Highlights from the Poseidon’s Web archives.

Seeing Sea Anemones – for Themselves

SEA ANEMONES ARE PROBABLY BETTER KNOWN FOR THE COMPANY THEY KEEP than for their unassuming, hard-working selves. On Caribbean dives, I rarely pass by one without checking it out for exotic little cleaner shrimps that might be in residence. If there aren’t any, I’m disappointed and move on. In the Pacific, of course, you hardly have to check them out to be aware of their frenetic, constantly on-the-move, high-visibility companions – clowns and other anemonefishes.

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Sea Pigs: Amazing Sea Cukes You’ll Never See

IF IT LOOKS LIKE A PIG AND IT WALKS LIKE A PIG AND IT’S UNDERWATER, THEN IT MIGHT BE A…SEA CUCUMBER. Specifically, a member of the genus Scotoplanes. Or, to its multitudinous fans worldwide, a sea pig. Whereas most of us are used to seeing sea cucumbers that actually more or less resemble cucumbers in body shape, Scotoplanes species like S. globosa really do remind people of pigs. Plump, pink and sporting rather porky “legs,”

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Black Coral: Many Colors – But Rarely Black

BLACK CORALS ARE PROBABLY BEST KNOWN AS SHINY, JET BLACK JEWELRY. As living coral in their underwater habitats, they’re actually unlikely to be black. So what does black coral look like, actually? They’re most likely to be found in shades of soft reds, greens, yellows and other colors. They’re not stony corals – they grow in complex linear structures resembling trees, bushes or sea fans. The “black” part is the protein-based chitin that comprises the

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Balloonfish & Porcupinefish: Big Eyes, Mona Lisa Smile

WHAT’S THE DIFFERENCE BETWEEN BALLOONFISH AND PORCUPINEFISH?  They’re both unobtrusive, usually little guys with an ability to inflate into spiny basketball-shapes when disturbed. It’s a defensive response to threats. And, divers are often confused as to which is which. First of all, when you see picture of them, they’re often inflated like stuffed pincushions. In fact, like this…. But the truth is that recreational divers who are minding their manners are unlikely to see them

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Stony, Soft or Gorgonian, They’re All Coral Polyps

WHEN PEOPLE SEE THE WORD “CORAL,” it very likely brings to mind the great mounds of star and brain corals that stand out on the reefs. In fact, “corals” include many organisms beyond the familiar stony formations, all built on similar, tiny, coral polyps. “Coral” itself is a flexible word. It applies to the coral exoskeletons that we see as the visible shells of hard corals, to the polyp animals that live within those exoskeletons

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Iguanas in the Galapagos: Here Come the Marines

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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Hamlet Fishes: Chasing the Hamlet Grand Slam

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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Stromatolites – The First Reefs, Living Fossils

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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In Deep Waters, Corals Glow to Grow

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 do fish sleep

How Fish Sleep: By Resting, Snoozing & Totally Zonking Out

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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