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Dotting the coastlines of several of the MHI are anchialine pools, formed when freshwater percolates through the ground and meets up with salty water that enters through subterranean cracks and fissures in lava or limestone. The result is a landlocked body of water with secret passages to the sea. The water is stratified, layered with salty, denser water at deeper levels, and brackish to fresh water near the surface. Salinity levels in these pools are also influenced by tidal changes and solar intensity. While this habitat would seem a rather challenging place to live, a surprising diversity of creatures call it home, including the poster child for Hawaii's anchilaine pools: Halocaridina rubra. The 'opae 'ula, a.k.a Hawaiian red shrimp, or volcano shrimp, is a little thing, just up to a half inch in length. These are the shrimp that you may see for sale in air-tight "ecospheres", and while their trade has brought attention to this otherwise little-known decapod, their fates are literally sealed. In their natural environment they feed on algal and bacterial mats within the pool, scraping and filtering these with hair-like structures on their chelipeds. Detritus and plankton may also be consumed. 'Opae 'ula were used by early Hawaiians in their fish ponds as food for larger fish, such as 'opelu, and they are also a favorite food of seahorses. They are unusually long-lived, with estimates from 10-15 years in he wild, and reproduce underground. Hawaii is thought to have approximately 650 anchialine pools, with the vast majority of them found on the island of Hawai’i. Much remains to be learned about these pools and the creatures that live there. In the meantime, it is important to respect these unusual habitats, leaving them undisturbed and free from alien species, such as guppies, tilapia and mosquito fish.
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These past few weeks, I have had the pleasure of witnessing the amazing metamorphosis of the vine hawk moth. It all began one night when a biggish blob fell from a shelf in my house, on which I had a Pentas (Pentas lanceolata) plant growing in a pot inside a large basket. Thinking it was a gecko, I moseyed on over to inspect it closer, when I realized it was a hefty and interesting-looking caterpillar. After a brief photo shoot of the critter, I went about trying to figure out what it was, so that I could rear it and watch into transform into a beautiful... something. I knew that caterpillars have specific plants on which they can feed, called "host plants," and that I couldn't just throw any old leafy green at it and hope that it would eat. Sure enough, I was able to whittle the search down, and it appeared that I had a vine hawk moth, Hippotion rosetta (hip-POE-tee-on roe-ZET-tuh), which has colonized Hawaii just recently, in the last fifteen years or so. Identification can be tricky because the larvae of some caterpillars can change in appearance as they get larger and molt their cuticle; this typically occurs four or five times in most larvae of butterflies and moths. An interesting thing I learned from the Enchanted Learning website is that: "after the molt, while the new skin is still soft, they swallow a lot of air, which expands their body. Then, when the cuticle hardens, they let the air out and have room for growth." The "Insects of Hawaii" website gave information on what my caterpillar ate, and Pentas was one of the plants on which it dines, thus explaining the sad looking state of the plant on my shelf. I placed the caterpillar in a big mason jar with a screen lid and supplied the hungry larva with lots of Pentas leaves. In the morning, I was happy to see that it had eaten many of them, reassuring me that the identification was likely accurate. But later that day I found that it had stopped eating... and moving for that matter. Oh dear! Had I done something wrong? Was it alive? I gave it another day, and still nothing.
A few days later, my conscience was relieved: the caterpillar had pupated. All moths and butterflies undergo complete metamorphosis, a four-staged life cycle that includes the egg, the larva (caterpillar), the pupa, and the adult. My soon-to-be-moth was in that critical stage that seems like suspended animation, but in truth, it was undergoing a most dramatic transformation. A tough pupal skin had encased the caterpillar body. During this time there was little movement, though it would wriggle a bit if I moved it. Inside, the caterpillar body was being broken down, and cells called histoblasts were using the byproducts to build new tissue in the form of a moth. After a few weeks, the most miraculous event occurred: as I went to check on it, I noticed that the pupal casing had broken open. There, resting on the screen of the jar was a most beautiful looking moth, the vine hawk moth, hungry and fluttering its wings in anticipation of food. This moth species enjoys the nectar from Lantana camara, Duranta erecta and Ixora, all plants that are commonly found in Hawaii gardens and landscapes. After sharing it with some students, the moth was released to find its nectar plants, and to begin the cycle once again.
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). Make way for the prickly-natured Scolopendra subspinipes, the biggest of three local centipedes, and the one known for their stinging bite. They are usually about five inches long, and are reddish-brown in color, though variations in color can occur. Damp and dark places are their preferred habitat, such as leaf litter, or under rocks or tent tarps. Normally terrestrial, they may burrow a bit, as I know only too well - I'm always on the lookout for them whenever I turn the compost pile. When the weather becomes overly wet or dry, they go slithering in search of alternate shelter. Venturing indoors, they seek out suitable areas which may include your shoes, clothing, or bedsheets. Oh my. I always shake out my sneakers and garden boots to be on the safe side. They are members of the Phylum Arthropoda, invertebrates characterized by their segmented bodies and jointed appendages. A pair of legs accompanies each of the twenty-one body segments of this solitary and nocturnal animal, making their "centipede" name a misnomer. They use their back legs to grasp and hold their prey, which includes insects, spiders, and worms, while they envenomate their hapless victims with their powerful jaws. Lucky for us, they rather scamper away, but will inflict a painful bite if bothered or threatened. Two puncture wounds mark their bite, which will hurt like the dickens. In some individuals, the venom may cause quite a bit of swelling, in which case a trip to the local medical facility is prudent.
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.
Some of the stunners of the butterfly world, the Swallowtails have only one representative in Hawaii: the Asian Swallowtail, a.k.a. Chinese Yellow Swallowtail, Papilio xuthus. They're a good-sized butterfly, with a wingspan that can get as big as 10 cm. or so, about 4 inches. They were first recorded in Hawaii in the early 1970's, and do not occur on the mainland, though they are widespread throughout Asia and the Pacific Islands. You can tell the males from the females by the coloration: males are blacker all over, and have just a reduced amount of blue scales near the tail, where you also find the yellow eyespot. The females have much more blue along the margins, and have an orange eyespot. Like many butterflies in the Papilio genus, the hindwings have an extension, or "tail," hence the name swallowtail. Host plants (used for laying eggs and feeding the caterpillar) for the Asian Swallowtail are citrus plants in the family Rutaceae, and include orange, lemon, lime, grapefruit, and tangelo. Often eggs are laid singly, which will hatch into a blackish-white caterpillar with spikes. The early instars of the larval stage look like bird droppings, and as such, are fairly well camouflaged. As the caterpillar molts and gets too large to pass themselves off bird waste, they change color to a beautiful green which blends in with the leaves of the citrus. They have prominent eyespots, and an orange osmaterium, a tentacle-like forked structure which can be inflated when they are threatened, emitting a smelly secretion. After about two weeks, they pupate, attaching themselves with the head side up. And then, let the remarkable transformation begin.
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.
Over the past few months, I have watched as more and more of these little hangy-things have grown in number on one of my plant containers in the backyard. They're different from the hangy-things in the laundry room, which are smoother and thinner, and probably belong to a case-bearing moth. No, these are spikier and more grassy. So a trip to the library and a bit of searching, and I think I have cracked the case, pun intended (thanks to Jamieson & Denny's Hawaii's Butterflies and Moths)! It's the home of the caterpillar of the bagworm moth, Brachycyttarus griseus in the family Psychidae. First reported in Oahu in 1984, the species is well established in South East Asia. The male moth is about one and a half centimeters in length, not so big, and the female is wingless. She's got it in the bag....living her entire life there, never to leave. The male impregnates her while she's in her protective casing and then she releases her eggs to the ground. Upon hatching, the little caterpillars eat grass, such as Paspalurn conjugaturn and Zoysia pungens, and immediately get to work constructing their casings. They drag them behind as they feed, and enlarge them with bit of grass and webbing as they go. Once they are about one centimeter in length, the larvae climb up to a spot, say, on a plant pot, the eave of a roof, or a garden shed, and attach themselves to pupate. Only the males will leave the casing, when they go in search of a mate. They are said to be pretty harmless, though I did find a website that said they were pests of basil and lemongrass. So, now the caterpillar is out of the bag. |
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