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Ferrebeekeeper has presented catfish which live beneath the water table, chickens which look like they have no head, 600 pound turtles, clams which have been alive since the 17th century, and turkeys which give virgin birth…not to mention the “King of Herring” the world’s longest bony fish. We are no strangers to strange creatures! But today we come face to face (?) with what might be the strangest creature of them all! Steel yourselves for a creature which is literally made of metal! [crazy metal guitar solo]

And here it is! Behold the scaly foot gastopod (Chrysomallon squamiferum) a tiny snail [5 cm] which lives in the Indian Ocean!

Um, maybe I need to add some context to help explain why this small drab mollusk is so exceedingly strange. First of all, the scaly foot snail is a creature of the deeps: the snails live on (in? around?) deep sea ocean vents which are at least 2,400 meters beneath the ocean surface. Specimens have been discovered as deep as 2,900 meters below sea level. In British Imperial measurement that is 1.5 to 2 miles underwater! And these snails live on/in/around hydrothermal vents where water temperature can reach 400° Celsius (about 750° Fahrenheit) and where oxygen is scarce and yet hydrogen sulfide is abundant. In case all of this was not unusual enough for you, the snails are all simultaneous hermaphrodites (meaning they have complete functioning sets of reproductive organs of both genders and frequently self-fertilize).

Yet the strangest thing about the scaly foot snail is what it eats: nothing! Or to be more specific the adult creatures are obligate symbiotrophs–the snails live on the secretions of gammaproteobacteria which live within their oesophageal glands. The bacteria are extremophiles which metabolize the chemical rich waters of the vents. These snails do not live directly or indirectly from photosynthesis!

The snail’s signature feature may be its armor. The shell is a three level composite of iron sulfide on the outside, protein in the middle, and calcium carbonate on the inside. Like wise the snails’ sensitive feet are covered in composite nodules of iron sulfide and protein. All of this armor keeps the little snails safe from the predators of the vent ecosystem–strange crustaceans which look like furry white lobsters and larger predatory snails. I wrote briefly about this snail about a decade ago, when I concentrated more on the uniqueness of its armor. Back in those days we thought that nothing could possibly harm the scaly-foot snail, a creature which I imagined to be perfectly safe in its own little alien world at the bottom of the ocean (except for occasional predation by those larger snail, of course). But Earth’s greediest animal has a habit of getting everywhere and lately the scaly foot snail has been endangered by deep sea mining operations which aim to harvest the rare and valuable minerals around deep sea vents. It is hard to believe that our arms have grown long enough to harass these poor little weirdos in their little suits of armor a mile and a half beneath the waves, but, frankly I may have misspoke about which animal is really the weirdest

A Black Smoker Geothermal Vent

A Black Smoker Geothermal Vent

The African Plate and the Indo-Australian Plate meet together deep beneath the surface of the Indian Ocean in a long line of tectonic divergence known as the Central Indian Ridge (CIR).  As new seafloor is created hydrothermal vents pour out molten hot fluids rich with minerals and an alien landscape is formed.  The hot minerals precipitate to form high cylindrical chimneys called smokers and strange communities of life form along these structures.  This ecosystem is entirely based upon chemosynthetic archaea (ancient one-celled life forms which take energy directly from the oxidation of inorganic compounds).  Great communities of eyeless shrimp, giant tubeworms, and annelids support themselves on the archaea.  Among the strange creatures is a very weird gastropod mollusk, the scaly-foot snail (Crysomallon squamiferum), which is different from every other mollusk (and indeed every other animal) because of the material it uses for its bizarre scale-mail armor.

The Scaly Foot Gastropod (Crysomallon squamiferum)

The Scaly Foot Gastropod (Crysomallon squamiferum)

The scaly foot gastropod has an armored foot which is covered in little scales made of iron sulfides.  Additionally the deep-sea snail has a triple layer shell.  The outermost shell layer is composed of iron sulfides, the middle is a thick protein coat, and the inner shell layer is composed of aragonite (a calcium carbonate).

I wish I could tell you more about the habits of this snail but since it is found in super heated water at the bottom of the Indian Ocean, it has not been extensively studied.  However, The US military is interested in the creature as a possible inspiration for next generation composite military armor so maybe we will all learn more about the scaly foot snail.

Detail of the Foot Armor of Crysomallon squamiferum

Detail of the Foot Armor of Crysomallon squamiferum

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