A Minor Marine Miracle

By June Dawley

    The Texas Longhorn represents one of Nature’s more whimsical moments. This small marine phenomenon looks like its popular name: two long horns point in opposite directions, each extending from the side of a flat spiral which resembles a coiled hose.

Ventral view of 118 mm. specimen

    This structure is built by a colony of tiny marine animals of the phylum Bryozoa, genus Hippoporidra, species (on our Atlantic coast) not known. Much as the coral polyps build large reefs, so these little bryozoa build the Longhorn, starting with a small deposit of calcareous material on a shell or shell fragment, and building in the coil outward until it is large enough to sustain the weight of the horns. After the horns are started, the whole building continues to grow, sometimes reaching an over-all span of six inches.

    All this design and growth is not with purpose: the Texas Longhorn houses a small hermit crab whose full name is Pylopagurus corallinus (Benedict). He differs from most other hermits in that his body lacks the twist to the left which makes it possible for other species to inhabit dead snails, most of which open to the right. Pylopagurus corallinus has a small, straight body because the spiral cavity he occupies is all on one plane. Like other hermits he has a shelly anterior and a soft, defenseless abdomen. His red and white striped legs end in points, so when he walks about on the ocean floor, balancing his beautiful pointed house on his head, he appears to be toe dancing. Pylopagurus corallinus has a large right claw, flat and oval in shape, which precisely fits the open end of the spiral. He can withdraw into his tube-like house and, using his claw as a trap door, seal himself safely away from predators.

    In this symbiotic relationship the benefits which accrue to P. corallinus are obvious: he has a permanent home which protects his soft parts, and it grows as he grows so the need to look for another home is not likely to occur. Probably, the small crab, moving about in search of food, carries the structure along the ocean floor, providing constantly changing feeding places for the tiny animals, which make up the colony. Each little animal is no more than a millimeter in length, often smaller, so it is very difficult for marine biologists to observe the life processes, which go on in the Texas Longhorn.

    The accommodation of these two very different life forms to each other, for mutual benefit, must have evolved over a period of millions of years. This kind of small miracle gives the observer a new and interesting perspective on time. We tick it off in hours and days, but Nature thinks in eons.

Texas Longhorn

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