Showing posts with label cephalopod. Show all posts
Showing posts with label cephalopod. Show all posts

Friday, September 9, 2022

OCTOPUS: TAK'WA

This lovely with her colourful body is an octopus. Like ninety-seven percent of the world's animals, she lacks a backbone. 

To support their bodies, these spineless animals — invertebrates — have skeletons made of protein fibres. 

This flexibility can be a real advantage when slipping into nooks and crannies for protection and making a home in seemingly impossible places.

On the east side of Vancouver Island, British Columbia, Canada, there is an area called Madrona Point where beneath the surface of the sea many octopus have done just that. This is the home of the Giant Pacific Octopus, Enteroctopus dofleini, the largest known octopus species.

The land above is the home of the Snuneymuxw First Nation of the Coast Salish who live here, on the Gulf Islands, and along the Fraser River. In Hul'q'umin'um' — the lingua franca of the Snuneymuxw First Nation, a living language that expresses their worldview and way of life — the word for octopus is sqi'mukw'. In the Kwak̓wala language of the Kwakiutl or Kwakwaka'wakw, speakers of Kwak'wala, further north on Vancouver Island, octopus or devil fish are known as ta̱k̕wa.

I have gone scuba diving at Madrona Point many times and visited the octopus who squeeze into the eroded sections of a sandstone ledge about 18 metres or 60 feet below the surface. 

On one of those trips, my friend Suzanne Groulx ran into one of the larger males swimming just offshore. I was surfacing as I heard her shriek clear as a bell. Sound moves through water about four times faster than it does through the air — faster than a jet plane. 

On that day, I suspect Suzanne was neck and neck both in sound and motion. Seconds later, she popped up a good three feet above the surf, still screaming. I have never seen anyone surface quite so quickly — dangerous and impressive in equal measure. It was on another of those trips that I met Philip Torrens, with whom I would later co-author, In Search of Ancient BC.      

While the entire coastline is beautiful to explore, it was visiting the octopus that drew me back time and time again. I have seen wee octopus the size of the palm of your hand, large males swimming and feeding and lovely females tucked into their nursery homes.

After forty days of mating, the female Giant Pacific Octopus attach strings of small fertilized eggs to the rocks within these crevices and call it home for a time — generally five months or 160 days. When I visit, I sometimes bring crab or sea urchin for her to snack on as the mothers guarding these eggs do not leave to hunt, staying ever vigilant in protecting their brood from predators. All the while she is here, she gently blows fresh water over the eggs.

And sadly, this will be her only brood. Octopus breed once in their too-short lives. Males die directly after mating and females die once their young have hatched. They live in all the world's oceans and no matter the species, their lifespans are a brief one to five years. I rather hope they evolve to live longer and one day outcompete the humans who like to snack on them.

Octopus are soft-bodied, eight-limbed molluscs of the order Octopoda. They have one hard part, their beaks, which they use to crack open clams, crab and crustaceans. They are ninja-level skilled at squeezing through very tight holes, particularly if it means accessing a tasty snack. The size of their beaks determines exactly how small a hole they can fit through. Looking, you would likely guess it could not be done, but they are amazing — and mesmerizing!

At the Vancouver Aquarium, they have been known to unscrew lids, sneak out of one tank to feed in another then slip back so you do not notice, open simple hooks and latches — burglars of the sea. They can also change the colour and texture of their skin to blend perfectly into their surroundings. You can look for them around reefs and rocky shores. There are 300 species of octopus grouped within the class Cephalopoda, along with squid, cuttlefish, and nautiloids. 

The oldest fossil octopus at 300 million years old is Pohlsepia mazonensis from Carboniferous Mazon Creek fossil beds in Illinois. The only known specimen resembles modern octopuses with the exception of possessing eight arms and two tentacles (Kluessendorf and Doyle 2000).

My favourite fossil octopus is the darling Keuppia levante (Fuchs, Bracchi & Weis, 2009), an extinct genus of octopus that swam our ancient seas back in the Cretaceous.

Wednesday, April 6, 2022

INSPIRED BY NATURE / AMMONITE BOUNTY

Argonauticeras besairei, José Juárez Ruiz
An exceptional example of the fractal building of an ammonite septum, in this clytoceratid Argonauticeras besairei from the awesome José Juárez Ruiz.

Ammonites were predatory, squidlike creatures that lived inside coil-shaped shells.

Like other cephalopods, ammonites had sharp, beak-like jaws inside a ring of squid-like tentacles that extended from their shells. 

They used these tentacles to snare prey, — plankton, vegetation, fish and crustaceans — similar to the way a squid or octopus hunt today.

Catching a fish with your hands is no easy feat, as I am sure you know. But the Ammonites were skilled and successful hunters. They caught their prey while swimming and floating in the water column. 

Within their shells, they had a number of chambers, called septa, filled with gas or fluid that were interconnected by a wee air tube. By pushing air in or out, they were able to control their buoyancy in the water column. They lived in the last chamber of their shells, continuously building new shell material as they grew. As each new chamber was added, the squid-like body of the ammonite would move down to occupy the final outside chamber.

They were a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. 

These molluscs commonly referred to as ammonites are more closely related to living coleoids — octopus, squid, and cuttlefish — than they are to shelled nautiloids such as the living nautilus species.

Ammonoidea can be divided into six orders:

  • Agoniatitida: Lower Devonian - Middle Devonian
  • Clymeniida: Upper Devonian
  • Goniatitida: Middle Devonian - Upper Permian
  • Prolecanitida: Upper Devonian - Upper Triassic
  • Ceratitida: Upper Permian - Upper Triassic
  • Ammonitida: Lower Jurassic - Upper Cretaceous

Ammonites have intricate and complex patterns on their shells called sutures. The suture patterns differ across species and tell us what time period the ammonite is from. 

If they are geometric with numerous undivided lobes and saddles and eight lobes around the conch, we refer to their pattern as goniatitic, a characteristic of Paleozoic ammonites.

If they are ceratitic with lobes that have subdivided tips; giving them a saw-toothed appearance and rounded undivided saddles, they are likely Triassic. For some lovely Triassic ammonites, take a look at the specimens that come out of Hallstatt, Austria and from the outcrops in the Humboldt Mountains of Nevada.

Hoplites bennettiana (Sowby, 1826) Christophe Marot
If they have lobes and saddles that are fluted, with rounded subdivisions instead of saw-toothed, they are likely Jurassic or Cretaceous. If you'd like to see a particularly beautiful Lower Jurassic ammonite, take a peek at Apodoceras. Wonderful ridging in that species.

One of my favourite Cretaceous ammonites is the ammonite, Hoplites bennettiana (Sowby, 1826). 

This beauty is from Albian deposits near Carrière de Courcelles, Villemoyenne, near la région de Troyes (Aube) Champagne in northeastern France.

At the time that this fellow was swimming in our oceans, ankylosaurs were strolling about Mongolia and stomping through the foliage in Utah, Kansas and Texas. Bony fish were swimming over what would become the strata making up Canada, the Czech Republic and Australia. Cartilaginous fish were prowling the western interior seaway of North America and a strange extinct herbivorous mammal, Eobaatar, was snuffling through Mongolia, Spain and England.

In some classifications, these are left as suborders, included in only three orders: Goniatitida, Ceratitida, and Ammonitida. Once you get to know them, ammonites in their various shapes and suturing patterns make it much easier to date an ammonite and the rock formation where it is found.

Ammonites first appeared about 240 million years ago, though they descended from straight-shelled cephalopods called bacrites that date back to the Devonian, about 415 million years ago, and the last species vanished in the Cretaceous–Paleogene extinction event.

They were prolific breeders that evolved rapidly. If you could cast a fishing line into our ancient seas, it is likely that you would hook an ammonite, not a fish. They were prolific back in the day, living (and sometimes dying) in schools in oceans around the globe. We find ammonite fossils — and plenty of them — in sedimentary rock from all over the world.

In some cases, we find rock beds where we can see evidence of a new species that evolved, lived and died out in such a short time span that we can walk through time, following the course of evolution using ammonites as a window into the past.

For this reason, they make excellent index fossils. An index fossil is a species that allows us to link a particular rock formation, layered in time with a particular species or genus found there. 

Generally, deeper is older, so we use the sedimentary layers of rock to match up to specific geologic time periods, rather like the way we use tree rings to date trees. A handy way to compare fossils and date strata across the globe.

References: Inoue, S., Kondo, S. Suture pattern formation in ammonites and the unknown rear mantle structure. Sci Rep 6, 33689 (2016). https://doi.org/10.1038/srep33689

https://www.nature.com/articles/srep33689?fbclid=IwAR1BhBrDqhv8LDjqF60EXdfLR7wPE4zDivwGORTUEgCd2GghD5W7KOfg6Co#citeas

Photos: Argonauticeras besairei from the awesome José Juárez Ruiz.

Photo: Hoplites bennettiana from near Troyes, France. Collection de Christophe Marot