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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.
The Amazon River is the world’s largest river and it has the world’s largest drainage basin—the vast Amazon rainforest, which stretches from the Andes in the west, to the Guiana Highlands to the north and the Brazilian Highlands in the south. The great river drains east into the Atlantic Ocean….but it was not always so. Before the Andes Mountains rose, the river drained west into the Pacific. Throughout the Cenozoic, the mouth of the river moved up around the continent. Thirteen million years ago, during the Miocene, the river drained north into the Caribbean through a huge tropical swamp–the Pebas mega-wetlands–which covered over one million square kilometers of what is now the Amazon Basin.
An illustration of Pebas Corocodilians–Gnatusuchus is underwater, gobbling clams (art by Javier Herbozo)
Like today’s Amazon Basin, the Pebas mega-wetland was a great riverine rainforest. And yet the ecosystem was very different from what is there today. The marshes and swamps were filled with bivalve mollusks that thrived in the oxygen-poor waters. Predators evolved to feed on these clams and mussels…and what predators! This is Gnatusuchus, a caiman with spherical teeth for crushing open shellfish. Can you imagine biting through the shell of a clam? Just thinking about it makes my jaw hurt and my teeth feel broken. Yet Gnatusuchus bit through heavy shells for every meal!
A life-sized reconstruction of the gigantic Purussaurus
The crocodilian grew to lengths of 1.5 meters (about 5 feet) and had a short round shovel-shaped mouth to focus maximum force on biting through clams. Life in the Pebas was not all basking and clam feasts for Gnatusuchus. The reptile was hardly the only reptile in the swamp, but was instead one genus among a hyper-diverse group of crocodilians including giant toothy predators capable of eating Gnatusuchus. One of these predators, Purussaurus neivensis grew to be 12.5 metres (41 ft) in lengt—making it a rival of the great Mesozoic crocodilians like Phobosuchus (maybe I should have mentioned this horrifying monster first, instead of alluding to him after the clam-eater, but Ferrebeekeeper is interested in mollusks and their predators not in giant crocodiles: this is not Peter Pan, my friend). There were also piscivorous crocodilians with long scissor snouts foll of hooked teeth (like modern gharials), and even little crocodilians on stilt-like legs that ran around plucking up small prey in the manner of pipers or herons.
Seven million years ago, the Pebas began to change from swamps to channels as Amazonian drainage became spread through an even more enormous basin. Still, the diversity of the creature that lived there became a heritage for the contemporary Amazon, arguably the most diverse ecosystem in the world today.
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.
Aplacophora is a class of small wormlike marine animals. For a long time they were a mystery to marine biologists: up until 1987 they were classified as sea cucumbers (which are echinoderms). However the shell-free Aplacophorans are not echinoderms at all, no more than penguins are insects. Aplacophorans are tubular and lack shells, but they are actually mollusks—like clams, belemnites, octoposes, and gastropods.
Aplacophorans are divided into two subclasses: (1) the Solenogasters, which are typically carnivores which feed on feeding on corals and worms; and (2) the caudofoveates which tend to be detritovores feeding on leftover bits rolling around the ocean floor (although some caudofoveates eat foraminiferans (which are large unicellular organisms).
All of this talk of small mollusks which look like little worms…or maybe like little echinoderms…or even possibly like little early chordates (which were basically little tubes) sounds unpromising, but some of the Aplacophorans have a subtle beauty. Additionally they throw a light upon a bygone time when the mollusks, cnidarians, sponges, worms, and proto-vertebrates really weren’t all that different. They help illustrate the common bonds of kinship which tie all of the animals together, no matter what airs some of us put on.
Here is a beautiful marine mammal which is somewhat underappreciated. The ribbon seal (Histriophoca fasciata) is a gorgeous medium sized true seal (Phocidae) which lives in the Arctic edges of the North Pacific. Populations of the seal range from northern Alaska down the Aleutians and from the Kamchatka Peninsula down along the coast of Asia to the Koreas and the northern tip of Japan. The ribbon seal is the sole surviving member of its genus and it is notable for its lovely yet bizarre coat—the adult seals are black with undulating ribbons of white running around their entire bodies.
Ribbon seals dive deep into the pelagic depths to hunt their prey. The diving mammals live on pollacks, eelpouts, cod, and cephalopods which they hunt at depths of 200 meters. The seals themselves are preyed on by polar bears, orcas, and large sharks—including sleeper sharks—huge predators of the benthic depths.
The seals are approximately human size: both males and females grow to about 1.6 m (5.2 ft) long, and weigh 95 kg (210 pounds). In ideal circumstances they can live longer than 25 years. Ribbon seals reach sexual maturity somewhere between the ages of two and six (depending on gender, diet, and heredity). They give birth to adorable fluffy white/silver pups who nurse for only four weeks before being forcd to hunt on their own!
Ribbon seals were overhunted by humans for their fur, but they live in such remote regions that they have probably never been in real danger of extinction. Their real numbers of ribbon seal populations are somewhat unknown but are estimated to be around 250,000. I can’t find any information about why they have such remarkable coats, so I will go ahead and guess that it is because they are fashionable!
We live on the threshold of an era of stupendous nanomaterials! In the near future, molecules will be engineered to be harder than diamonds or stronger than steel…yet these miracle materials will also be workable and light.
Well, at least that’s what they keep telling us. In practice our best nano-materials do not seem capable of besting nature in the truly important categories—like hardness, tensile strength, or elasticity (or, if our synthetic materials are superior, they prove difficult to build into structures which fully exploit their strengths). A case in point comes from the lowly yet resilient limpet. Limpets are marine gastropods (snails) which have shells without visible coils. Actually, the name “limpet” is an informal common name—scientists have a very different way of characterizing these mollusks.
Limpets cling tenaciously to rocks at the tidal line by means of a muscular foot designed to create suction. They also produce an adhesive mucus which helps the foot adhere to whatever surface the limpet wishes to cling to. They carefully scour their ocean rocks for nutritious algae with a radula—a tongue-like rasping organ covered with teeth. Limpets have been of note to humans principally as a metaphor for resilience…or as a nuisance. Yet scientists experimenting on a common limpet, Patella vulgata, found that the little snail’s teeth had greater tensile strength than spider silk. Indeed, limpet teeth are the strongest known material in the natural world and approach the tensile strength of our strongest carbon fibers. With these teeth the little snail can (and does!) chew through rocks.
The secret to the limpet’s mighty teeth is a miracle of molecular design in its own right. The cutting portion of the teeth are composed of fibers of goethite (a sort of iron hydroxide named after the great German poet). These fibers are under 60 nanometers in diameter—a size which allows them to be tremendously strong. The teeth are technically a composite–since the tiny goethite fibers are held together by chitin, a natural polymer (which the exoskeletons of insects are made of).
Technically there are human-created carbon fibers stronger than the astonishing teeth of the limpet, but these fibers can only be utilized in certain configurations and fashions–so the limpets’ teeth are of very real practical interest to materials scientists. Engineers are already working on duplicating the little snail’s teeth for mining and cutting equipment…and for human dental uses. Perhaps we really could someday have some of the powers of Jaws, the lovable hulking henchman from seventies James Bond movies. With our synthetic chompers we could bite through rocks and steel cables. Uh, wouldn’t that be wonderful?
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.
The green crab (Carcinus maenas) is a tiny brownish green crab native to the European shore line along the north-east Atlantic Ocean and the Baltic Sea. Although it measures only 90 millimetres (3.5 in) across, it is voracious omnivore which feeds on all sorts of small mollusks, tiny arthropods, and worms (not to mention whatever dead flesh it happens across). Green crabs are great and all, but this blog is not about crustaceans…Why is this little crab showing up here?
It turns out that the green crab is one of the most invasive species of our time. Like the fiendish zebra mussel, the green crab is capable of traveling by boat (either among barnacles or in ballast). As far back as the age of discovery they were hitching rides around the world on the hulls of wooden ships. The little crabs seem to have piggy backed into temperate climes along with the British Empire and they have set up ranges in Australia, South Africa, Argentina, and both coasts of North America. So far this has not been a big problem: for hundreds of years, cold waters and big hungry fish have kept the little crabs from proliferating. However as humankind moves forward with its dastardly plans to kill off every fish in the ocean (and as ocean temperatures rise) the crabs are beginning to flourish in places where they were once barely holding on by their claws.
Green crabs eat clams and juvenile oysters—so their success is causing hardship for mollusk fishers (while simultaneously removing filter feeders from the ocean). Along the Mid Atlantic coast of North America, the native blue crab has proven effective at out-competing (or just straight-up eating) the invasive green crabs. Similarly the rock crabs and Dungeness crabs of the Pacific northwest can hold their own against the invaders, but humans are overfishing these native crabs and allowing the invaders to proliferate (and seafood enthusiasts in America have not developed a taste for the tiny green crabs).
Will the warming of the oceans cause blue crabs to spread northward to defeat the invaders? Will humankind stop killing every fish in the ocean so that the green crabs are eaten by sea bass? Will we introduce a new species which preys on the green crabs (but brings its own problems)? Only time will tell, but already coastal Maine is being swept by a tide of little green claws (and delicious east coast oysters are becoming more expensive and more rare).
The world is a strange place filled with astonishing and bizarre animals. Among the strangest creatures are those which are transparent*—animals which barely seem to be there because the tissues that make up their bodies are permeable to light. There are transparent catfish, transparent insects, transparent crustaceans, and even transparent frogs (to say nothing of cnidarians, the majority of which are transparent!). Today’s post however concerns transparent mollusks. In addition to having transparent bodies some of these incredible invertebrates have transparent shells, can invert their bodies, or can glow. Check them out:
The Glass Squid (Teuthowenia pellucida) also known as the googly-eyed glass squid lives throughout the oceans of the southern hemisphere. The creature is about 200 millimeters (8 inches) long and has light organs on its eyes. Although transparent it has a bluish cast and it possesses the ability to roll into a ball or to inflate itself. These tricks do not always work and the little squid is frequently eaten by weird deep-sea fish and sharks.
Recently discovered in a huge cave system in Croatia, Zospeum tholussum, is a small delicate snail with a transparent shell.
This pterotracheid heteropod mollusk is a member of the Carinaria genus. It lives in the open ocean and flaps through the water scooping up plankton in a modified snail foot. Just as its snail foot has changed into a swimming/harvesting organ, the mollusk’s shell has shrunk into near nonexistence.
Vitrelladonella Richardi is a deepwater pelagic octopus found in tropical and subtropical waters around the world. The little octopus only measures 80cm (2.6ft) in length. Like many of these almost invisible mollusks very little is known about how it lives, but it is certainly beautiful in a very alien and otherworldly way.
*The author of this opinion piece is opaque. His opinion may not represent the larger community of organisms.
Nudibranchs are gastropod mollusks which live in the oceans worldwide from the polar regions to the tropics. The slugs live in virtually all depths and various species range from the shallow intertidal surf to depths of more than over 700m. Although the majority of nudibranchs are benthic creatures which crawl along the seafloor, some prefer other lives and float upside down under the oceans surface or swim in the water column.
Nudibranchs lose their vestigial shell during a larval phase. To protect themselves they rely on toxins or unpleasant tasting chemicals which are advertised with extremely vivid colors. In order to enliven the gray winter months, here is a little parade of lovely nudibranchs. Enjoy!