Despite their jelly-like appearance, these creatures are actually closer to humans than jellyfish.

Nature · Published 3 October 2026 Swipe more like this →

In short: Salps are often mistaken for jellyfish, but they are actually complex chordates with hearts, brains, and digestive tracts. As some of the fastest-growing multicellular animals on Earth, these transparent organisms use highly efficient jet propulsion to navigate the ocean, playing a vital role in regulating the global climate.

Salps belong to the Tunicata group, a classification that links them more closely to vertebrates than to the brainless jellyfish they resemble. While they appear as simple, barrel-shaped blobs, their internal anatomy is surprisingly sophisticated, featuring a nervous system, a heart, and intestines. During their larval stage, they possess a notochord—a flexible rod that supports the central nerve cord—which is a defining characteristic of chordates. Although adults lose this structure, it serves as a clear evolutionary marker of their kinship with animals that have backbones.

The life cycle of a salp is a complex, alternating process between sexual and asexual reproduction. Solitary individuals, known as oozooids, reproduce asexually by budding off long chains of identical clones. These clones, or aggregates, eventually mature into hermaphroditic sexual forms. Each aggregate nurtures a single embryo through a placenta-like connection before releasing it to begin the cycle anew. This rapid reproductive strategy allows salps to exploit sudden algal blooms, leading to massive population explosions in equatorial, temperate, and cold seas, with the highest concentrations found in the Southern Ocean.

Beyond their biology, salps are essential to the ocean's biological pump. As they filter-feed on phytoplankton, they produce carbon-rich fecal pellets that sink to the seafloor. This process effectively sequesters carbon in the deep ocean for years or even centuries, acting like a natural bank vault for greenhouse gases. Because of this, scientists are closely studying how shifts in salp populations might influence the global carbon cycle and, by extension, the trajectory of climate change. Their ability to grow at extraordinary speeds—sometimes increasing their length by a tenth every hour—makes them uniquely positioned to dominate marine ecosystems when food is abundant.

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