Despite the name, however, Vampire Squids are not really squids. They are more closely evolutionarily allied with octopods, but they aren’t really octopods either. Vampire Squids are evolutionary all alone residing in thier own long branch of the tree of life.

If we look at this phylogeny from Lindgreen and coauthors from 2012 based on multiple genes.

And zoom in at the upper part of the tree

Let’s zoom in a little more

You can clearly see that Vampyroteuthis infernalis resides on alone on its own evolutionary branch. It shares its last common ancestor with the octopods but this a distant relative at best. Many think the Vampire Squid may be”phylogenetic relict” the last surviving member of order cephalopods long ago extinct.

One truly is the loneliest number. While you reflect on this evolutionary and ecological isolation of the Vampire Squid enjoy these videos from the Monterey Bay Aquarium Research Institute.

The post The Lonely Existence of Vampire Squids first appeared on Deep Sea News.

It’s summertime and you’re sweating from the heat and humidity. You jump in the pool and feel a rush of relief as you suddenly feel cooler. The water might not be colder than the air, but it sure feels like it, and it does a great job of relieving you from the heat. We’re all familiar with this, but did you know it may also explain why whales are so big?

Almost 4 years ago, I began my PhD studies at Stanford University. I was interested in how changes in the environment impact biodiversity through time. I first decided to tackle the question of how transitions from land to water impact body size. Mammals are a well-studied group of animals, and they’ve made this transition multiple independent times. There’s also lots of data on their body size, of species in the modern and the fossil record, so they seemed like a great place to start to answer this question. The original goal was just to test whether aquatic mammals are bigger than we expect by chance, but I was really surprised by what we discovered about the drivers of their evolution.

We did (unsurprisingly) find that aquatic mammals are bigger than expected, but also noticed that, despite each group of aquatic mammals evolving from differently sized terrestrial ancestors, they all evolved to the same size of about 500 kg! Even stranger, we found that aquatic mammals are much more constrained in their body size than their terrestrial counterparts! This goes against almost all the reasons why people believe aquatic mammals are big. Once you’re in the water, the idea goes, you should be able to get as big as you want without being hindered by the limitations of gravity and food shortages. Rather, we found that aquatic mammals must get bigger.

After hitting the books, I was shocked that I was able to develop a simple mathematical model that explained the minimum, maximum, and average sizes that we were seeing in aquatic mammals. The minimum constraint in the model shows that these mammals need to produce more energy in their bodies and lose less of that energy, relatively speaking, to the water, to have any energy left over for reproduction and growth. Otters are the one exception to this trend: we’re thinking that this is because they only spend part of their lives in the water or are more efficient at conserving their body heat with their thick fur, although we haven’t been able to test either of those hypotheses yet.

Through developing the model, I also discovered that there’s a maximum limitation on size too. At a certain point, aquatic mammals just can’t eat enough food, no matter how much there is, to sustain larger sizes. For toothed mammals, it appears that this maximum is about the size of a sperm whale. However, baleen whales have figured out a way to eat more efficiently than their toothed cousins, in which they filter entire schools of krill at once from large gulps of water. This feeding strategy seems to allow them to exceed this maximum limit and achieve superwhale sizes.

Long story short, if you want to be a mammal and live in the water for your entire life, you need to get a lot bigger, but you also need to be careful, because you can’t get too much bigger. It’s a tricky balance that aquatic mammals have amazingly mastered at least three times! I’ll stick to my occasional dips in the pool, thank you very much!

The post So, You Want to Live in the Water? A Tale of Why Aquatic Mammals are So Big first appeared on Deep Sea News.

No not that hammer. This one.

The Malleidae, or the hammer oysters, is a suite of around 30 species, primarily in the genus Malleus, all with a hammer or T shape to the shell.  I mean look at this shell.

I like to think in the evolution process a conversation like this occurred.

Representative of all other clams, oysters, and scallops: So I thought we all a voted on this…and umm…agreed that our shells would be sort of roundish.

Malleus: You know I got to drop the Hammer!

Representative: Well you know is just that we kind of agreed on this. We really all need to be roundish.

Malleus: You can’t stop the Hammer!

Representative: What about a nice kind of tear drop shape?

Malleus: Can you feel the Hammer!

Representative: We could give you some cool wings or tabs?

Malleus: Hammer!

Representative: What about you some flashy spikes?

Malleus: HAMMER! HAMMER!

Representative: Now your just being unreasonable.

Malleus: HAMMER! HAMMER! HAMMER! HAMMER! HAMMER! HAMMER!

Representative: Why are you shouting?

Malleus: HAMMER! HAMMER! HAMMER! HAMMER! HAMMER! HAMMER! HAMMER! HAMMER!

So why the hammer shell? Does Malleus crawl around and drop the hammer pain on unexpecting prey or predators? Do the shelled wings allow allow for some other bad-assery?

The function of the hammer shell is perhaps a little more vanilla. Hammer oysters typically inhabit the course sands around coral reefs. Those wings, buried in the sand, serve as anchor, allowing the hammer oyster to stay in place as currents threaten to cary the oyster away.

Hammer oysters often take a battering from currents and debris propelled through the water. This often damages the shell. In the words of the famous naturalist, Charles Maurice Yonge, an expert on bivalves, “It is rare to find a large shell which does not exhibit extensive areas of repair. An example (from Rabaul) is shown in Figure 5A, the animal has withdrawn from a broken extent of distal shell and formed a new one at a somewhat different angle….Such changes may be in any plane and many adult shells are of grotesquely distorted appearance.”

The post Bring the hammer. first appeared on Deep Sea News.

*alternative titles include “Looking a gift seahorse (genome) in the mouth”, “My kingdom for a seahorse genome”, “Hold your seahorses“, and “The galloping evolution of seahorses“.

Let’s face it, seahorses, pipefishes, and seadragons are messed up. That’s not a subjective opinion but an evolutionary fact.  It’s like all the approximately 300 species in Syngnathidae (the family of fish that contains all these critters) held a meeting and decided unanimously “Nah, screw it, we’ll do things however we damn well please.”  The Syngnathids are revolutionaries of the fish world.  ¡Viva la Evolución Revolución!

Seriously, almost everything in these species is different.  There is the elongated snouts and small mouths and jaws.  The pelvic and caudal fins are often gone.  The scales are replaced with an armor of bony plates.  Let’s not forget about the whole “male pregnancy” thing where the males nourish the developing embryos in a pouch.  Seahorses take it all to a whole other level with the prehensile tail and the vertical body axis.

So ultimately, one is left wondering what’s up with those genes?  Well, thanks to an intrepid group of geneticist, the complete genome of the tiger tail seahorse, Hippocampus comes, is complete.  With the full genome comes great power, the ability to compare this genome to the other sequenced fish.

Part of the story regarding the bizarreness of seahorses is gene loss.   Secretory calcium-binding phosphoprotein (SCPP) genes code for matrix proteins that are important in the formation of bone and teeth.  These genes are completely missing in Hippocampus comes and may explain why seahorses do not have teeth.  Did I forget to mention that?  Yeah seahorses and seadragons are toothless. The tbx4 gene, conserved in jawed vertebrates, acts as a regulator of hindlimb formation.  The gene is completely absent in the seahorse genome and explains the absence of those pesky pelvic fins.

What about that whole “male pregnancy” thing?   The H. comes genome contains six pastn genes, part of a family of genes that regulate the hatching of embryos.  The researchers conducted extra work, like the genome was not enough, suggesting a role for these pastn genes in brood pouch development and/or hatching of embryos within the brood pouch prior to birth.

Seahorses have also apparently lost many conserved noncoding genes (CNEs) that function as enhancers, repressors, and insulators of other genes.  1,612 CNEs have been lost in seahorses.  Compare this to the 281 in the Nile perch.  It is unclear how the loss of the CNEs may be related to some of the oddities of the seahorse, but loss of CNEs is tied to moderate short stature and shortened limbs in humans.

How I imagine the scientists of the study acted once they finished the genome

The awesomeness of this kind of work cannot even be articulated.  The researchers have done an amazing job of unpacking the genome of a seahorse and showing how genome evolution directly leads to all the uniqueness of seahorses.  Admittedly, I am little disappointed in not seeing a discussion of the prehensile tails genes and armored plating discussed. I guess I’ll need to wait a bit to build my army of aquatic minions to take over the world.

The post In the evolution of fishes, this is a one seahorse race* 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.

If you’re still skeptical about barnacles, you must be a robot. C’mon, look at that thing! If ninjas lived in the deep sea, they would use these barnacles as their weapon. Case in point:

Barnacles live at hydrothermal vents all over the world, sometimes packed as densely as 1500 individuals per square meter. Currently, there are 13 described barnacles species across 4 taxonomic families. But morphology isn’t great at distinguishing species, so in recent years researchers have needed to rely on DNA sequences to untangle the relationships between deep-sea barnacle species.

In honor or Darwin’s birthday today (collectively known as #DarwinDay), the most appropriate marine biology homage is story about the evolution of deep-sea barnacles. Herrera et al. (2015) have a recent, really fantastic paper, in Molecular Ecology, where they used fancy genomics tools to ask:

• Do vent barnacles have a single evolutionary origin (e.g. did they all evolve from a common ancestor)?
• When and where did vent barnacles first evolve?
• Historically, how did vent barnacles spread (radiate) across the deep-sea?

Herrera et al. collected 94 barnacle specimens from 18 hydrothermal vents worldwide (it’s really hard to do deep-sea biology, so this is actually LOT of barnacles painstakingly collected with robotic claws). Next, they sequenced three genes from each individual (the mitochondrial cytochrome c oxidase 1 gene, the nuclear 28S rRNA gene, and the nuclear Histone H3 gene), and additionally got crazy amounts of whole-genome data from each barnacle using a technique called Restriction-site-associated DNA sequencing (RAD-seq).

<cue elevator music and montage of genomic data analysis, where a hacker-looking scientist sits in a dark room, furiously typing code and downing shots of espresso. Finally he/she builds evolutionary trees, glorious trees.>

The results of this study showed that, contrary to prior hypotheses, barnacles have colonized deep-sea hydrothermal vents at least twice in the course of their evolutionary history. This can be seen by the two distinct clades (red and yellow) recovered in Herrera et al.’s phylogenetic Tree O’Barnacles:

The largest group of vent barnacles (Clade A, the red clade above) seems to have originated in the Western Pacific Ocean and then moved east, colonizing “the Eastern Pacific, the Atlantic sector of the Southern Ocean and the Indian Ocean during the late Miocene to early Pliocene” (Herrera et al. 2015, using ancestral state reconstruction to analyze phylogenetic patterns). Once barnacles had adopted the hydrothermal vent lifestyle, it looks like they moved east. Based on molecular clock estimates using DNA sequences, the timing of their dispersal is concordant with geologic events such as the opening of the Drake Passage (41 million years ago).

Barnacle DNA also indicates that hydrothermal vent species arose fairly recently (well, in geologic time), emerging after a deep-sea mass extinction event during the Cretaceous– Paleogene period boundary. That boundary–65 million years ago–should be familiar. Deep-sea barnacles started their ascension as the dinosaurs were on their last breath.

We’ve only just begun dipping our toes into the world of deep-sea genomics. Given the time-machine-like powers of DNA sequences, and the fact that hydrothermal vents are essentially “islands” in the deep sea (thus giving us the perfect system to test some big evolutionary theories), the next few years should produce some really exciting deep-sea discoveries. Forget hoverboards: if Darwin came Back to the Future I’m sure he’d much rather have genomics.

Reference:

Herrera S, Watanabe H, Shank TM (2015) Evolutionary and biogeographical patterns of barnacles from deep-sea hydrothermal vents. Molecular Ecology, 24:673-689.

The post Deep-Sea Barnacle Genomics. Because, #DarwinDay 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.

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:

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The largest fishes in the oceans feed on some of the sea’s smallest organisms. Several massive plankton-feeding elasmobranchs – the group of fishes that include sharks and rays – evolved adaptations to gulp huge mouthfuls of water and filter out plankton, shrimp, and small fishes. Though these tiny tidbits in themselves may not seem like a meal fit for a giant, the sheer abundance of these minuscule organisms in the sea adds up to a bounty for animals designed for sifting and straining them out of the water. What’s even more interesting is that each of the four massive filter-feeders evolved their particular diet and feeding morphology independently of one another.

Whale Sharks share a common ancestor with the docile nurse sharks, basking sharks are part of the branch of the shark family tree that has great white and mako sharks, the megamouth shark may be descended from the Odontaspidids, which includes the sandtiger sharks, and the manta rays are related to the much smaller bat rays and eagle rays. This is called convergent evolution, where natural selection steers the similar re-engineering of preexisting anatomical traits to achieve a similar solution between different groups of unrelated organisms. In the evolution of elasmobranchs over the last 45 million years, three lineages of sharks and one lineage of rays all independently evolved to filter-feed feed on plankton, swarms of tiny shrimp, and schools of small fishes as a means to successfully increase their survival.

Farther back in time, during the Cretaceous period when dinosaurs roamed the land and huge marine reptiles swam the warm, shallow continental seas around the globe, this same experiment in filter-feeding evolved much earlier, and completely independently of any of today’s huge plankton-eating sharks. In a recent paper in the Journal of Vertebrate Paleontology, Kenshu Shimada and an international team of researchers unraveled the complex and confusing identity of several species of fossil shark teeth and found them to be the earliest known example of filter feeding in sharks. Small teeth from ancient marine rocks in Colorado, Texas, and Russia showed certain characteristics seen in recent giant filter-feeding sharks. In fact, the teeth looked so much like the huge deep sea filter-feeding Megamouth shark Megachasma, that the new genus was dubbed Pseudomegachasma.

All of today’s filter-feeding sharks use highly-modified gills to strain food out of water that flows from their cavernous mouth through their gill openings. Not once do they appear use their teeth for feeding, so in these lineages of sharks, the teeth have become exceedingly reduced in size, usually barely a quarter inch in size. Unlike other instances in evolution where useless organs or appendages are eventually lost, in filter-feeding sharks the teeth didn’t go away, but they shrunk,

and strangely, increased in numbers rather than disappeared altogether, so filter-feeding sharks and rays have hundreds of itty-bitty seemingly useless teeth in their jaws. Fortunately, all sharks and rays shed their old teeth to make room for the new ones growing in, which is how such teeth from ancient sharks later become today’s fossils that guide our understanding of shark evolution.

These teeth from at least two different species make Pseudomegachasma the oldest plankton-feeding sharks yet known, and is believed to have evolved from an earlier, extinct fish-eating shark. Pseudomegachasma lived between 92-99 million years ago, first appearing in coastal waters that is now southwestern Russia, and later extending into the ancient inter-continental marine seaway that once covered an area from Texas to Colorado.  Why Pseudomegachasma went extinct, and why there seem to be no giant plankton-feeding sharks between 50 and 91 million years ago is still a mystery that only future fossil discoveries can solve.

The research team consisted of Kenshu Shimada, DePaul University; Evgeny V. Popov, Saratov State University, Russia; Mikael Siversson, Western Australia Museum, Bruce J. Welton, New Mexico Museum of Natural History, and Douglas J. Long, California Academy of Sciences and St. Mary’s College of California.

Article:
Shimada, K., E. V. Popov, M. Siversson, B. J. Welton, and D. J. Long. 2015. A new clade of putative plankton-feeding sharks from the Upper Cretaceous of Russia and the United States. Journal of Vertebrate Paleontology, Vol. 35, No. 5.

The post Before Giant Plankton-Feeding Sharks, there were Giant Plankton-Feeding Sharks. first appeared on Deep Sea News.

The picture to the left is how many of his former students remember famed paleontologist David Raup (1933-2015): with a cigarette firmly in his mouth or hand. His nicotine addiction was more than once a source of amusement. The other students and I would often sit in the department lounge, with Dave holding forth while dropping his ashes into a Styrofoam cup. Once he forgot he had done so, and took a sip! Gwen Daley, then an undergraduate at the University of Chicago, remembers “We used to ask questions at the end of class to see how long he could resist before dashing to his office for a nicotine fix. When he started ‘smoking’ the chalk, we knew it wouldn’t be long.” Former University of Rochester graduate student Kraig Derstler, remembers him “crushing a piece of chalk into the ashtray while deep into a paleo-thought. And dumping his ashes into his pants cuff when there was no ashtray.” But behind these clouds of smoke and piles of ashes, was a scientist of boundless creativity and one of the most seminal figures in creating the modern day discipline of paleobiology.

David Raup’s prolific work profoundly shaped how we analyze the history of life on Earth and the interaction of life and geological processes. His work is expansive, ranging from fundamental contributions in how we view the form of ancient organisms to the development of analytical methods to describe the fossil record and perhaps most importantly the mechanisms and impacts of mass extinctions. More than anyone else, he introduced computers as a key tool for the study of paleontological problems. His seminal textbook with Steven Stanley, Principles of Paleontology (1971, 1978), has been used by generations of paleontologists. His two popular books on extinction, The Nemesis Affair: A Story of the Death of Dinosaurs and the Ways of Science (1986) and Extinction: Bad Genes or Bad Luck? (1991), are still widely read and discussed.

Raup is known as a key member of the “Chicago school” (aka the “Chicago mafia” to some), the group of paleontologists at the University of Chicago who trained many of the leading younger scientists in the discipline with continued influence on the field. Prior to coming to Chicago, however, he was a member of the faculty at the University of Rochester. This is the time I knew him best and where I did my master’s under his guidance. For a short time, this was one of the leading paleontology programs in the country; along with Dave, the faculty included other prominent paleobiologists including Jack Sepkoski and Daniel Fisher. But my interactions with David were vital to my career and shape how I view the dynamics of the biological world. He taught us all how to think about paleontology in the way that he did. I still have the syllabus for his advanced paleontology class, unique at the time in that it was a paleontology course taught effectively without fossils! It was a great introduction to the analytical methods and concepts that Raup pioneered. My thesis, on Geomagnetic Reversals and the History of Life, drew heavily on the probabilistic concepts that I learned from him. Given his love of statistics and random processes, I am not shocked by the rumor that Raup put himself through college playing poker.

Dave was actually somewhat proud of the fact that he did not directly study fossils themselves; in his Presidential Address to the Paleontological Society (1978), he stated “I feel in a somewhat strange position today as the first president of the Society who has never described a species.” Kraig Derstler, now a professor at the University of New Orleans, recalls that Dave was once asked if he had touched a fossil recently. He said that he kept one on his desk so he could roll it around occasionally. He was also given some grief about this. I recall that Bernie Kummel (Raup’s Ph.D. advisor at Harvard) visited Rochester. At the beginning of the talk, he called Dave forward and handed him a fossil, with instructions to have it identified by the end of the presentation. Although I do remember going on a field trip with him, then graduate student Lee Gray (now at Mt. Union College) recollects that the undergraduate student geology organization at Rochester asked Raup if he would like to attend a field trip: “His reply was, ‘No, I might get my hands dirty.’”

When discussing papers in seminar, Raup encouraged us to be highly critical. But, as Derstler recalls “we started to notice that Raup never went negative…We started wondering if he could critique a paper with the same enthusiastic feeding frenzy that we displayed. He showed up for a seminar that week and spent 5 minutes masterfully, colorfully ripping the paper a new one, then sat down, lit a cigarette, and smiled with that wide grin. After a long, silent pause, he returned to Raup mode, ignoring the crap and discussing the good stuff buried within the paper.” And Alan Cutler (former U. Rochester graduate student, author of an authoritative biography of Steno) adds: “I definitely learned more about critical thinking from him than from anyone else in my academic career. I also learned that there was more than one way of being a “real” paleontologist. “

In 1978 Raup decided to leave, to become head of the Department of Geology at the Field Museum of Natural History in Chicago. As he put it at the time: “Chicago has become the natural center for the area of scholarship in which I am interested.” The impact on the graduate students at Rochester was devastating. Most of us immediately started to plan to leave. Unfortunately, the decision was announced in mid-February, far too late for most graduate school applications. The faculty aided some of us (I ended up with Sepkoski in Chicago), but there was also the feeling that “triage” was going on, that certain of us would be helped and others left to fend for themselves. The suggestion was made that the picture of Dave grinning in the school paper (Right) be made in to a t-shirt with the phrase “Just Another Random Walk.” A less charitable suggestion was “So Long Suckers!”

Raup went on to have the rest of his career in Chicago, first at the Field Museum, then at the University of Chicago. Unfortunately, I had far fewer interactions with Raup in Chicago. He became a full time member of the University of Chicago faculty just as I was finishing my doctoral thesis. Nevertheless, his approach to science profoundly influenced my PhD research and it does to this day. When he retired in 1995 to Washington Island, WI, he effectively said goodbye to paleontology and academia. He sailed, involved himself the local community, and became an inveterate do-it-yourselfer. Cutler remembers seeing a “slightly different side of him when my wife and kids and I visited him on Washington Island. Still not warm and fuzzy, he was much more of a hands-on homeowner than I expected. I thought the only things he did with his hands were punching keyboards and smoking cigarettes, but there he was with that Dave grin showing off the drill press he jury-rigged out of spare parts. Dave never failed to surprise.”

I talked to Dave on the phone occasionally during those years, he seemed to be enjoying life away from science. I wish we had spoken more and that I had taken the opportunity to visit. Last year I nominated Raup for the prestigious Crafoord Prize, which he richly deserved. I regret that my fantasy of calling him with congratulations will never be realized.

Selected Publications of David M. Raup

Books:

RAUP, D.M and S.M STANLEY. 1978. Principles of Paleontology (2nd ed.).

RAUP, D.M. 1992. Extinction: Bad Genes or Bad Luck?

RAUP, D.M 1999. The Nemesis Affair: A Story of the Death of Dinosaurs and the Ways of Science.

Journal articles:

RAUP, D. M. 1962. Computer as aid in describing form in gastropod shells. Science (New York, N.Y.), 138(3537):150-152.

RAUP, D. M. 1972. Taxonomic diversity during the Phanerozoic. Science, 177(4054):1065-1071.

RAUP, D. M. 1976. Species diversity in the Phanerozoic: a tabulation. Paleobiology, 2(4):279-288

RAUP, D. M. 1976. Species diversity in the Phanerozoic; an interpretation. Paleobiology, 2(4):289-297.

RAUP, D. M. 1977. Removing sampling biases from taxonomic diversity data. Journal of Paleontology, 51(2):21-21.

RAUP, D. M. 1978. Cohort analysis of generic survivorship. Paleobiology, 4(1):1-15.

RAUP, D. M. 1979a. Size of the Permo-Triassic bottleneck and its evolutionary implications. Science, 206(4415):217-218.

RAUP, D. M. 1979b. Biases in the fossil record of species and genera. Bulletin of the Carnegie Museum of Natural History, 13:85-91

RAUP, D. M. 1988. The role of extraterrestrial phenomena in extinction. Revista Espanola de Paleontologia, 1988(Extraordinario):99-106.

RAUP, D. M. 1991. A kill curve for Phanerozoic marine species. Paleobiology, 17(1):37-48.

RAUP, D. M. 1994. The role of extinction in evolution. Proceedings of the National Academy of Sciences of the United States of America, 91(15):6758-6763.

RAUP, D. M., AND G. E. BOYAJIAN. 1988. Patterns of generic extinction in the fossil record. Paleobiology, 14(2):109-125.

RAUP, D. M., AND S. J. GOULD. 1974. Stochastic simulation and evolution of morphology – towards a nomothetic paleontology. Systematic Zoology, 23(3):305-322.

RAUP, D. M., S. J. GOULD, T. J. M. SCHOPF, AND SIMBERLOFF.DS. 1973. Stochastic-models of phylogeny and evolution of diversity. Journal of Geology, 81(5):525-542.

RAUP, D. M., AND D. JABLONSKI. 1993. Geography of End-Cretaceous marine bivalve extinctions. Science, 260(5110):971-973.

RAUP, D. M., AND A. MICHELSON. 1965. Theoretical Morphology of the Coiled Shell. Science, 147(3663):1294-1295.

RAUP, D. M., AND A. SEILACHER. 1969. Fossil foraging behavior: computer simulation. Science, 166:994-995.

RAUP, D. M., AND J. J. SEPKOSKI. 1982. Mass extinctions in the marine fossil record. Science, 215(4539):1501-1503.

RAUP, D. M., AND J. J. SEPKOSKI. 1984. Periodicity of extinctions in the geologic past. Proceedings of the National Academy of Sciences of the United States of America-Biological Sciences, 81(3):801-805.

RAUP, D. M., AND J. J. SEPKOSKI. 1986. Periodic extinction of families and genera. Science, 231(4740):833-836.

RAUP, D. M., AND J. J. SEPKOSKI. 1988. Testing for periodicity of extinction. Science, 241(4861):94-96.

SEPKOSKI, J. J., R. K. BAMBACH, D. M. RAUP, AND J. W. VALENTINE. 1981. Phanerozoic marine diversity and the fossil record. Nature, 293(435-437).

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