Month: August 2018

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What? I Don’t See It

A few years ago there was an ad campaign that ran in several national level magazines.

image of a US Navy Seals recruiting ad
Navy Recruiting Ad

The ad was designed to promote recruitment to the US Navy Seals.  It had a picture of a swamp and a caption underneath that said “Pictured from left to right . . .”  I’m guessing that there really were soldiers hidden in the picture but the only thing I know for sure is I never could see them.

I think of that ad when I consider the unique characteristics of a Commersons Frogfish.  Like a special forces soldier, the frogfish is aggressive and fearsome.  Unlike a special forces soldier, though, only fish need to fear a frogfish.

The Waikiki Aquarium says on its frogfish page that “The frogfish is superbly adapted for its habit of ambushing prey.”  The article explains some of the adaptations which make that statement true.  First, the fish’s head is mostly mouth which enables it to swallow other fish as large as itself.  Second, the fish’s small gill openings are tucked away behind the pectoral fins so that exhaled water will not reveal the fish’s presence to potential prey.  Third, and this is the part that reminds me of the Navy recruiting ad, is that frogfish are so good at camouflage that they can be difficult to distinguish from the section of reef they are situated upon.  They sometimes even have real algae growing on their skin!

image of a frogfish
Yellow Commersons Frogfish

When we scuba dive Kauai, we have the opportunity to view a number of creatures that are skilled at camouflage but frogfishes are among the most specialized of ambush predators; their camouflage is so effective that biologists call it “aggressive mimicry”.

image of a frogfish
Hiding in Coral

As members of the same family as the deep sea Anglerfish, frogfish have a special spine that they can use as a sort of “fishing pole” to lure in a potential meal that needs to get just a little bit closer to be food.  When an unlucky creature gets to within about the distance of the frogfish’s body length, the frogfish will open its cavernous mouth so quickly that the rapid suction will draw the prey into its mouth.  This whole process takes place in just six to ten thousandths of a second, making this one of the fastest capture mechanisms in the animal kingdom.

image of a frogfish
Commersons Frogfish

We have several resident frogfish living at Koloa Landing – one of Kauai’s best dives.  It is a virtual certainty that we pass by at least one of them on any given dive tour.  The trick is to actually see one.  For your best chance at coming face to face with a frogfish while scuba diving Kauai, book a tour with Garden Isle Divers today!

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Animal, Vegetable, Mineral?

My experience as a professional scuba tour guide on Kauai has been that people are most interested in seeing the colorful tropical fish that are found here.  It’s common to come in from a dive and have someone ask a question like “What was that blue one with the yellow tail?” There have only been a couple times that I’ve had a client ask about coral.  I’ve always assumed that’s because we can’t normally observe coral ‘behaviors’ like we can with fish.

image of Hawaiian Sergeant
Hawaiian Sergeant

That is easy enough to understand.  After all, I’ve never had a coral try to chase me away from its egg deposit like a Hawaiian Sergeant will do.

Maybe more people would be interested in coral if they knew how amazing they really are.  So, here is some cool stuff about corals.

image of coral polyp structure
coral structure

Coral is a fleshy animal that creates a stone ‘skeleton’.  With most corals some of its food comes from single cell algae that lives in its cells.  As Douglas Fenner says in his book Corals of Hawaii, this means that we can say coral is animal, vegetable and mineral.  What other living organism is this true for?

When you see a head of coral, what you are actually looking at is hundreds to millions of individuals.  Each of the individuals that makes up a particular head is known as a ‘polyp’.  Because a head of coral is made up of many individuals, I think of coral heads as being like cities – some small and others larger.

image of mound coral colonies in kauai
Mound Coral Colonies

In the picture shown here, some of the Mound Corals can be thought of as being like Los Angeles or Chicago (without all the murder) while others would be more like Springfield or Grand Rapids.

An individual coral colony starts out as the result of spawning.  Many corals release sperm and eggs into the water on a schedule that is known to marine biologists and frequently occurs in relation to a full moon.  This means you can plan carefully and then witness, firsthand, this event.  Once a colony is established, it will grow by a process of division which means that a given head of coral is a collection of genetically identical polyps.  When a polyp divides, the new polyp will secrete limestone to create its skeleton.  This process grows the substrate of a coral colony making the size of the coral head larger.  This growth can add up to about a quarter inch per year.  There is a particular Mound Coral at Koloa Landing that is roughly 15 feet in diameter which makes it thousands of years old.  In other words, that particular head of coral is one of the oldest living animals on the planet.

The largest coral heads I see while scuba diving in Hawaii are Mound Corals.  The polyps that make up this type of coral are about one sixteenth of an inch in diameter – slightly narrower than the lead of a standard pencil.

image of oval mushroom coral
Oval Mushroom Coral

The largest coral polyp in the world is Mushroom Coral which grows up to about 12 inches in diameter!  To continue the cities comparison, a normal coral head is Tokyo and a Mushroom Coral is Godzilla.

These are just a few of the things I think are interesting about coral.  If you like this then book a scuba dive tour with us today and I will share more with you.  Even better, I will take you on an underwater adventure to explore the reefs of Kauai where you can see many different corals as well as all the beautiful tropical fish we have here.

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