It seems a shame to call them Common. Pistaster ochraceus; the sharp syllables summon images of blunted spines and a pentacle of stout legs. In warmer oceans they are orange but here, creeping across submerged cliffs, their skin is a deep amethyst studded with white.
Environmental variance leads to stark discrepancies in appearance and diet. The purple eats voraciously. I distinguish one from the others, hunched over a Bay mussel, patiently prising the shell with its multitude of tubular feet. The mollusc is tiring. When the fissure opens, and this is inevitable, the starfish's stomach will disgorge and slip inside like a spy to digest the mussel within its own breached fortress.
Environmental variance. The purple is a brutal carnivore promising slow torture; there's nothing common about that. For three days it will covet this shellfish, absorbing nutrients and life, ingesting (or is it out-gesting?) the flesh of mytilus edulis. I caress its leg with one gloved finger, feeling the neoprene snag on its minuscule barbs.
Discrepancies in appearance. Is the starfish purple because of its diet, or does the royal lustre tempt it to gluttony? Does that which colors our appearance color our choices? I could easily knock the predator from the prey, and save the mussel from its tragic fate, but I am cruel, too. Instead, I descend. The jade-green sea darkens to blackness. Here, where the cold northern waters galvanize our sinister desires, a vicious purple resides in the core of even the most reticent orange.