A Very Strange Crab Indeed

A piece of barnacle conglomeration I found at Dead Horse Bay recently. Most species of barnacles need a surface to attach to, and sometimes that surface is other barnacles. These are a type of acorn barnacle, one of the two main groups. I understand differentiating the local species is difficult for the lay person. Give a shout if you know them on sight. Commonly seen species in the region are the Ivory barnacle, Balanus eburneus, which prefers less saline water (like Jamaica Bay, so this may be that) and the Northern rock barnacle, B. balanoides, which likes it saltier. A barnacle, as Cirripedia-mad Charles Darwin discovered, is actually a crustacean, akin to crabs and lobsters. A free-swimming animal in its youth, it has two distinctive larval stages, wonderfully called nauplius and cyprid. Then after swimming through several instars, most barnacle species settle down, literally, gluing themselves head/forehead first to a rock, pier, ship’s hull, or some such surface, and enveloping themselves within a carapace-like shell made up of (usually) six plates for an immobile maturity. The references to ship’s hull is a matter of some economic seriousness; humans have been scraping barnacles off boats since we took to the sea. The beak-like barn doors that protect the soft animal within its calcium fortress are visible in the above image; when feeding, these open to allow feathery modified legs that pull in plankton from the water. Barnacles at the mercy of the tide hunker down during the hours of low tide.There are many species of barnacles; I came across numbers ranging from 900-1100+. Pictured above are the ruins of Ribbed barnacles, Tetraclita stalactifera, which I found amid the rocks of Klein Bay, St John, USVI in January.

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