Dude, What’s Up With That Sea Star?

Last week we went out to the rocky intertidal, specifically Cattle Point.

I always like seeing patterns of zonation, watching the lichens descend into algae and anemones, plunge into deep water and mussels and kelps, and seeing a more exposed coast and who likes to live there versus a sheltered coast (sometimes within a two minute walk from each other). If you like finding patterns, the rocky intertidal is a good place to be.

That said, what caught my attention this time was a little red sea star we found in a pool filled with the surf grassĀ Phyllospadix scouleri.

Normally I’d look at it and say, “Oh. Yep, that’s Henricia,” and move on. But just as the sun was starting to really get up in the sky (and all of us were really beginning to get hungry) I could see how the surface of the star appeared like it was bubbled up with small glass beads.

When neither Moose nor Emily could tell us why, Ryan pulled a jar out of his trench coat and we packed it on home to look at.

My possible theories included:

  1. Parasite! Let’s be honest, I was hoping for a parasite because I think they’re just about my favorite thing in biology after learning so much about them this past summer.
  2. Disease or some kind of malformation–seemed possible.
  3. Predation: something had eaten off of his surface. This seemed possible because I know Harlequin shrimp in the wild will often keep a sea star at their mercy for weeks, eating one ray at a time, keeping them flipped over, feeding them food. By the time the shrimp is back to the ray it started on, there’s a good change it’s already regenerated a good deal of it (depending on how much food the shrimp gives it). It wouldn’t have surprised me if something was just picking off the delicious tube feet from sea stars.

Since looking at some others we had cruising around in the sea table in the lab, I’ve come to the conclusion that it’s much more likely this is on all of them–the specimen we found at Cattle Point was particularly large, so I think that’s why it seemed so unusual. They don’t have any pedicellariae according to literature I’ve seen so far, which seems to coincide with the occurrence of these strange tube-like holes on their surface.

I also have to face the possibility that maybe they always look like that and I haven’t taken the time to be a good observer and check for these baubles on each of the ones I’ve seen–I’ve written them off as soon as I saw them as “just another Henricia.” This is a little upsetting because I try and pride myself on taking the time to really look at an organism, rather than seeing what I think must be there and moving on before I’ve had time to go beyond my preconceived notions.

So, lesson learned. Even if I’ve seen it before, I should take the time to get a better understanding of how it looks, works, and functions in its environment. If anyone knows why, exactly, their holes end up looking bubbled and solid (still clear, however) I’m really interested in continuing to figure this out.

In the meantime, time to study more for this Sociology quiz.




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