Strange & Unusual Creatures
by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station
This week I wanted to talk about some of the fantastical creatures and living things that can be found in the water, our forests, and chomping on local cherry trees. Each of these organisms can be found on Nantucket at various times of the year.
I encountered the first one during a walk with a friend at Squam Swamp last week. Due to our cool and damp spring and summer, the island has become a haven for mushrooms of all types and sizes. Carpeting the floor of the forest was a sea of coral fungi in orange and yellow and white. Their bright colors really stood out among the ferns and moss. Coral fungi are named for the similarity to aquatic corals and some of them also are known as antler mushrooms. Originally they were all lumped into the Clavaria family, later they were split into a variety of different genera including Clavicorona, Clavulina, Clavulinopsis, Macrotyphula, Ramaria, and Ramariopsis, some of which are edible (the extreme sport aspect is in guessing which ones!). Here is a great web site with wonderful photos and very clear description of each type of mushroom family: www.americanmushrooms.com/gallery.htm. And while you are surfing the web, you should also check out this site: http://www.mushroomexpert.com/glossary.html#saprobe, which is not only kind of funny, but also has a nice glossary of mushroom-related terms. Many of the coral mushrooms we saw are performing a very important service by acting as saprobes which means they survive by decomposing dead or decaying organic material. Many wood rotting fungi are saprobes, and help decompose dead wood, but other wood rotters are parasitic and attack living wood. Most yard and garden mushrooms are saprobes.
Most of the ones we saw appear to be Clavulinopsis fusiformis although they could be their smaller cousin, Ramariopsis laeticolor (also known as Clavulinopsis laeticolor; “laeticolor” means joyful color). We also saw some that appear to be Clavulina cinerea, tiny white staghorn type corals delicately lining the path and peeking out from underneath the abundant under story. We also spied some small, club-like single tiny orange individuals that are most likely a small club-like coral in the clavariadelphus genus. These fungi are small, perhaps an inch tall, and grow in groups consisting of a couple of singular strands. The sight of literally thousands of the bright orange and yellow and white fungi really made our day. Although Squam Swamp can be pretty buggy sometimes, I highly recommend walking the trails and reading the accompanying information brochure at least a few times each year. Don't miss an opportunity to see another magical Nantucket location with its “magic trees” beloved by children.
Our next phantasmagorical creature is a translucent, gelatinous stick that waves to you from the ridges of the mooring ropes it is most often found on—namely the skeleton shrimp. Skeleton shrimp are perhaps my all time favorite creature hanging around the Brant Point Marine Department shellfish grow-out facility. These little guys are a bit creepy, but once you get used to them, they are really fascinating. Kids love them! They are clear and stick-like with a shape than can only be described as alien and bizarre.
Skeleton shrimp (caprellids) are amphipod crustaceans with very slender cylindrical bodies. Some people call them phantom shrimp. They look a bit like praying mantises or walking sticks and are often found clinging to sponges, hydroids, algae, and other aquatic organisms. The praying mantis resemblance is reinforced by their feeding technique as they face into the current with their clawed legs outstretched so they can capture drifting plankton. Like other amphipods, skeleton shrimp have two pairs of antennae, but the legs behind the first pair are greatly reduced in number. The first pair can be seen just under the head, the second pair carries the large grasping claws, and those at the hind end are used for holding on to the substrate. These animals can move by grasping alternately with the front and hind legs, like an inchworm. They can also swim by rapidly bending and straightening their bodies; one article described their swimming style as “thrashing” which sounds precisely like my swimming “technique.” The female of some species kills the male after mating, and then carries her eggs in a brood pouch on the middle part of her body. The females typically undergo live birth; this web site: http://www.projectufo.ca/drupal/japanese_skeleton_shrimp has a 15 second YouTube video of an invasive Japanese skeleton shrimp (discussed briefly below) giving live birth. I will warn you, it is pretty creepy and certainly memorable.
These little guys are frequently found on ropes and other netting and are considered a biofouling organism in some anti-skeleton shrimp circles. Any fixed object—wharf piling, boat bottom, or dock—placed in the ocean rapidly becomes the site of an unusual assortment of animals known as the “fouling community.” First barnacles settle out of the plankton, then hydroids, sponges, bryozoans, and other sessile forms. These in turn provide a vast habitat for a multitude of small organisms, including our bizarre skeleton shrimp, tube building amphipods, isopods, and small crabs. Algae and tunicates appear.
In this world flatworms, nudibranchs, and errant polychaetes crawl over the hydroids. Sometimes small nemerteans and nematodes appear, or tiny pink anemones. These fouling animals are a rich source of food and attract large numbers of fish. Under the dissecting microscope this collection provides a large diversity of invertebrate form and demonstrates the concept of the artificial reef. Every year, students at the UMass Field Station put out a variety of settling plates of different sizes and materials to see what type of organisms are floating around, looking for a spot to settle. We are always on the lookout for exotic invaders who may have entered our harbor latched onto the hulls of visitors or floating around in ballast tanks.
There is a notorious species that has been invading harbors and has traveled far and wide. It is the Japanese skeleton shrimp (Caprella mutica) and it has spread from its Pacific origin in the waters off northeastern Japan to twenty-nine non-native locations around the globe, spanning both hemispheres. Caprella mutica has been found in the British Isles, Ireland, Norway, Germany, Belgium, the Netherlands, North America, and New Zealand. Whether our local skeleton shrimp are predominantly this very successful invader is unknown and investigating the level of incursion would be a great undergraduate project.
The last of our creatures has been found all over the island this summer in huge numbers and recently has metamorphosed into clouds of tan colored small moths. Although very colorful and appropriately weird, their occurrence has played havoc with cherry trees and other trees as defoliation crops up in susceptible areas. I saw these little guys in huge numbers on almost every single type of plant while walking at Holly Farm near Polpis Harbor (a very nice Land Bank property) a few weeks ago. This creature is known as the white marked tussock moth (Orgyia leucostigma; from the Greek “ leuco” for white and “stigma” meaning “mark or spot”). Caterpillars are recognized by the bright red head and broad black stripe along the back flanked by a yellow stripe along each side. Two red glands on sixth and seventh abdominal segments, a pair of upright pencil tufts of black hairs on the prothorax, and four tufts of hairs (which may be white, gray or yellowish) on the first four abdominal segments are common to several members of the genus. You want to avoid handling the caterpillar as contact with hairs may cause an allergic reaction, which is why I am using a card to hold it in the picture. For some reason, I always call the red dot on the end a headlight.
The White-marked Tussock Moth is a common native of North America, living throughout the eastern U.S. and Canada. The caterpillars feed on a range of host plants, including birch, cherry, apple, oak, and even some coniferous trees like fir and spruce.
White-marked Tussock Moths produce two generations each year. The first generation of caterpillars emerge from their eggs in spring, and feed on foliage for 4 to 6 weeks before pupating. In two weeks, the adult moth emerges from the losse, tan or gray cocoon, ready to mate and lay eggs.
The cycle is repeated, with the eggs from the second generation overwintering. Flightless females are gray and lay a froth-covered mass of up to 300 eggs after mating. Since the females are flightless, the males have to come find them and the females release pheromones to help them out. They cannot spread into new ranges or areas unless “someone” (in this case the caterpillars) does some walking. In spite of this, they are very widespread, and seem to be common throughout most of eastern North America. And on Nantucket, their perambulations are somewhat limited by the surrounding ocean. Males are medium brown moths with a distinctive darker pattern and a single white spot on each forewing, hence the name “white marked.” Dr. Mark Mello, (Research Director of the Lloyd Center for the Environment based in Dartmouth, MA), has been conducting moth research on island for many years, and he finding thousands of these moths in some of his island moth traps over the past few weeks. Perhaps later this year and certainly next spring, keep your eyes out for these colorful, clown-like caterpillars, but look, don't touch!