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Clouds of reef fish and corals at Papahānaumokuākea Marine National Monument.

Clouds of reef fish and corals at Papahānaumokuākea Marine National Monument.

I know I just did a post on National Donut Day, but that piece was both tongue-and-cheek and nakedly self-interested.  Clearly donuts are ephemera with transient importance—scraps of fried dough which stay tasty for less time than flowers bloom (indeed I enjoy juxtaposing their cheap impermanence with the vast seemingly eternal universe in my paintings).  Today I looked at my calendar to find that June 8th is World Oceans Day!  Unlike National Donut Day (which is self-evidently a meretricious marketing “holiday”), World Oceans Day strikes me as an important and worthwhile day of observance.  The ancients celebrated the oceans with festivals and sacrifices to venerate the sea gods.  We tend to regard the oceans as an inexhaustible source of cheap fish and a place to dump our rubbish.  I worry that the careless industrialized spoiliation of the oceans is the gravest mistake humankind is currently making (and we have our grubby grasping fingers in lots and lots of pies—and are making plenty of errors).  Yet, I don’t want this blog to become an angry jeremiad or an environmentalist harangue.  I want to celebrate the beauty and grace of the oceans and their inhabitants while also underlining the stress and danger which these vast swaths of the world are facing.  What to do?

An infestation of Crown-of-Thorns Starfish

An infestation of Crown-of-Thorns Starfish

For World Ocean Day therefore I am writing about the lifeform which, to me, most exemplifies the oceans of the late Holocene/early Anthropocene, the crown-of-thorns starfish, Acanthaster planci. This echinoderm is a ravenous poisonous destroyer which is exploiting the sickness of the oceans to proliferate and succeed wildly (at the expense of everything else).  It is an amoral ravenous monster covered with toxic spines which is eating the coral seas bare.  It is also a beautiful creature magnificently evolved to thrive—we can hardly hold its horrifying success against it.  Maybe it should be on the cover of Forbes smoking a cigar and bloviating about its philosophy of success.  By chance the starfish also lies at an intersection of many blog topics—crowns, invaders, colors, poison, mollusks (for its fate is connected with that of predatory mollusks), opinion, and science…perhaps even “deities of the underworld”.  This is a lot of introduction…let’s meet our antihero!

Crown of Thorns (Acanthaster planci) photo by jon hanson

Crown of Thorns (Acanthaster planci) photo by jon hanson

The crown-of-thorns starfish (or “sea star”), Acanthaster planci takes the form of a spiked disk with up to 21 prehensile arms (also covered in spines). On its underside, the starfish has numerous sticky tube-like suction feet running along the bottom of each arm. These legs run in parallel rows beside a series of closely fitting plates which form a central groove on the bottom of each arm.  The arm grooves each run ominously into the starfish’s horrifying stomach/mouth.  The starfish can grow to a diameter of up to 80 centimeters (31 inches) although they are more commonly found in the 35 centimeter range.  Acanthaster planci has a wide Indo Pacific range and lives in tropical and semitropical coastal waters from the Red Sea and the East Coast of Africa across both the Indian and Pacific Oceans all the way to the West Coast of Central America.  The starfish are usually dull grays and reds but they can range to brilliant purple, blue, orange, aqua (or display all sorts of mixed ranges). Their colors are highly mutable and variable! crown-of-thorns-starfish These starfish eat coral polyps!  It crawls into corals by means of its many sucker feet—compressing or elongating its body as needed.  When in position the starfish extrudes its stomach over the polyps it wishes to eat: the stomach can cover an area approximately equal to the starfish.  The creature then releases digestive compounds which dissolve the soft parts of the coral into a soup which the starfish slurps up.  It then retracts its stomach and moves on, leaving a bleached (i.e. dead) patch of coral skeleton.  A medium sized starfish can consume up to 6 square meters (65 sq ft) of living coral reef per year.  If times are lean the starfish can go for months (or longer) without eating. http://www.arkive.org/crown-of-thorns-starfish/acanthaster-planci/video-00.html Crown-of-thorns starfish are male or female and they do not reproduce by budding, but female starfish lay from 6.5 million to 14 million eggs each per breeding season [hereupon the author wiped his furrowed brow].  When the eggs hatch there are several interesting larval stages which the echinoderm goes through before reaching their adult form.  Suffice to say, the starfish reaches sexual maturity after 2 years and it lives as long as 8 years. Fourteen million offspring per season is a lot!  If predators do not keep the crow-of-thorns starfish in check, they can swiftly overrun entire reef systems and eat all the coral into bleached uninhabitable wasteland.  This leaves all of the multitudinous reef inhabitants homeless.  The reef skeletons dissolve in our newly acidified oceans and one of earth’s most diverse ecosystems becomes a weed-strewn graveyard. The starfish are hard to stop since they are provided with tremendous defenses: each animal is covered with 1-5 centimeter long razor sharp spines which in turn are covered with toxic saponins—soaplike chemicals which interact with cholesterols to tear holes in cell membranes.  The starfish can regenerate arms.  If removed from the water, the starfish develops holes in its body and loses its water, but it can swiftly reconstitute itself if placed back in the ocean.

Crown-of-thorns starfish wash up in Japan (BBC)

Crown-of-thorns starfish wash up in Japan (BBC)

Fortunately there are some tough predators of the crown-of-thorns starfish.  Certain triggerfish, parrotfish, and blowfish can insouciantly crunch through the spines with hardened mouths.  Painted shrimp and polychaete worms can tear off and eat pieces of the starfish until the latter dies (whereupon the impatient scavengers devour the corpse).  Best of all, the magnificent Triton’s trumpet, a huge gastropod mollusk, can rasp the odious starfish to pieces with its sharpened radula and suck up the offending echinoderm!  Unfortunately, the fish are vanishing into the aquarium trade or the soup pot and the tritons have been killed en masse so their shells can be sold to tourists.  This results in a feedback loop wherein the crown-of-thorns devastate a reef to the extent that the predators can not survive at all.  The plague of starfish then descend of virgin reefs and kill them off too.

A plague of crown-of-thorns starfish (Photo: AFP/Getty Images)

A plague of crown-of-thorns starfish (Photo: AFP/Getty Images)

Healthy reefs have a certain ability to fight off the crown-of-thorns star, but today’s reefs are coping with overfishing, invasive creatures, acidification, pollution, and fluctuating temperatures.  The crow-of-thorns is exploting these weaknesses (and the diminished stock of its predators) to run rampant.  Humans have stepped in late to try to kill of the rampaging multi-armed villains, but, for all of our skill at doing in other organisms, we seem to not be very good at killing these fiendish starfish.  They are difficult to rip apart.  They are hard to net or trap.  They are surprisingly resistant to punctures.  Recently divers have had success suppressing infestations by injecting the starfish all individually with sodium bisulphate (which echinoderms and my great uncle cannot abide, but which is relatively harmless to most other lifeforms).   Obviously this is an expensive and labor intensive solution (although if somebody wanted to hire me as a starfish bounty killer, I would not decline).

New frontiers of pest control (via DIVE QUEENSLAND)

New frontiers of pest control (via DIVE QUEENSLAND)

The common name of the crown-of-thorns starfish is a reference to Christian mythology.  One of the tortures endured by Jesus was a crown woven of thorns (which pierced his temple and hurt him while simultaneously mocking his alleged crime—pretending to the throne of Judaea).  Throughout Christian art, the crown of thorns is the supreme crown of the king of kings which he wears during the passion or as he harrows the underworld.  The voracious starfish earned its sobriquet not by godliness, but by looking like a horrible alien crown made of thorns (and arguably also by bringing death and devastation to coral reefs).  I find it to be one of the most poetic and horrifying common names in all of taxonomy—and as the starfish destroys ecosystem after ecosystem, it seems fully earned.

A giant triton snail feeding on crown-of-thorns starfish. Image supplied by Australian Institute of Marine Science

A giant triton snail feeding on crown-of-thorns starfish. Image supplied by Australian Institute of Marine Science

Angolan Coral Snake (Aspidelaps lubricus cowlesi)

Angolan Coral Snake (Aspidelaps lubricus cowlesi)

I promised to flesh out last week’s Angola post with an entry concerning the animals and culture of that West African nation. Although the greater kudu can be found in Angola, it lives in such a broad swatch of Africa, that I don’t feel I have satisfied the requirement. So today, allow me to present a very Angolan animal—the Angolan coral snake (Aspidelaps lubricus), which lives in the Namib Desert of southern Angola and on down through Namibia into South Africa. Well, actually, the Angolan coral snake is technically Aspidelaps lubricus cowlesi—a subspecies of the Cape Coral snake, but the appearance, habitat, and behavior of the animals within the same species is so similar, that I am not sure the distinction is meaningful except maybe to people onsessed over minor differences in snake coloration.

The Cape Coral Snake (Aspidelaps lubricus)

The Cape Coral Snake (Aspidelaps lubricus)

 

Aspidelaps lubricus perfectly illustrates how coral snakes and cobras are in the same family, the Elapidae. This little snake has coral snake stripes & a cobra hood. Adult snakes only grow to 60 cm (2 feet) in length and they spend a great deal of time underground. The snakes live in arid scrublands and along the edges of deserts where they feed on small rodents, lizards, insects, and strangely fish (if they can find them). The venom of Aspidelaps lubricus is a dangerous neurotoxin—but the snake is small with little fangs and not very aggressive. To date it has never caused any human deaths (although it still might be a mistake to pet it like a small dog or a guinea pig).

A Giant Triton (Charonia tritonis) on an Indonesian Reef

A Giant Triton (Charonia tritonis) on an Indonesian Reef

Yesterday this blog took us to the depths of space to explore the frozen ice-moon of Triton.  Today we atone for that cold voyage with a trip to the inviting tropical seas of the Indo-Pacific.  In these vibrant waters can be found one of the greatest living gastropods, a prince among predatory sea snails, the mighty Charonia tritonis, (commonly known as the giant triton or Triton’s trumpet).

A Giant Triton climbs over a pillow coral in Hawaii

A Giant Triton climbs over a pillow coral in Hawaii

Charonia tritonis grows to over half a meter (20 inches) in length: it is one of the largest living snails in the world (and it is not much smaller than the biggest extant snails). Equipped with a powerful muscular foot, acute senses (particularly smell), and an agile tentacle-like proboscis, the snails are formidable hunters.  Additionally they are protected from predators—even big fierce ones–by their beautiful spiral shells which are vibrantly colored orange, brown, yellow, and cream.  Of course such a shell would become a liability for the snail if an animal ever evolved which killed the snails in order to harvest the magnificent shells solely for their beauty (but what are the chances of that?).

A man sounds a blast on a triton shell--which has spiritual significance in Hawaii

A man sounds a blast on a triton shell–which has spiritual significance in Hawaii

Giant tritons hunt at night.  Their main prey are echinoderms—starfish, which can be large powerful and armored.  Fortunately the snails are not just equipped with powerful muscles and superior brains.  They also have salivary glands that produce sulfuric acid AND a chemical which paralyzes starfish.  The tritons find starfish—even big spiny poisonous starfish like the invasive and all-consuming crown-of-thorns which bedevils the reefs of the Indo-Pacific—then hold them down and inject saliva into them.  As the starfish dissolves from within, the snails rip them apart and feast!

A triton kills a crown of thorns

A triton kills a crown of thorns

Tritons have a specific gender—they are male or female.  They seek each other out for courtship and the female then lays a large clutch of eggs.  When the eggs hatch, the young snails become part of the oceanic plankton for a (poorly understood) time before developing into adults.  Triton shells are esteemed by many cultures as sacred musical instruments.  The shells themselves are collector’s items and are arguably better known then the formidable long-lived predators which make them.  Although the snails are not threatened with extinction as such, there are fewer and fewer really big adult ones (or even small ones) on today’s reefs. This is a real shame, since those same reefs are being devoured by the horrible crown-of-thorns. Hopefully a new generation of divers and wildlife enthusiasts will appreciate the triton on the reef and leave them to their invaluable hunting.  Resist the urge to buy the beautiful shells and help save the reefs of the Indo Pacific!

Charonia_tritonis_a1

Texas Coral Snake (Micrurus tener)

Many reptiles and amphibians are beautifully colored, particularly the poisonous ones. When I was growing up, I had a set of field guides of the creatures of North America.  Of all the land animals of North America, the animals which I thought were most beautifully colored were the coral snakes. Coral snakes constitute four genera of snakes within the family of elapid snakes (cobras, mambas, sea snakes, kraits, and other poisonous snakes from warm climates).  Many coral snakes live in South America and the old world (where some coral snake species are evolving into sea snakes), but I’m going to stick to writing about the gorgeous red, yellow, and black coral snakes of North America.  These snakes are brightly colored to warn potential predators that they are extremely venomous.  This strategy has failed somewhat when it comes to intimidating humans, who have a collective fascination with pretty colors.

Eastern Coral Snake (Micrurus fulvius)

There are three coral snakes which live in the United States.  The eastern coral snake (Micrurus fulvius) ranges from North Carolina to Texas (including Florida and the Gulf Coast swamps). The Texas coral Snake (Micrurus tener) ranges from northeast Mexico up through Texas, Louisiana, and Arkansas.  The Arizona coral snake (Micruroides euryxanthus) lives in the Sonoran desert through Southern New Mexico, Arizona, and Sinaloa.  All species of coral snakes in the United States can be identified by the fact that their red bands touch the yellow bands (which is in marked opposition to mimics like king snakes and milk snakes).  Coral snakes from Central/South America and from Asia do not always follow this rule: the black bands can sometimes touch the red bands, or the bands can be colors other than red, yellow, and black–or there might be no bands at all!

Arizona Coral Snake (Micruroides euryxanthus)
Photographer: Wayne Van Devender

Coral Snakes are fossorial predators which spend most of their life just beneath the leaf litter or loose topsoil where they hunt lizards, frogs, insects, and smaller snakes.  Baby snakes are 18 centimeters (7 inches long) when they hatch from their eggs. Adult snakes can grow to 0.6 meters (2 feet) in length. Coral snakes can live up to seven years in captivity.

Coral Snakes are extremely poisonous, but they are also shy and retiring. Instead of hanging around biting, they would prefer to escape as quickly as possible.  This makes sense from the snake’s perspective, since their fangs are very tiny and they have to chew directly on their prey in order to inject a fatal dose.  Since they have tiny mouths, it is not necessarily easy for them to score a direct bite on humans.  Additionally their venom acts slowly—at first there is only a mild tingling associated with the bite. Lethargy, disorientation, and nausea set in hours later.  In extreme cases, coral snake bites can cause respiratory arrest.  Fatal bites are extremely rare: most sources state that nobody has been killed by a coral snake in the US since antivenin was released in 1967 (although I also found allusions to a 2009 case where a man laughed off a bite only to die hours later).

A coral snake’s little teeth.

Coral Snake antivenin was solely manufactured by one US drug company, Wyeth Pharmaceuticals (now a wholly owned subsidy of Pfizer Inc.). In 2003 Wyeth ceased manufacturing coral snake antivenin since too few people were bitten to make the product profitable.  There is still a small supply left on hand (although the expiration date has been extended twice), but Pfizer does not seem to have any intention of pursuing a microscopic niche market when it has more profitable businesses to pursue.  Foreign pharmaceutical companies continue to produce coral snake antivenin, but they do not sell it in the United States because of prohibitive licensing and regulatory costs (hooray! the United States health care system is unsolving problems which were figured out 40 years ago!).

Actually Wyeth just doesn’t want to save this guy.*

*Don’t be this guy.

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?

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