This short film's a love letter to wind.
(Photo from here.)
The thing about a shark is—teeth,One row above, one row beneath.
Now take a close look. Do you findIt has another row behind?
Still closer—here, I’ll hold your hat:Has it a third row behind that?
Now look in and...Look out! Oh my,I’ll never know now! Well, goodbye.
Prior to molting, a crab reabsorbs some of the calcium carbonate from the old exoskeleton, then secretes enzymes to separate the old shell from the underlying skin (or epidermis). Then, the epidermis secretes a new, soft, paper-like shell beneath the old one. This process can take several weeks.
A day before molting, the crab starts to absorb seawater, and begins to swell up like a balloon. This helps to expand the old shell and causes it to come apart at a special seam that runs around the body. The carapace then opens up like a lid. The crab extracts itself from its old shell by pushing and compressing all of its appendages repeatedly. First it backs out, then pulls out its hind legs, then its front legs, and finally comes completely out of the old shell.
Over the next few weeks, the crab gradually retracts all of its body parts from the outer shell by a few millimeters, while it begins to secrete a new shell beneath the old one. When a crab molts, it removes all its legs, its eyestalks, its antennae, all its mouthparts, and its gills. It leaves behind the old shell, the esophagus, its entire stomach lining, and even the last half inch of its intestine. Quite often, many crabs in a population molt at the same time of year, and their old shells wash up on the beach. If you find something on the beach that looks like a dead crab, pick it up, open the lid, and look closely inside. If nobody is home, it is a cast-off exoskeleton.
A king crab may molt 20 times in its life. After hatching out as a planktonic larva, it molts 4 times, at 1-2 week intervals, before becoming a small crab. In its first year of life, it may molt 6 more times. The time between molting (the inter-molt period) gets longer with every molt. A 2-year old crab may molt only 3 times, a 3-year old only twice. By the time they are 4 years old, king crabs will molt only once per year. They become sexually mature at about 5 years of age. After that, the females must molt every year in order to mate, but the males molt less and less often. Very old males may not molt for 3 years or more.
To say this is an amazing process is a major understatement, and it has been the focus of research by many scientists for decades. Molting takes place about 15-20 times in the life of a crab. A king crab may molt six times in its first year, four in its second, two or three times in it’s third, and after that, perhaps only once a year. After sexual maturity, the females continue to molt annually, while intermolt periods become continuously longer for the males, so that they only molt once every few years or so.
|Image by the NASA Earth Observatory. Caption by Holli Riebeek.|
Internal waves happen because the ocean is layered. Deep water is cold, dense, and salty, while shallower water is warmer, lighter, and fresher. The differences in density and salinity cause the various layers of the ocean to behave like different fluids. As internal waves move through the lower layer of the ocean, the lighter water above flows down the crests and sinks into the troughs. This motion bunches surface water over the troughs and stretches it over the crests, creating alternating lines of calm water at the crests and rough water at the troughs.
It is the pattern of calm and rough water that makes the internal wave visible in satellite images. Calm, smooth waters reflect more light directly back to the satellite, resulting in a bright, pale stripe along the length of the internal wave. The rough waters in the trough scatter light in all directions, forming a dark line.In DEEP BLUE HOME I spent a fair amount of time writing about the stratification of the ocean. At its largest scale, the motion of the waters of the globe are known as the thermohaline circulation, because they're driven by differences in temperature (thermo) and salinity (haline). Here's a snippet:
Just as gravity drains the rivers of the land, so gravity drains the rivers of the World Ocean. The saltier, colder, heavier rivers sink beneath the fresher, warmer, lighter ones. The three dimensional realm of the ocean is layered with watersheds running over and atop one another in multiple directions. An exploded view of the global thermohaline circulation looks something like an intricately entwined highway interchange system, with layers crossing and bypassing at many levels, in all directions, and at different speeds.This simplified NOAA diagram is worth a thousand words:
Along the campo, Manin’s bronze winged lion prowledamong the tanned intruders, licking their hands.Pools of iridescent shellfishlay open in the restaurant window,
a shop of otherworldly opals, the mussels’ sheenthe skies of a closed heaven, crabs flat on their backs,their armor intricate trapped plates and escapements.The squid slumped in its own ink, the octopus appalled
in its slime. Many and ingenious are the postures of death.But look! There, in a corner, beneath a willowware plate,a lone crab clicked its claws, creepingover a casket of walleyed fish,
through a valley of oysters keeping their counsel,only to shift warily under the shadow of a wine bottle.Which saint, O saints, watches over the saintly crab?The man of forks and spears, the man of arrows?
In the Ca’ d’Oro, the stiffened Sebastian takeseach arrow through his flesh like a skewer.He wears a little napkin around his middle.Saint, watch over the fragile boat of the runaway crab.
Let him steal his way back to the green lagoon,go floating down the Grand Canal on his own motoscafo.Let him take second life, a later martyrdom.Let him wave his bent claws in a mockery of farewell,
lest we eat in his hollow shell his captive meat.
"Self-propelling beach animals like Animaris Percipiere have a stomach. This consists of recycled plastic bottles containing air that can be pumped up to a high pressure by the wind. This is done using a variety of bicycle pump, needless to say of plastic tubing. Several of these little pumps are driven by wings up at the front of the animal that flap in the breeze. It takes a few hours, but then the bottles are full. They contain a supply of potential wind. Take off the cap and the wind will emerge from the bottle at high speed. The trick is to get that untamed wind under control and use it to move the animal. For this, muscles are required. Beach animals have pushing muscles which get longer when told to do so. These consist of a tube containing another that is able to move in and out. There is a rubber ring on the end of the inner tube so that this acts as a piston. When the air runs from the bottles through a small pipe in the tube it pushes the piston outwards and the muscle lengthens. The beach animal's muscle can best be likened to a bone that gets longer. Muscles can open taps to activate other muscles that open other taps, and so on. This creates control centres that can be compared to brains."
"Jansen's creatures begin to take shape as a simulation inside a computer, in the shape of artificial life organisms which compete among themselves to be the quickest. Jansen studies the winning creatures and reconstructs them three-dimensionally with light and flexible tubes, nylon thread and adhesive tape. Those moving around more efficiently will donate their "DNA" (length and disposition of the tubes forming their movable parts) to the following Strandbeest generations. Through this process of hybridization and Darwinian evolution, creatures become more and more capable of living in their environment, and can even take decisions to guarantee their survival. The Animaris Sabulosa, for instance, buries its nose in the sand to anchor itself when detecting the wind is too strong to be still standing."
You waves, though you dance by my feet like children at play,
Though you glow and you glance, though you purr and you dart;
In the Junes that were warmer than these are, the waves were more gay,
When I was a boy with never a crack in my heart.
"Every time we walk along a beach some ancient urge disturbs us so that we find ourselves shedding shoes and garments or scavenging among seaweed and whitened timbers like the homesick refugees of a long war." -Loren Eiseley