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Everybody loves squid, cuttlefish, and octopuses…and we all love all of the crazy belemnites, ammonites, nautiloids, and orthocones which came before them. But, if you are like me, you have probably been sitting around wondering what came before that. How old are cephalopods, really, and what were the first ones like? Yet, although cephalopods are amply represented in the fossil record from the Ordovician onward, their very earliest origins are shrouded in controversy and mystery. Although there are various fossils which might be cephalopods (or their antecedents) at present the oldest animals to be indisputably classified as cephalopods are the Ellesmerocerida. This order of nautiloids flourished at the end of the Cambrian and into the Ordovician 9approximately half a billion years ago).
Although they were definitely cephalopods, the Ellesmerocerida were somewhat mysterious themselves. They were typically quite small—or even minute. They seemingly had ten arms–although this is a conjecture based on where the muscles attached to their shells (and based on what we know of their descendants). The soft parts of the first cephalopods were not preserved and so we don’t exactly know.
Their shells reveal close-spaced septa–closed off interior spaces within the shell, which provided buoyancy. The Ellesmerocerida also had relatively large ventral siphuncles—tissues which pass longitudinally through the septa to allow buoyancy control. So the first cephalopods we know about were more or less built on the same line as the subsequent ones (until belemnites internalized the shells). I wonder what else we will find out about the origins of this fascinating group of animals as we learn more about paleontology.
In a long-ago post, Ferrebeekeeper wrote about the Ordovician–the age of mollusks–when big predatory cephalopods and gastropods overtopped nascent vertebrates as the apex predators of the world oceans. Cephalopods are fiercely intelligent, incredibly fast, and astonishing at camouflage. They can be infinitesimally small or remarkably large. They can even be transparent. However they don’t last well—they are squishy and even if they aren’t eaten they have very short lives. One of the most vivid memories of my adolescence was watching cuttlefish hover and change colors and feed with bullet-fast grabber arms at the National Zoo. The memory comes with a dark post-script. I returned a few months later with friends, only to find that the cuttlefish had entered a bizarre unnatural senescence and were literally falling apart at the seams. They do not die of old age in the ocean; something always eats them.
But this is no longer the lovely Holocene with its oceans full of fish and skies full of birds. We have entered the Anthropocene—an age of hot acid oceans filled with Japanese trawlers bent on catching every last fish in the sea by means of nets the size of Rhode Island. Suddenly it is not so beneficial to be a big bony ancient fish with hard scales and sharp teeth. The teleosts and the cartilaginous fish are being physically pulled out of the ocean by humans. It takes them too long to reproduce and rebuild their numbers (even as national governments subsidize fishermen to build more and larger fishing boats). The age of fish—which has lasted from the Devonian (420 million years ago) until now—is ending. So a new scramble to exploit the great open niches in the seas is beginning.
Unexpected life forms are flourishing. The sea floors are filling up with lobsters, which have not been so prevalent in a long time. Giant jellyfish are appearing in never-before-seen numbers. However it is beginning to seem like the greatest beneficiaries may be the cephalopods. Mollusks with shells are having their own troubles–as the carbonic acid oceans eat at their calcium shells, but the octopus, squid, and cuttlefish have no such problems. Not only are they well suited for tropical waters, they rcan also reproduce so fast that they can keep ahead of human’s bottomless appetite. A single squid egg cluster can have millions of eggs inside.
Cephalopods tend to be generalists—they eat all sorts of things including booming micro-invertebrates and jellyfish. They are clever enough and malleable enough to slip out of all sorts of hazards. Their swift lives are a boon. Because they reproduce so quickly and prolifically, they evolve quickly too—a necessity in our 24 hour world (as all sorts of out-of-work journalists, lamp lighters, factory workers, and saddlemakers could tell you). I wonder if in a few million years the waters will glow with great shoals of exotic tentacle beasts we have scarcely imagined. Will there be fast marlin-type squids with rapiers on their mantles and huge whale-shark type octopuses skimming the phytoplankton with their own giant nets? Will the skies darken with flying squids and the sea floor change colors as tens of thousands of cuttlefish take the roles of reef fish and reef alike?
It is possible. The world is changing faster than we would like to admit—becoming something brand new—becoming something very old.
This week’s big science news is that researchers have finally sequenced the gene for a cephalopod– the California two-spot octopus, Octopus bimaculoides. Geneticists and molecular biologists from the University of Chicago and Berkley worked together to unravel the entire gene—which turned out to be nearly as large as the human genome and did not contain any mass data duplication (which some vertebrate-centric scientists had thought might account for the size and complexity). To quote Business Insider, “The work will allow scientists to study the genetic factors that give way to the octopus’ odd physical traits, and may reveal novel insights not only about the unique biology of cephalopods, but also about the evolution of traits that give rise to a complex nervous system and adaptive camouflage.”
There are already some fascinating initial discoveries from the octopus gene sequence data. Not surprisingly, the scientists discovered completely unique genomic sequences for reflectins (which allow the octopus to change color instantly). Even more intriguingly, the researchers discovered a huge suffusion of protocadherins—which facilitate the interaction between neurons. Octopus seem to have many more of these neural development genes than expected–and indeed the eight legged sea creatures have twice as many protocadherins as more familiar mammalian creatures like humans. However the majority of the data requires additional study. Scientists also hope to contextualize the somewhat abstract genes by sequencing other cephalopods (particularly cuttlefish—which a different team is working on).
Unfortunately I am not a geneticist and the niceties of jumping genes are somewhat lost on me. I am however greatly interested in finding out more about the biology and evolutionary history of cephalopods. This class of organisms has attained a shockingly high degree of intelligence through a very different evolutionary path than the most intelligent vertebrates (like primates, proboscideans, cetaceans, and parrots). The clever mollusks are capable of solving difficult puzzles in unexpected ways and their donut shaped brains have long perplexed and intrigued neurologists. Perhaps further details of their genetic makeup will yield the seed for tomorrow’s transgenically created superbrains! Barring that, it would be good to understand the mechanisms of diverse neural systems and grasp more about the development of these beautiful yet unfamiliar creatures.
The mighty lion is clearly the king of beasts…or is he? For your holiday pleasure, here is a gallery of octopuses wearing crowns. Octopuses have short lives and they do not grow to immense sizes, but they are extremely intelligent. All of the regal tentacles below put me in mind of the Ordovician, a geological age when mollusks (in the form of giant cephalopods) truly were the kings of the animal world.
I have written before about the beautiful cuttlefish (marine mollusks of the order Sepiida). Cuttlefish are closely related to another order of mollusks, the Sepiolida, or bobtail squid, which are perhaps even more endearing. With huge expressive eyes, tiny little tentacles, and opalescent skin, bobtail squids look like they were designed by a Sanrio artist having a strange day. Sepiolida cephalopods appear to be all head (they are also known as dumpling squid or stubby squid because of this shape)–and their large rounded navigation fins, which stick out like Dumbo’s ears only add to the impression. Members of the Sepiolida do not have cuttlebones but they are far more similar to cuttlefish than to other squid—perhaps their taxonomical classification will change as they are better understood.
There are approximately 70 known species of bobtail squid living in the shallow coastal waters from the Mediterranean, to the Indian Ocean, to the Pacific. To quote the Tree of Life Website, “Members of the Sepiolida are short (mostly 2-8 cm), broad cephalopods with a rounded posterior mantle.” The animals are gifted hunters which eat shrimp, arthropods, and other small animals which they chomp apart with a horny beak at the center of their arms. During the day, bobtail squid bury themselves in the sand with only their eyes protruding and then they hunt at night. Certain species of bobtail squid are known to be poisonous, like the lovely Striped Pyjama Squid (Sepioloidea lineolata). This poison is not well understood and may be contained in the slime produced by the creatures.
Bobtail squid are bioluminescent and they use this ability to disguise their profile when viewed from below–a helpful sort of camouflage which serves them as predators and prevents them from becoming prey. Young bobtail squid are not born with the bioluminescent bacteria but must capture them from the water column in order to start the symbiotic colony within their own bodies. The symbiotic relation between the bobtail squid and the bacterial colony has been much studied in the laboratory.
It was thanks to such studies that scientists first began to understand the method through which bacteria communicate with each other. Called “quorum sensing”, such communication takes place within a group of bacteria by means of signaling molecules. The chemical conversations allow bacteria to respond quickly and in aggregate to changes in their environment (to such a degree that a bobtail squid can tell the bacteria within its own tissues how much to fluoresce and can thereby determine its own luminosity by communicating with millions of living entities inside itself). I have written before about how critical bacteria are to the planet and the Earth’s ecosystem. Studying the bobtail squid provided the first understanding of the way that bacteria communicate with each other, but we are now beginning to suspect that such communication might take place on a vast—perhaps even a global—scale.
I had a post all planned for today but the difference between reality and fancy has forced me to scrap my original idea. First, and by way of overall explanation, allow me to apologize for not writing a post last Friday. I was attending a stamp convention in Baltimore over Labor Day weekend in order to fulfill a social obligation. The stamp convention is where my idea for today’s post came from and, of course it’s also where my idea went wrong.
I had initially (optimistically) planned on selecting a variety of stamps representing categories from my blog. What could be better than a bunch of tiny beautiful pictures of snakes, underworld gods, furry mammals, planetary probes, gothic cathedrals, and so forth? But, alas, my concept was flawed. The international postal industry is vast beyond the telling, and, undoubtedly, some nation on Earth has issued stamps featuring each of those subjects, however stamp collectors do not categorize their collections by subject. Instead they organize their precious stamps by pure obsession (usually but not always centered around a particular historical milieu). Apparently there are also subject stamp collectors out there…but real stamp collectors think of them the way that champion yachtsmen regard oafs on jet skis.
True philatelists are more interested in finding oddities which grow out of historical happenstance. Their great delights are the last stamps issued by an occupied country just before regime change, or the few stamps issued with the sultan’s head upside down, or a stamp canceled by a Turkmenistan post office which was destroyed a week after it was built. The nuances associated with such a subtle field quickly overwhelmed me. Additionally, I was unable to approach gray-haired gentlemen in waistcoats who were shivering in delight from looking at what appeared to be identical stamps with identical potentates and ask if there were any stamps with cuttlefish. It seemed blasphemous. I ended up leaving the stamp show without any stamps at all!
But don’t be afraid. There is an entity which is even more obsessive than the stamp dealers: the internet! To add to my previous post on catfish stamps here is a gallery of mollusk stamps which I found online. The beautiful swirls and dots and stripes of this handful of snails, octopuses, slugs, and bivalves should quickly convince you that even the world’s post offices have nothing on nature when it comes to turning out endless different designs.