Wasting leather (star)

Until recently I hadn't closely observed what it looks like when a leather star (Dermasterias imbricata) succumbs to wasting syndrome. When I had the outbreak of plague in my table almost 18 months ago now, my only leather star was fine one day and decomposing the next, so I didn't get to see what actually happened as it was dying.

(Un)fortunately, one of the leather stars at the marine lab started wasting a bit more than two weeks ago, and this time I was able to catch it at the beginning. This animal wasn't in my care so I didn't check on it as frequently as I would if it had been living in one of my tables, but one of the aquarists pointed it out to me when it began getting sick.

The first symptom was a lesion on the aboral surface. I say "lesion" but it's more of an open wound.

Dermasterias imbricata with aboral lesion, 2 February 2015. ©Allison J. Gong
Dermasterias imbricata with aboral lesion, 2 February 2015.
© Allison J. Gong

You can see that the animal's insides are exposed to the external environment. In the photo above the whitish milky-looking stuff is gonad (I'm pretty sure this animal was a male) and the beige ribbon bits are pyloric caeca, essentially branches of the stomach that extend into the arms. What typically happens along with the development of lesions like this is an overall deflating of the star as the water vascular system and other coelomic systems become increasingly compromised, and the tendency for the animal to start tearing off its arms.

Which results in this, a week later:

Wasting Dermasterias imbricata, autotomizing its arm, 9 February 2015. ©Allison J. Gong
Wasting Dermasterias imbricata, autotomizing its arm, 9 February 2015.
© Allison J. Gong

This poor animal had torn its arm off, and continued to live for a while. I find it fascinating that the lack of a centralized nervous system means that this animal literally didn't know it was dead. It was finally declared officially dead two days later. Compared to how quickly wasting syndrome kills the forcipulates that I've seen (Pisaster, Pycnopodia, and Orthasterias), the leather stars take a long time to die--several days from start to finish, opposed to a matter of hours as I saw with my stars. The leathers didn't seem to be hit as hard by the first wave of the disease outbreak, either. Is Dermasterias somehow able to fight off the infection a bit longer? It would be interesting to know, wouldn't it?

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