Sunday, June 26, 2011

Comb Jellies in the East River

Today I saw an animal I've never seen before. A comb jelly.

I was at a public educational program in Brooklyn Bridge Park in New York City called Seining the River Wild (Click here for details). A big group of kids showed up with their parents and everybody had a great time. (There’s another seining event coming up; you can click here to see the park's calendar of events.)

We met under the Manhattan bridge on the Brooklyn side, on a strip of sandy East River beach. We watched as scientists repeatedly waded into the water with seining nets to catch small wildlife, which was returned to the wild after everyone had a good look. They unfurled the nets on the shore to reveal algae, crabs, shells, shrimp, tiny fish (silversides, blue fish, flounder), and lots of little comb jellies.

I held a comb jelly in my hand for a moment. It felt like soft jello and seemed so insubstantial that I was afraid it would fall apart. But when it was released into a little tub of water its fine transparent structure appeared. Comb jellies don’t photograph well without some advance planning but you can see enough of one in the following photo to get an idea of it. It is that tangle of pale threads below and to the right of the handsome baby bluefish.

In the lower right corner -- a ghostlike comb jelly. Click on the photo to enlarge.

 The comb jelly is egg shaped and simple. It has a mouth at one end, an anus at the other, and a stomach in between. Its body is a jellylike mass with thin layers of cells inside and out, surrounding a hollow cavity. Most species are hermaphrodites that release sperm and eggs into the water where external fertilization occurs and jelly babies grow.
The comb jelly gets its name from long rows of plates that look like tiny combs. The combs are made of fused hair-like cilia; they beat back and forth to propel the jelly through the water. Comb jellies are the largest animals that use cilia to move. (The method is wildly popular among microorganisms.) The moving combs sometimes scatter daylight and look rainbow colored. Some species of comb jellies are bioluminescent and glow in the dark. 

Comb jellies are predators; they eat plankton and larvae, small crustaceans, and smaller jellies. The comb jellies we caught in the East River ranged from tiny to small; the largest was a wavy fluid inch or so long. They resemble jellyfish, but they are not, and they don’t sting.

Today’s comb jelly sighting was timely. The lowly comb jelly recently received a lot of press coverage when a scientific study identified comb jellies as the first animal group to branch off of the common evolutionary tree -- a position previously given to sponges. The change was based on a comparison of DNA sequences of many genes from many animals. Comb jelly DNA is least like that of other animals suggesting that comb jellies may have been the first animals on Earth. 

Nevertheless, just like my highly evolved self, comb jellies spend occasional Sunday mornings near the shores of the East River. 

Sunday, June 19, 2011

A Different Ladybug

The 14-spotted ladybug, Propylea quatuordecimpunctata, or P-14. 

Square spots. Tan background. Ladybug? Yes! It's Propylea quatuordecimpunctata.

Propylea quatuordecimpunctata, also called the 14-spotted ladybug, or P-14, is one of the common ladybugs of Europe. There are about 5000 species of ladybugs worldwide. And now P-14 can be added to the roughly 400 kinds of ladybugs that live in North America.

I found this one on an ornamental plant in the garden of the River Cafe on the Brooklyn shore of the East River near the base of the Brooklyn Bridge. It's the first one I have ever seen and I was lucky because it is a shy and fast-moving beetle. It passed artfully through the shadows of  leaves and kept to the undersurfaces -- especially when it noticed that I was watching. It eventually slipped into the shade and ran down a plant stem as fast as six legs can go.

A riverbank in a port city is a fitting spot to find a P-14,  since its ancestors probably traveled to North America by water from Europe. Some of them are thought to have arrived in Canada via the St. Lawrence River by ship; it is not known exactly when they entered or became established. They may have been helped by the opening of the Saint Lawrence Seaway in 1959, which linked the Atlantic to ports as far as 2000 miles inland on Lake Erie. Stowaways could easily fly off. P-14s were found in the wild near Quebec City in 1968. They are now established in New England, Pennsylvania, New York, and New Jersey.

Identifying ladybugs can be challenging because there are so many of them. Even worse, individuals of some species don't look much alike. For instance, the 10-spotted ladybug comes in a spotless form. The Asian ladybug comes in colors from yellow to orange to black and can have 0 to 22 spots.

P-14 itself is never red but can by creamy, tan, or pale orange. Its spots are sometime round and distinct but most often they look square and they run together in places. Like the one in the picture, the overall effect is of a black checkerboard pattern on a tan background. P-14 has the familiar domed ladybug shape and is about one-quarter of an inch long.

Like other ladybugs, p-14 is a voracious predator on aphids and a consequently welcome visitor to gardens and farms. The immigrant ladybugs have found their way to agricultural regions where they are probably munching on crop pests right now. Ladybugs are particularly good at aphid control because both the adult and larval stages eat aphids.

Ladybug stories tend to end with ladybug lore or cute poems. Almost all of these say something about black polka dots and red wings, things that do not apply to P-14. But voracious appetites apply to all ladybugs, so here is a stanza from "A Ladybug's Complaint" by Mayme Baker Cunningham.

My children have such appetites;
I don't see how they do it. 
They eat large quantities of pie,
and hardly stop to chew it!

Sunday, June 12, 2011

The Northern Mockingbird

The northern mockingbird, Mimus polyglottus.
I am never on  my porch for very long before I notice a bird singing above the traffic and other city noise. The mockingbird in my garden sings all the time. Perched conspicuously on a rooftop antennae or treetop he lowers his wings, throws his head back, opens his beak, and sings. And sings. And sings.

Male mockingbirds sometimes sing continuously for more than an hour. In spring and summer they may start before dawn and some of them keep right on singing into the night, especially if seeking a mate and especially if there are bright lights or a full moon.

They are famous for singing a varied repertoire that includes phrases from other birds' songs. They are creative mimics and can pick up and string together surprising things like the sounds of frogs, or doorbells, or humans whistling. The mockingbird typically repeats a phrase 3 to 6 times and then sings another, all at a very loud volume. The singer may jump from his perch and quickly return with some fancy wing flashing. Mockingbirds are resident throughout North America all year but they draw our attention by singing mainly from February to July and then again from late August through October. 

Why all the singing? Mockingbirds are territorial; males chase away other males, females chase away other females. When a mated male sings, he mostly directs his songs into the territory -- he sings to the female within. But when an bachelor male sings, he broadcasts in all directions, probably hoping to impress a female  somewhere out there. Singing is a big part of a mockingbird couple's interaction; during sex the male sings when he approaches the female, sings during copulation, and sings after.

Loud! Loud! Loud! Walt Whitman quotes the bird. Read more below.
What kind of song impresses a female mockingbird? Something complicated! A recent study of mockingbirds around the world showed that those living in areas with more variable climate sing more complex songs, suggesting that better singers are smarter and better able to deal with the challenges of harsh weather; they just might make better, more resourceful fathers. (Click here for more details about the mockingbird climate study.)

Mockingbirds are gray above and white below. They are about 10 inches long, including the tail. The legs and tail look longish. The wingtips look rounded. White patches on wings and tail stand out when the birds fly.

In Leaves of Grass, Walt Whitman wrote about a pair of mockingbirds nesting on Long Island, capturing the cadence of mockingbird song in his words. Parts of the poem are pasted below, click here for the rest.

 Out of the Cradle Endlessly Rocking – Walt Whitman, Leaves of Grass 

OUT of the cradle endlessly rocking,
Out of the mocking-bird's throat, the musical shuttle...

Once Paumanok,
When the lilac-scent was in the air and Fifth-month grass was
Up this seashore in some briers,
Two feather'd guests from Alabama, two together,
And their nest, and four light-green eggs spotted with brown,
And every day the he-bird to and fro near at hand,
And every day the she-bird crouch'd on her nest, silent, with bright
And every day I, a curious boy, never too close, never disturbing
Cautiously peering, absorbing, translating. 

Shine! shine! shine!
Pour down your warmth, great sun.'
While we bask, we two together. 

Two together!
Winds blow south, or winds blow north,
Day come white, or night come black,
Home, or rivers and mountains from home,
Singing all time, minding no time,
While we two keep together...

Loud! loud! loud!
Loud I call to you, my love!
High and clear I shoot my voice over the waves,
Surely you must know who is here, is here,
You must know who I am, my love. 

Out from the patches of briers and blackberries

Sunday, June 5, 2011

The spotted cucumber beetle

The spotted cucumber beetle, Diabrotica undecimpunctata.
Cucumber beetles are pretty insects with bright yellow-green bodies and contrasting black spots, head, legs, and antennae. They are about 1/4 inch long.

They are sometimes mistaken for rare green ladybugs. Nope. They are beetles, like ladybugs, but in another scientific family -- the Chrysomelidae -- commonly called Leaf Beetles.

 The cucumber beetle's good looks don't count for much with gardeners and farmers; the little green varmint is a big agricultural pest. Cucumber beetles eat more than cucumbers. Their menu includes melons, squash, pumpkins, corn, beans, soybeans, and even cotton.

Adult cucumber beetles munch on leaves, fruits, stems, and other juicy plant parts and the little yellow larvae burrow into plants mouth first, eating as they go. Like a superhero with an alter ego, the larval stage of the cucumber beetle is also known as the notorious Southern Corn Rootworm! Cucumber beetles are found throughout North America even where there are no crops. I find them in Brooklyn on the leaves of ornamental plants and in rose blossoms.

Every year some of them overwinter as adults under leaves or trash.  They emerge in spring and lay eggs. After a few weeks, the larvae become handsome adults. There is time for multiple generations each summer.

Their lives are so short that I am inclined to forgive them for eating cucumbers. But I am not a gardener or a farmer, just an insect watcher who sometimes wonders what it would be like to be a green beetle. Dylan Thomas wrote a  poem that begins -- To-day, this insect and the world I breathe. Today, me too.