Highlights from the Poseidon’s Web archives.
FAMOUS AS LIZARDS THAT SWIM IN THE OCEANS, marine iguanas (Amblyrhynchus cristatus) are found in only one place: the Galapagos Archipelago in the eastern Pacific off Ecuador. Galapagos iguanas also include three species of non-swimming land iguanas. Some land iguanas found in the West Indies – like green iguanas (Iguana iguana) and rock iguanas (nine species in the genus Cyclura) – are also known to swim when called for, but not with the marine lifestyle of A.
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WHO KNEW THAT SPOTTING LITTLE GUYS LIKE BUTTER AND BARRED HAMLET FISHES could be challenging? I’ve thought of them as fairly bland little fishes of modest interest. I’m aware of occasionally seeing vivid blue indigo hamlets (Hypoplectus indigo) in Bonaire and Belize but not the other dozen or so species to be found around the tropical Atlantic/Caribbean. Which sounds fishy considering that Humann and DeLoache’s Reef Fish Identification says barred hamlets (Hypoplectus puella) constitute the most
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SOME TWO BILLION YEARS AGO THE CLOSEST THING TO LIVING REEFS ON OUR PLANET were widespread masses of stromatolites, mounds of cyanobacteria and sediment held together by calcium carbonate they secreted. Before they arose to dominate the seas, the earth was a hellish place. Afterwards, it was a world on the road to the evolution of life as we know it. FOREBODING PLANET Before stromatolites, the planet was largely a worldwide ocean, with landmasses no
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CORALS’ ABILITY TO GLOW WITH FLUORESCENT LIGHT has been known for some time. The understanding with shallow water corals has been that fluorescent proteins absorb harmful ultraviolet rays, protecting the zooxanthellae algae that provide them with significant nutrition through photosynthesis (See “Corals’ Colors Are More Than Just Eye Candy”). IN DEEP WATERS, A DIFFERENT STRATEGY Now scientists have found that corals in deep waters, which receive very little solar energy, use different colors for a
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HOW FISH SLEEP DEPENDS ON THE SPECIES. Nocturnal fishes, like cardinalfishes and those closely packed platoons of grunts and gray snappers you see just hanging around by coralheads and pier pilings during day dives, are likely resting rather than actually sleeping. Some species, like parrotfish, clearly sleep at night, although they seem like they can be awakened with minor disturbances (I base this on my own clumsiness around them on night dives). FISH BASICS ON
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IF IT LOOKS LIKE A CRAB AND IT WALKS LIKE A CRAB, THEN IT MIGHT BE A PORCELAIN CRAB, which is a different thing entirely. Which leaves the question: What’s the difference between true crabs and porcelain crabs? They’re both decapods – crustaceans that resemble each other with hard outer shells and 10 appendages, including walking legs extending on their sides and large claws out in front. They both walk sideways, or “crab-like.” But the
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SHARKS ARE KIND OF NOTORIOUS FOR HAVING TEETH – it is, after, all the principal reason we fear them. But they’re also famous for losing them. And some of us diving human beings are famous for hunting shark teeth. In fact, sharks drop teeth continuously. Inside their powerful jaws, they have multiple rows of choppers. When one falls out, one behind it moves forward to take its place, as if on a conveyor belt. Over
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WHAT’S THE DIFFERENCE BETWEEN FEATHER DUSTER AND CHRISTMAS TREE WORMS? For one thing, the conical feathery crowns of Christmas tree worms shout out their presence with color and beguiling shapes. Feather dusters’ fan-shaped crowns often whisper with subtle elegance. If it’s simply about appreciating the beauty of the reef, that’s the main point – conical versus fan-shaped, bold versus muted. It’s the fan shape that gives feather dusters their other common name, fan worms.
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DO SHARKS HAVE TO SWIM CONSTANTLY IN ORDER TO BREATHE? The answer is yes – for the relatively small number of shark species that excite us the most, like great whites and hammerheads. But it’s not the case with most of the 400-plus species of sharks in the oceans, like the familiar nurse shark and lesser-known species like bullhead, angel and carpet sharks. WATER, OXYGEN & GILLS Like all fish, sharks breathe by extracting oxygen
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WITH FIVE ARMS STRETCHING IN FIVE DIRECTIONS, you’d think that starfish could move along the seafloor like Indiana Jones. In fact, usually they creep along on hundreds of little tube feet that line the undersides of those arms. But, researchers studying how starfish walk found something else: sometimes starfish bounce along for speed. As echinoderms in Class Asteroidea, starfish walk by operating their multitudes of little tiny feet through intricate networks of fluid-filled canals. With
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