Invertebrates
Salp
Salpidae · also called salps
A salp drifts through open ocean, nearly invisible, pumping water through its barrel-shaped body in a steady rhythm that does two jobs at once: pushing the animal forward and straining out the phytoplankton it needs to survive. Left to multiply, salps can link end to end into chains stretching many feet long, an entire drifting colony built from a single, repeated body.
Overview
The salp, family Salpidae, is a barrel-shaped, gelatinous filter feeder found drifting in open ocean waters worldwide. Muscular contractions pump water through its body for both movement and feeding, and asexual budding can link individuals into long floating chains.
Boom, bust, and a role in the carbon cycle
Salp populations can bloom explosively when phytoplankton is abundant, and the dense, fast-sinking fecal pellets these blooms produce give salps a genuine, if easily overlooked, role in transporting carbon from the ocean surface into deeper water.
Status
Least Concern — common and widespread throughout the world’s open oceans, with naturally fluctuating populations tied to phytoplankton availability.
Salp: common questions
Is a salp a type of jellyfish?
No, despite its nearly transparent, jelly-like appearance, a salp is a chordate, placing it, distantly, in the same broad group as animals with backbones, whereas a true jellyfish belongs to an entirely separate and more distantly related group, making the resemblance between the two largely a case of superficial appearance rather than close biological relationship.
How does a salp move through the water?
A salp moves using jet propulsion, contracting its barrel-shaped body to pump water through itself in a rhythmic pattern that pushes the animal forward, and this same pumping action simultaneously draws water past an internal mucus net that filters out the phytoplankton the salp feeds on.
Why do salps form such long chains?
Many salp species reproduce asexually by budding, and the resulting individuals often remain physically linked end to end rather than separating, forming chains that can stretch several feet or more and drift together through open water, an arrangement that is part of the species' complex, alternating life cycle.
Why do salp populations sometimes explode in number so quickly?
Salps are capable of extremely rapid asexual reproduction when phytoplankton is abundant, allowing populations to bloom and multiply dramatically over a fairly short period, and because their numbers are closely tied to fluctuating food availability and ocean conditions, these blooms can appear and subside relatively quickly.