Black Water: Salp

A single salp oozoid that will never get laid.
Salps are the most common organism in the epipelagic environment and thus, far and away the most common animals we see on a blackwater.  Unlike most of the blackwater inhabitants, salps, aka tunicates or sea squirts, share our Phylum chordata.  That means that at some point in their lives they have a notochord.
I will be the first to admit that all of this taxonomy isn’t very interesting, so lets change the subject to sea squirt sex.  The individual oozoid stage is asexual and reproduces by selfing or making a whole bunch of genetic copies of itself in the form of a chain that can either be circular (cyclosalpa) or in a long string (salpa).  These chains are composed of a bunch of individuals known as blastozooids which are all attached by a complex network of “plaques” or information sharing connections that allow the salps to swim in a coordinated, synchronized fashion.  The blastozooid, or colonial, phase of a salp is the sexual one.  To simplify this, if you lived life like a salp, your kids, the result of sex with your spouse (or the mailman-we don’t judge at KHD!), would spawn a bunch of identical twins (reproduction through parthenogenesis) that would then go off to find someone else to reproduce with.
Are you creeped out yet?  No?  Because it gets weirder.  The blastozooid, or sexual form of a salp, undergoes sequential hermaphroditism. So they are females that produce female gametes (eggs) when they first mature, but eventually change sex into males as they get older.  While this process seems very complicated, it is also very efficient.  Salps can reproduce almost as fast as some bacteria!  That means that when conditions are just right (lots of phytoplankton food) they can bloom and inflict severe repercussions on the local plankton productivity.

Cyclosalpa blastozooid 2 small watermarked

Argonauta watermarked
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Cyclosalpa blastozooid colonies-These are many salp zooids in their sexual phase.

Phronima and eggs small watermarked
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The empty cavities of salp zooids are habitat for a whole host of organisms.  Look for crustaceans like this phronima, argonauta octopodes and even fish inhabiting the interior of salps.Salp oozoid 2 watermarked

Amphipods on pyrosome watermarked (1)
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Pyrosomes: A different kind of salp

-Jeffrey Milisen
MSc.

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