What does a gooseneck barnacle use to attach to a rock?
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Of all the sea-life we tin can view with the naked eye, the barnacles or Cirripedia are simultaneously amidst the most plentiful and the most overlooked. They gradually build upwardly on almost whatsoever submerged object, the tell-tale fingerprints of the sea's briny clutches. Seldom do people stop to realize that these crusty petty lumps, peppered over every rusty anchor and waterlogged pier, are just a whole agglomeration of incredibly baroque bugs. Crustaceans, specifically; just similar crabs, lobsters and shrimp.
"Acorn" barnacles like the ones in a higher place are usually the barnacles that first jump to mind, and to begin our understanding of these weirdos, we're going to go over how an acorn barnacle develops. From there, we'll take a look at progressively more peculiar features of the grouping.
Like all Crustaceans, Cirripedia begin their lives equally microscopic plankton. The commencement stage, characterized by a single eye, is called the Nauplius, and is a form shared by virtually all Crustaceans at some point in their development, whether as a larva or in early embryonic stages.
After up to six months equally a Nauplius, the barnacle begins to deviate from other Crustaceans past becoming a Cyprid. This stage is enclosed in a clam-like set of hinged shells, and it exists only to seek out a resting place; a rock, a seashell, a whale, another barnacle, anything solid will do, though most species will follow pheromone trails and settle alongside their ain kind. One time information technology finds a suitable location, it secretes an agglutinative from its antennae and anchors in place upside-down.
On the exterior, our barnacle will rapidly grow into the armored fortress we all know and beloved, simply on the inside, it still follows a shrimp-similar body programme. Our squishy bug volition spend the residuum of its life rooted inside its spacious exoskeleton, employing its feathery legs as a net to collect plankton and other nutrients from the water's electric current. Layers of its own natural "cement" keep information technology firmly adhered equally information technology grows, one of the strongest attachment compounds institute in nature.
Of course, reproduction tin can be a bit of a problem for animals that don't motility around. Some, like the corals and sponges, solve it by pumping sperm and eggs into the h2o. Some just clone themselves. Acorn barnacles are a little more than sophisticated than that; as arthropods, they're more than complex animals with an anatomy closer to you or I than to a coral polyp. What I'1000 maxim is that barnacles have penises, and since they tin't walk around, they have really, really long, prehensile penises.
WwwwoooooooOOP!
The penis of the barnacle is in fact considered i of the largest proportionate members in the entire animal kingdom, assuasive the creature to simply reach over and fertilize its neighbors. To add to the convenience, all acorn barnacles are hermaphroditic, so each individual tin can both excogitate and conduct young.
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Simple acorn barnacles take on many different shapes and sizes for dissimilar environments; these hexagonal pits are but the tops of large barnacles embedded deep in the skin of a whale, painless and harmless to the titanic sea mammal equally they filter food from water passing over its body. These in turn provide a abode for whale lice, another harmless hitchhiker and fellow crustacean related to skeleton shrimp.
Excavated whale barnacles - Source
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Slightly odder than the acorns are the stalked or "goose" barnacles, many of which prefer to grow on floating objects such as seaweed, driftwood, boats or lengths of rope. These barnacles are and so named not simply for their advent, simply for the bizarre medieval-era misconception that they were the eggs or young of actual geese. This was so readily accepted that goose flesh was recognized as "fish" by the Catholic church, and thus acceptable to eat on a Fri when red meat and poultry were forbidden.
Unlike acorn barnacles, some goose-necked species accept two singled-out sexes, but adult males may be picayune more than tiny tubes of sperm, attached to the larger females or even living inside their shells.
On more one occasion, goose barnacles accept been mistaken for "body of water monsters" when thousands congregated on a single object such as this length of rope, unrecognizable beneath their squirming bodies.
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Not content to depend on passing flotsam, "buoy" barnacles secrete their ain flotation device from buoyant, foam-like cement, riding the current of their own volition like a Portuguese Man O' War.
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These niggling surfer bums may merge together with others of their kind, and these communal rafts may in turn pick up other species of barnacle! In a sense, these barnacles have taken an evolutionary pace back towards mobility - could full-fledged swimming exist adjacent?
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Whatsoever they adhere to, nearly all barnacles attach to objects that either don't movement at all or motility slowly enough for those tiny little cyprid larvae to go a comfy grip; it's ane reason you don't encounter barnacles fastened to most speedier petty fish or shrimp. A startling exception exists, however, in the genus Xenobalanus, which tin be establish exclusively on the fins of dolphins and other porpoises including the mighty orca. At a altitude, they might look like rows of slimy, blackness leeches, and up close, yous might assume they're related to some of the stalked barnacles we simply looked at, but no! These are actually another type of acorn barnacle, but one that evolves a long, soft shape. This makes them "pseudostalked" barnacles, since they don't have a true flexible stalk like their goosier cousins.
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Xenobalanus even so don't authorize as "parasites," since they don't feed on their host, merely their attachment mechanism doesn't look like a fun time at all. Their star-shaped base is lined with hundreds of tiny teeth, and digs deeply enough into the host's flesh that they exit a killer six-lobed scar behind when they finally die and drop off. It's the only way they can remain attached as their hosts jet through the h2o at up to 20 miles an hour, which may non sound like much to us automobile-driving anthropomorphs, merely under h2o, information technology's a pretty intense current the barnacles have to endure, and it actually is incredible that they aren't yanked off. It's fifty-fifty more than incredible that they always get there in the first place, and I don't believe their larval stage has even undergone much study to determine how they pull off such a feat!
Photo by Alisa Schulman-Janiger, off California, 2016
Y'all already recognize acorn barnacles, but the softer, pinker tubes hanging off of these specimens are Conchoderma auritum, goose barnacles of a group sometimes known as "rabbit ear" barnacles for a pair of soft flaps above their mouths. The remarkable affair nigh these is that they exclusively attach themselves to acorn barnacles, and exclusively to the acorn barnacles institute on whales! They crusade harm to neither the whale nor their boyfriend barnacles, but relish all the benefits of whale zipper without having to adjust to the whale'due south slippery peel directly. The acorn barnacle simply provides a much easier base of operations!
Largely barren of plankton, our beloved abyssal zone is by and large inhospitable to traditional filter-feeders, but some barnacles, such as this cute Vulcanolepis species, find their niche near hydrothermal vents; the boiling, toxic undersea volcanoes where bacteria thrive like nowhere else on Earth. Rather than take hold of food from the water, these guys expose their fuzzy legs to the heat and abound their own personal "crop" of edible bacteria.
Not slow in the "how long will nosotros talk about all these damn barnacles" sense, but ho-hum in the "tunnels through soft flesh" sense, which is most the exact polar opposite of the other blazon of ho-hum! The drawing above portrays an adult female Lithoglyptis mitis, one of the Acrothoracica. These extremely tiny barnacles burrow their way into snails, clams or even other barnacle species to live parasitically, never developing the thick armor of their relatives. Males are much tinier than females, and may in plough live in or on the bodies of their mates (the object in the lower right, hither).
We at present come to i of my favorite monstrosities of the deep bluish sea; the rhizocephalan ("root caput!") barnacles such as those of the genus Sacculina. I talk most these wonders in farther detail here, but I could but go along going well-nigh them all solar day.
At that point in life where other barnacles attach to a rock or a sea-turtle, a rhizocephalan cyprid finds itself a crab, inserts a needle-like appendage into the larger crustacean's body and injects a single, tiny clump of cells. This microscopic hulk is the get-go of its developed stage, and the residuum of its body is discarded. Soon, the parasitic cells grow into long filaments throughout the crab'south body, even invading its eyes, and it's no surprise that these organisms were once mistaken for a type of mucus. They metamorphose into what is more or less crab cancer, and they only get weirder from there, manipulating their host in downright agonizing ways. If yous oasis't already, become read all about it. Our other barnacles can expect; they are sessile, after all.
Sacculina are favorites of mine and definitely among the strangest animals I've always known, but if you're having trouble relating to the plight of a crab, here's a barnacle that parasitizes some of your own vertebrate cousins; small sharks (dogfish) of the deep sea abyss. Many other barnacles may attach to larger animals, as nosotros've seen, but generally only as harmless hitch-hikers feeding from the surrounding water. Anelasma squalicola is an exception, and you lot're looking at 1 securely anchored in a shark's back.
Rees 2014: doi:10.1016/j.cub.2014.05.030
Here we take an anatomical comparison between A. squalicola and one of its closest relatives, a more ordinary goose barnacle. You lot can see how the long legs typically used to collect food are atrophied inside its vanquish, and tin can't even reach outside of it at all. The stalk, meanwhile, has evolved into a fleshy bulb that anchors alarmingly deep within the shark with a multitude of short roots, steadily draining nutrients from the surrounding tissues. They may really attach near anywhere on the host body, and it's even common to find them crowding in the shark'southward nostrils, lips and eye sockets, all effectually the edge of the shark's eyeballs. Like the unrelated rhizocephalans, they desexualize their host, which is really fairly routine for the parasites of invertebrates. It is not routine for vertebrate parasites, and in fact, this is i of the just parasites in the world that deliberately renders a vertebrate infertile. This is likely considering life in the abyss can exist a life of fairly exceptional meals, and the barnacle would prefer its tasty host to non waste matter any nutrients on reproduction.
In 1835, Charles Darwin collected a tiny parasite from the crush of a conch, a beast very like to one of the deadening barnacles. It intrigued him, but would be filed abroad for over a decade before he would finally settle downwards and examine it. At the time, barnacles were understood quite poorly, and had even been considered mollusks only years prior.
Darwin affectionately nicknamed his discovery "Mr. Arthrobalanus" or "Mister Jointed Barnacle," began comparing its anatomy to various other barnacle species and intended to spend a few months studying the animals before returning to the subject of natural selection. Instead, faced with a wealth of unexplored territory and pressured past colleagues, barnacle enquiry would consume the aging naturalist for eight grueling years, his wellness severely deteriorating equally he spent twenty-four hours subsequently day dissecting and comparing thousands of specimens from all over the world, living and fossilized, before completing four unabridged volumes on barnacles alone.
Through these studies, Darwin constitute answers to many of his deepest questions on the processes of adaptation, and to this mean solar day, this writing is among the most extensive and valuable research ever devoted to a single brute grouping. The discovery of Mr. Arthrobalanus - whom Darwin would later dub Cryptophialus - was nigh certainly 1 of the nigh life-changing and influential finds of the homo'southward entire career as a naturalist, and Darwin allegedly had this to say on the affair:
"I detest a Barnacle equally no man e'er did earlier."
Where'southward your god now?
Source: https://bogleech.com/barnacles.html
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