Wednesday, June 29, 2011

A Brief Primer on the Cuttlefish. With links.

The Giant Australian cuttlefish is the largest of the cuttlefish species known to man.  A member of the taxonomic class coleoida, it have a venerable lineage - stretching back almost 200 million years in time, it outlived the dinosaurs, trumpeted proudly past the mammals as they arose, and  survived to grace the waters of our present day oceans.
            The Australian giant cuttlefish is, in principle and in general, a solitary creature.  It lives its life in a race for mass and volume, spending almost 95% of its day in hiding,  pouring its metabolism into brute size, waiting for the one great event of its life.
It is a short lived creature.  It grows, it mates, and then it dies, its weakening body falling apart on the seabed.  Most male cuttlefish live solitary lives, waiting for a female to pass - and be seized and impregnated and sent on her way to lay her eggs. 
            The Giant Australian Cuttlefish plays life differently. Giant Australian Cuttlefish live their lives in quiet obscurity, eschewing company, abhorring fuss, painting themselves the color of the seabed, and sending marine biologists frantic  with curiosity.  Where?  Where do they go?  Where do they hang out?  Nobody knows.
Once a year, however, something extraordinary happens right in my backyard.  The Spencer gulf has a flat-bottomed sandy bed, and cuttlefish require rocky coasts for laying their eggs.  They attach the eggs to the under-sides of rocks, where they can mature undisturbed by predators and currents.  Sand flats don't provide much scope for growing baby cuttlefish.
            But right here, on the edge of town, there is one rocky shore.  Thin slabs of sandstone shingle tumbled together make a long, shallow, sloping seabed.  And when the temperature drops at the beginning of winter, the cuttlefish arrive.  All of them.
            Thousands of them.  This is the only place in Australia - in the world - where cuttlefish congregate in numbers like this.  They play a whopping mating game - the giant males collect harems, the females scope partners for size and skill, and the males face off, threatening each other with a sort of display that must be absolutely unique  -anywhere. 
            Cuttlefish skin is colored by pigment-filled sacs called chromatophores.  These pigment sacs are under conscious control, and the cuttlefish can change its coloration to match its environment, to reflect its mood and, and uniquely, to indicate its intentions.  The chromatophores can not only be controlled individually, but also sequentially, so that the cuttlefish becomes a floating movie screen.  The enormous males face off - streams of color rippling down their bodies, the colors become wilder and more intense, until one male will give way and retreat - or the confrontation becomes physical, and the two males fight, slashing at one another with their sharp parrot beaks.
            While the largest males are lighting up the seabed, the females in their harems are quietly getting the best of all possible  sperm-sets for their eggs.  The large males are the ones who have had two seasons to grow.  The males who come to maturity in the first season of their life are very small - too small to compete head to head with their larger compatriots. 
            Their opportunities require guile.  The same size as the small females, they adjust their color, their posture, even their behavior to match the ladies.  While the males guard their harem, these small male mimics will sidle up to them and mate with their females right under their bellies.  The females are enthusiastic and complicit - by taking a variety of partners, they can maximize the potential of their offspring - producing great bruisers as well as small, sly sneakers, and  increasing the probability that their male offspring will all mate in the next few seasons.

            Like all wonderful nature stories, the tail has a human sting.  There are plans to build a desalination plant on this coast, so that the mines up in the red center won't have to rely on Southern Australia's over-burdened sources of fresh-water.  The gulf has hundreds of miles of coastline of no particular distinction, but this short stretch of coast- this singular, extraordinary stretch - is the one that has been chosen.   By eminent domain.  A team of marine biologists is working on an environmental impact statement, and their present conclusion, based on current data and probability, is that the currents and the water densities will keep higher levels of salinity out of the breeding area, and the plant has governmental approval - but around here - we want to know why.  Why this coast?  Why not 30 kilometers  - fifty kilometers - further out of town?  Or ten kilometers out of town on the other side? 
            Murmurs of special interest - farmers and graziers playing NIMBY with the regional council - make the rounds.
            People nod knowingly.  But they're upset and bewildered, so of course they nod - and nothing is confirmed.  
            This place and this annual event is so special.  Ecosystems are fragile.  Unstable.  Full of unexpected, or mis-estimated, factors. Why push for this coast?  Why take the risk?  

Further Resources:
Or if you want to see some really extraordinary footage, check out the BBC documentary series Life (2009). Look up the episode "Creatures of the Deep" and prepare to be astounded.

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