Salps: The Fastest Growing Animal in the World
Salps are small marine creatures that are members of the phylum Chordata, the subphylum Tunicata, class Thaliacea, and order Salpida. They are small, translucent barrel shaped animals that look like sea combs and are found in many oceans, but the densest populations are found in warm oceans in the southern hemisphere (Britannica, 2023). 70 species of salps have been identified and they range in size from 1 to 20 cm long (Creature Feature, n.d.). They are distinguished from sea combs and jellyfish due to having a cartilaginous notochord as larvae. This puts them as a close relative to sea squirts, which are also in phylum Chordata (Murray, 2019). In fact, they are more closely related to vertebrates than they are to actual jellyfish. They possess muscles, circulatory, nervous, and digestive systems. Although some species are known to express bioluminescence, the most visible part of salps are their intestine and eye, which are either brown or orange against their translucent body.
Salps use a jet propulsion system that is two-fold in use. It uses muscular contraction and two siphons–one on their anterior and another on their posterior end–to move through the water. This siphoning of water also moves particles over a mesh-like gill that catches the particles, mainly algae and phytoplankton, and passes them to the intestine to be digested.
The life cycle of salps is definitely their most bizarre characteristic. They are hermaphrodites and first undergo asexual reproduction in their life cycle by budding. However, instead of producing a single individual, salps produce massive chains of salp oozoids, or stolons, that can contain around 120 zooids and reach several meters in length (Ballance, 2018). Once these oozoids mature, a male salp can mate with one to form one or two larvae nurtured by a placenta. Once the female gives birth, she develops testes and becomes a male, ready to mate with a female (Ballance, 2018).
Besides multiplying in massive numbers, they currently hold the record as the fastest growing animal on the planet, reaching maturity within 48 hours of being born. This rapid growth rate allows them to congregate offshore around algal blooms to feed and reproduce in massive numbers that are also referred to as blooms.
Along with other tunicates, salps are the second most abundant zooplankton on Earth and they can cause massive turnover in the environment when they bloom (Murray, 2019). When they congregate, the number of phytoplankton in the water drops dramatically due to them being consumed. Salps have very carbon concentrated fecal matter and their bodies are dense, so their feces and bodies (when they die) sink to the sea floor very quickly. This causes a carbon influx in the ecosystem that can provide a food source for benthic creatures that can last for several months (Nereus Program, 2016). Some scientists speculate that this carbon turnover helps regulate climate change. While alive, they are also food for fish, turtles, shellfish, and other marine dwelling creatures.
Salps are chordates that, though they resemble jellyfish, and more related to human beings than they are to cnidarians or ctenophores. They are filter feeders with muscular siphons, complete guts, and circulatory and nervous systems. They have a very unique life cycle that results in them making long chains of clones. These chains are characteristics of salps and one of the most bizarre phenomena that many scientists have observed in the ocean. They are also the fastest growing animal on the planet and respond very quickly to algal blooms and sudden increases in their other food sources. As such, they are good indicators for changes in the biosphere, and provide needed carbon circulation in the ocean. They don’t play any direct role in interacting with humans, but the carbon turnover is likely linked to regulating climate change, which makes them a very important creature to preserve and monitor in the oceans.
Ballance, A. (2018, December 20). Salps - a surprising jelly-like relative. RNZ. https://www.rnz.co.nz/national/programmes/ourchangingworld/audio/2018676118/salps-a-surprising-jelly-like-relative
Britannica, T. Editors of Encyclopaedia (2023, September 27). salp. Encyclopedia Britannica. https://www.britannica.com/animal/salp
Bryant, P. J. (2012, August 20). Salp: Cyclosalpa affinis. Salp, Cyclosalpa affinis. https://nathistoc.bio.uci.edu/Tunicates/Cyclosalpa%20affinis/Cyclosalpa%20affinis.htm
Creature feature: Salp. Twilight Zone. (n.d.). https://twilightzone.whoi.edu/explore-the-otz/creature-features/creature-feature-salp/#:~:text=Salps%20go%20through%20two%20life,each%20parent%20in%20the%20chain.
Home. Nereus Program. (2016, September 28). https://archives.nereusprogram.org/our-jelly-like-relatives-common-misconceptions-about-salps/
Murray, A. M. (2019, November 27). Salps. The Australian Museum. https://australian.museum/learn/animals/sea-squirts/what-is-a-salp/#:~:text=Salps%20have%20a%20complex%20life%20cycle%20alternating%20between%20a%20sexual,released%20by%20a%20solitary%20parent.