” The barnacle is a shrimp-like animal standing on its head in a limestone house and kicking food into its mouth with its feet.”, according to Louis Agassiz, the Swiss-American naturalist, succinctly summing up a few of the interesting facts about barnacles.
Barnacles were thought to be mollusks until 1830 when their larval stage was discovered. This fact landed them squarely into Arthropoda, crustacea, cirripedia. Most of the actual scientific research on barnacles was done by none other than Charles Darwin. Spending the better part of the decade after returning from his voyage on the Beagle in the meticulous study and classification of both living and fossil specimen, the process required him to restructure the entire classification field which had been in considerable disarray until that time, and then publishing this exhaustive treatise in the mid 1800’s.
There are, in general, two types of this sessile hermaphrodite. The first is the gooseneck barnacle, having a calcareous shell attached to a base such as a rock, a piece of wood, metal, or even some other marine creature by a stalk that is leathery on the outside but very edible on the inside. The gooseneck barnacle may be steamed (over wine and herbs), boiled, grilled, or served in broth, soup, or chowder. Do be careful when peeling the stalk, the liquid may stain.
The second type of barnacle is the acorn barnacle, which is a rounded hexagon of six plates attached at the wider base to a rock, dock, or other object and that narrows to the apex in a volcanic sort of way having another two plates to close up the top, when necessary, or open to allow the six pairs of legs to extend out with the elegant, feathery plumes that are characteristic of their “feet”.
There are some barnacles that are mobile even though they are permanently attached to a base. That base just happens to be a porpoise, turtle, or even a gooseneck barnacle that grows on an acorn barnacle that grows on a whale. Another mobile member of the family is the parasitic Sacculina barnacle that attaches to a crab through a seam or joint in the crabs shell. At this point it sends out tendrils throughout the crabs body, not killing it but making it infertile and changing its behavior. When another Sacculina joins the first after being alerted by secretions from the established parasite the two mate and lay millions of eggs in the host crab which lives and is manipulated to tend the larva of the barnacles. The alterations are made at such a basic level that a Sacculina barnacle will change the physiology of a male crab to be more female so the host will care for the offspring of the parasite with a mothers nurturing attention.
Bio-fouling of shipping and luxury liners provide further mobile platforms for these ocean going hitchhikers. The estimates of fuel waste due to the drag caused by colonies of barnacles on these commercial vehicles runs between two billion to seven billion dollars per year. With speeds reduced by as much as thirty percent, much time is lost as well.
The bio-fouling statistics alone would indicate that barnacles are prolific even if it was not known that the Leaf barnacle lays seven broods of eggs per year with an average of 240,000 hatchling larva per brood.
This type of proclivity helps put into perspective the impact that the depletion of the overall marine biomass is having on barnacle populations along coastlines throughout the world. During the year 1954, along the Nova Scotia side of the Bay of Fundy, the Barnacle Belt’ was photographed and described as “A barnacle population richer than any in the region.”. By the year 2001 the “Barnacle Belt” was conspicuous by its absence.
The barnacle comes from the very base of the food pyramid, its food source is the smallest of the small, such as plankton and even bacteria. Big fish eats little fish, little fish eats tiny fish and so on only if the tiniest are there to be eaten. Could this tiny shrimp standing on its head be the “canary in the coal mine” for marine life?
Last, but by no means the least, an interesting fact about barnacles is the astounding male half of these marine hermaphrodites. The male reproductive organ not only gets shorter and stouter in rough weather as well as longer and thinner in placid waters but is usually eight times its entire body length to make up for the fact that both members of the amorous couple are firmly attached at separate locations. A six inch barnacle has, well, you do the math.
