At the surface, each of those cups was 90% air and 10% tiny polystyrene beads. After each cup is artistically adorned with deep-sea imagery, they take a plunge to the abyss. At the crushing pressures of the depths, the air is squeezed out, leaving only those tiny polystyrene beads, and each cup becomes a miniature of its former self. One of the most extreme environmental gradients is the increase of pressure with increasing depth, starting at 1 atmosphere at the surface and reaching well over 1,000 atmospheres in the deepest parts of the ocean. How do organisms survive this great pressure, and what happens to them when they are brought to the surface?

The highest known pressure in the deep oceans coincides with the maximum known depth at the southern end of the Mariana Trench, the Challenger Deep. The actual maximum depth of Challenger Deep is disputed. The deepest reported measurement was by a Russian research vessel at 11,034 meters. The International Hydrographic Organization adopted 10,924 meters in 1993, but a subsequent 2010 survey, the most accurate to date, places the depth at 10,984 meters—25 meters greater. With every 10 meters corresponding to 1 atmosphere of pressure, this places the maximum known pressures in the deep between 1092.4 and 1103.4 atmospheres (110.7–111.8 MPa). Notably, several other deep-sea trenches—Tonga, Philippines, Kuril-Kamchatka, and Kermadec—in the Pacific Ocean also reach depths greater than 10,000 meters. In the Atlantic Ocean, the two deepest trenches are the Puerto Rico Trench at 8,800 meters and the South Sandwich Trench at 8,428 meters.

Exploring the depths of the ocean reveals a fascinating array of life forms, showcasing the incredible adaptability of both prokaryotic and eukaryotic organisms to high-pressure environments. Even in the Challenger Deep, where pressures exceed 110 MPa, microbial life thrives. Interestingly, several large multicellular organisms have been discovered at these extreme depths. A striking 74% of species found below 7,000 meters are endemic to these very deep areas. Among these invertebrates are the sea cucumber Myriotrochus bruuni, which inhabits the Mariana Trench at 10,710 meters, and the amphipod Hirondellea gigas, one of the most abundant creatures in the Challenger Deep at 10,897 meters. The hadal snailfish Pseudoliparis swirei holds the record for the deepest known vertebrate, living at an astonishing 7,966 meters.

How do organisms survive this depth? In short, there is a host of remarkable physiological and biochemical strategies that allow organisms to survive and thrive under the immense pressures found in the ocean’s depths. These adaptations include unique cellular structures and molecular mechanisms that confer resilience to high-pressure environments, such as specialized cell membranes, pressure-resistant enzymes, and unique protein folding techniques.

As you may remember from high school or college biology, a cellular membrane consists of a lipid bilayer. The structure is maintained entirely by the interaction of charges (or lack thereof) between water and the phospholipids. This makes the membrane semipermeable, much like a layer of oil on water. Extreme pressure results in tighter packing of the phospholipids, which lowers the permeability of the membrane. One adaptation by deep-sea animals to increase cellular permeability is to increase the percentage of unsaturated fatty acids. In a saturated fatty acid, all the carbons in the chain are linked by single covalent bonds. As you recall, a carbon can form four chemical bonds. If all these bonds are covalent (single), then a carbon could potentially attach to four other atoms. The term “saturated” comes from the fact that the carbon chain is loaded with hydrogens. If a carbon forms a double bond with another atom, it would bond with one less hydrogen. Thus, an unsaturated fatty acid has double bonds and is not “saturated” with hydrogens. The double covalent bond between adjacent carbons in an unsaturated fatty acid leads to a kink in the tails of the molecule. Thus increasing their concentration in the membrane leads to looser packing.

Pressure also selects for different enzymes. Changes in protein structure can influence their cellular function. Selection for rigidity is needed to counteract pressure and the resulting warping of proteins. Proteins contain hydrogen and disulfide bonds between different subunits and parts of the amino acid chain that dictate structure. Selection for proteins with increased bonding minimizes changes in shape due to pressure. Pressure can even make molecules more (or less) toxic. Urea is a good example: it becomes far more toxic as pressure increases. Deep-sea sharks, which like all sharks have a lot of urea in their blood, also have more of the protective chemical TMAO to offset this effect than their shallow-water cousins.

Pressure also does not favor air-filled volumes and sacs. The deepest diving submersibles require titanium spheres to hold the air-filled volume for their human inhabitants. For deep-sea animals, titanium is not an option, so most avoid having air-filled sacs. For example, deep-sea fish lack swim bladders. Other deep-diving animals like whales and seals have collapsible lungs to deal with extreme pressure (not to mention a whole host of other adaptations)!”

The post How Life Thrives Under the Ocean’s Crushing Pressure first appeared on Deep Sea News.

As I watched the monitor as we descend a 75-foot-tall chimney. Charcoal black to grey fluid is violently erupting from the top and several cracks along the chimney’s surface. You could see the shimmering sheen in the water, indicating that the temperatures were far above those of the surrounding, freezing abyss. Hydrothermal vents are home to the highest recorded temperatures on Earth. At oceanic ridges, where rocks are often brittle and fractured, cold seawater percolates down through Earth’s crust, gets superheated by magma, and rises back to the surface. Currently, the “Two Boats” vent in the Turtle Pits field along the Mid-Atlantic Ridge holds the record for the hottest hydrothermal vent, with fluid temperatures reaching up to 867.2˚F (464°C), nearly four times greater than the boiling point of water at 212˚F (100˚C). The extreme pressure prevents this boiling from actually happening.

At some vents lives the curious little worm, Alvinella pompejana. Discovered in the early 1980s by French scientists, the Pompeii worm is about 4 inches long with tentacle-like, scarlet gills on its head. Its name hints at its high-temperature habitat, being derived from the ill-fated Roman city of Pompeii, destroyed abruptly during an eruption of Mount Vesuvius in 79 A.D. The scarlet worm is found on the sides of hydrothermal vents, with its tube often reaching across the chimney to access some of the hottest vent fluids. The worms can be briefly exposed to 212˚F (100˚C) waters, although temperatures adjacent to the worm’s tubes more often range between near freezing and 113˚F (45˚C). In fact, the rear end of the species likely experiences extreme heat while the front end experiences extreme cold, making it the most eurythermal (capable of surviving a wide range of temperatures) species on earth.

How Alvinella pompejana survives in this boiling hot environment is still somewhat of a mystery. One theory is that the worm can keep itself cooler, between 68-83°F, by pulling cold water into its tube when it moves in and out, and with the help of bacteria that circulate the water around its body. This gray layer of bacteria covering the worm’s back, besides moving water, may also provide it with a sort of thermal blanket. The worm’s skin and connective tissue also have the most heat-resistant proteins known, thanks to their special structure. Additionally, the worm’s DNA has more triple bonds from guanine-cytosine (GC) pairs compared to other similar species, which helps it stay stable at temperatures up to 190˚F (88°C).

The post A Journey to the Hottest Place on Earth: Hydrothermal Vents and the Resilient Pompeii Worm first appeared on Deep Sea News.

We fly along the shoreline and notice dozens of dead urchins.  The brine’s high density, which prevents it from mixing with the ocean above, also means that oxygen is not mixed in, creating an anoxic deathtrap for unsuspecting respiring organisms.  As we continue to explore, a small, semi-submerged mound in the middle of the brine pool begins to pulse and vent.  As we maneuver the Global Explorer closer, we see hundreds of cavities all venting fluid.  We take a sample of mud around one of these pits, in hopes of capturing its invertebrate builder.  Later on board the vessel, we examine the sample and discover a type of worm, a sipunculid, half the size of hot-dog with the bright green, gold, and purple colors. Students in my research group begin almost immediately referring to it as the Mardi Gras Worm.  How can this worm survive in such a toxic place?

Both cold seeps and their chemical and geological relatives, hydrothermal vents, are rich in reduced chemicals, particularly hydrogen sulfide.  These chemicals are toxic.  Sulfide and oxygen don’t naturally coexist for long because they react spontaneously and rather aggressively. However, this sulfide also provides a unique energy source, by willingly donating electrons, to chemosynthetic microbial live. These microbes use this to fix carbon and produce food. This makes vents and seeps different than the rest of the deep in being largely independent of sunlight and the photic zone above.  Many organisms in these environments either feed on free-living bacteria or form symbiotic relationships with chemosynthetic bacteria to obtain their food. This makes life challenging for both microbes and the animals that depend on them, as they need both sulfide and oxygen.

Despite these harsh conditions, these unique ecosystems flourish, showcasing the remarkable adaptability of life in extreme environments.  The hydrothermal vent worms, the Alvinellids, build tubes projecting from chimney walls, giving their gills access to oxygen-rich water.  The other end of the tube can then access the vent fluids rich in hydrogen suflide.  Mobile predators like the crab, Bythograea thermydron can move between areas with and without oxygen. Ice worms, so names because they are found on methane ice in the cold seeps of the Gulf of Mexico, circulate oxygenated water around itself using its bristle-bearing appendages. The adaptations extend well into the biochemical level.  The massive vent worm, Riftia pachyptila and the Alvnellids contain hemoglobins, giving them bright red colors, which bind insistently to oxygen.

But once dealing with oxygen issue, how do these species survive the toxic sulfide and heavy metal soup of vents and seeps. One way means of survival for these organisms is prevent sulfide from even reaching sensitive tissues.  Creating sulfide barriers may mean creating thick tubes or cuticles to prevent the skin from encountering suflide. For example, the Pompeii worm, Alvinella pompejana, at hydrothermal vents secretes proteinaceous tube that it shares with bacteria. Animals that inhabit chemosynthetic habitats also often possess a specialized blood protein that binds to sulfide—forever—preventing it from mucking up the business of respiring oxygen.  At hydrothermal vents, metals reach such high concentrations they precipitate out of water.   These heavy metal solids form the impressive chimney structures of vents and even coat the tubeworm tubes and the shells of snails and clams.  Chemosynthetic organism have ways of dealing with this too.  Special metal-binding proteins, called metallothioneins, grab toxic metals and even grouping together to form little bodies or particles distinct from the rest of the cell. These consolidated and enclosed heavy metals then stay out of the way and do not gum of the cellular works.

Overall, the exploration of these deep-sea ecosystems reveals the astonishing resilience and adaptability of life in extreme conditions, offering valuable insights into the limits of biological diversity and the potential for life beyond Earth.

The post Surviving Toxic Havens first appeared on Deep Sea News.

In the profound darkness of the ocean’s depths, organisms face a choice concerning their visual capabilities. Some species evolve specialized eyes that grow to astonishing sizes, as seen in creatures like the giant squid or owl fish. Alternatively, there’s the option to abandon the concept of eyes altogether. It’s the latter scenario that introduces us to an intriguing case: the “blind lobsters,” a peculiar group of 38 lobster-like crustaceans known as Polychelidae. These creatures exclusively inhabit the deep sea, dwelling at depths exceeding 5,000 meters (16,000 feet). Members of this group typically exhibit either absent or vestigial eyes, along with reduced or entirely absent eye stalks.

However, their lack of eyesight isn’t the most remarkable aspect of these creatures. Unlike typical lobsters, which possess two claws, Polychelids boast up to 5 pairs of claws. They feature two larger claws, followed by four smaller yet equally intimidating ones. The name of the group, “Polycheles,” derives from the Greek words meaning “many-clawed.”

While one might assume scientists are primarily intrigued by the blind, multi-clawed nature of these creatures. But they are complex. Scientists and Poychelids alike.  Polychelid bodies provide evidence of a transition from shrimp-like to lobster-like forms. Despite their lobster-like appearance, they lack certain primitive characteristics, such as a pointed telson (back-end) instead of the rounded telson found in typical lobsters. This appearance is similar to another group of unusual crustaceans, Eryon, dating back to the Jurassic and thus making Polychelids somewhat of a living fossil similar to the Coelacanths.  Yet intriguingly Eryon dwelled in the warm shallow seas of the Jurrassic.  The question of why they migrated to the deep sea remained unanswered—did they seek refuge in these depths, as suggested for other deep-sea taxa? Recent fossil and genetic evidence suggests that they have always inhabited these depths since their evolutionary origins in the middle Jurassic period.

Chang, Su-Ching, Shane T. Ahyong, and Ling-Ming Tsang. “Molecular phylogeny of deep-sea blind lobsters of the family Polychelidae (Decapoda: Polychelida), with implications for the origin and evolution of these “living fossils”.” Molecular Phylogenetics and Evolution 192 (2024): 107998.

Bezerra, Luis Ernesto Arruda, and Felipe Bezerra Ribeiro. “Primitive decapods from the deep sea: first record of blind lobsters (Crustacea: Decapoda: Polychelidae) in northeastern Brazil.” Nauplius 23 (2015): 125-131.

The post The Many Clawed, Blind Lobsters of the Deep first appeared on Deep Sea News.

The post The Sports Cars of Worms first appeared on Deep Sea News.

In this luminescent tapestry, sea cucumbers emerge as unexpected stars. While we might not associate these echinoderms with bioluminescence, they contribute significantly to the underwater light show. Interestingly, in shallow waters, only a mere 1% of species can emit light, whereas the seafloor teems with bioluminescent activity, showcasing the radiant abilities of over 50% of its inhabitants. Venture to the depths of one kilometer, and you’ll find that luminous sea cucumbers constitute an astonishing 99% of all sea cucumbers.

Research by Manabu Bessho-Uehara, Jerrome Mallefet, and Steven Haddock have cast light on the bioluminescent secrets of sea cucumbers. Documenting not only 42 known species of glowing sea cucumbers but also six independent evolutions of bioluminescence within the sea cucumber lineage. The earliest illuminated sea cucumber may have been nearly 400 million years to the Devonian era, coinciding with the establishment of the first land animals.

While the precise details of how sea cucumbers produce their blue to greenish bioluminescence remain a mystery, the process involves a small organic compound known as luciferin. This compound is catalyzed to oxidize by an enzyme fittingly named luciferase.

The question of why sea cucumbers, or holothurians, need bioluminescence remains unanswered. Like other organisms that exhibit this phenomenon, the glow may serve various purposes. From communication to startling, misdirecting, and warning predators, to attracting, stunning, or illuminating prey, and even facilitating mate recognition—the role of bioluminescence in sea cucumbers raises intriguing hypotheses. One such theory suggests that it functions as a burglar alarm, attracting larger predators to deter potential threats—a fascinating manifestation of the age-old adage, “the enemy of my friend is my friend.”

Photos from : Bessho-Uehara, Manabu, Jérôme Mallefet, and Steven HD Haddock. “Glowing sea cucumbers: Bioluminescence in the Holothuroidea.” The world of sea cucumbers. Academic Press, 2024. 361-375

The post Holy Glowing Sea Cucumbers! first appeared on Deep Sea News.

The highest known pressure in the deep oceans coincides with the maximum known depth in the southern end of the Mariana Trench, the Challenger Deep. The actual maximum depth of Challenger Deep is disputed. The deepest reported measurement was by a Russian research vessel at 11,034 m. The International Hydrographic Organization adopted 10,924 in 1993, but a subsequent 2010 survey, and the most accurate, places the depth at 10,984 – 25 m greater. With every 10 m corresponding to 1 atmosphere of pressure, this places the maximum known pressures in the deep between 1092.4 and 1103.4 atm (110.7–111.8 MPa). Notable is that several other deep-sea trenches—Tonga, Philippines, KurilKamchatka, and Kermadec—in the Pacific Ocean also reach depths >10,000 m. In the Atlantic Ocean, the two deepest trenches are the Puerto Rico Trench at 8800 m and the South Sandwich Trench at 8428 m.

The prevalence of prokaryotic and eukaryotic life through the range of high pressures in the deep oceans suggests that organisms can easily adapt to these conditions. Even at the extreme pressures (>110 MPa) in the Challenger Deep, microbial life flourishes and differs from the background abyss. Several large multicellular organisms have been found at extreme depths and pressures and can be characterized as primarily hadal and trench species. Endemism of species occurring greater than 7000 m is 74% of surveyed species, implying a strong evolutionary pressure and the unique adaptations required to exist at extreme depths. Among invertebrates, several reach trench depths, including the sea cucumber Myriotrochus bruuni at 10,710 in the Mariana Trench, the extremely abundant amphipod Hirondellea gigas at 10,897 m in the Challenger Deep, the isopod Macrostylis species at 10,710 in the Mariana Trench, the polychaete genus Macellicephaloides at 10,700 m depth, and the sea anemone family Galatheanthemidae at 10,700 m depth. The deepest known vertebrate is the hadal snailfish Pseudoliparis swirei found at 7966 m.

How do organisms survive this deep?

1. Cell membranes: As you may remember from high school or college biology, a cellular membrane consists of lipid bilayer. The structure is entirely maintained by the interaction of charges (or lack of) between water and the phospholipids. This makes the membrane semipermeable much like a layer of oil on water. Extreme pressure results in a tighter packing of the phospholipids which lowers the permeability of the membrane. One adaptation by deep-sea animals is to increase cellular permeability is to increase the percentage of unsaturated fatty acids. In a saturated fatty acid all the carbons in the chain are lined by a single covalent bond. As you recall, a carbon can take four chemical bonds. If all these bonds are covalent (single) then a carbon could potentially attach to 4 other atoms. Thus the saturated comes from the fact that the carbon chain is loaded with hydrogens. If a carbon forms a double bond with another atom then the carbon would have to bond with one less hydrogen. Thus an unsaturated fatty acid is one with double bonds and not ‘saturated’ with hydrogens. The double covalent bond between adjacent carbons in an unsaturated fatty acid leads to a ‘kink’ in the tails of the molecule. Thus increasing their concentration in membrane leads to a looser packing.
2. Enzyme shape: At the basic level, pressures would also select for different enzymes. Changes in protein structure can influence their cellular function. Thus selection for rigidity is needed to counteract pressure and the resulting warping of proteins. Proteins contain hydrogen and disulfide bonds between different subunits and parts of the amino acid chain that both dictate structure. A selection for proteins with increased bonding would minimize changes in shape to do pressure.
3. Urea: As note by Al Dove previously, “Pressure can even make molecules more (or less) toxic.  Urea is a good example: it becomes far more toxic as pressure increases.  So deep sea sharks, which like all sharks have a lot of urea in their blood, also have a lot more of the protective chemical TMAO to offset this effect than do their shallow water cousins.”
4. Air filled sacs: Basically this is bad for an animal under pressure, so most deep-sea animals avoid having them. Deep-sea fish lack swim bladders. Other deep diving animals like whales and seals have collapsible lungs to deal with extreme pressure (not to mention a whole host of other adaptations)! Penguins basically shut down all their organs except for their heart and their brain when doing deep dives.

The post The Hidden World of Extreme Ocean Depths: Life and Pressures in the Trenches first appeared on Deep Sea News.

One species of anglerfish was filmed off the coast of Monterey, California, revealed drifting and tumbling along, humming Taylor Swift songs.  One of these may not be true.

While it was conventionally thought that anglerfish females swim upright with their lure positioned ahead, a case of inverted swimming emerged about two decades ago—a surprising deviation from the expected norm. Cue original Top Gun reference here. 

Recent research, adding eight new observations to the pool, proposes that this inverted swimming might actually be the norm for these fish. In these instances, the anglerfish maintained a rigidly straight body, with their unpaired fins erect and the lure held downwards when inverted. The tendency of these fish to swim closer to the seabed suggests a potential focus on bottom-dwelling prey. This inverted orientation likely aids in swiftly luring prey away and clearing the path for a well-aimed strike—a tactical advantage in their hunting strategy within the depths.

Stewart, Andrew L., et al. “Upside‐down swimming: in‐situ observations of inverted orientation in Gigantactis, with a new depth record for the Ceratioidei.” Journal of Fish Biology (2023).

The post The Upside Down Feeding Fish of the Deep first appeared on Deep Sea News.

Connecting the oceans to land are numerous carbon highways.  These conduits bring food from land to the ocean, supporting an abundance of life.  Our group explores these carbon chains and explores some potential methods of carbon delivery to the deep.  Thus, alligators on the abyss.

At first it may seem fanciful that an alligator carcass might find its way to the deep.  However, dozens of species of alligators and crocodiles are found across the globe, in high numbers, and often in coastal areas.  Through either their normal migrating or foraging activities, or during flooding events, individuals may be found offshore in the ocean.  If one of those individuals meets an unfortunate end, it may fall to the seafloor.

In prehistoric times, the impact to the deep oceans could have been even larger, as large reptiles such as ichthyosaurs and plesiosaurs dominated the sea. Deploying a reptile in the deep sea today may reveal the animals that specialized on the carcasses of long-extinct ancient emperors of the sea.

Earlier this year, our research group placed three alligator carcasses 1.5 miles deep on the seafloor of the Gulf of Mexico in the first-ever alligator fall experiment.  Each of the three alligators met a different fate.

The first alligator had been on the bottom of the ocean for less than 24 hours. Despite the tough hide of the alligator, scavengers quickly got through and began to gorge themselves on the flesh of the alligator. Football-sized animals called giant isopods, relatives of rolly pollys or pillbugs, penetrated the hide in this short time-frame.  This demonstrates the speed and precision with which deep-sea scavengers can utilize any carbon source, even food from land and freshwater systems.

A little over 60 miles to the east of the first alligator, the second alligator had been sitting on the seafloor for a little over a month and a half.  All the soft tissue of the alligator had been removed by scavengers.  A small animal called an amphipod was still darting around looking for scraps, but the only thing that remained was a skeleton.  All of the soft tissue had been consumed. The spine curved just as it had been left.  A depression in the sediments indicated where the full body once laid.  The skull was turned over, likely by scavengers while picking at the flesh on the skull.

A fuzzy carpet covering the bones of the second alligator represented a brand-new species, previously unknown to science.  These zombie worms, or Osedax, colonize the bones of many types of vertebrates and consume the lipids within.  This was the first time zombie worms had ever been observed in the Gulf of Mexico or from an alligator fall.  They also demonstrate yet another pathway in which carbon from land makes its way into deep-sea food webs.

Another 60 miles east lay the third alligator.  It had only been eight days since it was laid on the seafloor.  As the camera panned to the marking device, a floating bucket lid attached to a rope like an underwater flag, it became clear that the alligator was missing.  All that remained where it had been dropped was an alligator-shaped depression in the sediments.  Drag marks in the sediment paved a path to what remained of the alligator fall.  An animal dragged this alligator 30 feet and left only the 45-pound weight and rope.  The rope had been bitten completely through. To consume an alligator, and create this disturbance, the animal must have been of great size.  We hypothesize that most likely a large shark, like a Greenland shark or sixgill shark, consumed this alligator whole.

Three alligator falls in the abyss met three very different ends, from being consumed by football-sized cousins of rolly polys, to zombie worms eating their bones, to a large shark dragging it away and consuming it whole.  This research has given us a glimpse into what impact large reptiles had in past oceans, as well as the role they play today.  It is clear that deep-ocean scavengers have no qualms about successfully and quickly consuming food that originated on land or freshwater.

Read more about this research in our group’s recent publication in PLOS One: “Alligators in the abyss: The first experimental reptilian food fall in the deep ocean.”

The post Alligators in the Abyss: Part 2 first appeared on Deep Sea News.

A four-leaf clover represents just one kind of rareness. One might find a 4-leaf clover just about anywhere. Four-leaf clovers are not just restricted to Ireland. Four-leaf clovers are rare because at any given locality they occur in very minuscule numbers.

The idea of whether rareness imparts values has tormented philosophers, including Nietzsche. “Whatever can be common always has little value. In the end it must be as it is and always has been: great things remain for the great, abysses for the profound, nuances and shudders for the refined, and, in brief, all that is rare for the rare.” But of course, Nietzsche does not define rare. What does “all that is rare for the rare even mean?” Freakin’ Nietzsche.

We all feel we know what rare means. But contrast the case of four-leaf clovers with platinum. Platinum is special for me. For my 10th wedding anniversary, I had a custom wedding ring made of platinum for my wife. This platinum band was to replace one from our youth when I had more limited income and could afford a metal less “precious” and less “rare.” Yet, platinum represents another kind rarity, occurring in great abundance but only at a few locations. Locally abundant but geographically restricted.

In a classic 1981 paper, Dr. Deborah Rabinowitz, a professor at the University of Michigan, laid out the seven forms of rarity. What makes something rare depends on three characteristics; geographic range, habitat specificity, and local population size. First, is a species found globally or only at a single location? Two, is species seen at any given site in low numbers? Third, is the species only found in a specific type of habitat?

As Rabinowitz notes in elegant writing., “If each of these attributes is dichotomized, a 2 x 2 x 2 or eight-celled block emerges. Although creating the hazard of false reification – that is, converting an idea into an object – such a simple scheme can aid in focusing our thoughts, and this is my intention. The patina – a gloss or incrustation conferred by age – of monolithic rarity may have hindered our understanding of an exceedingly heterogeneous assemblage of organisms. Since the products of rarity are diverse, the causes of rarity and the genetic and population consequences of rarity are undoubtedly equally multiple.”

But obviously, 2x2x2 does not equal 7. One state is lost, a species found everywhere, in high numbers, and several different kinds of habitats. This species isn’t rare at all! You can think of the seven forms of rarity as three singe type cases (geographically limited/small numbers/habitat specialist), the three double type cases (geographically limited and small numbers/geographically limited and habitat specialist/small numbers and habitat specialist), and the last triple case (geographically limited and small numbers and habitat specialist).

The most uncommon form of rarity is a species found all over but in limited numbers at a single location. One such species is the exceptionally beautiful deep-sea snail Oocorys sulcata found in the eastern and western corridors fo the Atlantic and reaching will into the Indian Ocean and the western Pacific. Oocorys sulcata also show incredible depth tolerance found all the way from the shelf at 150 meters down to the deepest abyss over 5000 meters. Yet, despite this fantastic distribution, it is rarely found. A famous sampling effort off of New England did not capture a single individual in 41 samples. Another 24 samples later as part of later effort only yielded a single specimen. Indeed, based on some very rough calculations, you would probably only find about 15 every square kilometer or roughly 45 Manhattan city blocks.

Hydrothermal vents possess mollusks that are both unique and fascinating. A snail first described in 2003, the unusual snail Chrysomallon squamiferum, maybe the most exciting find thus far at a hydrothermal vent. I admit my bias here, as most of my interest lies with studying deep-sea snails. Nonetheless, the discovery of “gold-footed” snails a the Kairei vent field in the Indian Ocean is fascinating.

At this point, I should state that the foot of the snail is mineralized with pyrite and greigite. Many of you might note the misnomer here, as pyrite is only ‘Fool’s Gold,’ but in deciding on a temporary ordinary name Fool’s Gold-Footed Snail seemed a bit lengthy. I hope all will forgive the intentional misnomer for the sake of creative writing. Although other names due include the big-hearted iron snail (it also possesses an abnormally large heart for its size). And of course the scaly foot snail. So maybe the big-hearted, iron gold, scaly foot snail.

The scales, or sclerites, that cover the entire length of the snail’s foot can be up to 8mm long. The presence of mineralized scales is remarkable in itself, but the existence of iron sulfide as skeletal material is unknown from any other animal. The purity of sulfides, among other lines of evidence, suggest that the building of the scales is controlled by the gastropod itself. The sclerites are thought to have evolved recently and homologous to the operculum. It is believed they may serve as a defense against cone shells also occurring at the vent.

Chrysomallon squamiferum is rare, not only for the oddity of its features amongst the animal kingdom but because the snail is known from only three hydrothermal vents in the Indian Ocean. While abundant at any of these vents it is geographically restricted, like platinum. The scaly foot is actually a “double rare” case both geographically restricted and a habitat specialist. Given this potential habitat of only a few square meters, some of which endangered by deep mining interests, led a new paper by Dr. Sigwart and colleagues establishing Chrysomallon squamiferum as endangered on the IUCN RedList. This listing places the big-hearted, iron gold, scaly foot snail with 25 species all either bony fish, cartilaginous fish, or cephalopods all assessed to be either endangered or critically endangered.

Helen Macdonald writes in H is for Hawk “The rarer they get, the fewer meanings animals can have. Eventually rarity is all they are made of. The condor is an icon of extinction. There’s little else to it now but being the last of its kind. And in this lies the diminution of the world. How can you love something, how can you fight to protect it, if all it means is loss?”

I am hoping for future where Chrysomallon squamiferum I remember this elegant mollusk for the rarity of beauty, adaptation, and morphological marvel not the rarity of its existence.

Sigwart, J. D., Chen, C., Thomas, E. A., Allcock, A. L., Böhm, M., & Seddon, M. (2019). Red Listing can protect deep-sea biodiversity. Nature Ecology & Evolution, 1.

Rex, M.A., Stuart, C.T., Etter, R.J., & McClain, C.R. (2010). Biogeography of the deep-sea gastropod Oocorys sulcata Fischer 1884. Journal of Conchology, 40, 287.

Rabinowitz, Deborah. (1986). Seven forms of rarity and their frequency in the flora of the British Isles. Conservation Biology: The Science of Scarcity and Diversity 

Rabinowitz, Deborah. (1981) Seven forms of rarity. Biological Aspects of Rare Plant Conservation

The post The Beauty of Rarity first appeared on Deep Sea News.