Short spines and blue rings

We spent this morning tidepooling in Pacific Grove, so I'll probably feature some observations from that outing during the next few days.  The low tide was very early, so this post will be simple.

Here are two extreme close-ups to start with:

 

 

Do you have any guesses about what type of animal this is?  

The answer is in the image below.

 

This is a Giant Sea Star (Pisaster giganteus).  This species is found occasionally in the Bodega Head area, especially near the Spud Point Marina and the jetties at the entrance to the harbor.  Although we found these sea stars in the low intertidal zone, they're more common in deeper waters.  

The first two pictures highlighted the short, purple/pink spines surrounded by blue rings.  Spine color is helpful in differentiating juvenile and adult Giant Sea Stars.  Spines are pink/purple in juveniles and white in adults.  The other individual we encountered this morning was an adult (see below).  For scale, the juvenile above was ~12 cm across, while the adult pictured below was more than 15 cm across.