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Earth’s oceans today are defined by the disasters and exigencies of the past. When you dip a net in a shallow tropical sea it does not emerge from the waves seething with conodonts…because they died out completely during the Triassic. You could fish from the beach every night from now until the sun burns out and never catch another belemnite nor see an Archelon drag her 5 meter carapace from the sea to lay her eggs. Past disasters (and the constant ebb and flow of evolution) have removed some of the core cast from the great drama. Yet the oceans are vast: sometimes we find that an organism known only from fossils and presumed long lost has been swimming around the Comoro Islands or living in an ancient grove in Hubei. Today’s post involves a “living fossil” of this sort, but this creature was presumed lost for longer than the lobe-fin fishes or the purple frog.
This is a fossil monoplacophoran, a strange ancient superclass of single shelled mollusks which thrived in the ancient oceans of the Palaeozoic (or earlier) but then was known only through fossils. I can understand if you are shrugging about some primitive snail/limpet thing–but, my friend this is no gastropod–it is an entirely different class of mollusk which was presumed to have died out 380 million years ago. A look at the (long and complicated) taxonomy of monoplacophorans on Wikipedia is like looking at a World War I cemetery (extinct taxa are noted with a funereal superscript cross).
Yet, scientists came to discover that not every name on the list had a cross. The monoplacophorans never fully died out. They just moved to the bottom of the oceans and stayed there for the long ages as continents drifted across the world and dinosaurs came and went. As mammals scurried out of burrows and across the world, the monoplacophorans lived their ascetic lives upon the floor of the ocean. They are still there right now, as you read these words! If you look at a picture of the colorless gray ocean bottom, you will see colorless gray ovals–the monoplacophorans (their very name makes them sound like some implacable cthulu-ish monk)
It is funny to me that ancient fossils in 400 million year old rocks were more accessible to scientists than the bottom of the ocean up until about the time I was born. Yet, since then, the bottom of the ocean has become closer as humankind’s ever-grasping arms have become longer. Lately our robot probes have reported a bit of summery warmth at the cold ocean bottom. And mining cartels are eagerly pushing to vacuum of nodules of precious ore upon the distant seabed. I truly wonder if we could look 380 million years into the future whether we will still find these tough little eremites still going about their business in the crushing depths? Or will the field of taxonomical crosses finally be complete, with these ultimate living fossils turning into yet another victim of our insatiable appetite?
This is Danilia octaviana, a tiny marine gastropod of the family Chilodontidae (the mollusk family Chilontidae—because of a taxonomic mishap, there is apparently a fish family of the same name). Danilia octaviana throughout the Mediterranean Sea (and in the Atlantic near the mouth of the Mediterranean). It is a tiny snail. Adults measure between 7 and 11 millimeters (about a third of an inch). It scrapes up algae and microscopic plants and bacteria with its radula, and is in turn eaten by numerous predators of all different stamps. There is nothing remarkable about Danilia octaviana: there are thousands of small snails like it which live at the margin of our attention (although that perhaps is remarkable, in its own way). Based on information on the internet, is a bit unclear whether the snail is currently alive or not (the photo above makes it seem like it is a fossil, but some sources speak about it today). I post it here because I think it is surprisingly beautiful and interesting as a textured sculptural whirl.
(Picture: AFP/Getty Images)
Every day, major news outlets pick up a few trivial “offbeat” stories in order to pad out the international mayhem, barely concealed commercials, punditry, and celebrity gossip which constitutes the news. One such puff-piece in the news today features the story of a spa in Tokyo which is offering snail facials. Apparently credulous yet affluent Japanese women can pay to have snails crawl on their face for approximately an hour. The snails are fed on organic carrots and greens so that their mucous–and whatever else passes out of them–will be, well, organic.
There is a rationale behind this wacky beauty regime. Snail slime contains hyaluronans (aka hyaluronic acids), long unbranched polysaccharides found in animal tissues which promote healing and flexibility. Hyaluronans have been found to play a major role in wound healing and it is a major component of cartilage and skin (they are also implicated in the prevention of cancer—and malfunction of hyaluronan-producing cells is likewise implicated in cancerous mutagenesis). Cash-seeking dermatologists have long used hyaluronan as a “filler” to inject into skin to minimize the appearance of wrinkles and as a relatively inert ingredient in their creams and unguents, however recently hyaluronans made the news in an even bigger way with a fascinating, albeit erudite article about the longevity of naked mole rats. You can read the actual research abstract here, but ABC News more concisely summarizes the possible implications of the research by writing, “Last month, researchers at the University of Rochester wrote that naked mole rats’ super-long hyaluronan molecule actually tells cells to stop reproducing, which is why they think naked mole rats don’t get cancer.”
Heterocephalus glaber: The naked mole-rat
Unfortunately, whatever actual importance hyaluronans have in the human body (and whatever importance super long hyaluronans have for the doughty naked mole rat), it does not seem that being coated in snail mucous necessarily has much benefit. Dermatologists aver that, as the snail slime (which may be of dubious benefit anyway) simply lies on top of the dead waterproof dermis, it cannot have much if any magic mole-rat age-reducing effect. That still doesn’t deter desperate people who let gastropods crawl all over their face in a quest for eternal youth.
The Common Limpet (Patella vulgata)
Limpets are gastropods with simple cone-shaped shells. The majority of limpets are herbivores which live by grazing up films of algae by means of radula—an organ which is a tongue covered in rows of teeth. The most salient feature of limpets is their incredible tenacity. They cling to rocks and other haed surfaces with incredible tenacity—to such an extent that they have become synonymous with tenacity and obduracy. Brute force will not compel a limpet to stop clamping to a favored surface and the animal will allow itself to be destroyed before giving up its grip.
There are a number of limpet-like gastropods but the true limpets are named Patellogastropoda. The majority are tiny—less than 8 cm (3 inches) although a few larger species are known. Some limpets have a “home scar” on their favorite rock—a niche which fits them carefully and where they are perfectly camouflaged. Such limpets tend to be territorial and will fight for the grazing rights to algae near their scar.
Although limpets are most familiar to people at the tidal line (where rockbound limpets survive above the low tide line by adhering to rocks and tightly maintaining moisture) the creatures exist in numerous different marine ecosystems, including the depths of the sea, coral reefs, whale skeltons, seagrass forests, black smokers, and cold seeps. The deepwater limpets are probably detritivores. Limpets begin sexual life as males, but when they mature to a couple of years old they turn female. Young limpets undergo a brief larval stage before clamping down on a hard surface and stating to graze or forage.
A limpet shell pillbox
Biologists estimate that there are approximately 8.8 million species of eukaryotes (animals with complex cell structure) currently alive on Earth. So far, humankind has only cataloged 1.9 million species and entire biomes remain largely unknown to us.
Unknown Order of Nudibranch Sea Slug swimming in the depths off Monterey (Image Credit: NOAA/Monterey Bay Aquarium Research Institute)
To illustrate this point, here is a photograph of a completely unknown genus of nudibranch mollusk photographed 1 mile beneath the surface of the ocean near Davidson seamount (which is an extinct underwater volcano just off the coast of Monterey). I wish I could tell you more about the strange mollusk, but this photograph, taken from a robotic deep sea submersible in 2002 is pretty much all that humankind knows about this species. The mission photographed a huge number of other gelatinous creatures in the middle depths of the ocean, and in fact caused scientists to rethink the importance of such animals in the oceanic ecosystem. The Monterey Bay Aquarium Research Institute (MBARI) worked on the mission with the National Oceanic and Atmospheric Administration. Their website explains the robotic study by paraphrasing Bruce Robinson, an ecologist who pioneered the use of robot submersibles:
One of the most important discoveries has been the realization that gelatinous animals are important as grazers and predators that comprise a large percentage of the open ocean animal biomass. Robison estimates that gelatinous animals make up about 40 percent of the biomass in the deep sea water column.
Nudibranch mollusks are largely thought of as colorful predators of the tropical reef, so it is a big deal if they (together with other floating mollusks, cnidarians, and siphonophores) constitute such a substantial percentage of the biomass of the largest portion of the ocean. As an unscientific postscript I think the delicate translucent nudibranch is very beautiful with its alien and ghostlike (and, yes, gelatinous) features.
The same mollusk (Image Credit: NOAA/Monterey Bay Aquarium Research Institute)
The Mountains of Antarctica as seen from the Southern Ocean
The great Southern Ocean which swirls in a clockwise circle around Antarctica is home to many of the Earth’s largest animals. Blue whales come here to gorge on vast schools of krill. Among the icebergs and the towering waves, southern elephant seals (the largest member of the order Carnivora) fight duels to build their harems, and highly intelligent killer whales hunt together in pods. There are populations of sperm whales living in the Southern ocean as well and these leviathans dive to the cold floor of the world hunting for the world’s largest mollusk, a huge cephalopod which can only be found in the Southern Ocean. In fact this bizarre creature, the colossal squid (Mesonychoteuthis hamiltoni) is also the world’s largest invertebrate. Also known as the Antarctic squid or the giant cranch squid, the colossal squid lives in the abyssal depths. Unlike other squid, the colossal squid does not have tentacles–its powerful arms are studded with sharp hooks (much like the long-extinct belemnites). Some of these hooks swivel while others have three barbs in the manner of a fish spear.
The Colossal Squid (Mesonychoteuthis hamiltoni)
The measurements of the colossal squid are staggering. Its eye alone (the largest of any known creature) measures 27 centimetres (11 in). A fully grown adult squid is estimated to be 12–15 metres (39–49ft) long. Although giant squid have longer tentacles, the colossal squid a long stout mantles and are thus much more massive. Their upper weight limits are unknown but are well over 500 kg (+1000 lbs).
The colossal squid is believed to be an ambush predator, which lurks in the depths waiting for chaetognatha, other squid, and benthic fish (such as the Patagonian toothfish) to pounce upon. It is hypothesized that they have a slow metabolism and do no need great reserves of food (unlike the energetic endothermic sperm whales which prey on them). The colossal squid are believed to be sexually dimorphic—the females become much larger than the males.
A rare specimen of colossal squid
There is a reason that so much of this article is couched in ambivalent language such as “estimated”, “believed” and “probably”: colossal squid live in an environment where humankind can barely venture. The colossal squid are fast enough and clever enough to usually evade our nets, lines, and traps (although fishermen trying to catch Patagonian toothfish hooked a 450 kg (990 lb) specimen which was about 39 feet (13 m) long). Additionally our submarines and submersible robots are too slow and noticeable too stalk the squid in the abyssal depths. Other ocean creatures do not suffer from the same problem. Juvenile colossal squid are eaten by beaked whales, elephant seals, sharks, toothfish, and even albatrosses, however the adult squid are so large that only massive sleeper sharks and giant sperm whales can threaten them. Sperm whales are often covered with scars from their battles with the giants but the whales easily have the upper hand. Sperm whale stomachs have been found filled with hooks and beaks (which coincidentally were much larger than those found on the largest squid specimens recovered by humans to date).
Pinna nobilis growing in the wild
Luxury fiber is a strange thing. Linen comes from flax (which has some legitimate claims to being the first domesticated plant). Silk is derived from the cocoons of lepidoterans. Qiviut comes from the undercoats of musk-oxen. One of the rarest of all luxury fibers comes from an even more peculiar source. “Sea silk” is produced by collecting and spinning the long micro filaments or “byssus” secreted by several kinds of bivalve mollusks–expecially Pinna nobilis (a large saltwater clam once widespread in the Mediterranean ocean). Pinna nobilis can grow up to a meter (3 feet) in size and anchors itself to the ocean floor with an extremely fine fiber it excretes from a land in its foot.
A Pinna nobilis shell and naturally colored sea silk gloves
The fiber was mentioned in various Greek, Egyptian, and Roman sources (and an analog seems to have existed in ancient China) but differentiating sea silk made from mollusk fibers from similar luxury fibers like cocoon silk, or fine linen seems to be more a matter of context rather than of terminology. Sea silk is finer than the true silk produced from silkworm cocoons. It was said that a pair of ladies’ gloves made of sea-silk could be folded into one half of a walnut shell because the fiber was so profoundly delicate. Sea silk was warm and durable but it was infamous for attracting clothing moths. A few pieces have survived in museums including the extraordinary mediaeval chasuble of St. Yves pictured below.
The chasuble of St. Yves in Louannec (woven of byssus/sea silk)
Unfortunately the Pinna nobilis clams which are the source of byssus fibers have declined rapidly in number thanks to overfishing, pollution, and the general decline of the Mediterranean sea-grass beds. Other fibers like seaweed based cellulose or watered silk have adopted the “sea silk” name further confusing the issue. Today the sea silk industry only barely survives in Sardinia where a handful of aging practitioners keep it alive–more for tradition’s sake than economic reward.
Chiara Vigo, one of the last sea silk textile masters
Ferrebeekeeper has written a lot about how long trees can live. Individual yew trees can survive for thousands of years, bristlecone pines can live even longer, and clonal entities like Pando, a super-colony of quaking aspen, can potentially live for hundreds of thousands of years. Likewise colonial animals (coral, gorgonians, tubeworms, and so forth) tend to live the longest—although the constituent individuals come and go. Yet colonial animals frustrate our selfish human perception of the world. When we talk about an organism we mean an individual, and in this category, the world’s longest living animal comes as a surprise!
Arctica islandica
As you read this, somewhere, off the coast of Greenland or Virginia there is a smug little clam which was alive when Oliver Cromwell was in diapers and before Galileo discovered the moons of Jupiter. Arctica islandica, the “Ocean Quahog” or “Black Clam,” is believed to live for more than 400 years! The little bivalve laughs at nations, dynasties, and vampires as short-lived.
The venerable mollusks do not live flashy or extravagant lives. They live under a light drift of substrate on Atlantic coastal shelves at a depth of 25 to 100 meters (75 to 300 feet) although they have been found much deeper. The species is very successful and ranges from coastal Portugal up around Iceland down to the Carolinas. The little clams feed on plankton suspended in the water and they only grow to about 12 cm (5 inches) in diameter. Amazingly these Methuselah mollusks are harvested by dredge for the dinner table, so if, like me, you love spaghetti alle vongole, you might have inadvertently eaten something that lived longer than the United States has been around!
James Fort at Jamestown ca. 1610 (to give some perspective on how long 400 years is)
The secret behind the small bivalve’s longevity is unclear. Some scientists have speculated that antioxidant enzyme activities and the avoidance of waste accumulation are partially responsible for the clam’s age but the British Society for Research on Aging somewhat dryly remarks that, “Despite interest in this clam’s longevity and the measurement of growth increment series, little research into how this species has apparently managed to defy the onset of the ageing processes has been conducted.”
This shines a poor light on our priorities. Instead of grasping the molecular secrets of the longest living animals on Earth, the people who allocate resources to various things have decided to buy learjets and build a bunch of hokey Mcmansions for themselves. Argh! Maybe the clams’ sense of frugal austerity is what gives them such staying power.
Escargot
Heliciculture is the farming of snails for human consumption (and for snail mucous used in make-up and skin cream in the Latino community). Garbage middens from prehistoric settlements contain large numbers of cooked shells–so snails have been utilized as food for a long time. Sustained snail farming dates back at least to pre-Roman Phoenician colonies, however the ancient Romans took heliciculture and snail cooking to new levels. Romans gastronomes regarded snails as a particular delicacy and they introduced certain Mediterranean species to everywhere they conquered. When the empire fell apart Gaul continued the Roman tradition of enjoying escargot. Today the French alone consume 40,000 tons of snails per year. Serious agricultural effort is required to keep up with that sort of appetite.
Snails at market
Roman heliciculture apparently involved building little islands from which the snails could not escape. Today, however, snails are kept in carefully fenced garden plots. A small gauge metal wall which extends into the earth is necessary to keep snail predators out (particularly mice, shrews, raccoons, skunks, and toads) while a second interior wall made of specially constructed material keeps the snails in. A net can be added so that birds do not eat the tasty gastropods. Since pesticide and herbicide could injure the snails or the people eating them, organic greens are grown for the snails to consume. Apparently snails operate by Tron-style rules and do not like to cross another snail’s slime path—which means that only 20 snails can be kept per square meter. There are two principal species which are consumed as escargot. The smaller and more common Helix aspersa is also known as the “petit gris” or “escargot chagrine” whereas the larger, rarer Helix pomatia is called the “Roman snail,” “apple snail,” or “escargot de Bourgogne”. Both of these Mediterranean species have been widely introduced around the world for agricultural purposes. They are now endemic pests in Asia, Africa, Australia, New Zealand, North America and southern South America (and probably elsewhere). It’s funny to think that the snail eating your cabbages is the descendant of a snail which escaped from some long-dead hungry French chef. I can sort of imagine the scene as a black and white early Disney cartoon with giddy jazz playing in the background.
Snail Farming
Everybody and everything seems to enjoy eating snails including…other snails. A particular source of difficulty for snail farmers is cannibalism. Larger snails will eat eggs and hatchlings for the calcium. If not eaten by something, snails can live a long time. They hibernate in winter and Helix pomatia can live up to 35 years.
Helix pomatia
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?
ferrebeekeeper 