Posts Tagged 'barnacles'

Young Barnacles

Barnacle sets. Found on a rock on the rocky glacial shore of Cold Spring Harbor at Sagamore Hill NHS. Barnacles are crustaceans, related to shrimp, crabs, lobsters. Shrimp that have glued their heads onto surfaces and built up walls to stand the siege of low tide…

These strange sedentary — at least as adults — creatures fascinated Charles Darwin. They are hermaphrodites who reproduce thusly: eggs are fertilized by sperm tubes extended from one barnacle to another. (At least one species broadcasts the sperm in the water.) The eggs hatch inside the barnacle and are released as planktonic larvae in winter. The larvae have two stages. The first, called the nauplus, molts multiple times. The second, the cyprid, has the job of finding a substrate. The little dudes float around for six weeks until late winter/early spring, when they start settling out of the water onto any available surface.

Are these Northern Rock (Balanus balanoides) or Little Gray (Chthamalus fragilis), the two types found in Long Island Sound? Someone on iNaturalist voted for the later, which, by the way, were named by Darwin. A saltmarsh bank anchored by Ribbed Mussels (Geukensia demissa). Look closer:Encrusted with little barnacles!

Barnacles

IMG_7082I just pulled these acorn barnacle shells out of a side pocket of my backpack. I picked them up in Maine a couple of months ago and promptly forgot about them.

Crustaceans, acorn barnacles begin life as free-floating larvae. The tiny head and telson affair is called a nauplius. These grow into a second larval stage, the cyprid, whose job is to find a nice surface — rock, wooden piling, ship hull — to glue its head to. Once stuck, it stays that way. It’ll grow the six hard, overlapping calcareous plates that form these thoothy-looking thimbles. These are the now-sessile animal’s castle walls. But how then do they reproduce if they’re not going anywhere? Well, for starters most species are hermaphroditic, so it doesn’t matter who their neighbors are, and the penis is extraordinarily long — the longest in terms of body size ratio of any animal is a goose barnacle species’s — so it can go cruising, as it were, from home base. Some species also release sperm into the water, like trees release pollen into the air.

Our man Darwin was obsessed by them; before him, it wasn’t realized they were related to shrimp.

Hung Like a Barnacle

The Dawn of the Deed: The Prehistoric Origins of Sex, by John A. Long.

“We all know about the birds and the bees…” goes the jacket and webpage copy for this book, but do we? In fact, I can’t think of a stranger duo of examples to be used as an euphemism for courtship and sex. Queen honey bees, for instance, are impregnated by multiple drones on their mating flights; the male bees are torn asunder in the process and fall to earth to die afterwards. While many birds have complicated courtship rituals, including nest and bower building, the actual fertilization is extremely brief. Cloaca (charmingly, from the Latin for sewer) connect, sperm is exchanged, and that’s it. The fastest copulation on record is a bird’s; the dunnocks take a tenth of a second, while flying. Since birds are essentially dinosaurs, does this mean the dinosaurs did it the same way, too? Probably not, actually, because flightless birds like ostriches and emus have penises (defined here as “any male reproductive structure used to transfer sperm into a female” for internal fertilization), and so do ducks and geese, and these species are genetically more primitive, that is, closer to the originating dinosaurs, than perching birds. Passerines don’t need penises and have dropped them, so to speak, over evolutionary time.

Author Long was one of the discoverers of a 380-million year old placoderm fossil in Australia that revealed an embryo, the oldest evidence of internal fertilization. Placoderms were armored fish-like animals common on earth until extinction about 359 million years ago; current thinking pegs them as the ancestor of all jawed animals. This finding becomes the wide-ranging focus of the question of internal fertilization, perhaps the most complicated form of animal reproduction, and the nature of the tools necessary for such processes.

Speaking of tools… is it inevitable that such a topic brings out the bad puns? Maybe only amongst us boys. There a couple such groaners here, including the title. The original Australian title of the book suggests some extra-cultural differences: Hung Like An Argentine Duck. The males of the duck species in question have a corkscrew-shaped penis longer than their bodies, but it’s the goose barnacle that takes the prize. In some species, the barnacle penis can be up to eight times the length of the body. Barnacles also shed and then grow new ones every year. Barnacle willies are also habitat sensitive: rough water will result in different shapes than calm water. Somehow, though, I doubt this information will be entering the popular discourse.

This edition was published by the University of Chicago Press. There are examples of horrendous editing in its pages. There’s a lot of this in books now, but it’s more distressing when found in a university press edition.

A Very Strange Crab Indeed

A piece of barnacle conglomeration I found at Dead Horse Bay recently. Most species of barnacles need a surface to attach to, and sometimes that surface is other barnacles. These are a type of acorn barnacle, one of the two main groups. I understand differentiating the local species is difficult for the lay person. Give a shout if you know them on sight. Commonly seen species in the region are the Ivory barnacle, Balanus eburneus, which prefers less saline water (like Jamaica Bay, so this may be that) and the Northern rock barnacle, B. balanoides, which likes it saltier. A barnacle, as Cirripedia-mad Charles Darwin discovered, is actually a crustacean, akin to crabs and lobsters. A free-swimming animal in its youth, it has two distinctive larval stages, wonderfully called nauplius and cyprid. Then after swimming through several instars, most barnacle species settle down, literally, gluing themselves head/forehead first to a rock, pier, ship’s hull, or some such surface, and enveloping themselves within a carapace-like shell made up of (usually) six plates for an immobile maturity. The references to ship’s hull is a matter of some economic seriousness; humans have been scraping barnacles off boats since we took to the sea. The beak-like barn doors that protect the soft animal within its calcium fortress are visible in the above image; when feeding, these open to allow feathery modified legs that pull in plankton from the water. Barnacles at the mercy of the tide hunker down during the hours of low tide.There are many species of barnacles; I came across numbers ranging from 900-1100+. Pictured above are the ruins of Ribbed barnacles, Tetraclita stalactifera, which I found amid the rocks of Klein Bay, St John, USVI in January.


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