Abby Thompson, a UC Davis mathematician, is back with more photos (and a video!) from the intertidal of northern California. Abby’s captions and IDs are indented, and you can enlarge her photos by clicking on them.
Jellyfish!
I thought I’d throw some jellyfish into the lull between the great winter tides and the great summer ones.
The reproductive cycles of the tidepool creatures are wildly varied, with behaviors ranging from maternal (see Epiactis prolifera from my last post), chancy (see mussels), through incessant (see nudibranchs). But for sheer baroque complication, I vote for the jellyfish. Many who stroll on a beach will see the quivering gelatinous masses of jellyfish stranded by the tide, and the less fortunate will have encountered their stinging tentacles while in the water. This describes, a little, how they get there.
There are several jellyfish species common on the Northern California beaches; here are some of them:
Aurelia labiata (Greater Moon Jelly):
Chrysaora fuscescens (Pacific sea nettle):
Chrysaora colorata (purple-striped sea nettle) These are big, about a foot across:
Another Chrysaora colorata (handsome creatures):
Genus Aequorea (crystal jelly):
Scrippsia pacifica (giant bell jelly):
The Chrysaoras and Aurelia labiata are in the class Scyphozoa; the rest are in the class Hydrozoa.
For all of these, males and females get together in the same vicinity, and release eggs and sperm (see “chancy” above), which form little “planulae”. Then things get complicated. Because (usually) the planulae settle down and attach themselves to something, and become polyps. Like these tiny things:
Genus Sarsia:
But how do they get from here (e.g. something like Sarsia) to there (e.g. something like Polyorchis haplus)? Well they don’t, always, and sometimes they don’t get from there to here, either, but here’s an illustration of the process when it goes through a “typical” complete cycle:
And in fact if you look closely at that photo of H. bodegensis, you can see a little medusa just budding off, circled in the photo below:
Here’s a video of a set of newly-formed “baby jellyfish” (they look excited) which swam into my microscope view. I didn’t know what I was seeing, so don’t have a photo of the polyp from which they likely emerged. This means I have no idea of the genus (or even the class- if these are Scyphozoa then these are really ephyrae which will turn into medusae).
There seem to be many species for which the complete reproductive process is not documented – for example, if you search for the polyp stage of Polyorchis haplus, the answer is that we don’t know what it is, nor where it can be found.
A final oddity of this elaborate reproductive process is the existence of the so-called “immortal” jellyfish. (not found in the cold waters of Northern California). If damaged at the medusa phase, this one can revert to its earlier (genetically identical) polyp phase- and so on ad infinitum, apparently. As though, when things go wrong in your life, you could go back to your childhood and try again.
I’m grateful for help with IDs from experts on inaturalist and elsewhere. All mistakes are mine.
