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.

Sub-Neritic Gentrification

For November we will be doing some deep thinking about deep-sea mollusks in an attempt to understand the complex history and adaptations of these animals living in the depths of our oceans. Biodiversity of today’s marine snails can be traced to several different ecological and environmental phenomena, but in the Deep-Water Helmet Shell Galeodea keyteri, it is likely a case of adaptive radiation exploring new realms. The Helmet Shells (Cassidae) are a speciose group of large, shallow-water tropical and temperate marine snails that range among the intertidal coral rubble and sand flats to offshore muds, but as this evolutionarily successful group of gastropods continued to diversity into different niches, several species moved into deep-water to establish new ways of living. At these depths staying alive presents serious challenges with an extremely cold, low oxygen, nutrient-poor, and high-pressure environment, so some deep-water species trended to smaller, slow-growing physiologies like as a way to successfully conserve energy and resources. Since the dark depths lack sunlight needed for algae to grow, most species of deep-sea mollusks are either scavengers or predators, with little resources for vegetarians to survive. Like all Helmet Shells, Galeodea keyteri is a carnivore, specializing on starfish, brittle stars, and urchins. Catching their slow-moving prey with a muscular foot, glands in the proboscis secrete a fluid rich in acids that dissolve the echinoderm’s calcium-carbonate skeletons, while a radula drills into the weakened parts of the body to extract nutrients from their internal organs. A tough environment requires innovative strategies and hardy adaptations for a species to survive. Ain’t natural selection grand?

Molluscan Methuselah

While some species of deepwater mollusks are derived from shallow-water taxa that extended into and adapted within deep ocean ecosystems, other taxa of marine mollusks are taxonomic geezers with a much longer history. The Slit Snails (Pleuorotomariidae) are perhaps the oldest still-living lineage of marine snails, extending back in the fossil record more than 500 million years. Named because of its long slit at the aperture allowing for extension of their respiratory siphon, they were abundant in the shallow reefs throughout the world. Between the Late Cretaceous (ca. 90 million years ago) and the middle Eocene (ca. 40 million years ago) is when most modern lineages of shallow-water reef-living gastropods originated and diversified, and also the time when slit shells seem to disappear from that same fossil record. Among paleontologists and malacologists, the general hypothesis is that these modern taxa somehow out-competed the slit shells for food, or perhaps were more adapted to changing marine climates or fluctuating sea levels of the time, forcing the slit shells into progressively deeper and deeper water. This type of ecological displacement and bathymetric submergence has been seen in many other deep-sea groups, including corals, crinoids, brachiopods, and fishes. Today, slit shells are found in depths exceeding 3,000 meters, living the hi-life eating sponges in a cold, dark, lonely, nutrient-poor world.

Die-Hardest

As far as the origins of deep-sea gastropods go, we’ve visited two scenarios: new lineages of shallow-water snails radiating into deeper waters, and those formerly shallow-water taxa that have been out-competed in the shallows and forced into deeper, less productive habitats. But there’s a third group of deep-water snails that are so tough, so extreme that they can live in shallow and deep water. Here is the Checkered Hairsnail (Trichotropis cancellaria; Capulidae), the James Bond, the Bruce Willis, and the Rock all coiled up into one extreme snail that ranges from the intertidal zone to depths of nearly 2,000 ft. (600m). Is it true grit or it’s hard-boiled soul that make it impervious to the relentless cold, pressure, and darkness of the deep sea? Their broad range is more likely the result of two things: (1) a wide and variable physiology that can tolerate the extremes of shallow to deep; and (2) its broad diet that it can obtain at any depth. You see, the Checkered Hairsnail is a suspension-feeder, meaning it feeds on the decomposing bits of animal debris suspended in the water, which it traps by sticky mucous, and that kind of detritus is found in all habitats. However, it’s a sneaky critter. When the floating slurry of decomposition becomes scarce, they will parasitize tube worms by inserting their proboscis down the mouth of the worm and pumping out the contents of the worm’s stomach. Evolution: the weirder the better.

Slo-Mo Snail
Shallow-water gastropods live the good life. Warm water, a sunny sea rich in oxygen, and plenty of food provides them the metabolism to live fast, grow big, and die young, relatively speaking, of course. The flipside in the deep sea is a life of constant near-freezing cold, little available food, and water suffocatingly sparse in oxygen. This shell of the Catalina Turrid (Antiplanes catalinae, Pseudomelatomidae) who lives at depths of up to 4800 ft (1460 m), tells its story of life in this harsh realm. Growth lines, which indicate the increase and cessation of shell development, are seen as wide bands often far apart in curving spire of fast-growing shallow-water shells. In this species, the growth lines are close and compact, showing very slow growth and likely a long life. Their low metabolism provides little extra energy for their minimal growth and reproduction, so these snails probably take the developmental route of the tortoise over the hare. This shell tells another and more concerning story. Once only collected during deep-ocean trawls by research vessels, this species was prized by collectors as a rarity and an oddity. With commercial fisheries abandoning over-exploited fishing grounds along the shallower coasts, fishing has gone into the deep ocean to tap into those fragile resources. This specimen was taken as unintentional bycatch by a deep-water shrimp trawler, and though it wasn’t the target of the fisheries, the sparse populations of these slow-growing snails cannot sustain even the modest impact by commercial fisheries

Post-Docs Please Enquire

The curse of working with deep-sea gastropods is how few specimens are in museum collections, and what very little is known about them. That too is the siren’s call of opportunity in deep-sea malacological research. The Japanese Pagoda Shell (Columbarium pagoda, Turridae) has been known to science for close to 200 years, based on relatively few well-documented specimens in museums and private collections scattered throughout the world, yet virtually nothing is known about their ecology. Diet, trophic niche, age, growth rates, reproduction, population structure, predators, parasites, physiology, ecological associations, movements – none of that has been adequately documented. If all mysteries in the ocean were solved, there would be no jobs for future under-paid post-docs or over-worked assistant professors. Those with grant funding, a modicum of workaholism, and access to deep-sea technology could pioneer new directions into a richer ecological understanding of the deep ocean’s marine mollusks. That siren’s call can just as easily dash unfeasible projects on the rocks of financial destitution and lead to deep regret of one’s research program and entrée into a life of constant self-medication and personal validation. These mysteries await the bold, but favor the wise.

The post Malacology Monthly: Going Deep first appeared on Deep Sea News.

The Tongue that Bites

Take this shell for example, so smooth it’s hard to tell if it was even in focus when photographed, is that of the Flamingo Tongue snail (Cyphoma gibbosum, Ovulidae). With satin pastel hues of pink and orange, the shell is worthy of a Miami Art Deco speakeasy, but the mantle that shrouds the shell adds a flair of early 1960’s cubist psychedelia. Most are barely

longer than an inch in length as adults, but size doesn’t matter since what they eat are the tiny, succulent coral-like polyps that make up the colonies within a sea fan. In the warm, shallow Caribbean Sea, a Flamingo Tongue Snail will graze on a sea fan, scraping and plucking out polyps, leaving a stark, lifeless trail behind. In areas where mollusk-eating fishes have been eliminated, the absence of their natural predators causes the snail population to explode, wreaking long-term and widespread damage to the slow-growing sea fans and the habitats they create.

Oyster Shooter

Who doesn’t love oysters? Ok, except vegetarians, and sure, those with shellfish allergies, but slurping down a raw oyster with a dab of Tabasco sauce and a squeeze of lime followedby an ice-cold lager is a marine biologist’s equivalent to a dose of Ativan. This water-worn little shell, less than two inches long, also loves oysters, but eats them in an entirely different way. The Japanese Oyster Drill (Ocenebra inornata, Muricidae) is far too small to eat an entire oyster, and too weak to pry open the shell, so it tries an entirely different method, one that you would expect in some freaky David Cronenberg film. The radula that in most species of snails are used as a rasp to scrape food off a

substrate, say algae off a rock or bits of meat off a dead fish. In this species, the radula is developed into an abrasive augur-like structure that can literally drill through the shell of other mollusks, and in particular, the sedentary oyster. Secretion of acidic enzymes through the proboscis containing the drill softens up the shell to make drilling quicker. Once the shell is perforated, the snail will then suck out the oyster’s fluids and soft tissues. Even more interesting, the evolution of a drill-like radula has been achieved independently in several different unrelated

lineages of predatory snails. But too many oyster drills can wreak havoc in an oyster bed, and this species in particular has been accidentally introduced into ecosystems far outside eastern Asia, proving them to be a serious invasive pest in regional shellfish industries.

Neritic Nosferatu
If you thought that a marine snail with an auger-like set of teeth drilling into an oyster to

suck out its juices was weird, I’m going to up the ante. As you’ve read in various postings about marine gastropods, you know the tooth-studded radula is a diverse and effective organ to acquire food. But scraping and drilling are just a few of the adaptations among marine snails, and this ruggedly handsome Cooper’s Nutmeg snail (Cancellaria cooperi, Cancellariidae) has another trick. Its sharp, almost scalpel-like teeth bite a small slit into their sleeping prey, and when the prey begins bleeding, their proboscis is pressed against the wound to casually sip the flowing blood. A vampire snail on its own seems earn

enough weirdness points, but it doesn’t stop there. Cooper’s Nutmeg seems to be an ectoparasite specializing on the California Electric Ray (Torpedo californica), a fish with high enough voltage to knock out any potential prey and foe alike, but somehow it doesn’t seem to detect the snail. Experiments in aquarium settings, as well as observations in the wild, suggests this snail specializes only on electric rays, with some observations showing over a dozen snails feeding simultaneously off a single ray, and has yet to be documented feeding on any other species of fish.

Cone of Silence

Last up in our series of marine gastropods and their strange adaptations for feeding is a good candidate for the next campy horror film. You may remember from past episodes that

cone snails (Conidae) have a highly-specialized harpoon-like radula and associated venom gland that makes them highly toxic predators. The Geography Cone (Conus geographus) is a slow, silent hunter on the midnight reefs where it seeks out sleeping reef fishes (yes, fish do sleep) by their acute sense of smell. Once within close range of a fish, the large mouth, really an expandable funnel-shaped shroud, releases a complex cocktail of nearly two dozen different paralytic toxins called the “nirvana cabal” including insulin that causes the prey to become lethargic by creating hypoglycemic shock, like the knock-out gas in an old James Bond movie. When the dazed fish is engulfed by the mouth, the harpoon is fired into the fish, quickly killing them. One look at the aperture of the shell shows an opening much wider than most other species of cone snails, and this allows the snail to swallow the entire fish into the main chamber of the shell. While their venom is primarily used for prey capture, it can be turned defensively on their predators. In fact, the Geography Cone is regarded as one of the most venomous of marine animals, and is responsible for no less than 30 documented cases of death in humans, though the actual number is likely much higher since traces of the venom are difficult to detect and effects of the toxins may mimic other more common causes of death, like heart attack.

The post Malacology Monthly: It Eats Whaaaat? first appeared on Deep Sea News.

Scorpion Without a Sting

This leggy shell belongs to a group of gastropods called the Spider Conchs, and this particular species is the Scorpion Spider Conch (Lambis scorpio), which can neither bite nor sting. The group gets its name from the leg-like extensions along the edge of the expanded opening of the shell (aperture) that serve no function in locomotion. Living in the intertidal and shallow subtidal mud, sand, and coral rubble where the surge of waves can be intense, researchers believe these spines serve to prevent the snail from rolling on the bottom. As an added benefit, long, thick spines could make it more difficult for mollusk-eating fish to eat the Scorpion Spider Conch. But as nobody has ever conducted any field studies or laboratory simulations of how these spiny shells actually function, they are untested assumptions. If scientists knew everything, there would be no work for graduate students.

Spiny Shield

Limpets rarely get much respect among malacologists, let alone shell collectors, yet they have a subtle magnificence. I bring you the Bearded Limpet (Scutellastra barbara; Patellidae). Mollusks that live in the intertidal zone are the cage-fighters of the invertebrate world. You’ve got to be extra tough to withstand tons of force from a crushing wave, survive the hot and dry exposure from low tide, and have sure-fire ways to avoid being eaten by predators both on the land and in the water. This shell has a series of strong ridges that radiate out from the crest of this pyramid-like shell to the outer margins of the shell. Architecturally, these ridges act as girders not just strengthening the shell, but directing the power of a breaking wave to the outside edge of the shell. This causes the power of the wave to be divided across the shell along these girders, but since these ridges end in spines that are in contact with the rocks, the wave force actually causes the shell to be pressed against the rock, holding it in place as the wave is breaking around the shell. Further, the bumpy, spiny edge of the shell could also make it harder for limpet enemy number one – the African Oystercatcher – to eat it. The bill of the oystercatcher is shaped like the flat end of a standard screw driver, and the oystercatcher wedges this sharp edge under the shell and pries it off, flips it over, and scrapes out the fleshy tidbits. The uneven spiny edge makes it much more difficult for the oystercatcher to slip the bill underneath the shell, and theoretically a few more Bearded Limpets survive to pass on this morphology to the next generation.

Twice the Spines, Twice the Fun

The Spiny Oysters (Spondylus: Spondylidae) such as this dandy Spondylus foliaceus, are a widespread group in tropical and subtropical waters, shallow and deep seas, with a diversity of colors and shapes, but they are all united in the spines, thorns, and prickly bits that cover their shell. The function of these spines, as imagined by unimaginative malacologists, it to protect the oyster from piscine predators, but that’s what they always say. Three other possible ways that could potentially increase the survival of the spiny oysters are as follows: (1) these spines could act to deter the settling of barnacles, anemones, and even other oysters on their shell. Acting as a figurative layer of barbed-wire the spines keep other large invertebrates from plopping-down on their shell and growing on them, weighting them down, and competing for food; (2) the expanded surface area these spines provide could promote the settlement and growth of other small marine organisms. Algae, bryozoans, and encrusting sponges, could provide a natural camouflage to better conceal these oysters on the sea floor; and (3) these spines could act as a ‘baffle’ to slow water flowing around the clam. As you all remember from your hydrophysics courses, moving water carries objects (sand particles, plankton, delicious detritus, etc.), and the faster the water moves, the larger particles and the greater number of particles the flow can carry. If there are impediments to water flow, such as dozens of spines on an oyster’s shell, the water slows and drops its particles. So, the spiny oyster’s spines may act to slow moving water around it, and that water would drop its suspended detritus and plankton right around the edge of the shell where the oyster is drawing in that water to filter out a meal. Or maybe it’s just to deter fish from eating them after all.

Shell Superstar

Behold the Japanese Star Turban shell (Guildfordia yoka; Turbinidae), a flat and radially spiny gastropod from the western Pacific Ocean that looks like a nasty weapon hurled in a kung-fu movie. One hypothesis concerning their spines is that it helps to distribute the weight of the snail outward so that it doesn’t sink into the soft deep-sea muds where it lives. Where broad, flat spines might accomplish this feat, their thin, narrow spines would seemingly cut into the soft mud, offering no real support for the weight of the shell in the center. But dang it if those spines don’t give up clues themselves; because they often show signs of breakage and regeneration, like one of the spines seen in this shell, they are likely for protection from predators. If the spines don’t actively repel foraging deep-sea fishes by a painful jab in the roof of the mouth, the spines may simply make the snail too big to even swallow in the first place. When the Japanese Star Turban survives a potential attack with a few spines broken, the snail will repair or regrow the protective spines to live another day.

Spines Fit for a Goddess

Sorry that I didn’t mention there would be a final exam for the end of this post, so sharpen that No. 2 pencil. Spines on shells, much like a Swiss army knife, can serve one or many functions. They deter predators, strengthen the shell, and support the animal in various ways. But this gastropod shell, the Venus Comb Murex (Murex pecten; Muricidae) is the most glorious example of spines. As the name might suggest, it is the natural comb that keeps a sexy Roman goddess’ hair smooth and manageable. After all, as legend has it, Venus was born of sea foam, and you can imagine what ruin the tides can do to her hairdo. But no, none of the ancient texts or depictions in paintings, mosaics, or bas-reliefs show Venus using this shell as a styling tool. So then, what evolutionary, ecological, and/or morphological function do you expect the spines to serve? Watch the video below for some clues:

The post Malacology Monthly: Spines and How to Use Them first appeared on Deep Sea News.

Snail shells have a very important feature—they spiral logarithmically. This feature was noted Greek philosophers, Christopher Wren, and expounded on in depth in 1917 by D’Arcy Thompson in his seminal book On Growth and Form. In a very crude sense, these early tomes provide the first steps into actually representing the entirety of a shell’s shape with numbers. Raup in the 1960’s devised a model with four parameters that went far beyond a simple line drawing in a single plane (Raup 1961, Raup 1962, Raup 1966).

The first parameter was the shape of the generating curve. Imagine a tube of Play-Doh extruded from press. We could have a different mold to give this tube different shapes and ridges. This is the shape of the generating curve.

The next parameters deal with the actual spiraling of this tube. If the tube is bent around an axis, how far does this tube move away from the axis with each turn? This is the variable D, the distance from the axis. If the value is zero then tube produces a coiled cylindrical shell, similar to the  shells just above, but if the value is greater than zero the shell gets a little wider with each whorl becoming triangular.

The third value, W, is the whorl expansion rate expressing how much the tube’s diameter increases as it spirals. The fourth, T, is the translation rate quantifying how that tube moves vertically (D is the horizontal movement) with each subsequent whorl. Nowhere are these parameters better explained than in Raup’s original work.

But the true beauty of Raup’s model was that each species could have its own unique set of parameter values.

You can envision calculating the values for D, T, and W for each snail and plotting them in a three-dimensional space with the axes corresponding to Raup’s parameters. If we did this would some parts of this space be uninhabited?. As stated by Raup himself,

Do the relatively unused regions represent physiologically impossible shell forms or has the evolution of these taxa simply not had sufficient time in which to populate the entire [region]?

In doing this, Raup had launched a new courses of study focused on using both mathematical models to explore organismal shape and where organisms did and did not exist in these spaces. We now refer to these spaces in which species can be placed as morphospaces. These morphospaces can be any number of dimensions and defined by the different metrics of the morphology of an organism.

David Raup passed away last Thursday after a long, productive, and inspiring career. His research on extinctions and biodiversity are heralded as transformational in the field of paleontology. What will receive less attention, but touched me the most, was his little model to measure the shape of snails.  Raup’s snail model papers inspired a wide diversity of research after including: how crinoids have occupied different regions of their morphospace through time, how coral growth and branching can be mathematically modelled, morphospace recovery after extinctions in ammonoid, and more complex representations of shell shape.

Raup’s papers even inspired one intrepid, young graduate student holed up in lab to explore how the deepest parts of the oceans impact shell shape. This project that took me several years and found me x-raying millimeter size shells so I could see internal growth patterns to parameterize Raup’s variables. Years ago while visiting the University of Chicago, Raup’s old stomping grounds, I noticed the same print on several of the graduate students’ and postdoctoral fellows’ walls. I of course was drawn to the image with mouth agape. The images were original prints from the negative of figure four from Raup’s 1966 paper—the shell morphospace. Multiple prints were found in box in the department long after Raup had retired. I still covet those prints immensely.

The post Digital Seashells and David Raup first appeared on Deep Sea News.

The carrier shells of the family Xenophoridae are the most remarkable bunch of snails.  Both their common name and their Latin name give away their uniqueness.  Xenophoridae in Latin actually translates to foreign carrying.  A carrier shell will cement stones, other shells, sponges, and other debris to its shell.  The individual pieces of foreign matter become larger as the snail grows and is often cemented to outer shell at regular intervals.

Why would an animal glue other things to itself, including other snails?  Shell spines serve as a wonderful defense for snails.  Obviously spines are pokey but they also increase the effective size of shell.  Pain and size make it hard of predators to manipulate the shell into their mouths and down their gullets.  Indeed, the objects also afford some camouflage.  Most interesting, is that Xenophorids stay between the shell and ocean floor to feed.  That cage of spines, or “spines” as the case may be, protects them. Nothing can get in there to munch on their little heads.

But, making spines is costly. It takes o’ so much energy and really who can be bothered?  Shell material is soooo expensive.  So instead of running down to the Home Depot to buy your own lumber why not steal your neighbor’s instead?  Or in this case steal your neighbor and use his body as a ceiling support.

Three groups of Xenophorids exist. Onustus with four species and Stellaria with five species glue small things to themselves but most of the shell remains exposed (>70%).  In contrast the Xenophora with about 20 species is ostentatious in how much bio-bling they will put on themselves.  They are the Mr. T of gastropods.

How exactly do Xenophorids glue these foreign bodies to themselves? Snails possess a mantle, thin layer of tissue that covers the body and contacts the internal shell. This is the part of the sail that secretes calcium carbonate in a protein matrix to grow new shell.  A Xenophorid will grab an object with their muscular foot and hold it place on the shell while the mantle secretes a little mollusk glue, that calcium carbonate cocktail, to fix it.

Also see

THESE ARE A FEW OF MY FAVORITE SPECIES: THE TORPEDO RAY

THESE ARE A FEW OF MY FAVORITE SPECIES: ALMOST ZOMBIE LIKE BRACHIOPODS

THESE ARE A FEW OF MY FAVORITE SPECIES: ANYTHING WITH AN INSTRUMENT ON IT

THESE ARE A FEW OF MY FAVORITE SPECIES: CARNIVOROUS SPONGES

THESE ARE A FEW OF MY FAVORITE SPECIES: SPOTTED PORCUPINE FISH

THESE ARE A FEW OF MY FAVORITE SPECIES: PISTOL SHRIMP

THESE ARE A FEW OF MY FAVORITE SPECIES: PIG BUTT WORM

THESE ARE A FEW OF MY FAVORITE SPECIES: PAINTED FROGFISH

The post These Are A Few of My Favorite Species: Carrier Shells first appeared on Deep Sea News.

Readers of DSN may think they know my favorite organism. Did you guess the giant isopod or did you guess the giant squid?  Those beasties are truly fantastic.  Large and dwelling in the deep oceans, they both check two of my boxes for awesomeness.  Yet, I’m drawn to another animal. A handful of species that is neither particularly large nor particularly deep in their affinity for habitat.

The carrier shells of the family Xenophoridae are the most remarkable bunch of snails.  Both their common name and their Latin name give away their uniqueness.  Xenophoridae in Latin actually translates to foreign carrying.  A carrier shell will cement stones, other shells, sponges, and other debris to its shell.  The individual pieces of foreign matter become larger as the snail grows and is often cemented to outer shell at regular intervals.

Why would an animal glue other things to itself, including other snails?  Shell spines serve as a wonderful defense for snails.  Obviously spines are pokey but they also increase the effective size of shell.  Pain and size make it hard of predators to manipulate the shell into their mouths and down their gullets.  Indeed, the objects also afford some camouflage.  Most interesting, is that Xenophorids stay between the shell and ocean floor to feed.  That cage of spines, or “spines” as the case may be, protects them. Nothing can get in there to munch on their little heads.

But, making spines is costly. It takes o’ so much energy and really who can be bothered?  Shell material is soooo expensive.  So instead of running down to the Home Depot to buy your own lumber why not steal your neighbor’s instead?  Or in this case steal your neighbor and use his body as a ceiling support.

Three groups of Xenophorids exist. Onustus with four species and Stellaria with five species glue small things to themselves but most of the shell remains exposed (>70%).  In contrast the Xenophora with about 20 species is ostentatious in how much bio-bling they will put on themselves.  They are the Mr. T of gastropods. You can see some great examples at ebay.  Though I would encourage you not to purchase any of them as they are often collected live.

How exactly do Xenophorids glue these foreign bodies to themselves? Snails possess a mantle, thin layer of tissue that covers the body and contacts the internal shell. This is the part of the sail that secretes calcium carbonate in a protein matrix to grow new shell.  A Xenophorid will grab an object with their muscular foot and hold it place on the shell while the mantle secretes a little mollusk glue, that calcium carbonate cocktail, to fix it.

But this is just the start! Xenophorids do not dissuade neighbors from joining the party on their own volition. Shells can have sponges, corals, hydroids, polychaetes, brachiopods, and sea squirts.  I’ve personally seen specimens that have sponges 5 times larger than the actual carrier shell.

Given that Xenophorids date back to the Jurassic, they are the true originators of bling.

The post The masters of bling, carrier snails first appeared on Deep Sea News.

To these lists, I will add the Twelve Days of Snails.  Consider it a list of the top 12 reasons why snails are bad ass.  This post is dedicated to my current student who is convinced turtles are cooler than snails.  Hope he has position next semester…just kidding.

On the twelfth day of Christmas, my beautiful wife gave to me…

12 Bone snails snacking

11 Larvae lounging

10 Sequential lovers lovin’

9 Parasites piercing

8 Shells spiraling

7 Ladies laying

6 Radulas rasping

5 Iron-Clad Samurai Snails

4 Head penises

3 Hairy shells

2 Endosymbiotic bacteria

And a gastropod in a lit shell

The post The Twelve Days of Snails first appeared on Deep Sea News.

Geerat Vermeij’s new paper “Sound reasons for silence: why do molluscs not communicate acoustically?” is a thought exercise on the adaptive possibilities of life. The deliberate production of sound for communication is known in arthropods and vertebrates. But why not in the over 100,000 species of mollusks ranging 11 orders of magnitude in size that occupy just about every niche on earth from marine parasites on sea cumbers to tree dwellers?

For a new adaptive trait to appear first the appropriate genetic material or developmental infrastructure needs to be in place. Second, selection must favor the novelty.

Why would mollusks even need to produce sound? The deliberate production of sound is used to attract mates, ward of predators, locate prey, and in social communication. Of course there needs to be recipients to hear and interpret the sound. The actions of the recipient must also be predictable from the emitted sound of the producer. One of these criteria falls and sound moves from communication to noise.

Organisms that release their sperm or eggs into the water, like many molluscs, don’t need to attract a mate. On the other hand, many gastropods and cephalopods do internally fertilize so mate attraction would be important. Some of the main predators, i.e. crustaceans and vertebrates, use sound for communication and thus are able to detect sound. Yet sound detection by another major predatory group on molluscs, the echinoderms, is lacking.

Detection of sound is a mechanical ability. In the human ear, sound waves are ultimately transmitted to the cochlea where hair cells detect the mechanical movement and convert it to a chemical signal. Sound and vibration detection is known also in molluscs. On the tentacles of gastropods sensory cells can detect vibration. Cephalopods possess an equilibrium organ, the statocyst, which detects movement with the changing position of hair cells. Coquina, that colorful and tasty little bivalve common on Florida and Caribbean shores, when sensing the vibrations of coming wave will jump out of the sand to ride it. A common intertidal gastropod, the Nerite, is known to fall off boulders back into the water when humans approach.

Sound production is known in molluscs. Kitting in 1979 noted that the varying sounds produced by limpets and snails scraping algae from rocks while feeding could be used to distinguish species. The variation in sound stemmed from differences in the structure and movement of the teeth, i.e. radula. In perhaps the best example, a gastropod in Hong Kong will strike its shell against the rock when predatory snails or sea stars attack it. But it is unknown whether the sound production is intended for predator warding or simply the outcome of another anti-predator behavior, e.g. moving the shell to make predatory capture more difficult.

But if an animal produces sound it risks detection. In the animal kingdom passive defenses and defensive sound production often do not go together. An animal must back a sound up with a quick escape or the ability to confuse or resist the attacker. These are active defenses, which while common in cephalopods, are not common in other mollusks. No molluscs are the kings of ultimate passive defense…the shell. High speed escapes among molluscs like snails and bivalves are rare and most do not have the metabolism to produce athletic activity. Exceptions do exist like the scallop that can swim away, razors clams that can quickly bury themselves deeper, swimming sea slugs, and of course the cephalopods. But, those mollusks capable of fast escapes lack the raw hardware to produce sounds. They are often soft-bodied mollusks lacking a shell or air filled spaces that could produce sound. Interestingly, many of the predators of molluscs, for example sea stars, aren’t fast moving themselves.

O’ but if molluscs could acoustically communicate, who would be the prime candidates? Vermeij suggest that molluscs with co-optable structures are the cephalopods with their beaks and quick movements. But a snail contender is also present. With internal fertilization, a shell, and operculum (the little calcareous shell door that many snails have), some of the quicker moving predatory gastropods might be having whole conversations we don’t know about.

Christopher L. Kitting (1979). The use of feeding noises to determine the algal foods being consumed by individual intertidal molluscs Oecologia, 40, 1-17 DOI: 10.1007/BF00388806

Geerat J. Vermeij (2010). Sound reasons for silence: why do molluscs not communicate acoustically? Biological Journal of the Linnean Society, 100, 485-493 DOI: 10.1111/j.1095-8312.2010.01443.x

The post If Molluscs Could Communicate What Would They Say? first appeared on Deep Sea News.

You might have noticed that my posting frequency is down recently.  Why?

1. Kevin Z convinced me to start Tweeting.  There seems to be an inverse relationship to my writing for DSN and posting Tweets.  Previous attempts to integrate our Twitter content into DSN were rocky at best and met with many complaints.  Suggestions on how to integrate the two meaningfully are welcomed. You can follow me at DrCraigMc

2. I am working on a review of this book for American Scientist.

3. I am also writing a feature article for American Scientist following on the theme of my talk last year at Sigma Xi.

4. Isopocaplyse 2010 consumed a bit of my time.  If you didn’t catch it already check out GlassBox Design and National Geographic’s coverage.  I am delightfully snarky!

5. I worked with the spectacularly talented Robin Smith to put together a press release and video for my recent paper in Ecology.  That was met with a fair amount of cricket chirping.  O’ well Bora, Science360, and I think its cool.

6. Multiple scientific papers in the works right now on deep-sea biogeography, source-sink dynamics in the deep sea, the evolution of body size in deep-sea bivalves, what drives the evolution of size on islands, describing the new species above, changes in energy consumption of snails through geologic time, changes in seamount diversity with increasing depth, and how microhabitat diversity in the deep sea drives biodiversity.  Whew!

7.  My day job.

8.  The fact there is only 24 hours in a day.

So what would I like to blog on but haven’t found time?

1. The discovery of the world’s deepest hydrothermal vent. It’s really hot and deep!

2. What will likely be the coolest discovery of the year and decade…anaerobic multicellular organisms in the deep sea.  This one is so cool I just decided to stay up late to write about it.  While I grab another Ardbeg and you wait for the next couple hours, check out Susan Milius’s spectacular write up.

3. Larvae from afar colonize deep-sea hydrothermal vents after a catastrophic eruption

Any other papers or news I should add to this list?

The post What’s New With the Dr. M and the Oceans? first appeared on Deep Sea News.