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.

I am not sure when this obsession with both small and large things began. One of the earliest photographs of me is in a giant rocking chair. With a big smile on my face, I am dwarfed by the colossal piece of furniture. Sadly, in researching this post I discovered this rocking chair is not the largest. That title is bestowed to a towering rocking chair, a 56.5 feet tall behemoth in Casey, Illinois, not only the world’s largest rocking chair but also the largest chair in all of America. I will of course need to visit, and photograph, myself next to the massive chair. Another photograph to add to my photo collection of myself with oversized objects. The world’s largest Adirondack chair and me…got it. Largest chest of drawers…done. Largest frying pan…visited. Giant 6-foot tall cheese grater…photographed and almost bought. I could go on and on.

I never realized I could get paid for my obsession. I did not at some point in high school realize or declare I wanted a vocation focused on extreme sizes. Nor was such a trajectory flagged as a possibility on those mandated vocational tests. I got flagged for being perfect for cake decorating. No joke. Nothing about decorating tiny or giant cakes. Of course, who would even think you could make a career out of a passion for size, except maybe Guinness World Records? No, I came by it all by accident.

As an undergraduate, I applied for a summer program to conduct research with a biologist. Knowing at the time I wanted to be a marine biologist, I applied to do summer research counting fish on the coral reefs of St. Croix. An unshockingly, popular choice among undergraduates, I did not get the position. My second and third choices were the only other ocean-based projects in the program. When the scientist involved with my second choice project called to invite me to work with him that summer, I didn’t even remember what the project was. I wasn’t really concerned with the specifics of the other projects because how could I not be selected for my first choice, St. Croix, dream project. Opposed to the beautiful tropical beaches of the Caribbean, my destiny would be to work in a windowless lab all summer in Boston. The project didn’t exceedingly interest me at the time as I wanted to be a field scientist and microscopy in the lab sounded…well dull. But working in an air-conditioned lab in the big city sounded better than living with my parents in rural Arkansas working in the intense Southern heat sweating in a factory. So off to Boston I went. Within a few hours of the first day, I fell in love with the project. So much so I asked that scientist, a preeminent deep-sea biologist and expert on the body size of marine invertebrates, if I could pursue a doctorate with him.

In the biological world, size is more than a novelty. How an organism relates to the world around it is determined by its size, and understanding what influences size is key to understanding the diversity of life itself.  That summer I measured the size of 100’s of tiny snails and when I returned to pursue my Ph.D. I measured thousands more. In total I measured 14,278 deep-sea snails. The largest no bigger than Abraham Lincoln’s head on the face of the penny. The smallest the size of his nose. Those snails I measured were collected from off the coast of New England from depths of over 600 feet to well over 18,000 feet, from the shallows of the New England continental shelf to the abyssal plains.

Why would anyone measure close to 15,000 snails? In the late 1800’s Henry Nottidge Mosely wrote: “Some animals appear to be dwarfed by deep- sea conditions.” By the 1970s, Hjalmar Thiel of Universität Hamburg observed that the deep sea is a “small organism habitat.” Increased depth typically translates into less food in the oceans with the deep-sea being a very food poor environment. As you might expect this has profound effects on the body size of deep-sea animals. Thiel’s seminal 1975 work demonstrated that with increased depth, smaller organisms became more dominant. At depths greater than 4 kilometers on the vast abyssal plains where food is extremely limited, you find some of the most diminutive sizes. In a particularly striking example of this, my doctoral advisor Michael Rex and I calculated those nearly 15,000 deep-sea snails I measured could fit completely inside a single Busycon carica, a fist-sized New England knobbed whelk found along the coast. But by measuring all those snails, Mike and I were able to document exactly how size in these snails changes over a 3.5 mile increase in depth. That study was the first of its kind and remains the largest number of deep-sea animals ever individually measured.

But to say that all creatures of the deep are miniaturized overlooks the complexity of size evolution in the deep sea. Some taxa actually become giants. The Giant Isopod, a roly-poly the size of very large men’s shoe, and sea-spiders the size of dinner plates, quickly dispel the Lilliputian view of the deep sea. Although all those deep-sea snails are smaller than their shallow-water relatives, shockingly Mike and I also found that they actually increase in size with greater depth and presumed lower food availability. To further confound the situation, other scientists have reported the exact opposite pattern in other types of snails, whose size decreases with depth. The same appeared to be true in other taxa, such as crustaceans. How can the deep-sea be both a habitat of dwarfs and giants?

To answer that, I turned from the Earth’s largest habitat to one of its smallest—islands. On islands both giants and dwarfs exist. The diminished kiwi and the enormous Moa of New Zealand, the colossal Komodo dragon on the island of Komodo, the extinct pygmy elephants on the islands of the Mediterranean, the ant-sized frog of the Seychelles, the giant hissing cockroach of Madagascar and the giant tortoise of the Galapagos represent just a few of the multitudes of size extremes on islands. In 1964, J. Bristol Foster of the University of East Africa demonstrated that large mammals became miniaturized over time on islands. Conversely, small mammals tended toward gigantism. This occurs with such frequency that scientists refer to it as “Foster’s rule” or the “Island rule.” Big animals getting small and small animals getting large.

My colleagues and I discovered a similar pattern in 2006 between shallow and deep seas. As shallow-water gastropods evolved into deep-sea dwellers, small species became larger and large species became smaller. Interestingly, size did not shift in a parallel manner. Larger taxa became disproportionately smaller sized—that is, both converged on a size somewhat smaller than medium. I’ve since observed this pattern in radically different taxa, such as bivalves, sharks, and cephalopods.

The fact that islands and the deep sea have so little in common represents a wonderful opportunity that allows elimination of several hypotheses. Of course, what the deep sea lacks is food. The absence of sunlight precludes plants.   Thus, for the majority of organisms living there, the food chain starts with plankton, dead organisms and other organic debris descending from the ocean’s surface. Less than five per cent of the total food available drifts to the sea floor, leading to an extremely food-limited environment. On islands, less food is available because the small land areas support fewer plants at the base of the food chain.

In either case, island and deep-sea animals need to be efficient and creative in their acquisition of food. In both habitats, there may not be enough total food to support populations of giants only. Unable to travel long distances to search for food or to store large fat reserves to fast through periods of food scarcity, smaller organisms are also at a disadvantage. If these contrasting evolutionary pressures were equal, size would be driven to an intermediate. However, the selection against larger sizes is greater, leading toward an evolutionary convergence that is slightly smaller than the intermediate size. Thus, differential responses to food reduction by different- sized organisms may resolve the outstanding paradox of divergent size patterns in the deep. In the interests of reaching this ‘golden medium’, some species become giant while others miniaturized.

In that summer of 1996, as a clueless undergraduate, I started my scientific adventure that fueled my obsession with size. Two decades later, I still am excited by the body size of animals. Much of my research, and the students who work with me, is dedicated to understanding how the expansive variety of sizes on Earth from bacteria to blue whales emerged. Did I mention the great selfie I took recently with a giant whale vertebra the size of coffee table?

The post Craig With Big Things (and Small Things) 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.

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.

Reason #381 that I love my job
I spent this morning doing this:

In the last few days I have been tracking down the world’s largest snail. It is my own contribution to the Sizing Ocean Giants project. The Australian Trumpet shell, Syrinx araunus, is generally agreed to be the largest living snail. Shell lengths at the high end usually range around 2.5 feet (~0.75 meters). My goal has been to track down the largest known individual of the species. My first place to look was the Registry of World Record Size Shells that as origins back to 1964 and is the sort of Guinness Records of shell sizes. Noting a recent 2014 update, I ordered it and await patiently.

The longest recorded specimen, unless updated in the most recent registry, is the one in the top photo at 36 inches or 0.9144 meters. Surprisingly, at near a meter long this is not largest snail to ever live. Campanile giganteum (photo just above) from the Eocene is the largest fossil gastropod and considered to be the largest gastropod species ever. However, the maximum reported length is just 90 centimeters suggesting that Syrinx araunus could be larger. Given that the C. giganteum has longer slender shell than S. araunus, in terms of biovolume S. aruanus may undoubtedly be larger even given approximately similar shell lengths.

The post Sleuthing the Largest Snail 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.

At beginning of  a Gastropod’s life, at the tiny larval stage (the veliger), the parts of the body begin to rotate.  Not of all them, just the organs for digestion, reproduction, circulation, the shell, and the body wall that covers the former and secretes the latter, twist 180˚ counter clockwise.  This process, called torsion, eventually places the organs previously on the right side on the left. The central nervous system becomes a pretzel.  Torsion quite literally ties the snail’s stomach in knots with the whole gut eventually twisted into a U-shape. This gut spin also has the unfortunate consequence of placing the anus right above the snail’s head in proximity way to close to the gills.

Why evolution has favored this round robin of body parts in Gastropods, and how exactly it occurs is a fascinating story and one not yet fully understood.    In 1929, Walter Garstang, proposed a hypothesis both for how and why torsion occurs.  Garstang was born in 1868 in England and ascended the ranks of academia to work on everything from slugs to sand crabs to sea gulls.  His life’s work is divided into three periods: the first occupied primarily with pure marine biology and larval development; a second devoted to fishery investigation of which he is pioneer; and third as full professor and into retirement concentrated on fundamental problems in zoology and evolution with ventures into bird song.  As noted in his obituary, in 1949, he was a poet and lover of nature.  And although noted for many things, Walter Garstang, is probably best remembered for his poems about form, function, and development in invertebrates.  A collection of his poems was published two years after his death as Larval Forms and Other Zoological Verses, an epic volume that resides in a special spot on my and other zoologist’s bookshelves.

In a poem about Tunicates or sea squirts, Oikopleura, Jelly Builder, Garstang waxes poetically,

A filter in front collects all the fine particles

Micro-flagellates and similar articles

Which pour in a stream through a jelly-built tunnel

Into its mouth and its mucillage funnel.

However best known among his prose is The Ballad of the Veliger or How the Gastropod Got Its Twist, a 400 word poem dedicated to and explaining torsion in Gastropods.

The Veliger’s a lively tar, the liveliest afloat,

A whirling wheel on either side propels his little boat;

But when the danger signal warns his bustling submarine,

He stops the engine, shuts the port, and drops below unseen.

He’s witnessed several changes in pelagic motor-craft;

The first he sailed was just a tub, with a tiny cabin aft.

An Archi-mollusk fashioned it, according to his kind –

He’d always stowed his gills and things in a mantle-sac behind. 

Young Archi-mollusks went to sea with nothing but a velum –

A sort of autocycling hoop, instead of pram – to wheel ’em;

And, spinning round, they one by one acquired parental features,

A shell above, a foot below – the queerest little creatures. 

But when by chance they brushed against their neighbours in the briny,

Coelenterates with stinging threads and Arthropods so spiny,

By one weak spot betrayed, alas, they fell an easy prey –

Their soft preoral lobes in front could not be tucked away! 

Their feet, you see, amidships, next the cuddy-hole abaft,

Drew in at once, and left their heads exposed to every shaft.

So Archi-mollusks dwindled, and the race was sinking fast,

When by the merest accident salvation came at last.

A fleet of fry turned out one day, eventful in the sequel,

Whose head-and-foot retractors on the two sides were unequal:

Their starboard halliards fixed astern ran only to the head,

While those aport were set abeam and served the foot instead.

Predaceous foes, still drifting by in numbers unabated,

Were baffled now by tactics which their dining plans frustrated.

Their prey upon alarm collapsed, but promptly turned about,

With tender morsel safe within and the horny foot without!

This manoeuvre (vide Lamarck) speeded up with repetition,

Until the parts affected gained a rhythmical condition,

And torsion, needing now no more a stimulating stab,

Will take its predetermined course in a watchglass in the lab.

In this way, then, the Veliger, triumphantly askew,

Acquired his cabin for’ard, holding all his sailing crew–

A Trochosphere in armour cased, with a foot to work the hatch,

And double screws to drive ahead with smartness and dispatch.

But when the first new Veligers came home again to shore,

And settled down as Gastropods with mantle-sac afore,

The Archi-mollusk sought a cleft, his shame and grief to hide,

Crunched horribly his horny teeth, gave up the ghost, and died.

Garstang’s hypothesis about Torsion was that it occurs in two steps.  The veliger possesses two retractor muscles.  One of these extends from the shell on right, over the gut, and attaches to the left side of head and foot.  The other starts on the left and attaches to the right.  Garstang proposed that these muscles were asymmetrical in their size and strength.  The right-to-left retractor causes the larval shell to twist the first 90˚ in a matter of minutes.  The second 90˚ requires deferential cellular growth to accomplish.  Garstang suggested further that torsion was an adaptation for protection.  Without torsion, larval snails would retract into the shell tail first leaving the head and other important parts exposed to the teeth, claws, and tentacles of hungry predators.  With torsion, larval snails would retract the head first.  And in the grand coup d’état that was characteristic of so many of Garstang’s bold evolutionary hypotheses he offered one additional item.  That evolution of no torsion to torsion all occurred through a single, not an accumulated set, of mutations.

Over 80 years later, what has happened to Garstang’s Torsion Hypothesis?

As one author put it 1958 “more controversy has been devoted to the adaptive explanation [of torsion] than to any other point to of molluscan biology.” (Morton 1958)  More recently in 1992 another author noted that torsion is still one of the “grand traditional controversies among malacologists [that] have not been resolved.”  (Beiler 1982)

Much like a snail, the story of understanding their past, is also full of twists.  Walter Garstang himself is both praised and belittled. “He often appropriated the ideas of others without attribution, ignored earlier studies conflicting with his theories, and clung to [outdated scientific ideas]” (Holland 2011).  Indeed, Garstang’s Torsion idea and others, may largely live on “chiefly though their perpetuation in numerous textbooks” (Gee 1989) and their importance colored by obituaries and commentaries on his work written by his son-in-law.  As Stephen J. Gould wrote, “We cannot blame a man very strongly for lavishing too much praise on his father-in-law.” Alternative hypotheses, including one that requires a land dwelling octopus, have come and gone, and in rarer cases stayed only after dueling with the Garstang’s ghost.

Check in next week for Part 2!

The post How the Gastropod Got Its Twist first appeared on Deep Sea News.

A tragic event has befallen a rattail fish at 1,100 meters. The fish is alive, barely, and visibly quivering. Not able to swim any longer it falls to seafloor, continuing to tremble, and slowly dies for another hour.

When the fish first arrives to the seafloor, whelks are rare. However the chemical cue of the dying fish soon lures the snails from afar. During the first hour only two were present. Within four hours, moving slowly (a meter an hour) as they creep along the muddy seafloor, 78 whelks swarm the fish. The whelks are here to speed up the fish’s death. The hungry scavenging snails, cannot wait for pleasantries, like a fish dying before they consume it. There is no predicting when the next food fall will arrive to their part of the seafloor.

Within eight hours, the fish transitions from dying to dead, not taken by the original calamity but by a pack of flesh hungry snails. In the abyss, a dwindling life begets continued life even if the path is not attractive.

Based on Aguzzi J, Jamieson AJ, Fujii T, Sbragaglia V, Costa C, Menesatti P, Fujiwara Y (2012) Shifting feeding behaviour of deep-sea buccinid gastropods at natural and simulated food falls. Mar Ecol Prog Ser 458:247-253

The post With a snail’s help a fish transitions from dying to dead first appeared on Deep Sea News.