about how man has language and animals do not, man uses tools while animals do not and man is capable of emotion but animals are not. But we have since learned that many species other than man do use tools, have forms of language and show emotion.

Scientists now study the sounds and body language of other species, and I remember the astounded exclamations of biologists who first witnessed a chimpanzee making a tool in order to retrieve ants from a tree cavity.

Another fact drilled into our heads in school was that only plants produce chlorophyll. Not so says Dr. Sidney K. Pierce, University of South Florida Tampa, and his research partners! Once again, the sea, a universe so different from that on terra firma, has divulged another amazing secret.

In January 2010, Dr. Pierce announced that Elysia chlorotica, the leaf-shaped Green Sea Slug, does much more than store chlorophyll from the Vaucheria algae upon which it feeds; it also steals the algal genes that establish the ability to photosynthesize.

"Solar powered" sea slugs have been studied for a few decades and the common train of thought was that, as they sucked the sap from algal branches, they ingested some of the algae's chloroplast (photosynthesizing) cells. These ingested cells continued to live for a period in the slugs' gut where they produced chlorophyll, the sugars on which the slugs live. Eventually, however, the photosynthesizing ceased and the solar powered slugs had to feed again in order to replenish the chlorophyll supplies.

The more the various species of solar powered slugs were studied, the more it seemed that Elysia chlorotica, the Green Sea Slug, was somehow different. Unlike the other solar powered sea slugs, the Green Sea Slug only needed to feed once in its lifetime of approximately one year. As long as the Green Sea Slug had access to sunlight, it ate once as a brownish colored juvenile, turned green after its first meal, and did not eat again throughout its life.

Was it symbiosis, was the Green Sea Slug tucking away a beneficial form of life upon which it depended like corals and the algae tucked into their tiny crevices? No, the slug had no hitchhikers or boarders externally or internally. It had to be sunlight because as long as the Green Sea Slug could sunbathe, it did not have
to eat.

However, if that were true, these animals had to be producing their own food. They were behaving like plants and had to be manufacturing chlorophyll.

In 2007, Dr. Pierce and his associates discovered that the Green Sea Slug genome incorporated photosynthesis-related algae genes ingested during their first feed. Even the embryos of the Green Sea Slug contained the algal photosynthetic genes that had to be inherited from the parents since the unhatched embryos had not yet been exposed to algae.

Pierce and his colleagues also found additional algal genes in the slugs' genome that related to the creation of photosynthetic pathways. Could the Green Sea Slug actually be an animal species that produced chlorophyll, the sugars thought only to be produced by plants?

To find out, Dr. Pierce's group isolated a group of slugs in the dark for five months. While the slugs still contained chloroplasts there was no chlorophyll found and all digestion and elimination of waste products had long since ceased. The unfed slugs were given an amino acid that contained a radioactive carbon that attached to chlorophyll.

The control group of the slugs was kept in the dark while the other was exposed to sunlight. The results turned the established definition of plants and animals upside down.

The unfed Green Sea Slugs kept in the dark did not produce chlorophyll and remained a ghostly pale; however, those exposed to sunlight were producing chlorophyll in spite of not feeding for five months. Their bright green coloration also returned. That the Green Sea Slug is an animal behaving like a plant was proven. It is an animal that actually photosynthesizes chlorophyll rather than merely kidnapping it. The Green Sea Slug is the first known "planimal."

As invertebrate zoologist John Zardus stated, "This could be a fusion of a plant and an animal – that's just cool." Zardus further commented, concerning the effects on evolutionary theories and the tree of life, the Green Sea Slug "raises the possibility of branch tips touching."

What other secrets may our seas reveal that could turn so many too-readily accepted "facts" on end?

Becky Bauer became a scuba instructor and award-winning journalist covering the marine environment in the Caribbean after 30 years as a wild and domestic animal rescuer, rehabber, and educator in the states. She is a contributing photographer to NOAA.

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