Billions of years ago two bacteria formed a partnership. One lived on inside the other and became a mitochondria. Mitochondria harness energyEnergy and nutrients are the same thing. Plants capture energy from the Sun and store it in chemicals, via the process of photosynthesis. The excess greenery and waste that plants create, contain chemicals that animals can eat, in order to build their own bodies and reproduce. When a chemical is used this way, we call it a nutrient. As we More. They are the battery that fuel animal cells. These first cells eventually multiplied and diversified, creating all the animals you see on Earth now. So today, every cell in your body shares the same DNA blueprint of those first bacteria, also identical to every cell in every other animal on the planet. A similar thing happened when plants were born. But instead of mitochondria, plants made chloroplasts. These give plants their green colour and enable them to harness sunlight. Although it’s rare, some animals have been able to cross the animal-plant boundary. One such animal is a type of photosynthesising sea slug. It does this by stealing the plants internal organs and making them its own.
Photosynthesising sea slugs that steal plant organs
We came across a photosynthesising sea slug while snorkelling in shallow water near Melbourne, Australia, the other day.
It’s like a reverse zombie-ism, where the animal deliberately injects itself with the contents of a totally foreign organism
This Plancida sea slug is a ‘sapsucker.’ It drills a hole in the protective skin of seaweeds and sucks out the content of its cells. Along with the cytoplasm and other parts, the slug ingests chloroplasts. In the image above these can be seen as green dots throughout its body, as well as a network of microscopic branches. These are extensions of the digestive system.
For a long time there was debate on whether the slugs were simply storing these to eat later. However, research has now revealed a more interesting fact. Not only do the slugs harness the power of the chloroplast cells, they reconnect them inside their own bodies, so they can function(Of an ecosystem). A subset of ecosystem processes and structures, where the ecosystem does something that provides an ecosystem service of value to people. More as part of their own biology.
Solar-powered survivalists
Chloroplasts can’t survive in the bodies of animals as the chemistry is different. Under any normal conditions they would disintegrate on exposure to sunlight.
But photosynthesising sea slugs are able to change the chemistry turning light into heat. In addition, they turn off and modify other pathways, so harmful compounds are not created. While this reduces efficiency, the frilly extensions all over the animal’s back, compensate to some extent by increasing the sunlit surface area.
It’s like a reverse zombie-ism, where the animal deliberately injects itself with the contents of a totally foreign organism so it can survive longer. Another study has demonstrated a direct path between this ‘alien’ photosynthesis and the animal’s reproduction. Carbon and Nitrogen created via chemistry in the chloroplasts ends up in totally separate organs, where no chloroplasts occur. This establishes two things. First that the animal is directly using the plant organs, and second, that it contributes to better survival.
Other animals do this too. Corals are the most famous examples. The only vertebrate known to date is the spotted salamander that incorporates algae into its eggs to improve the chances of its young surviving.
