Hard Times in the Conch Republic
Posted by Richard Conniff on January 8, 2014
Stupidly, I’ve always thought of conchs and other sea snails as sedentary things, clinging to their bit of rock like limpets. Now it turns out that they can leap, or at least frog-hop across the ocean bottom. They do this when pursued a little too closely by a sort of slow-motion knight-in-armor–that is, a marbled cone snail plodding along with its venomous lance poking forward.
Why have National Geographic or the BBC never filmed this curious pursuit? The rather poor video above is the best I have been able to come up with.
Now the bad news, from Sue-Ann Watson of James Cook University, lead author of a new study in Proceedings of the Royal Society B:
Dr Watson explains that increased carbon dioxide and ocean acidification levels disrupt a particular neurotransmitter receptor in the snail’s nervous system, delaying vital decision-making on escape. This leaves the snail more vulnerable to the poisonous dart of its slow-moving nemesis, the marbled cone shell.
The effects may be quite profound. “Altered behaviours between predators and prey have the potential to disrupt ocean food webs,” Dr Watson said.
While this study shows that disrupted decision-making with elevated carbon dioxide levels can occur in marine invertebrates, scientists have also observed similar effects before, in fish.
Co-author Professor Göran Nilsson, from the University of Oslo, explains, “this neurotransmitter receptor is common in many animals and evolved quite early in the animal kingdom. So what this study suggests is that human carbon dioxide emissions directly alter the behaviour of many marine animals, including much of the seafood that is part of the human diet.”
The authors note that carbon dioxide levels in the oceans are now 30 percent higher than they were at the start of the Industrial Revolution, and rising 100 times faster than they have at any time in the past 650,000 years.
Thus the conchs whose shells we have picked up from the beach and held to our ears to hear the sounds of the universe may soon be history, along with much else we love in this world.
That is, unless we act. In India, warriors once used conchs as trumpets to sound the call to battle.
Here’s a call to arms from the great Bengali poet Rabindrinath Tagore.
How can we bear to see your conch lying there in the dirt?
The tragedy of it cuts off air and blocks out light. Warriors, rise, brandish your banners!
Singers, get up and sing! Doers,
Charge into action.! Do not falter!
How can we
let your inspiring conch stare up at us from the dirt ?
I came to the prayer-room with an offering of flowers neatly laid out,
Longing to end my long day’s labours with heavenly quiet.
I thought this time my heart’s lacerations
Would heal; I thought my absolutions
Would purge me-till I saw the degradation
Of your great conch lying on the path, lying in the dirt.
What am I doing with this prayer- lamp, what do I mean by this prayer?
Must I drop my flowers of peace-weave scarlet garlands of war?
I hoped for calm to end my struggles;
I thought my debts had been paid, my battles
Won, now I could thankfully settle
In your lap: but suddenly your mute conch seemed to sound in my ear.
O change me, touch me with youth, alchemize me! Let fiery melody
Blaze and twirl in my breast, life-fire leap into ecstasy!
Let night’s ribs crack; let skies,
As they fill with dawning enlightenment, raise
Terror in remotest dark. From today
I shall fight to seize and carry aloft your conch of victory.
Now I know I can no more close my eyes to slumber.
Now I know that monsoon showers of arrows must batter
My heart. Some people will rush to my side;
Others will weep and sigh in dread;
Horrifying nightmares will rock the beds
Of sleeping hearers: but today your conch will joyously thunder.
When I looked to you for rest I received nothing but shame;
But dress me for battle now, let armour cover each limb.
Let new obstructions chafe and challenge me;
I shall take all blows and hurts unflinchingly;
My heart shall drum redress for your injuries;
I shall give all my strength, win back your conch and make it BOOM.
Source: S.-A. Watson, S. Lefevre, M. I. McCormick, P. Domenici, G. E. Nilsson, P. L. Munday. Marine mollusc predator-escape behaviour altered by near-future carbon dioxide levels. Proceedings of the Royal Society B: Biological Sciences, 2013; 281 (1774)