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.