Now is not a good time to be a sea star in my care. Although to be honest, I doubt these animals would be better off in anybody else’s care, either. And what’s going on today isn’t so much a series of unfortunate events as a trio of additional episodes in the two-year serial catastrophe that we call sea star wasting syndrome (SSWS).
Episode 1: My third Leptasterias star finally bit the dust today, a full week after the first one tore itself into pieces. Yesterday I was teaching all day and didn’t have time to take pictures when I checked on things at the lab, but the star was intact. Today, not so much:
On Monday, four days ago, the star had a small lesion on the aboral surface of its central disc. It was crawling around and aside from the lesion appeared healthy. While this individual survived longer than the other two, the progression of SSWS from small lesion to total dismemberment is surprisingly rapid. I shouldn’t be surprised, as I’ve watched SSWS take apparently healthy Pisaster ochraceus stars and turn them into piles of rotting disembodied arms in a single day. That was almost exactly two years ago. Maybe it’s something about the Labor Day holiday.
Episode 2: Since I lost two of my bat stars (Patiria miniata) to SSWS back in July, I’ve been keeping an eye on the five that remain. They seemed to be doing fine until this week, when I noticed that one of them had developed a lesion. It was a very small superficial lesion on Monday but now it has grown both larger and deeper.
Here’s a brief note about sea star anatomy. The small inter-radial clean-edged pale orange structure located at 6 o’clock is not a lesion. That is the animal’s madreporite, the ossicle through which water passes in and out of the water vascular system. The madreporite of Patiria tends to be pretty conspicuous; in other species it can be more difficult to find.
The lesion is the larger, paler, fluffier bit that doesn’t have clean edges. It’s an open wound, and the white fluffy stuff is the star’s soft tissue. Today the wound measures about 1 cm across its widest dimension:
I’ll keep checking on this star and see how quickly the lesion grows.
Episode 3: Scott and I have had to accept that we aren’t having much luck growing up our tiny Pisaster stars. This afternoon we counted 16 of the 0.5mm orange dots that are juvenile stars. We consolidated 12 of them into a single jar and kept the other four in a bowl with a piece of mussel shell. We have failed to determine what it is they eat when they’re this small, unless it’s more than sheer luck that the four with the mussel shell haven’t experienced any mortality in two weeks. And yes, we will continue to change the water in the jar and the bowl twice a week.
For broadcast spawners such as Pisaster ochraceus, which shed gametes into the water, reproductive success is all about numbers–numbers of spawning individuals in a population as well as numbers of gametes produced. In our experiment the numbers just weren’t working in our favor: (1) we got usable quantities of gametes from only two females and two males; (2) fertilization success was pretty low for both crosses (Purple x Purple and Orange x Orange); (3) all embryos for the Orange x Orange cross died in the early developmental stages; and (4) settlement and metamorphosis success was low for the Purple x Purple cross survivors. And now we’re down to 16 stars. By this time next week we may be down to zero stars, although those four on the mussel shell might still be hanging on.
We knew going in that the crux of the problem would be feeding the juveniles; I was reasonably certain that we’d be able to get through the larval stages successfully. And this is indeed what has been the case. Right now I feel more than a little disheartened even though the result we got (i.e., we can’t get the damn things to eat once they metamorphose) is far from unexpected. Fortunately it will be months before our brood stock can be spawned again so I have lots of time to decide if it would be worthwhile to try the experiment again. I will need to come up with some new ideas of what to feed the juveniles.