|Salps do it two ways.|
Posted by Merry on March 04, 2013 at 15:21:33:|
In 2012, we were absolutely inundated with salps. Caught in current lines, individual salps littered the surface. Dense swarms of salps at depth appeared either as wheeled bouquets, elegant coils, or slithering chains. In fact, a 2012 survey by the NOAA Southwest Fisheries Science Center in Santa Cruz, performed from the ship Bell M. Shimada, yielded trawl nets that contained as many as 500,000 salps. Contrast this with 235 salps per trawl in 1999!
There are about 50 described species of salp. What can be confusing in their identification is that the solitary animal is physically different from a member of the aggregate. Not only are the solitary and aggregate forms morphologically different, but each reproduces differently as well.
The solitary form is the asexual phase of the reproductive cycle. It simply clones itself, producing hundreds of babies that are joined together in chains or coils. The aggregate form, the sexual phase, uses the old-fashioned egg and sperm approach, and produces a single embryo per salp. The two forms alternate each generation, allowing salps to proliferate rapidly and in huge numbers when food is abundant.
A portrait of Chamisso with one of his drawings.
I chose Cyclosalpa bakeri to illustrate the reproductive cycle with its alternation of generations.
Here are both forms of Cyclosalpa affinis.
Here are individuals in the Pegea confoederata aggregate, producing one embryo each. The embryos are attached to the dorsal wall. Theyíll develop into a single, globe-shaped animal.
This solitary Pegea confoederata is cloning babies from its reproductive stolon.
Hereís another view of the salp chain emerging from the stolon, plus a hitchhiker.
After detaching from the stolon, the small buds of Pegea confoederata rapidly grow into a chain of 5-inch long individuals.
A section of a Salpa maxima chain in the aggregate phase of the life cycle.
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