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A ghastly Crown-of-Thorns Starfish denuding a coral reef

A ghastly Crown-of-Thorns Starfish denuding a coral reef

Today’s post is simultaneously inspiring and hopeful and terrifying.   Marine researchers have long been worried about the crown-of-thorns starfish, a monstrous invasive invertebrate which eats coral, doing irreparable damage to the Great Barrier Reef (the world’s largest coral reef).  Human divers have proven ineffective at stemming the onslaught, so conservationists have teamed up with mad scientists to build COTSBOT—an autonomous killing robot submarine which will haunt the reef like a bright yellow uboat/shark.  The COTSBOT will locate and identify crown-of-thorns starfish with robot eyes and then jet over and deliver a lethal injection to the vile invertebrates.  The injectable solution is uniquely poisonous to starfish so any goddamn MFAs doing starfish cosplay projects on the reef do not necessarily need to worry about more than being jabbed and pumped full of weird chemicals by a nightmarish (albeit comic) undersea robot.

COTSBOT (image from Queensland University of Technology)

COTSBOT (image from Queensland University of Technology)

COTSBOT (which I should have mentioned stands for “Crown-OF-Thorns Starfish Robot”) is going to debut in Moreton Bay by Brisbane, a starfish free location where the operators can refine its navigation systems.  If all goes well it will then move on the Great Barrier Reef itself.  The robot (or fleets thereof) will scour an area of the reef killing,  Then human divers will sweep in afterwards to mop up any hardened survivors.   I am extremely impressed at how quickly science managed to make my futuristic ocean sketch come true.  I am also struck with admiration at this high-cost high tech salvation for one of Earth’s most diverse and imperiled ecosystems.  Take that, evil starfish!  You have messed with a reef protected by the fell hand of man.  The alarmist in me can’t help but notice that this is like the first 15 minutes of a horror movie, but, presumably if COTSBOT becomes sentient and decides to protect the reef from ALL dangerous invasive animals we can still pull the plug.  I’m also a bit sorry that humankind has so injured the Giant Triton–nature’s COTSBOT–that the lovely snail can not do the job.

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The Yellow-lipped Sea Krait (Laticauda colubrina)

The coral reef is a super-competitive ecosystem where every surface hides a hidden mouth, a poison dart, or a camouflaged hunter.  However the reef is also a place rich in resources where it is possible to make a good living.  It is sort of the New York City of ocean habitats.  Some animals have been part of reef-like ecosystems for a tremendously long time, but one of my favorite reef animals, the banded sea snake or yellow-lipped sea krait (Laticauda colubrina) is a latecomer.  Like the coral reef catfish (which descended from freshwater river fish ancestors but evolved into a saltwater coral reef dweller), the krait has put its land-dwelling roots behind it and moved out into the ocean—although it remains an air-breather like all snakes and it must also come ashore to drink freshwater since it has not yet evolved the super kidneys necessary for dealing with saltwater. Yellow-lipped sea kraits are widespread throughout the Indo-Pacific Ocean.  They grow up to 2.2 meters (6 and a half feet long).

Laticauda colubrina

An accomplished hunter, the banded sea snake lives on cuttlefish, squid, fish, fish eggs, and small arthropods which throng the shallow reef.  The krait’s venom is among the most poisonous on earth, but fortunately the creatures have easy going dispositions (and small fangs) and they rarely bite humans.  Their closest relatives among the land snakes are the cobras.


Yellow-lipped sea kraits shed their skin far more often than do land snakes in order to protect themselves from parasites: sometimes they change skins as often as every fortnight.  Kraits are viviparous and do not bear eggs but rather give birth to completely autonomous baby snakes which are born with their parents’ swimming and hunting ability.  The snakes are such gifted swimmers thanks not just too their sinuous bodies but also to laterally compressed tails which they use like paddles to propel themselves through the water. Another feature which the kraits possess to deal with their watery habitat is nostrils which clamp shut
The kraits are extremely beautiful: their bodies are banded with black and pale blue rings.  They have a balck head with a yellow snout. Their beauty gives them a special place in art and literature.  I like to imagine that the yellow-lipped krait was one of the mysterious beautiful “water-snakes” who caused the ancient mariners unconscious epiphany which broke the curse he labored under and marked the climax of Coleridge’s The Rime of the Ancient Mariner (a profoundly beautiful miniature epic about the importance of treating animals kindly):

Beyond the shadow of the ship,
I watched the water-snakes:
They moved in tracks of shining white,
And when they reared, the elfish light
Fell off in hoary flakes.

Within the shadow of the ship
I watched their rich attire:
Blue, glossy green, and velvet black,
They coiled and swam; and every track
Was a flash of golden fire.

O happy living things! no tongue
Their beauty might declare:
A spring of love gushed from my heart,
And I blessed them unaware:
Sure my kind saint took pity on me,
And I blessed them unaware.

Banded Sea Snake (Jennifer Belote, acrylic on canvas)

Crescent-shaped rudists on the floor af a Cretaceous Sea

When we think of living reefs we are likely to think of coral reefs, since the biotic reefs of today are most often composed of cnidarian corals (and coralline algae).  Such has not always been the case –convergent evolution means that other animals have sometimes jumped in and taken over the central reef building role occupied today by corals (indeed there are still oyster reefs in some parts of the ocean although human hunger for oysters has greatly reduced their size).  One of the more interesting and successful of these coral analogs was actually a modified colonial mollusk—the rudist.  Rudists were bivalve mollusks very similar to the clams you enjoy on your linguini.  Like clams, rudists had two shells (or valves) joined at a hinge. However the rudists possessed very different shapes from modern clams.  Some had horn-shaped shells which lay flat on the bottom of the ocean shore (the horns prevented currents from flipping the mollusks or washing them away).  The other major group had cone-shapes with little hinged lids on top –like a cross between a lidded beer stein and an ice-cream cone).  This latter group formed together in huge super colonies.

Rudist Types (with a modern bivalve in the top left for comparison)

Rudists evolved in the Jurassic Era and burgeoned throughout the Mesozoic, but their greatest success came during the Cretaceous when they pushed out corals and sponges to become the major reef-building organisms in the Tethys Ocean and various other warm tropical shelves around the world.  It is believed that rudists were so successful because the ocean’s temperature was so much higher during the Cretaceous (as was the salt content of the water).  It must have been amazing to see a rudist tropical reef thronged with strange colorful belemnites, ammonites, and unknown teleosts.  Huge prehistoric diving birds, mosasaurs, and super sharks would have lurked in the depths beside the reef.

A Fossilized Rudist Reef from the Cretaceous Era

Like the dinosaurs and the ammonites, the rudists were wiped out by the Chicxulub impact. Sometimes I think about the rudists as I fret about coral die-offs.  Coral quickly evolved back into the warm shallow tropical niche left open by the extinction of the rudists.  Is there some little clam with a big destiny waiting for the corals to falter in the ever-warmer, ever-more-acidic oceans of the present?

The Spanish Dancer, Hexabranchus sanguineus (photo by David Doubilet, National Geographic)

Nudibranchs are among my favorite animals to look at.  These tropical marine mollusks feature extraordinary colors and fantastical shapes which would make the most flamboyant nineteen eighties rock star weep with envy. One of the largest and most powerful nudibranchs is also one of the most beautiful.  Hexabranchus sanguineus lives thoughout the tropical waters of the Indo-Pacific Ocean and can be found from the Red Sea to Hawaii. The creature’s common English name is the Spanish Dancer because, when it swims free, it undulates its bright red paradodia in the manner of a flamenco dancer.

A Spanish Flamenco Dancer

Hexabranchus sanguineus

Although the Spanish Dancer is surprisingly quick and agile when it uses this means of locomotion, it has an auxiliary method for getting around and can also be found crawling in a much more traditional slug-like manner.  The creature grows to be 40 centimeters or larger and has several distinctive color patterns ranging from bright red to bright yellow to pale pink (or sometimes various combinations of these colors).

The Spanish dancer can afford to be extravagantly colorful because it contains toxic chemicals inside its body (again one is drawn to comparisons with 1980’s musical entertainers).  Predators therefore avoid the creature as it proceeds about the reef feeding on various sponges and bryozoans.  Spanish Dancers are hermaphrodites.  Although each Spanish dancer possesses the reproductive organs of both genders, it is very rare for an individual to fertilize itself.  When they do mate, the parent carefully deposits a large pink rosette of eggs which is almost as distinctive and lovely as the adult.

The Egg Rose of a Spanish Dancer (photo by Peter Korn)

The Spanish dancer is sometimes inhabited by one or more Emperor Shrimps.  These little arthropods do not help their mollusk host, but neither do they harm it (a commensal relationship). Chameleon-like the little shrimp can adapt to the extraordinary coloring of their vivid hosts.

An Emperor shrimp living on a Spanish Dancer (photo by Goos van der Heide)

Plotosus lineatus

The Striped eel catfish (Plotosus lineatus) lives in the reefs of the Indo-Pacific ranging from the Red Sea to Australia up to Japan.  The Plotosus genus of catfish are notable for abandoning freshwater (where catfish evolved and where the majority of catfishes live) in favor of the oceans.  Plotosus lineatus is entirely oceanic: the species makes its home in the colorful and dangerous  world of the coral reef. Young Striped eel catfish live in schools which can be composed of hundreds of fish however older individuals lose their schooling instinct.

The catfish grub through the sand for tiny invertebrates, shrimp, and minnows. They possess electrosensory organs which allow them to sense the prey’s nervous system beneath the sand. Although they are very endearing walking along the sand on their little whiskers, you should not pick them up!  These catfish have venomous spines on both sides of their body.  The poison is acutely painful but not always lethal for adult humans.

A river of baby catfish on the reef

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