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.