Highlights from the Poseidon’s Web archives.
FOR A LONG TIME, DURING MY NEW ENGLAND DIVING DAYS, the northern moon snail (Euspira heros) represented a mystery to me. I kept seeing these structures I knew were moon snail “sand collars,” mucus-bound masses of sand that were said be be egg-laden. Except that there didn’t appear to be any eggs. SANDY SAND COLLARS MOON SNAIL SAND COLLAR MYSTERY SOLVED Then, one day, I found this: BIGFOOT SIGHTED! Thinking about moon snails brings to
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DIVING WITH MANTA RAYS WAS SORT OF A DISTANT FANTASY. I just wanted to see them. The giant Atlantic mantas I had seen in the past were fast-moving and, mouths agape, totally focused on sweeping up the plankton they make their livings on. Suddenly here, there, gone. Spending extended time in close-up choreography with one of these gentle giants was not in my vision. Until it was. The dive was at Flower Garden Banks National
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IF YOU’VE DIVED IN THE TROPICAL ATLANTIC/CARIBBEAN, you’ve almost certainly seen bluehead wrasses. Of course, most of them weren’t blue. The blueheaded members of bluehead wrasse world are terminal-phase males, or supermales. Despite their high visibility, they make up no more than 10 percent of a given bluehead wrasse population. The overwhelming majority of bluehead wrasses are yellow – juveniles or initial-phase adults or something in between. Blueheads (Thalassoma bifasciatum) are among those fish that
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ONE THING IS CLEAR – FISH HAVE BETTER BUOYANCY THAN YOU. And, they don’t have to press any buttons. Many bony fishes have built-in versions of the buoyancy-compensators that divers use to control their position in the water versus changing ambient pressures. In these fishes’ case, it’s an internal gas-filled sac called a swim bladder that automatically works to counteract the ambient pressures applied by the waters surrounding it and keep the fish at neutral
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WHAT’S THE DIFFERENCE BETWEEN JELLYFISH AND COMB JELLIES? They both come in blobby shapes and gelatinous, transparent bodies. But comb jellies – ctenophores – are entirely different from their oceanic jellyfish neighbors. Most importantly: They don’t sting. And some of them put on fantastic light shows. Note that I said “neighbors,” not “cousins.” The difference between jellyfish and comb jellies runs far deeper than the absence of stinging. Recent research suggests that combs evolved with
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ANIMALS IN THE OCEAN ARE ALWAYS LOOKING FOR FOOD (and trying to avoid being food). Some times it involves more than one animal. On Bonaire, one year, I encountered several instances of group fish hunting. Sort of. There’s a known phenomenon called Nuclear Hunting in which a small eel (like a goldentail moray) and one or more other fishes (like rock hinds) meet up, identify a nearby coral head as a target site and race toward
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AT FIRST PASS, “CORALS EATING JELLYFISH” SOUNDS LIKE AN OXYMORON. But newly published research confirms that for at least one variety of stony corals, the concept of corals eating jellyfish is indeed a reality. Moreover, these tiny colonial animals appear to work together to capture and devour the much larger jellies. It’s the first described case of “protocooperation” among corals, say the authors of the article published in the journal Ecology. NORMALLY CARNIVORES, ANYWAY Coral polyps
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IF IT LOOKS LIKE A RUBBER BALL AND IT FEELS LIKE A RUBBER BALL, IT MUST BE…ALGAE, a version commonly called a sea pearl (Ventricaria ventricosa). Sea pearl algae is an occasional reef denizen found worldwide that stands out because it so often looks like a delicate glass ball. Typically about the size of a golf ball, sea pearls are remarkable for their structure. Each one is a single cell, all by itself. Its round,
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INVASIVE LIONFISH HAVE BEEN A PROBLEM FOR NATIVE FISH SPECIES throughout the Atlantic/Caribbean since their introduction into Florida waters in the 1980s. For one thing, they have the advantage of preying on fishes unaccustomed to their modus operandi. For another, lionfish hunting techniques are fast, crafty and sneaky. In the Indo/Pacific basin, they’re formidable predators anyway, equipped with a wealth of venomous spines, superb camouflage in colorings and body shape and an ability to herd
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A POST HERE SEVERAL MONTHS AGO closed with the “Really Odd Fact” that blenny-like pearlfish (Periclimenes imperator) have a habit of taking up residence in the … well…rear ends of sea cucumbers. The overall post, “Sea Cucumbers – Superheroes of the Sea,” was about the fact that sea cucumbers, often ignored as inert, unimportant creatures, actually had a lot to recommend them. THE PEARLFISH/CUCUMBER EQUATION The pearlfish/cuke interaction is generally described as commensal relationship, but that term implies a
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