A salp is nothing so much as an open-ended barrel
of elastic gelatin
bound by hoops of muscle
. Salps tend to be only several inches long, and are all but invisible in the water. They are plankton
of the blue water, dwellers near the surface of the deep sea far from shore.
For a salp, to move is to feed. As water flows into the mouth of the barrel, the animal contracts from the front backwards, shooting water out the back, pushing the salp forwards, and at the same time straining all the water through a tiny conical net of mucus suspended inside the barrel. Particles as small as bacteria are snared and digested.
The animal makes a speed of perhaps a tenth of a mile per hour, and never stops. Not fast, but steady.
As a solitary salp feeds, a chain of clones like paper dolls buds from its back, and they are already feeding. Eventually the chain breaks free. Members of a new chain are all females; they are waiting for a (slightly older) chain of males to fertilize them. After they have given birth to a new generation of solitary salps, the former mothers will switch sexes themselves, to become fathers. It is no wonder, then, that when conditions are good, the water is dense with a population explosion of salps.
Oddly, what salps do not like is too much food. Their delicate feeding apparatus easily clogs in rich coastal waters. A bolus of undigestable food can be seen in the esophagus of a salp which has encountered such abundance; often the salp cannot clear the obstruction, and dies.
Where food is plentiful, salps starve; where it is small and scarce, they thrive.
phylum CHORDATA, subphylum UROCHORDATA (TUNICATA), class THALIACEA, order SALPIDA