We all know that plants are photosynthetic – they can create their own energy by harnessing sunlight through chloroplasts or carotenoids. However, in recent years, a small number of photosynthetic animals have been discovered that process sunlight through symbiosis with algae and even generation of their own electric current.

Sea Slug - Elysia chlorotica

The first of these amazing photosynthetic animals is a sea slug, Elysia chlorotica, which effectively steals genes from the algae that makes up its diet. When E. chlorotica eats the algae, it integrates chloroplasts into its own cells – this process is made possible due to the fact that these slugs have a much less complex food breakdown than most animals. Its intestine lining forms a cell pouch to engulf whole cell parts of whatever it is digesting, allowing the chloroplasts to come through.

Researchers have found that in addition to chloroplasts, E. chlorotica can intake other photosynthetic genes in a horizontal genetic transfer – a process in which genes are transferred between organisms where one is not the offspring of another. HGT is very uncommon in organisms other than bacteria, and causes the slugs to not only retain the algal cells for themselves, but pass them on to their offspring as well. The stolen chloroplasts can be so efficient that these slugs can live up to nine months without eating and still maintain normal nutritional rates.

Spotted Salamander - Ambystoma maculatum

The spotted salamander is similar to the sea-slug in that in order to be partially photosynthetic, it maintains a symbiotic relationship with algae cells. While it has long been known that a relationship existed between the salamander and the algae, it was presumed to be a relationship in which both organisms worked separately. However, when researcher Ryan Kerney was studying a batch of spotted salamander embryos, he found a bright green color coming from inside their cells.

The chloroplasts were found near the mitochondria within the salamander’s cells, meaning that the mitochondria were likely directly consuming the oxygen and carbohydrates that are created through photosynthesis. The most amazing part about this relationship is that all vertebrates have strong immune systems that tend to destroy any foreign material found within their cells. Although the reason for this is unknown, this makes the spotted salamander the first vertebrates to be discovered to have the ability to photosynthesize.

Oriental Hornet - Vespa orientalis

The oriental hornet, in contrast to the sea slug and spotted salamander, was discovered by Dr. Jacob Ishay to conduct electricity through the cuticle of its exoskeleton, as well as through silk surrounding the hornet pupae and the colony’s comb walls. As opposed to stealing chloroplasts from algae, this photosynthetic insect’s yellow band contains xanthoperin, which actively absorbs light and converts it to electricity. Microscopic grooves in the hornet’s exoskeleton trap sunlight, and as the photons reach the yellow pigment, they build up voltage.

This voltage is released as current when the hornet is in darkness, and seems to be important for the development of the hornet pupae. The oriental hornet also differs from other wasps in that higher temperatures and current flows correspond to higher activity in the colony – making them most active in the early afternoon as opposed to most wasps that are most active in the first hours after dawn. A solar cell was created by Dr. Marian Plotkin to asses the efficiency of the xanthoperin pigment, and while it was found to be inefficient, the project demonstrated that the pigment really could create electricity from sunlight.

Pea Aphid - Acyrthosiphon pisum

The pea aphid takes advantage of its food source for photosynthetic powers as well as our first two organisms, but it doesn’t make use of chloroplasts. While a fungal gene was copied within the aphid’s cells, research on the little bugs shows that they make use of production of carotenoids – a type of pigment used for various functions like vision, bone growth, and vitamin production. You might be more familiar with beta carotene, a carotenoid found commonly in carrots, which is often suggested to upkeep vision and bone growth.

After measuring the aphid’s adenosine triphosphate (ATP – or energy) levels, it could be seen that different colored aphids had different levels of ATP. Aphid coloring ranges from white to orange to green, white having the lowest amount of carotenoids and green having the highest. Green aphids were found to have significantly more ATP than white aphids, while orange aphids were seen to generate more ATP in light rather than dark. While more research is necessary to be sure that aphids really have photosynthetic abilities, it is clear that carotenoids can absorb light and pass that energy on to the aphids.

Through better understanding and research of these unique animals, we can gain a better understanding not only of how they function, but how they became what they are, and how we may apply our knowledge of them to ourselves and our ever-growing technologies.

Source: SciShow