Salps are small animals, typically round 10 cm long, swimming freely in the oceans in enormous amounts.
Many of them are colorless, traslucent and difficult to spot, but some are brightly colored. They belong to the class thaliacea. The systematic place of salps is: Kingdom - Animalia, Phylum - Chordata, Subphylum - Tunicata, Class - Thaliacea, Order - Salpida, Family - Salpidae
Animals of this class, thaliacea, have an outer mantel surrounding the rest of the body with a space filled with water between the mantel and most of the core body parts. As the only animal group this class uses cellulose for strengthening of the outer body parts.
The mantel has one great opening which in the salps are at the back end of the body. They have a big mouth and past the mouth there is a very broad intestine part with many openings out to the mantel.
A salp is steadily gulping in water through the mouth and pressing this water through all these openings out into the mantel space, and further out through the back opening of the mantel. Thereby it achieves three results. The broad perforated front intestine performs the breathing, it filters out plancton used as food and the animal propels itself foreward by the stream of water pressed out through the back opening.
The life of salps have two great faces. In the first face it lives freely. But eventually new individuals grow out asexually from the side of its body. This happens many times until you have a chain of up to several hundreds of individuals hanging together side by side.
When these individuals mature, they became females. When they mature further they turn into males, so that it will be both males and females in the chain. Sperms from the males in the same chain or from nearby chains will fertilize the eggs of the females. These are released and from the eggs hatch new free individuals, and the cycle repeats once again.
Another closely related group of animals, pyrosomes, meaning fire-bodies, make colonies formed as great siphones. They emit light in the dark, which has given them their name. Much of what is said in this articles can also be said about pyrosomes.
Salps is a very important food source for animals in the sea. They turn plancton into meat that can be used by fishes and other animals. They reduplicate very fast, grow very fast and are typically eaten very fast.
Also feces from the salps sinks to the bottom and provide enormous amount of nutrition for the bottom life in the sea.
At periods the salps can consume nearly all the plancton in an area and the nomber of salps can nearly overwhelm an area. When there is not much plancton left, most of the salps die out and the amount of plancton again increases and these wil now overwhelm the area. Then the number of salps again increaes and the cycle repeats itself. This Plancton-salp cycle is ecologically important.
In the last years the amount of salps in the seas have increased greatly, while the amount of plancton has decreased. This change may cause problems for the whole marine ecology and has begun to cause practical problems for the life of humans along the coastlines that are steadily more polluted by salps aggreagating along the beaches.
There are speculations that steadily warmer oceans is the cause of this fenomenons. But stedily more data suggest that there has not been any global warming during the last decades, so that is probably not the cause.
But salps may become a source of economical income, because they may be used as food for animals, as raw material for ecologically beneficial fertilizer and also possibly as food for humans.
You can easily faind visual information about salps and pyrosomes at youtube and typing the keywords "salps" or "pyrosomes".
By Knut Holt
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