Tegula, or black turban, snails are tiny anchors of Pacific Coast tidepools; yet they cast their molluscan presence through three countries, from Canada's Vancouver all the way south to Mexico's Baja California. They have adapted to succeed abundantly in the harsh, upper intertidal zone. In this zone, during low tides, they may become exposed to the dry air and harsh sunlight. Only the crusty barnacles seem to exist higher above the water. The tegulas often cluster together under crevices where they find shade and the last remaining puddles of water before the return of high tide. Scientists have found that higher spots are the homes of smaller snails while lower spots, more often filled with comfortable amounts of water, are the homes of larger snails. This habitat pattern makes sense-- better conditions result in larger size, a fun hypothesis to investigate during a trip to the beach.
These small snails, only 20 mm to 40 mm in diameter, nonetheless contribute a great deal to tidepool life. They scrape away algae and wrack (brown seaweed), as part of their herbivore diet. Shells abandoned to bad fortune become homes for hermit crabs. If you observe a tegula snail moving rapidly, most likely there is a crab underneath rather than a snail. Even while snail-occupied, the outside of the shell is often home to a miniscule limpet or slipper snail.
Tegula snails have the color scheme of an Oreo cookie. The shells (and indeed feet underneath) are black, blue-black, or purplish black. Where the shell is oldest, on top, the upper layer erodes, revealing a beautiful white pearly texture and color underneath.
To find tegulas on the Pacific Coast, consult a local tide guide to determine when low tides occur. Then visit the tidepools that appear as the tide goes out. The black and white shells are abundant even in the pools closest to land. However, if they are moving fast, you are likely observing a hermit crab using a tegula shell. Look for the shells that are still or moving slowly. Make sure to leave the tidepool as you found it. If you pick up an animal or rock, put it down gently in the same place. Always face the ocean so that you can observe when the tide begins to come back in. And most of all, enjoy the chance to see ocean creatures up close.
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