Ochre Sea Star Distinguishing Features

[Chevayea]

So, I'm looking at my books and my photos and I'm having a hard time telling if some of the star pics are Ochre Sea Stars (Piaster ochraceus) or False Ochre Sea Stars (Evasterias troschelii). Does anyone have any distuingishing features to look for?

Here's a bunch of pics that I'm trying to ID:
I think the prominent star shape indicates a true Ochre Star like in these pics



But then there are ones lacking the star in this but otherwise look the same, leading me to think this might now be a good identifier:


Then I'm lost on these ones:





Any pointers?

[nwscubamom]

Here's what I look for:

First off, if they're bright purple, only the Ochre sea stars come in that color. If it's more blandly colored, then you might need to look carefully.

Ochres have a distinct star shape in the center of the disc, made out of little white raised bumps, as well as distinct and raised white bumps all over, at random.

False Ochres have longer leg-to-body ratios, and a pretty distinct white line running down each leg.

That should pretty well nail it for you!

I highly recommend Sea Stars of British Columbia - by Phil Lambert.

- Janna

[Chevayea]

Thanks!

So it looks like all the brown ones above are false ochres, correct?

[nwscubamom]

Yup, you got it! I think the mottled/false ochres are...well...ugly. And the real ochres are kinda purty. They usually come in purple and orange and are found quite shallow, whereas the mottled/false ochres are found deeper.

- Janna

[Chevayea]

Cool, thanks Janna. You da man!...well, you know what I mean.

[Greg Jensen]

When the markings (star on Pisaster, white line on Evasterias) are missing, look at where the arm meets the central disk. On Evasterias they usually pinch in a little bit, and don't do that on Pisaster.

[Chevayea]

When the markings (star on Pisaster, white line on Evasterias) are missing, look at where the arm meets the central disk. On Evasterias they usually pinch in a little bit, and don't do that on Pisaster.

Cool, thank you Greg. I just encountered that issue today so now I know.