Even during a pandemic, there is no reason to be bored. Unless, as Bernadine Hiller-Greenman of Aquinnah discovered, you are a mollusk pierced by a special sponge.
Bernadine wrote last week to inquire about clam shells with curious round holes she found on Red Beach in Aquinnah. Some online detective work led her to conclude that the holes were caused by a boring sponge of the genus Clionia.
Boring sponges, as they are known, are anything but boring, and live by the slogan, drill, baby, drill. These simple animals need calcium carbonate, and break down and create holes in shelled animals such as clams, oysters and scallops to obtain it. The shell damage (which can easily be observed when trying to shuck affected oysters, as they virtually crumble under the knife) is not an attempt at predation and feeding by the sponge. Rather, it is its imperative to obtain calcium carbonate to support its skeletal structure. As filter feeders, sponges acquire nourishment by moving water through their bodies and extracting plankton and other foodstuff from the water.
They are not much to look at. Boring sponges appear as a group or colony of encrusting yellow wart-like bumps or pores that can cover part or all of a shell. The Blob is an apt comparison, and, according to an article in a Nantucket seasonal newspaper, Yesterday’s Island, they are called monkey dunk by island scallopers, who bring them up in their drags.
A common type of boring sponge found in our ponds and ocean is the red boring sponge, so named because of the reddish tint around the pores of this species. A few other species are found in our marine environments, but identification is only possible by examining their spicules, or skeletal structures, under a strong microscope.
Regardless of their species, they all share form, function and habit. As members of the phylum Porifera, or pore bearer, boring sponges claim an ancient heritage, having been identified in the fossil record over 600 million years ago. These sponges can appear as an aggregation of single yellow papillae, or protuberances, or as a mass of flattened papillae covering their host.
Either way, this sponge doesn’t intend to kill its host, but that is often the unintended consequence as more and more of the shell is dissolved. When the bivalve shell is weakened, the animal inside can be eaten or harmed by other forces. Though the boring sponge starts by making penetrating chips and holes in the shell, its work can expand to include the disappearance of the entire shell. An ecological benefit is the recycling of calcium in the marine system, so some good does come from this shell destruction, an activity that incorporates bioerosion and biorecycling.
To add to the remarkable nature of this boring species is the sponge’s reproductive methods. Though simple animals, their reproduction is multifaceted — they can spawn asexually by budding off a section that will then grow independently into another organism, or sexually by releasing gametes into the water. Adding to the confusion is that they are hermaphrodites, having both sexes, though are unable to self-fertilize.
As this pandemic continues, consider the words of actor Viggo Mortensen, who explained: “There’s no excuse to be bored. Sad, yes. Angry, yes. Depressed, yes. Crazy, yes. But there’s no excuse for boredom, ever.” Unless, of course, you are the victim of a boring sponge.
Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature and The Nature of Martha’s Vineyard.
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