Caller-Times Interactive: ATTRACTIONS
Saturday, April 19, 1997

Beach comber

Lots of jellyfish are dotting Matagorda Island

   There are so few things washed in on Matagorda Island beach that even jellyfish are a prominent feature. The island has many strandlings now; mostly cabbageheads. These are the tough, whitish, almost spherical jellyfish that have no tentacles around the edge of the bell. They feed on plankton caught in thick mucous on the stiff clump of mouth stems hanging down below the bell. Cabbageheads do have the stinging cells characteristic of the phylum, but so weak that they have very little effect on humans.
    Moon jellies and sea nettles have not only marginal tentacles with stinging cells, but also have oral arms: a set of four long, wide drapes that hang below the center of the bell. Moon jelly is the wide, flat one with four horseshoe shaped gonads showing through the translucent top layer; its sting is weak. The many, short marginal tentacles strain out little swimmies, and the oral arms carry them to the mouth.
    Sea nettles are about the same size as moon jellies but with fewer, long tentacles, longer oral arms, no horseshoes and a pretty strong sting. Luckily, they are not so common as moon jellies.
    A new jellyfish appeared on the beach this month. The purple jellyfish is not really new or even rare, just usual on these beaches. Purple jellies are related to sea nettles and have a sting. They come as big as 4 inches across with a clear bell stippled generously with brownish purple, pale oral arms, and eight thin, dark purple marginal tentacles as long as a foot.
    Purple jellies are delicate; their color lasts one day on the beach, and the clear lump of jelly lasts another day; then they are just a dark spot on the sand. But the lump can be recognized by a radial pattern of warts on the surface. The most intriguing thing about these jellyfish is a strong luminescence. If you can get to the beach at night when the jellies are fresh, gently poke one and see the glow.
    It may seem unlikely at first glance, but jellyfish and anemones are sort of mirror images of one another; they belong to the same great group of animals in which the body plan is basically a two layered bag with the opening surrounded by tentacles. This plan has two versions: the jellyfish form, or medusa, which is the bag swimming with the open end down, and the anemone form, or polyp, which is the bag sitting on the closed end with the open end and its tentacles up.
    A sandy beach in temperate climes is not ideal for either anemones or corals, but a few of kinds of each frequently wash up here. The most common anemone is the hermit crab anemone, which lives close offshore attached to various bits of stuff -- sand dollars, shells, crab carapaces -- and gets washed in on a rough surf. The recent extremely rough surf has been washing out the burrowing anemone called sea onion. When dislodged, it contracts to a sphere with about the size and appearance of a cocktail onion and bounces along until it is left in a still place. Then it extends its body and burrows deep into the sand leaving just its floret of small tentacles at the surface.
    Area beaches even get a few corals. Most striking is sea whip, a type of coral that makes a soft supporting structure. These are the long, thick, yellow strands that look like an insulated wire. They live near shore and are mostly alive when they wash in. Stony corals are quite tender, and pieces we find are all just skeletons.
    Besides the jellyfish and the corals/anemones, another branch consists of small polyps that are mostly colonial but not in massive or colorful colonies. They all have the stinging cells, but are mostly too small to affect humans. These are actually fairly common here, but most require a substrate (not sand) to fasten to and many are so small that they escape notice unless you are looking for them. They can be found attached to sea weeds and dead shells.
    But the most spectacular member of this group is neither tiny nor colorless nor even sedentary. Though we call it a jellyfish, the man-of-war belongs in this group. The group also includes by-the-wind-sailor and blue button. These have similarities to jellyfish but not, in fact, jelly; they all float with a gas filled structure. They are also considered by most students of the subject to be colonies of many individuals while each true jellyfish is one animal, but that's too esoteric to get into.
    All in all, this is a much larger and more diverse group than most beachcombers realize. However, many forms are small and/or transparent; they are economically unimportant and the only bizarre behavior is the sting of lager forms, so the group is not well represented on TV. From such a simple basic structure, these animals show an amazing variety of form, but then, they've had lots of time; they've been around almost since the beginning.