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Salp

life science Maturity 11-13 Next article →

Salps are barrel-shaped, planktonic tunicates belonging to the family Salpidae. They are gelatinous animals that drift through the ocean's water column. While they may look like jellyfish, they are actually chordates. This means they possess a dorsal nerve cord, making them related to vertebrates like humans. Salps play a massive role in the ocean's biological pump. They help move carbon from the surface to the deep seafloor.

Stamp of Azerbaijan 318
Stamp of Azerbaijan 318

Movement in a salp is a highly efficient process. They use a method called jet propulsion to travel. To do this, they contract their gelatinous bodies in a rhythmic way. This contraction pumps water through their transparent bodies. This water movement provides the thrust needed to swim. As they move, they also feed on tiny organisms called phytoplankton. They collect this food by straining the water through internal feeding filters.

Sea Salp Chain
Sea Salp Chain

The life cycle of a salp is quite complex. It involves an obligatory alternation of generations. This means the species must move through two distinct life stages. Both stages live in the sea at the same time. They look different but remain mostly transparent and tubular. The first stage is the solitary oozooid. This single, barrel-shaped animal reproduces asexually. It produces a chain of tens to hundreds of smaller individuals.

Salp colony, Aorangaia PA171899
Salp colony, Aorangaia PA171899

The second stage is known as the aggregate portion. These individuals are called blastozooids. They are released from the parent at a very small size. These blastozooids remain attached to one another while swimming and feeding. Each individual in the chain grows larger over time. They are also sequential hermaphrodites. This means they first mature as females. They are later fertilized by male gametes from older chains. Eventually, new oozooids grow on the body wall and are released.

23 salpchain frierson odfw (8253212250)
23 salpchain frierson odfw (8253212250)

History shows us how much salps can impact the environment. In 1763, Peter Forsskål introduced the genus Salpa from waters near Yemen. The English name "salp" did not appear until 1835. In 1920, a massive incursion of Salpa fusiformis occurred in the North Sea. This event caused the Scottish herring fishery to fail. Today, we see changing patterns in their populations. In the Southern Ocean, salp populations appear to be increasing since 1910. This is happening even as krill populations have declined.

Salp colony, Aorangaia PA171899
Salp colony, Aorangaia PA171899

Salps are incredibly important to the ocean's carbon cycle. They respond very quickly to phytoplankton blooms. When food is plentiful, they can bud off clones rapidly. This allows them to grow faster than almost any other multicellular animal. They can quickly strip phytoplankton from the water. When salps die, their bodies and fecal pellets sink. This process carries carbon down to the seafloor. Because they are so abundant, large changes in their numbers could affect climate change.

23 salpchain frierson odfw (8253212250)
23 salpchain frierson odfw (8253212250)

These creatures can be found in many different environments. They live in equatorial, temperate, and cold seas. In the Southern Ocean near Antarctica, they form enormous swarms. These swarms are sometimes even more abundant than krill. In some cases, salp blooms can become so dense that they clog. This causes the salps to sink to the bottom. During these times, beaches can become covered in slimy mats of salp bodies. Even small fish interact with them by swimming inside for protection.

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🖼️ Images & Media (4)
File:Salp colony, Aorangaia PA171899.JPG
Salp colony, Aorangaia PA171899.JPG
File:Sea Salp Chain.jpg
Sea Salp Chain.jpg
File:23 salpchain frierson odfw (8253212250).jpg
23 salpchain frierson odfw (8253212250).jpg
File:Stamp of Azerbaijan 318.jpg
Stamp of Azerbaijan 318.jpg
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