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.
Posts Tagged 'St. John'
Tags: Brooklyn, Dead Horse Bay, invertebrates, Jamaica Bay, St. John
Even though we have at least one species of chiton, or coat-of-mail shell, in our northeastern waters, I’ve never come across one. The eight plates, or valves, that make up the shell usually break apart and scatter to the waves. This one was actually in a pile of shells placed as decoration in the villa we stayed in at Klein Bay. The scales on the animal’s girdle have a look of snakeskin. Speaking of girdles, the name chiton, for you fashion-backwards types, means mollusc in Latin, and comes from the Greek khiton, meaning tunic. Some of the statues in your neighborhood Greek Wing are wearing these tunics still.
Hermit crabs range from these little guys, scavenging the back end of rocks along the shoreto the landlubbers known as “soldier crabs,” which can get up to baseball sized, shell (usually the West Indian topshell or whelk as below) included.These are the ones who swarm out of the mountains in August to mate by the sea.
There is another land crab, not a hermit, which I only caught glimpses of. Mud around their nest holes is evidence of recent activity below.They are still hunted for food so their shyness is excusable.
The western edge of Klein Bay is rocky, but I scrambled about three-quarters of the way along its edge the first morning of our trip. I wanted to see the sun come up over Dittlif Point peninsula (unseen to the left in the above image). I found a nice flat rock to stand on – it was too wet from the night’s surf to sit on -and while waiting heard a noise behind me.
St. John, like Virgin Gorda, is hopping with lizards, anoles, and geckos, most of them just a few inches long. And I do mean hopping: they will often jump to get ahead of you. This one, for instance, was barely 1.5 inches long.
I don’t think Virgin Gorda, which is smaller, has a drier and more cactus-dominated habitat, has any of these long-tailed reptiles, so this was my first opportunity to see one. So we spent some time waiting for the sun to crest the land, iguana and I. But just as the sun was cresting, it was suddenly obscured in clouds. I scrambled back in time to take shelter under a maho tree before it started to pour. Luckily, these tropical downpours are brief this time of year. I then found this on the way to our villa:I think it’s a piece of shed iguana skin. It looks like it came from the chin, where those large eye-like spots are. It seemed a red-letter day, and was eager to tell my crew about my finds, all before they even awoke.It turned out, however, that this was just the beginning of the iguana watching. We had them as neighbors, just a few feet way. Seven was the high count one day. They loved to hang out atop the trees and bushes and palms right next to the house. I saw one crossing the road slowly, dinosaur-ishly; another time I saw one scramble up a tree rather quickly, monkey-ishly. They were by the side of the roads, in trees, all over, even downtown in Cruz Bay.Unlike a lot of things on the island, iguanas are native to the region. The very name seems be a Spanish version of the Taino name. Though plenty fierce-looking, they are herbivores. Their common name is Green Iguana, Iguana iguana, and are most immediately differentiated from the endangered Lesser Antillean iguana by the bold stripes on their tails.
Tags: invertebrates, St. John
One of the ubiquitous arboreal termite colonies, or termitaria, found on the island. Known locally as wood lice or wood ants, this Nasutitermes species builds large nests of partially digested wood pulp mixed with their own saliva and feces. The material looks like mud from a distance. The nests are often found broken up on the ground, brought down by their own weight. Here’s a chunk of the brittle, friable nest: These critters do not like the light: they even turn their trails into tunnels, as this one, snaking up a tree:I found this tunnel across a path. It had been stepped on by an earlier walker:If you look closely, you can see two of the three termite castes in this scrum: the round-headed workers and the pointy-headed soldiers (their heads are also darker). The soldier’s proboscis sprays noxious chemicals in defense of the colony. I didn’t smell anything unusual, probably because the disruption was already over and now the termites were working to repair the damage. The third caste, the reproductives, are generally only seen in the fall when they take to wing.
Termites from a single nest may build tunnels in a territory as large as a football field. They generally don’t eat living wood, so they are recyclers of dead wood in the forest. Their waste pumps nitrogen back into the soil. Wood pulp is really hard to digest, so the termites’ guts are loaded with cellulose-digesting bacteria. It’s a symbiotic relationship — like that of humans and our intestinal flora, which consists of something around
500 — the latest count says some 10,000 species of bacteria inhabit human beings inside and out — one passed on, literally, via the young eating the liquid intestinal stew secreted from the business ends of older termites. “Proctodeal feeding,” to the pros. Now, carry on with your breakfast, and feed that gut flora!
Tags: birding, birds, St. John, Virgin Gorda
Last year on Virgin Gorda, the Green-throated Carib was the hummingbird species we saw everyday. The island’s other hummingbird, the Antillean Crested, waited until our last morning to put in an appearance. This year, on St. John, the Antillean was the omnipresent species. GTCs were around, but nowhere in the same abundance. The Crested is tiny, looks black in flight, and, if male, has a diamond-shaped crest that, when the light is right, shines like a jewel.These photos give only a hint of this little bird’s startling beauty. Like most hummingbirds I know, they move very fast and are very hard to photograph with the technology and skill level at hand.Another relatively common species on St. John, as on Virgin Gorda, is the American Kestrel. We seemed to be staying in a pair’s territory. One day I saw the male being chased off by three little black bolts: they were these hummingbirds. Small, but fierce.