From the life-sustaining oceans, the ancients found many gifts. One was this, the Triton's Trumpet. The shell, beautiful and large, could produce a rich sound when its tip was filed down. Resounding out across the land and water, the blowing of the pu was used in various forms of communication, and often signified events of importance; for example, the arrival of royalty, or the beginning of the Makahiki season. Sacred protocols guided the use of the pu and the much cherished shells were passed down from generation to generation. In Hawaiian waters, pu were often made from the Horned Helmet (Cassis cornuta) and the Triton's Trumpet (Charonia tritonis), both large marine gastropod molluscs. Today's post features the Triton's Trumpet, the largest snail in our waters, reaching sizes up to twenty inches. Like many sea snails, it has a shell that is spirally coiled (some snails have conical shells, and are generally referred to as limpets). The shell is ribbed and is a mottled brown and white in color. Locomotion is achieved by a strong, muscular foot, which this snail uses to pursue such prey as sea urchins and seastars. The triton's trumpet is one of the few organisms that prey on the crown-of-thorns seastar, which is notorious for feeding on and destroying corals, making our snail and important player in the marine ecosystem. Once the seastar has been captured, the triton holds it down with its strong foot. A saliva is injected which paralyzes its victim, then the snail gains easy access to the seastar's soft insides with its serrated radula, a tongue-like organ with scraping teeth. Though many sea snails are hermaphroditic, the tritons are either male or female. After internal fertilization, a cluster of eggs are laid. The buoyant young hatch and become part of the free-drifting plankton. Tritons can be found in waters from fairly shallow to about seventy-five feet deep, which makes them vulnerable to collectors. If you are lucky enough to spot this treasure, best to simply admire and leave it be, as they are becoming rarer across the globe. The corals will thank you for it.
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Inhabiting shallow reef flats, as well as reef slopes, is the playfully splotched Carpilius maculatus. It is known locally as 'alakuma, or the seven-eleven crab, due to the seven conspicuous red spots (four near the eyes and three in the center) with four more less prominent along the back edges of its carapace, making a total of eleven, though some reports have varying numbers of spots. Legend has it that a hungry god thought he would make a nice meal of the 'alakuma, but the crab pinched back, drawing a bit of blood. After several attempts and a few more pinches from the crab's powerful claws, the god eventually got his supper, but the crab's descendants sport the bloody prints of its captor. The seven-eleven crab is a good sized crab, getting as large as five or six inches across its smooth and thick shell. By day, the crab holes up in the reefs nooks and crannies, resting up for a night of foraging. Dinner includes molluscs and marine snails, which they gain access to with their massive chelae (claws). Wow... the beauty in the natural world! Looking like a piece of art, Porpita porpita (also known as Porpita pacifica), or the Blue Buttons are real stunners, literally. They belong to the phylum Cnidaria, which are known for their stinging cells used to capture prey. Blue buttons don't deliver a real wallop, but they could cause some discomfort if handled. Passively floating along on the sea's surface, they eat planktonic copepods, a group of small crustaceans, and other drifting larvae. They are not true jellyfish, but a colony of animals, each performing a function such as reproduction, feeding, or defense. The central float is made of chitin, and just about an inch in diameter. This rather flat disc is filled with gas and keeps the Blue Button afloat. Two predators of this beauty are just as striking: the sea slug Glaucus atlanticus, and the violet shells, planktonic sea snails in the genus Janthina. Scuttling along in tide pools throughout Hawaii are some familiar critters that really deserve a second look. They are hermit crabs, probably one of the creatures most responsible for getting children interested in the natural world. Today's post features a few from the genus Calcinus that inhabit tide pools and shallow reefs, though other hermit crabs live in deeper waters. With a closer look, you'll notice that the rainbow of colors on their eyes, legs, and claws that help to identify them. What you don't see, of course, is the soft and vulnerable abdomen that is modified to fit into the protection of a discarded shell, with back legs specially designed to grip and hook. As hermit crabs grow, they need to find a suitably sized new home. Empty shells are a valuable resource to hermit crabs, and a prospective home is thoroughly explored to see if the fit is right. The crabs try it on for size, and take up residency if everything is snug. If, for whatever reason, they begin to outgrow a shell but are unable to find a new one that fits well, they are more vulnerable to predation from any number of enemies, including crabs, reef fish, and octopi. They themselves are omnivores, and are happy munching on the abundant algae in the tide pools, as well as whatever tidbits float by, including debris. So next time you visit a tide pool, take a closer look at these colorful little guys, but leave any empty shells you may see. Housing is in short supply.
Meet ula-päpapa, the slipper lobsters. Looking a bit like a flattened bulldozer, these crustaceans are decapods, "ten-leggers," as are shrimp, prawns, and crabs. Their most prominent feature are two modified and flattened antennae that appear like shovels sticking out of their heads. Three species that may be seen on the reef include the scaly slipper lobster (Scyllarides squammosus), the Antarctic slipper (Parribacus antarcticus), and the hump-backed slipper (Scyllarides haani). Slipper lobsters generally lie low during the day, either blending in with their surroundings or holing up in the many crevices the reef affords. Come nightfall, they scavenge and dine on the brok da mout smorgasbord of the reef, consuming shrimp, worms, snails, urchins; some even snack upon anemones. Of course, they themselves are pretty ono. Predators include octopi, triggerfish, and groupers, as well as humans. Regulations have been established for the taking of slipper lobsters: 1) they must be of a certain size (2 3/4" tail length), 2) they may only be taken from September through April, 3) no taking of hapai "berried" females, and 4) they may not be spearfished. Their life cycle begins with the laying of eggs, which the female carries around under her body. Upon hatching, the larvae drift around for the better part of a year, eventually taking up life on the reef. Because their exoskeleton is inelastic, slippers must moult periodically to accommodate their growth. A new but soft shell forms beneath the old, and when ready to go, the exoskeleton will crack at the junction of the body and tail. With a bit of wriggling, the lobster slips out. Chee, I wen bus my slippah! This is a particularly vulnerable time for the not so crusty crustacean, and they tend to go into hiding until the shell hardens.
You've seen them, and pretty likely, you've felt them. The blue bottle, or Portuguese man-of-war makes it's presence known, with its beautiful blue-tinged gas float above and its stinging tentacles below. The can trail beneath the water as long as thirty feet, ensnaring and paralyzing unsuspecting prey. Blowing in with the trades, the man-of-war land en masse, usually on our windward shores. Not to be confused with their Atlantic cousins which go by the same name (but are larger, more tentacled, and pack more of a wallop), the critter we see here in Hawaii is a different species, Physalia utriculus. While often thought of as a jellyfish, it is actually a siphonophore: a predatory, marine colony made up of individual animals called zooids. The zooids have different forms and functions; some specialize in digestion, others in reproduction, prey-capturing, or flotation. One has to admire the design of the pneumatophore, the gas-filled float that keeps the blue bottle buoyant. A ridge along the top acts like a batten, creating a sail that transports the colony, along with the ocean currents. While the blue tinge makes it easy to spot on the beach, on the open ocean it is well camouflaged, much to the dismay of many swimmers and surfers. It is important to remember that the nematocysts - the stinging cells on the tentacle - can continue to inflict pain long after the organism has washed up on the beach. Leave it to the ghost crabs to do a little beach clean-up.
All critters needs a way to defend themselves, so why not put it all out there, with a splash of color to boot? That's what Heterocentrotus mammillatus, or the red slate pencil urchin does, star of today's creature feature. Thick, blunt spines cover its test (the rigid, calcium carbonate structure enclosing the internal organs) and are attached in a ball and socket manner, allowing them to move in any direction. Turns out that the red color rubs off easily, and so the spines were used like pencils or chalk, thus their name. A small red shrimp, Levicaris mammilata, may be found among the spines as well, blending in magnificently. The spines help the urchin to wedge itself into small crevices, which is typically where you'll spot them during the day. At night they're more mobile, using their spines and tube feet to traverse the reef. The tube feet radiate out in five rows, and the urchins use muscles to force water in and out of them, alternately extending and then relaxing the feet in order to move. The mouth is located at the bottom, with five "teeth" and a modified tongue used for scraping and eating algae, it's primary food. These urchins are sensitive to light, as well as touch, and have a sensory receptor that they use to keep themselves upright. Good thing, as some predators try to knock them over to get at the softer bits. I bet that sends a shiver down their spines.
This is a video clip of a heʻe that I video while at the fish pond with Paepae o Heʻeia. This is a remarkable creature, this day octopus, or he'e mauli. Just marvel at the oddly beautiful body. They're cephalopod molluscs, cephalopod meaning head-foot, which pretty much sums it up the design plan. Since they have no shell for protection, he'e have developed an extensive toolbox of defenses to help them evade predators such as monk seals, sharks, and humans. Lacking an internal skeleton, they are able to squeeze into small places and hide. Rapid getaways can be accomplished by taking in water through the mantle and forcing it out of the siphon. They have chromatophores in their skin that allows them to quickly change color and they use muscles to transform their skin texture, camouflaging into their surroundings magnificently. And when things really get tough, there is always the squirt of ink, ejected from an ink sac in the mantle. The ink can work in several ways. It may impede predators from smelling, and thereby locating, the octopus. It also can act as a screen, or be used to create a false shape, acting as a decoy as the true octopus flees. As hunters themselves, they are just as masterful. Well developed eyes, sense receptors on their arms, and chemoreceptors on their suction cups help the octopus to see, feel, and taste for its food, which include crustaceans, fish, and molluscs. Swooping down on their prey, they enfold them in their web and hold them tight with their suckers. They then inject them with a paralyzing venom and digestive enzymes which help break down the body of the prey. The he'e mauli has a sharp beak which it uses to tear the flesh.
The day octopus is found in shallow waters to depths of around 150 feet, and as its name suggests, they are diurnal. The lifespan is very short, around one to one and a half years. Reproduction occurs just once at the end of their lives. Females lay hundreds of thousands of eggs, attaching them to the substrate in the lair and tending them with care, including fanning the eggs to help oxygenate them. She does not leave the eggs to feed, and eventually dies, becoming nourishment for her young upon hatching. Now you see them, now you don't. Ghost crabs, a.k.a. sand crabs, or 'ohiki, belong to the genus Ocypode, which means fast footed, and that they are. A day at the beach wouldn't be the same without them; all that digging and chasing and scuttling is fun to watch and provides a pleasant diversion after a cool dip. We have two species here: the pallid ghost crab and the horn-eyed ghost crab, and both species may occupy the same beach. The horn-eyed prefers to dig its burrows closer to the shoreline, and makes pyramid-shaped piles of sand when excavating. They are the larger of the two species, getting up to three inches across the carapace, and as the name suggests, they have horny stalks on top of the eye. The pallid ghost crab is a messier excavator, digging higher up on the beach and fanning out the sand around their burrows. They are typically an inch across the shell. Ghost crabs have ten legs to help them do all the digging and running, and of course, feeding. These nocturnal predators and scavengers dine on seaweeds, portuguese man-of-war, mole crabs, detritus; pretty much any debris that's edible. They're like a beach clean-up crew. Breathing is done with gills, so they can take a dunking, and they are able to run around on land as long as the gills are kept moist.
An interesting feature of these crustaceans is their coloration. Ghost crabs on white beaches are white, and on black beaches, they're black. Scientists have experimented with these crabs by placing the white crabs on black sand and black crabs on white sand. And yes, indeed, they were able to change their coloration over a period of time. Anything to help you from seeing a ghost.
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