Blocky eyes

The hermit crabs in my aquarium carry their eyes on stalks. The eye itself is round, with a pale stripe across the centre, and the circular lens in the stripe.

Hairy hermit, Pagurus hirsutiusculus.

Tonight, while I tried to photograph a snail eating algae, trying to get a glimpse of its radula, a small hermit photobombed the scene. Maybe it's the angle: the hermit is above me, staring straight down at the flashing light that had attracted her attention: the whole eye is dark, and looks rectangular. I'd never seen one like that before.

"My turn! Forget that boring, slowpoke snail!"

She stepped on the snail's head, and he (the snail) promptly retreated into the shell. End of photo op.

Gaze

Hermit crab, watching me watching her.

The "flames" in front of her are the remains of a kelp holdfast she's grazing on.

Sparkly eyes

The hermit crabs disguise themselves with algae and gunk on old shells, in their hair, on their backs. But they can't disguise the lights in their eyes.

Hairy hermit, Pagurus hirsutiusculus

Ol' Hairy, with red and green algae, an anemone, and a tubeworm waving two tentacles from the rear of OH's shell. And those glowing eyes.