Copepods and Photosynthesis

Photosynthesis, the process by which light is converted into chemical energy is usually thought to only take place in the realm of plants and algae, but  some animals also make use of this life sustaining mechanism.

In nature it’s rare to see animals that harness the sun’s energy (besides the corals), only a few species thus far have been discovered to have this ability in some fashion. Some examples include:

The Oriental hornet, Vespa orientalis,  which has a yellow stripe on its abdomen that contains the pigment xanthopterin that is able to transform the sun’s light into electrical energy, allowing the hornet to be more active in the sun.

The Pea aphid, Acyrthosiphon pisum, is unique in that its genome  can synthesize carotenoids, a pigment usually found in plants, which allows it to produce energy from the sun’s rays.

oriental-hornet

The embryos of the spotted salamander, Ambystoma maculatum, have a symbiotic relationship with algae, which is the only documented photosynthetic symbiosis in a vertebrate, and are able to incorporate the algal chloroplasts in their own cells and egg capsules. These chloroplasts allow the embryonic salamanders to utilize an extra source of oxygen and potentially sugar in their growth, while the algae is able to use the nitrogenous waste that the embryo produces.

The Eastern emerald elysia sea slug a.k.a. Elysia chlorotica eats algae and is able to take the algal chloroplasts and incorporate them into its own digestive system where they can continue to photosynthesis for months afterwards, providing the slug with energy.

phytoplankton

Studies have shown that some species of copepod such as Acanthocyclops vernalis and Xarifia fissilis might be able to utilize photosynthesis in a primitive sort of symbiosis. Much like the Eastern emerald elysia, these copepods include algae as part of their diet, although they don’t take the chloroplasts into their own cells. Xarifia fissilis inhabits corals and evidence points towards it feeding on ejected Symbiodinium algae that are symbiotic within the coral. While the copepods do digest algae and use them as a source of nutrition, some algae cells are able pass through the copepod gut undamaged. This undamaged algae has been shown to continue photosynthesis with the gut, consuming C02 and providing oxygen to its temporary host, which could improve efficiency in movement and gathering food. Photosynthates such as sugars could also be released, providing more energy to the copepod.

The close relationship between algae, coral and copepod could be an example of of a three way symbiosis; a contributing factor to the productivity and high species diversity seen in coral reefs.

References

Cheng, Y.R., Dai, C.F., 2010. Endosymbiotic copepods may feed on zooxanthellae from their coral host, Pocillopora damicornis. Coral Reefs. DOI: 10.1007/s00338-009-0559-8

Lewis, W.M., 1981. Photosynthesis in Copepods. Science. 214:1349-1350

Plotkin, M., Hod, I., Zaban, A., Boden, S.A., Bagnall, D.M., Galushko, D., Bergman, D.J., 2010. Solar energy harvesting in the epicuticle of the oriental hornet (Vespa orientalis). Naturwissenschaften. 97:1067-1076

Valmalette, J.C., Dombrovsky, A., Brat, P., Mertz, C., Capovilla, M., Robichon, A., 2012. Light-induced electron transfer and ATP synthesis in a carotene synthesizing insect. Nature.com Scientific Reports.2: 579

Kerney, R., 2011. Symbioses between salamander embryos and green algae. Symbiosis.54(1)

Rumpho, M.E., Worful, J.M., Lee, J., Kannan, K., Tyler, M.S., Bhattacharya, D., Moustafa, A., Manhart, J.R., 2008. Horizontal gene transfer of the algal nuclear gene psb0 to the photosynthetic sea slug Elysia chlorotica. PNAS.105(46):17867-17871


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