Some subjects, like mammals, are pretty easy to identify, from a combination of few varieties to be found in any given area, distinct markings or anatomy, and plenty of online resources. Arthropods often become a bit harder, since there are a lot of varieties and many distinguishing characteristics are tiny and hard to spot. And then there are things like crustaceans, where online resources are so thin that I couldn’t tell you if a lot of species look like this, or if this is the only one. So when I say that I think this is a pelagic gooseneck barnacle (Lepas anatifera,) well, pay attention to the italicized “think.”
And yes, crustacean is correct – they’re not mollusks, and in fact are quite mobile when they’re younger (a stage I have yet to photograph, though it’s definitely on my list.) But now things get a bit sticky. When first posted about in 2019, I said these were in the Order Pedunculata, but as I was checking details just now, I found I was incorrect – they’re from the Order Scalpellomorpha. Yet at the time I wasn’t actually incorrect – the texonomy changed two years later, and Pedunculata is no more. Makes me feel a little better, because I try to be as accurate as reasonable for my posts, and I was worried that I’d screwed up back then. I mean, I may still have screwed up and these are not pelagic gooseneck barnacles, which I’m now compounding, but anyway…
When I collected these specimens with the exorbitant effort of picking up an old bottle on the beach, I placed the bottle in a macro aquarium (what I could of it anyway,) and waited in vain for those little fan-fingers (cirri) to start sweeping through the water in feeding behavior. I later found out that they don’t do this, but simply let the current or the motion of their anchoring object bring food to them, the lazy sods. Are you sure you can handle drawing it in to your mouth, or do you need help with that too?
One of my specimens was found to be discharging some ‘stuff,’ and not putting a lot of effort into that either – it was closer to falling out than anything. While I initially thought this to be indigestible sand, close examination showed it all to be uniform, smooth, and oblong, like eggs – except barnacles don’t produce eggs. You know where I said above that I had yet to photograph the young, the larval stage? I’m not actually sure I haven’t, now, but what isn’t visible, even at high magnification, are the slightest details that demonstrate that these are crustaceans, which is what I’m really after. That quest will continue, even though I’m not exactly sure what I’m looking for or will know it when I find it.
For the record, barnacles swim around on their own until adulthood, whereupon they attach their heads to a fixed point, floating or well-anchored like a rock, and then their chitin extends to make an encapsulating shell that makes them appear more like mollusks; the cirri that you see here are actually their feet. And yet, they reproduce after they’re anchored – they’re hermaphroditic and possess both male and female organs, but do not self-fertilize, so they rely on being exceptionally well-endowed to mate with all other barnacles attached to the same general area. Something else that I did not actually capture, but I’m not on a quest to photograph this as much as the mobile young.
Still…