Far Travelers

Saturday morning Pat and I saw a sight few people witness; Freshwater jellyfish in the pond at Locust Shade Park in Prince William County, Virginia. Scattered far and wide, freshwater jellyfish have been found on every continent except Antarctica and on many oceanic islands including Guam and New Zealand. They are not particularly rare, but like the pookah in Harvey, they "appear here and there, now and then, to this one and that one (and how are you Mr. Wilson?)". Freshwater jellyfish may show up in a pond one year and not be seen again for the next twenty, if ever, although they have been reported from the pond at Locust Shade for the past three years. A big reason that few people see them is that almost nobody looks. Freshwater jellyfish are not very high on the average person's list of things to see. Craspedacusta sowerbii, although not a true jellyfish, is close enough so as to make no difference; a few slight anatomical differences put freshwater jellyfish in the same group as hydras (tiny stalked critters resembling miniature sea anemones). However, if it walks like a duck, quacks like a duck, and swims like a duck...Actually freshwater jellyfish don't quack or walk and they don't swim like duck either, but you get the point.

These are interesting little blobs of protoplasm. They swim, like their saltwater cousins, by pulsating the bell and trailing their tentacles to pick up small plankton such as water fleas and daphnia. Stinging cells on the tentacles kill prey which the tentacles pass up to the mouth for digestion. The stinging cells on freshwater jellies are too small to penetrate human skin, so if you really wanted to, you could pick one up with impunity. Like sea nettles, fifty miles east in Chesapeake Bay, freshwater jellyfish are 90% water. They have an inside layer of cells and an outside layer of cells and in between, they contain gelatinous mesoglea (jelly) which gives them buoyancy. Since they are basically animated water, jellies are nearly clear with an X-shaped set of gonads standing out in white. The biggest ones are about the size of a quarter, with nickel-sized specimens far more common. Pat described them as "swimming edelweiss".

Freshwater jellyfish undergo alternating generations. Colonies of polyps, the stalked form, grow on the bottom, reproducing by branching off clones. The freshwater jellyfish part, or medusa, is the sexual generation, produced by the polyp under favorable conditions. The polyp clones several copies, stacked up like saucers, each of which separates off swims away. Once the medusae release eggs and sperm, they die. In winter, polyps go into a resting state, called the podocyst, which withstands cold. These resting cysts are picked up on bird feet and feathers and move from pond to pond, a few miles at a time, until freshwater jellyfish are found all over the world. Podocysts jump across oceans probably by hitching a ride long-distance migrants which can traverse whole hemispheres. Being a clone species has advantages; the same species of freshwater jellyfish is worldwide and is therefore unlikely to become rare. On the other hand, the medusa stage seldom bears fruit, since all the freshwater jellyfish in a pond are likely descended from a single podocyst and the medusae are all males or all females. Only when podocysts are from different ponds, of different sexes, and both clones manage to survive to the medusa stage, do genes get mixed.

Some researchers postulate that jellyfish represent an early "experiment" of life, unrelated to anything else. Indeed, fossils of jellyfish-like creatures show up in some of the oldest rocks with any traces of life. Called the Edicaran fauna (after some god-forsaken spot in the middle of the Australian outback), they were thought by some to show no affinities to any other known life forms although recent research seems to disprove this theory.

Jellyfish have always seemed to me to be too ethereal to be real (except when I get stung). Maybe it's the ghostly coloring and the unhurried pulsating swimming that makes them seem as if they really are not of this earth. Indeed, the late Carl Sagan, in speculating on possible life forms that could exist in the thick clouds of Jupiter, used jellyfish as a model. He never mentioned if they got there on bird feet.

Paw Paws

I was walking the banks of the Potomac on a warm late summer Saturday morning, looking for dragonflies and assorted other targets of opportunity to photograph. As I rounded a bend in the trail, I suddenly had a mental flash of "Juicy Fruit", as in the gum. They say the sense of smell taps into your deepest memories and creates the strongest associations. So why was I thinking of a chewing gum that I haven't even cared for since I was a kid? A short bit of looking turned up a forest floor littered with ripe paw paw fruits. Paw paws are middling-sized understory trees, usually found on the rich flood plains of streams and rivers. They have large leaves, always in threes, and the flowers in early May look like those of wild ginger, even though the two plants are not remotely related.


Paw paws are the northern representative of what is a huge tropical family of trees, including the tropical custard apple, which my old economic botany text book calls "the queen of tropical fruits".


Paw paws are loaded with aromatics; crush a leaf and you smell green peppers. Cut open a ripe fruit and you get a whiff of sweet potato and banana. The taste is the same; sounds kind of ghastly, but is surprisingly good on the pallate. Just make sure the fruit is fully ripe - green ones can be mouth puckeringly astringent. Paw paw leaves are the only food plant for caterpillars of the zebra swallowtail butterfly, and the Potomac valley is well known among lepidopterists as the best place to see this hauntingly beautiful species.


The late Euell Gibons, in his Stalking the Wild Asparagus, gives a recipe for paw paw chiffon pie, although you would be hard put to find enough ripe fruits to give it a try; I only found enough unchewed fruit to fill a baseball cap. Everything in the woods, from bears to mice, eats paw paws. Paw paw seeds are the size of nickels, and as hard and brown as mahogany. They are designed to be gulped down with the sweet pulp and (ahem) deposited some distance away from the parent tree. Dan Janzen, an ecologist at the University of Pennsylvania writes that these fruits, along with those of persimmon, honey locust, and others, were originally dispersed by Ice Age megafauna such as mastodons and giant sloths (or as those in the business call them, BHMs - Big Hairy Mammals). If that is true, when you enjoy a ripe paw paw, fresh off the forest floor, you are fulfilling a role once played by extinct beasts. Just remember to swallow and do like the bears do.

Bluegills, Satellites, and Sneakers

Ask any angler what was their first catch and, nine times out of ten, the answer will be "bluegill". Bluegills are perfect pan fish. Small enough for a kid to handle, aggressive enough to bite on any bait, and abundant as anything that swims. They are also very scrappy at the other end of the line. There is a whole subculture of fly-fishers whose art is devoted to the deception of bluegills. The local sporting goods shop sells more artificial flies designed for bluegills than for trout. Trout in this area are fading aristocrats; the last local population of native brook trout vanished when the town of Reston was constructed and the last self-sustaining population of brown trout is in danger from a planned highway. Bluegills and their many cousins, however, proliferate in any body of water bigger than a a wading pool. I have netted bluegills from a golf course pond no bigger than an average suburban bathroom.



Bluegills are are related to the perches and are members of the family Centrarchidae, which includes large- and small-mouth bass. Centrarchids are an ancient North American speciality; found coast-to-coast and from Mexico to above the Arctic Circle. They have survived the dinosaurs and have been transplanted by humans to all parts of the globe. Bluegills (and their cousins the basses) are native to the Mississippi River drainage system and were brought to the Atlantic rivers in the late 19th century. Bass were taken to California in the water tenders of steam locomotives almost as soon as the Golden Spike was driven. Now that the Potomac has been cleaned up, thanks to gazillions of your tax dollars (thanks!)and the introduction of an aquatic weed that thrives in polluted water, it has become a major stop on the Pro Bass Fishing Tour. Yes, there are professional bass anglers. One of the cable channels carries pro-bassin' programs. I guess it's entertainment, but watching someone else fish is slightly more boring than watching paint dry.

Bluegills are colonial breeders, meaning all the bluegills in the pond will be nesting at the same time. From about late June until now, if you haunt ponds, lakes, slow moving creeks, and other assorted wetland areas, you will see what looks like a series of small bomb craters lining the banks in water about a foot or so deep and going out into deeper water. These are bluegill nests. Given the limited area for nesting, competition is fierce. Males stake out hexagonal territories, build a round depression in the bottom, and stand guard with all their breeding colors showing. A bluegill in breeding fettle is as pretty as any exotic fish from the rain forests that you may see in the local aquarium store. Males build and guard their nests fiercely; they will attack anything encroaching into their territory and a small lure trolled near the surface is sure to get a strike. Females flit from nest to nest, sizing up the males and deigning to lay a few eggs in whatever nest whose male strikes their fancy. One female can produce up to 50,000 eggs, but she will distribute them around several nests, mating with several males. A single nest can hold up to the same number of eggs produced by a single female, so the numbers even out. Eggs hatch in about a week, and the young spend their first year or so hiding in weeds or submerged brush. Two- and three-year olds begin breeding and five-year old bluegills are rare. Nests near the center of the colony are preferred and males compete for them, the bigger guys ousting the smaller ones. Nests on the edges are more heavily preyed upon by catfish and surprisingly, snails, which may account for up to half the egg losses. A closely related sunfish, the pumkinseed, is a solitary nester. Pumkinseeds feed on snails and may cruise around the bluegill colony hoping to pick up a quick snack.

It may seem that the big alpha males have all the advantages in colonial nesting, but they are not alone in the sweepstakes to get their genes out to the next generation. Aside from other alpha males constantly patrolling the colony, hoping to take over an established nest(any male you catch will be almost instantly replaced), two other male types; satellites and sneakers, also lurk the shallows. Satellites are males, but with female coloration and some their behaviors. When a couple begin to go into their breeding behavior, a satellite will come into the nest and join in, mimicking the female. This is the stuff of Penthouse Letters for the alpha male and he happily and blindly sets forth. When the real female releases her eggs and the alpha male begins to fertilize them, the satellite also releases a cloud of milt to mix in. Up to half the eggs in a nest may be fathered by satellites. Unless the sneakers get into the act as well. Sneakers are dwarf males, hanging around the edges of territories, looking inconspicuous, and staying out of trouble. At the right moment, a sneaker will dash in upon the happy couple, release his milt, and be gone before the alpha male realizes what's happening.

Bluegill population genetics are such that neither satellites nor sneakers will ever get too abundant; both populations are dependent, almost parasitic on a good number of territorial alpha males who stake out territories and defend the nests, eggs, and young. Even so, next time you take a kid fishing, don't forget to ask your catch "Who's your daddy?"

Happy Birthday, Carl Linnaeus, the Man Who Saved the Loch Ness Monster

This year (June actually) marks the 300th anniversary of the birth of Carl Linnaeus, the Swedish botanist who invented the system of biological nomenclature. An excellent article by David Quammen on the man and his achievement (Quammen calls him the first "information architect") may be found in the June, 2007 National Geographic.

Without going into the detail so well described in the Geographic article, let me present, for your amusement, a couple of stories told me by a taxonomist and member of the Linnean Society.

It seems that Carl was either a) possessed of an extremely dry wit, or b) a cranky old fusspot. The Norway rat (actually from the steppes of central Asia) was named Rattus norvegicus by Linnaeus because, as a Swede, he despised Norwegians. He must really have had it in for Germans since the German cockroach (Blatella germanicus) is really from tropical west Africa.

Linnaeus named both the house mouse (Mus musculus) and the blue whale (Balaenoptera musculus). Here we have one of the smallest of mammals and the largest creature who ever lived, both sharing a name. One wonders why...perhaps a joke? "Hey Sven, go get me a musculus"; leaving poor Sven to wonder if he needs a jar or a harpoon.

Linnaeus' legacy is the orderly system of naming living things (he tried it for minerals, but gave it up as way too complex). The foundation of the system is the genus and species. All living things must be named according to the rules set forth by the rules of nomenclature. Plants must be described in a scholarly journal in Latin, and a specimen, called the type specimen, must be deposited in an accredited institution. The type and associated description ultimately are what all members of that species are measured against when taxonomists try to determine what ever it is they may have in hand. The rules for animals are pretty much the same with the exceptions that the description need not be in Latin, and the type specimen may be a part or even a photograph of the animal. If you discover a new species, you get to name it. Linnaeus described and named us; Homo sapiens. Guess who he named as the type specimen? Himself. We are all held comparable to a middle-aged Swedish man. Go figure.

On to the Loch Ness Monster. In the 1970's, a plan was hatched to depth-charge Loch Ness in an effort to bring some closure (dead or alive) to the myth of the Loch Ness Monster. To thwart this, Sir Peter Scott (son of Captain Robert Falcon Scott, of Antarctic fame, and a founder of the World Wildlife Fund) and Robert Rimes co-published a paper in the journal Nature, describing the beast. They named it Nessiteras rhombopteryx (Greek for "the wonder of Ness with the diamond shaped fin"), "affinities uncertain". As a type specimen, the authors used a pair of blurry photos, purported to be of the Nessie, one showing what could be imagined as a squarish fin, the other just a blob. Under the rules of zoological nomenclature, the photos counted as a type specimen. Nessie was placed on the British list of endangered species and saved from a cruel fate. Some skeptics have noted Nessiteras rhombopteryx is an anagram for "Monster hoax by Sir Peter S." Robert Rines responded to these critics with his own anagram: "Yes, both pix are monsters, R."

Plan B

"If we had a Plan B, it would have been Plan A"
--Unforgettable line from an unremembered movie


A catbird has claimed the overgrown corner of the yard by the swing set. A Chinese wisteria has been climbing the framework for a couple of years now, despite my best efforts to tame it. It has attracted hangers on as well, including a blackberry. The bramble attracted the catbird who drives off any other birds remotely in the area. Blackberries are among the early- to mid-summer ripening fruits that drive the birds nuts. When I say "ripen", I mean turn red. Red blackberries are to this palate, slightly sour and insipid. It's only when they become that deep purple-black with the intoxicating fruity aroma that I get interested. I used to eat myself sick on them when I was a kid. Little did I know that I was just part of Plan B for the plant to scatter its seeds.

Red fruits are hugely attractive to birds. Hence, cherries, dogwood, magnolia, and holly berries. These trees produce large numbers all at once and the birds swarm to them. I have seen a cherry, red fruits glowing in the woods like Christmas ornaments, filled with orioles, grackles, robins, and who knows what, all gorging together. Dogwood, magnolia, and holly, their berries loaded with high-energy lipids, ripen just in time for the south-bound migrants and I have seen the trees in my front yard striped in only a few short hours by hordes of robins and cedar waxwings.

Blackberries go a slightly different path; only a few berries ripen each day, keeping the catbird coming back for more, ensuring a steady customer. The catbird inspects all parts of the vine, looking for the telltale red berries. Finding one, it gobbles it down and keeps looking for more. In places where blackberries are abundant, like in the woods where I grew up (along the creek by the old leaky buried sewage line...who knew?), birds just can't keep up with the sheer poundage of fruit. This is where Plan B comes in. If the red berries are not eaten, they just keep ripening until they drop off the vine or a mammal, a raccoon, deer, opossum, or ten-year old kid, happens by. Purple, loaded with sugar and smelling vaguely like strawberries, they are definitely a come-hither treat. Enough of the seeds pass through the gut without being chewed (or stuck between molars) to ensure deposition some ways off. Even if the berries drop off the vine, they are sought out by box turtles who have a surprisingly sweet tooth (actually, they have no teeth at all, but you get the picture).

If you can find a trove of blackberries that the birds couldn't keep up with, and the turtles haven't beaten you to, pick a pint or so to take home (what you eat on the spot doesn't count), crush lightly to get the juices going and serve over vanilla ice cream. Better yet, pick two pints and freeze one for later; Summer in January never tasted so good.

The Eternal Dance

Every member of a prey species can take it as given that they will never die of old age. Something faster, more clever, or just luckier will find them first. Every gazelle knows, deep down in its DNA, that it needs to outrun the fastest cheetah it encounters today, and every cheetah knows it needs to outrun the slowest gazelle. The slow genes are remorselessly weeded out of the population, resulting in ever faster animals - predator and prey drive each other's evolution. Case in point, the American pronghorn. This elegant creature can hit speeds of close to 70 miles per hour, a leftover trait from 15,000 years ago when the American cheetah stalked the Great Plains. The cheetah is extinct (probably due to the advent of humans crossing the land bridge from Asia), but the pronghorn's speed abides.

Prey species have a whole bag of tricks to keep from becoming dinner. Fish school, birds flock, mammals herd. The idea is that a predator needs to pick out one individual to concentrate on in order to maximize success. Most predators make a kill only about one in ten tries at best. So, if you are bunched up and moving at top speed, the predator you are trying to avoid will lose you in the crowd. At least that's the theory. But predators have tricks up their proverbial sleeves as well. School of fish crowding into a tight ball so any individual is lost? Attack the whole ball like swordfish and marlin do. Lash about in a crowd and you are certain to hit something which can be eaten at leisure. Humpback whales go one better; they swim below the packed school of fish, and blow a stream of bubbles while circling the base. This "bubble net" serves to pack the school even more densely and the whale comes up from below, mouth open, to engulf the whole shebang.

I was beach combing at Bethany last fall when I saw a flock of sanderlings swirling up in a tight spiral. At first, I thought it was smoke until my eyes made out the individual birds. Sanderlings are those tiny sandpipers everyone sees at the beach but no one really notices. One of several related species of small sandpipers, known to birders as "peeps", they run up and down the beach, always staying just out of the wash of the surf. Running like clockwork toys, they examine each new swatch of wet sand for any tiny mole crab or other crustacean exposed by the receding wave. In fall, they form small flocks, some of which stay along the mid Atlantic, others travel to points south. The flock I was watching spiraled even tighter when a peregrine falcon appeared from out of nowhere. The sanderlings had seen it and recognized it for what it was and were taking the only defense they knew -keep moving, keep shifting. They seemingly moved in precise unison. Ornithologists originally thought flocking birds were telepathic by the way they seem to move as a single unit. Researchers, using high speed movies, were able to notice how one bird begins the move with the nearest neighbors mirroring it. The movement ripples across the flock too fast for the unaided human eye to see.



A peregrine can outfly any bird in the sky, so fleeing was not an option. The peregrine dove through the spiral, splitting it in two. The two smaller flocks, still spiralling, separated and the falcon dove through the smaller of the two. The birds veered as one and kept the tight spiral. All but one - too old keep up, too young to recognize the signals,or just plain out of luck. One sanderling found itself alone. The Japanese have a saying: "the lone nail gets hammered down". The falcon knew this and now had a single individual on which to concentrate. While the rest of the flock, knowing they were safe, sped down the beach, the lone peep, in a final defensive maneuver, dropped like a rock onto the water. The peregrine hovered over the hapless sanderling floating on the surface, and with all the grace and precision of a dinner party guest picking up a canape, plucked the peep from the surface and quenched it in one great yellow talon. The falcon flew up-beach to pluck and devour its meal. The sanderlings settled back down on the beach to continue their clockwork minuet with the waves, searching for tidbits.



Everybody eats. Everybody dances.

Silent Sentinels

They march, in an irregularly spaced line, from Fenwick Island, to the entrance of Delaware Bay at Cape Henlopen, in the north. The casual tourist may be forgiven for mistaking them for lighthouses for they share the same tall windswept, somewhat foreboding isolation. Closer inspection, however, shows bricked-up doors and windows, ending in a steel-railed parapet 40 to 75 feet on the topmost deck. These are coastal watch towers, their usefulness almost 70 years past, and abandoned to the elements, with the occasional historical plaque to tell half-interested readers exactly what they are and why they are there.

By 1942, the Battle of the Atlantic was going badly for the Allies; German U-boats, operating seemingly at will off the East and Gulf coasts, sunk an ever higher toll of shipping each month. While U.S. shipyards were building replacement ships at an accelerated pace and would soon catch up with and surpass the losses, the toll extracted by the wolf packs was fearful and went largely unanswered. U-boats lay in wait off coastal and resort towns, torpedoing ships as they passed silhouetted by the city lights. Burning tankers drew curious crowds of boardwalk spectators in much the same way a traffic accident would at rush hour. Bodies of merchant seamen regularly washed ashore along the Eastern Seaboard.

Delaware's coastal defenses construction began in 1939 and lasted for three years. Fort Miles, built at Cape Henlopen, was essentially a land-locked battleship sporting two 16-inch guns (the same as carried on the USS Iowa), two 12-inch guns, and a battery of four 6-inchers. The 16-inch battery could fire one-ton projectiles nearly 25 miles. Fort Miles also controlled a minefield, which could be turned off electronically for ships to pass, and stretched the width of Delaware Bay. Thirteen towers; eleven in Delaware and two near Cape May, New Jersey, manned by troops from the US Army's 261 Coast Artillery Regiment, were the spotters for the formidable guns at Fort Miles. Equipped with radios, fire control radar units, and various optics including azimuth sighting range finders, the soldiers kept vigil over the approaches to Delaware Bay. Azimuth sighting range finders visually determine a target's position using the measure along the horizon of the angle between the object and a fixed reference point. Sightings from two towers were triangulated and sent to the the fort to position the guns. At least that was the theory; the guns were never fired at a target.

Tower 7, located in Henlopen State Park has been restored and is open to the public. If you don't have a head for heights, don't visit, even though the steel ladder was replaced by a steel circular stair.

The towers were built on creosoted pilings hammered into the sand and a concrete base was laid on top. The towers themselves were constructed from reinforced concrete, strengthened by wire mesh and steel rebar. The concrete was poured into a hollow 16-foot diameter form, with walls a foot thick, in a singe 24-hour pour. After the concrete cured for about a month, steel ladders and wooden decks were added, and the tower was open for business. Beach sand was used to cut costs and the towers had a life expectancy of 20 years or less.

The towers continue to keep vigil after nearly 70 years, weatherng nor'easter storms and hurricanes, their footings washed by high tides. Pigeons roost on the rusted steel railings and rise in clouds when the odd falcon passes in migration. Pink at dawn and sunset, the Delaware towers have become as much a part of the landscape as the beaches themselves over which they loom.