Snow Angels and A Carpet of Stars

By Mary Sue Brancato

Jeff Hyland and I had just endured a very tedious and long set of transects at a study area where we found no hard substrate, only sand and brittle stars, (Ophiura sarsi), as far as the eye could see. Occasionally, a pink urchin (Allocentrotus fragilis), white urchin (Stronglyocentrotus pallidus), a few whelks and shrimp, and groups of the sea star Luidia foliolata would break up the monotony.

Every dive is a thrill for me, even if brittle stars command the scene. They color the seafloor in lavender sometimes three deep, with the pink urchins blazing a clear path through them as they graze. We were cruising along over the brittle stars when all of the sudden the sea floor was bare - not a brittle star in sight. Suddenly groves, pods, groups, constellations - of 5-armed, tan-colored Luidia appeared.

Presumably, a chemical signal tells the brittle stars to move out of the area to avoid the predator Luidia. And wow can they move! It is always a thrill to see to see brittle stars move in a wave across the bottom! Luidia and other sea stars can also move faster than you would guess all those tube feet could carry them.

I have often thought the sea star "footprints" on the seafloor on a muddy bottom (they look like "snow angels") were from currents picking up a star and moving it. That could be, but I have also watched the stars fold backwards in half so that the tips of arms on one side touch those on the other. Unfolding them quickly, they leap along the sea floor.

See video of the stars moving!

We watched as Luidia made this "leap" seemingly in response to another Luidia that approached it. A predator-prey reaction? The "leap" left behind an imprint of the 5-armed star in the mud - a "snow angel" or a record of a safe escape?

Even when I don't see great species diversity, the animals I do see always intrigue me...but this was a coral-sponge cruise and finding rock meant finding coral. The sand was going on forever and ever.

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