Emma Deen
What is an amphipod?
Amphipods are crustaceans that are often mistaken for shrimp. Amphipods range in size from small being ~1-2 mm to the largest ever observed being ~340 mm (Jamieson et al. 2013). The largest amphipod ever observed was not collected in the field and instead was regurgitated by an albatross (Jamieson et al. 2013)! Their bodies are laterally compressed, so they look thin like the sides of their bodies are squished together. Most species are marine with some freshwater species and few terrestrial species. Within the marine habitat the amphipods range from the deep ocean all the way to the rocky intertidal.
A new discovery…
Amphipods are discovered all the time. In 2020, an adult female individual was captured in a baited trap. This amphipod was found in the Mariana Trench in the Pacific Ocean within the hadal zone between the depths of 6010 and 6949 m (Weston et al. 2020). The name of this newly discovered species is Eurythenes plasticus and is named for the plastic found in its hind gut (Figure 1). This name originates from the genus, Eurythenes, which consists of giant deep-sea amphipods, and the species, plasticus, comes from the Latin word for plastic (Weston et al. 2020). These amphipods are white in color and the females are larger than the males. The adults range in size from 48.1mm to 47.6 mm, and the juveniles range in size from 12.5 to 15.7 mm (Weston et al. 2020). These deep-sea dwelling creatures are benthic scavengers that feed on a variety of things such as detritus (Weston et al. 2020). As scavengers, they are not particular with what they ingest due to the scarcity of food in the deep ocean. They sometimes consume plastics, particularly microplastics, like polyethylene terephthalate, one of the most common plastics used by humans (Weston et al. 2020). Researchers examined four juvenile individuals and found plastic in one of their hind guts proving adults and juveniles are both consuming plastics (Figure 2, Weston et al. 2020).
Image from the journal article: New species of Eurythenes from hadal depths of the Mariana Trench, Pacific Ocean (Crustacea: Amphipoda) by Weston et al. (2020).
Image from the journal article: New species of Eurythenes from hadal depths of the Mariana Trench, Pacific Ocean (Crustacea: Amphipoda) by Weston et al. (2020).
…and the bigger picture
The discovery of this new amphipod not only demonstrates that new species are being found in the oceans, but it highlights the impact humans have on the oceans and the scope of pollution. Anthropogenic, human caused, pollution has a huge impact on many different ecosystems and can cause damage in the deepest parts of the ocean that are not directly accessible to humans. It is known that microplastics are present in the hadal zone, but the discovery of Eurythenes plasticus is the first report of an organism ingesting it at this depth in the ocean (Weston et al. 2020). Other organisms, such as sand crabs, consume microplastics affecting their embryonic development and increasing mortality in adults (Horn et al. 2019). It is likely that amphipods experience similar effects, however more studies are warranted to fully understand how the consumption of microplastics affect them.
References
Horn, D. A., Granek, E. F., & Steele, C. L. (2019). Effects of environmentally relevant concentrations of microplastic fibers on Pacific mole crab (Emerita analoga) mortality and reproduction. Limnology and Oceanography Letters, 5(1), 74-83. doi:10.1002/lol2.10137
Jamieson, A., Lacey, N., Lörz, A., Rowden, A., & Piertney, S. (2013). The supergiant amphipod Alicella gigantea (Crustacea: Alicellidae) from hadal depths in the Kermadec Trench, SW Pacific Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 92, 107-113. doi:10.1016/j.dsr2.2012.12.002
Weston, J. N., Carrillo-Barragan, P., Linley, T. D., Reid, W. D., & Jamieson, A. J. (2020). New species of Eurythenes from hadal depths of the Mariana Trench, Pacific Ocean (Crustacea: Amphipoda). Zootaxa, 4748(1), 163-181. doi:10.11646/zootaxa.4748.1.9
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