Happy clams

The blissful lives of bivalves on Oak Bay beaches

Victoria’s coastline was once fed by dozens of streams delivering sediment and organic detritus to beaches, making a fine habitat for clams, crabs, mussels and sea worms. Dredging, infilling and development have changed the shoreline, but bivalves and crabs still exist (although in reduced populations) on most of our urban beaches.

Because the decay of organic debris uses oxygen, the muddy sand below the high tide line may be oxygen-poor, which is just how the hypo-active clam likes it. We could even call clams the couch potatoes of the beach, although they do continually squirt a thousand tiny fountains to the delight of bare-footed beachcombers.

Maybe it’s because clams don’t have far to go or much to do that the phrase “happy as a clam” was invented (by an American newspaper in 1844). The full phrase is “happy as a clam at high tide,” a reference to the fact that when the beach is covered by water clams can’t be dug up. Although presumably free of anxiety, the happy clam doesn’t do nothing however: it filters seawater through its double-sided shell, extracting nutrients from an inhalant siphon and expelling wastes through an exhalant siphon. It breathes through gills which secrete mucous which traps the food. Together with its muscular foot, this delicious-sounding sludge is what clam-eaters eat. The foot pulls the clam down into the sand, slowly in most species but quickly in the razor clam.

Bivalves (of which there are 180 species in B.C.) also have sensitive nerve endings, and laboratory researchers have discovered that when subjected to boiling water or electric shock they react with a pain response. Maybe being happy as a clam, then, simply means not knowing what might happen to you. Yet something gives clams the genetic unconscious wisdom to “clam up,” and nature has provided a powerful muscular hinge between the halves of its shell.

They aren’t the showiest creature on the beach, yet beaches would feel much the poorer if clams weren’t there. Unlike them, those other common local bivalves, the mussels and oysters, need hard surfaces like rock to anchor on, as do their co-residents, the barnacles. They attach by secreting a calcareous cement, or in the case of mussels by muscular threads which fix their purplish blanket of elongated shells onto rock — a delicious smorgasbord much appreciated by crows and shorebirds.

How do these sedentary creatures accomplish the central job of all species: reproducing the particular manifestation of life which they embody? The hermaphroditic barnacle, a spiky fortress of plates surrounding tiny but complex inner organs, copes by extending the largest (relative to body size) male organ in nature, which delivers clouds of sperm to neighbouring barnacles via surrounding water.

Most bivalves release sperm and eggs to be fertilized externally, but some clams fertilize eggs and brood their larvae inside the shell. Individual oysters have the ability to alternate between male and female. You thought we humans invented that? Not so: every conceivable type of reproduction and gender combination already exists somewhere in nature.

The other popular phrase inspired by a bivalve is Shakespeare’s “the world is his (or your) oyster,” a statement which appears in more than one play. Whatever Shakespeare meant by it, the oyster’s shell does indeed comprise a world, as does the material-energetic body of any creature. Lucky are the experts whose career is to study them — they must all be as happy as clams.

To kick off B.C.’s new Orca Awareness Month, the Friends of Uplands Park host a tide pool event at Cattle Point, 9:30 a.m. June 5, followed by a Family Orca Picnic with kids’ crafts table at 11 a.m. Come celebrate your favourite sea creatures, from bivalves to whales.

Barbara Julian is a local author and nature enthusiast who writes monthly about area wildlife.

 

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