HEART COCKLE
Mary, Mary Quite Contrary
Copyright © 2006 Joan Gerteis
Among the larger, more stand-outish of commonly encountered bivalve shells on our island beaches is the Heart Cockle.
Somewhat heavy, but brittle, and rather puffy appearing, Heart Cockles are generally soft pastel and beige in coloration – have up to over 40 very strong, well defined “ribs” fanning out from the distended area above each valve’s strong hinge which give them a scalloped margin look. (Older specimens will have more worn ribs.) The radiating ribs are crossed by somewhat darker concentric earth-tone bands an indication of growth.
Attaining lengths of close to five inches at times, individuals on our beaches are commonly well over three inches.
They are the same cockle shells that “Mary, Mary quite contrary” had in her rather unusual garden – the planting place bearing, as well, silver bells and something-or-others all in a row! There is also “cockles of one’s heart” – the place of one’s innermost feelings.
But it is in rather quiet protected water – low tide to some 600 feet deep – where muddy fine sand deposits build up around rocks and rich eelgrass flats are found, that real-life living cockles prefer to take up habitation. And there they will be found “sitting” atop the sandy bottom or buried just a little below the surface of the substrate feeding on microscopic plankton, detritus, and bacteria. They may live 16 years in such places.
And although these bivalves’ short siphons restrict them to shallow digs, (no pun intended) it’s still a habitat where they are able to thrive: pumping water in through their in-current siphons: on through the gills where oxygen is extracted and where they filter out food: and then passing water and body wastes on out through the ex-current or out siphons.
When the shell is open, the Heart Cockle can extend its muscular “foot” which it uses in digging. And when predators come close, this foot allows a cockle to become remarkably mobile. In trying to escape harm’s way, like from a hungry sea star, it can use this strong foot to push off from a water-covered floor – jump about – even flip itself over! Camano Island Beach Watchers and children noted such movements with awe in temporary sea-life holding and viewing pools during Education Days at Camano Island State Park and low-tide beach walks there.
But escape hungry critters. cockles are not always able to do. Some wading birds present a formidable challenge to them, for it has been estimated that each of these avians consume half a ton of cockle flesh each year. And there is also the local seafood market. Cockles are but one of the mollusk phylum that have for a very long time been part of the Homo sapiens diet.
A bit more complex than they may appear, Heart Cockles protect within their calcareous shells various organs such as nerve-type nodules, hearts and brains, stomachs, gonads, and respiratory and excretory systems.
I think, however, we sometimes don’t realize, as we glance at or even more closely scrutinize cockle and other shells at the beach, that these are more than just empty valves and shell collectibles to some. We tend to overlook the fact that they were part of relatively complex life forms and systems. And that even these empty shells scattered about provide home bases for other life. A reminder that “the destiny of each is inter-connected with that of all”.
Pat Nash
Beach Watcher
Class of '94
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