Beach Invertebrates

Beach Invertebrates. Discover Nature at the Beach. Animals without backbones are called invertebrates. Standing on the beach, wading in the surf, or swimming in the waters, you can encounter many varieties of Gulf invertebrates such as sand dollars, jellyfish, snails, crabs, and shrimp. , , Sand Dollars , Sand dollars use numerous short spines on their round, flattened bodies to move beneath the nearshore sand where they escape waves and gather food. When sand dollars die, their spines wear away as the body washes ashore, leaving the bare, often broken skeletons found on the beach. , , Traveling Clams , Coquina clams are members of a class of invertebrates known as bivalves, having two-part shells. They appear on the sand near the water’s edge during periods of tidal change. Waves wash them up the beach on a flooding tide and seaward on an ebbing tide. This movement keeps them in a favorable position to obtain food. , , Predatory Snails , A hole in bivalve shells on the beach is the work of moon snails that live nearshore. Moon snails search for bivalves beneath the sand. When one is located, it is held with the foot while a toothed belt (radula) slowly creates a small circular hole in the shell. The meal is extracted through the hole. , , Stinging Jellyfish , Cannonball (sometimes called “cabbagehead”) jellyfish are harmless, but the Portuguese man-of-war is not. The latter, actually a colony of very different individuals, is blown shoreward in large numbers and is recognized by its blue snail-like float. Avoid the tentacles that trail many feet beneath the float, because they can deliver a painful sting. Even ashore, tentacles remain alive for several days. , , Crabs and Shrimp , Speckled crabs and blue crabs occur in the surf, so you might see or step on one. If you do, don’t panic; stand back and they will move away. Commercially important shrimp are found offshore. Shrimp move from bays into the Gulf of Mexico to mature into adults. Shrimp boats, sometimes visible on the horizon, catch the adults and sell them to local seafood markets.