Little Brother worm

When I changed the water and cleaned the aquarium yesterday, I separated out the empty snail shells, to look them over later. Maybe they weren't as empty as they looked, I thought.

Most of them turned out to be temporary hideouts for amphipods. One held a baby anemone, so small I needed the microscope to identify it. A few had been colonized by the rose seaweed. And one is home to a curious polychaete.

Side view, showing his fleshy palps and many tentacles. The shell is about 1 cm across. The worm has made himself a tube for protection.

Curious critter; if I jostled the shell, or even the tray, he instantly retreated into the shell, but less than a minute later, there he was again, reaching out, casting about, looking this way and that. Curious, or hungry.

Top view, showing his bristly paddle feet, one pair per body segment. He has four eyes, but in this photo, only two are visible.

Earlier, sifting the sand, I had carefully removed another worm, maybe the same species, but this one is now 6 inches long. They're fragile, out of their protective coverings, so I make sure they're safe before I wash the sand. And then, they're the first critters to be replaced once the tank is clean; within seconds they bury themselves in the sand, not to be seen again until next cleanup.

Little Brother's shell went back into the tank, gently buried under a fingertip's depth of sand. I found two more in the tray; tiny red hairs, identifiable as bristle worms only under the microscope.