By Barb Whitman My last article ended with a little fish trying unsuccessfully to wiggle out of a ring of stinging tentacles and being drawn into of the mouth of a coral polyp.” What horrors await inside?” The answer is to come. First, you need to know that there are many types of corals and they have many relatives.” The group of animals that coral belongs to are the Cnidaria (Ny-dare-ee-uh).”” Think of it as a family name like Hobson or Pemberton.” The Cnidaria family members include jellyfish (now referred to as sea jellies), hydroids like “fire coral”, sea anemones (like the little clownfish, Nemo, lived in), and other organisms like Man of War “jellyfish” ” the ones with the blue bubble on the top, coralimorphs and zoanthids which are animals that look like a cross between sea anemones and corals. They all share a family resemblance.” They have jelly-like bodies and stinging tentacles in a ring around the mouth but there are two distinct body shapes:” the polyp and the medusa.” Polyps, like sea anemones and corals, attach to something, stand upright and have the tentacles on the top and medusae, such as jellyfish have tentacles that hang down from a jelly-like bell.” While jellyfish roam the world swept along by wind, waves, tides and currents, corals, anemones and other polyps are homebodies and stay in one place.” Anemones can move short distances if they want to ” corals cannot.” One coral animal is referred to as a polyp.” It sits in a calcium skeleton.” Next to it is its clone.” Corals began cloning way before humans even thought about it.” All coral colonies begin with one coral.” This coral animal then divides into two, the two divide into four, the four divide into eight and so forth.” So each little polyp is genetically identical to the one next to it.” Each polyp surrounds itself with hard white calcium walls that connect to the walls of the polyps next to it just like rooms in a house with adjoining doors.” If you touch one coral polyp it retracts into its calcium home and warns the others near it which do the same until all the polyps have tucked themselves into the safety of their hard skeleton.” (Think of a row of dominos falling one after the other.) Most of us have seen videos of magnificently colorful coral reefs but the coral animals themselves have clear bodies. Their color comes from algae living in their tissues. The algae are called zooxanthellae (pronounced zoe-zan-thelly).” Around Nevis most of the zooxanthellae are golden colored which is why most of our coral is golden although a few are purple, yellow and even fluorescent green and pink. Zooxanthellae photosynthesize just like any other plant, using sunlight to make food, which it shares with the coral.” In return, the coral provides the zooxanthellae with a safe place to live.” Corals can also ensnare prey in their tentacles.” (Remember our little fish?) Although they can catch food, corals can’t survive indefinitely without their zooxanthellae.” It’s kind of like us eating only fish with no rice or fruit or veggies.” Corals need a balanced diet as much as we do. The tentacles of corals, anemones and others in the Cnidaria are covered with microscopic stinging cells which are triggered by touch or the presence of a chemical.” When something comes into contact with the tentacles, they shoot out sticky stinging cells (nematocysts) with little spear heads which impale the prey’s skin and inject a poison.” The poison is a neurotoxin which, like the name implies, affects the nervous system.” The more its quarry fights the more it comes into contact with the tentacles and the more it is stung.” The fish, shrimp or other animal (uh oh, our little fish”.) which is caught, becomes paralyzed by the toxin allowing the coral to move it with its tentacles into the mouth. Envision the guy in the television ad being passed hand to hand along over everyone’s heads to get a drink and then passed back.” Eventually the prey is passed tentacle by tentacle to the mouth and pushed inside the body. You know what’s inside the body?” Nothing.” Well, nothing much.” Corals, anemones and other cnidarians are basically empty inside ” no stomach or intestines, kidneys or liver.” Their food is digested by enzymes similar to the way our food begins to break down in our mouths by saliva.” The cells absorb the useable food and indigestible material is expelled through the mouth. (Makes me think of my sister who used to spit her peas into her napkin and then be excused to go to the bathroom where she threw them away.) Just like the Scarecrow, the Tin Man and the Cowardly Lion from The Wizard of Oz, corals have no brain, no heart, and no guts.” They are such simple organisms physically but their behavior doesn’t seem simple at all.” I”ve been amused and amazed by two minuscule coral polyps participating in a tiny tug of war over a shrimp caught in their tentacles.”” I”ve watched in astonishment as one type of coral attacked another coral colony in a territorial dispute.” The two colonies had expanded until there was no more rock left so they battled until one coral colony lost and the other began to grow over the top of it.” It’s amazing the little dramas that go on every day out on the reefs.” Even more remarkable is that they are dramas that we can relate to as human beings. Speaking of dramas, our little fish lost his battle and his body became lifesaving nutrition for another living organism.” That’s the circle of life.” But there is another type of battle that the corals must fight often.” It’s a dirty story and I”ll tell you all about it next week.
