JIM CONRAD'S
NATURALIST NEWSLETTER
Issued from the valley of the Dry Frio River on the
southern slope of the Edwards Plateau, northern
Uvalde County, southwestern Texas, USA

February 9, 2014

BAGWORM STORIES
Nowadays on a leafless branch of Netleaf Hackberry in the Dry Frio's cobblestone floodplain there hangs a bagworm cocoon, shown at http://www.backyardnature.net/n/14/140209bx.jpg.

Also at this moment, on an Ashe Juniper branch beside Juniper House, there's the cocoon shown at http://www.backyardnature.net/n/14/140209bw.jpg.

Notice that at the bottom of the last cocoon the bag becomes narrow and long, and at the very bottom there's an amber-colored, cellophane-like "exuvia," an exuvia being the remains of a molted arthropod such as an insect. Comparing the two cocoons, questions arise, and in answering them, stories about the bagworm's life history form in our minds.

Many different kinds of bagworms exist, at least if by the term "bagworm" we're referring to the caterpillar stage of a species of moth belonging to the Bagworm Moth Family, the Psychidae, of which about 1350 species are known. Many of those species produce cocoons very different from the ones in our pictures. The bagworm known by people in the US from New England and Nebraska south and throughout Texas is THYRIDOPTERYX EPHEMERAEFORMIS, which probably produced the cocoons in our pictures. That species places its cocoons on a variety of plants, especially evergreens but also deciduous trees, adorning the cocoon's exterior with items gathered around the cocoon site, so that accounts for our cocoons bearing different coverings.

To understand what the bags are about, and why extra stuff might appear at the bottom of one but not the other, we can take a look at the life cycle of Thyridopteryx ephemeraeformis:

In the spring, inside an overwintered cocoon, tiny, caterpillar-type larvae emerge from eggs inside the body of their mother, who has been dead since the previous fall. Emerging from the cocoon's bottom, the caterpillars drop down on a strand of silk, the wind often blowing them to neighboring plants. Once a caterpillar is settled on a good host plant, it begins building its own cocoon from silk and fecal material, over the weeks gradually adding leaves and twigs to the growing cocoon's exterior; this camouflages the cocoon and adds a bit of armor. During this time the growing caterpillar feeds voraciously, and if there are enough of them they can damage a plant or even kill it. The caterpillar moves about on legs at its front end, which protrude through its cocoons.

In late summer when the caterpillar reaches its largest size -- its last instar -- it wraps silk around a branch, dangles from it, and pupates head down. Adult males metamorphose into moths in four weeks, and fly away looking for females, but the females never leave their cocoons. This situation is met by the male mating with her through the open end at the bottom of her cocoon. The poor female is hardly more than a baby-producing machine. She has no eyes, legs, wings, antennae, and can't eat. She just mates and dies. After her death with hundreds to thousand of eggs inside her, her offspring hatch, and over a period of several months pass through her body, pupal shell and cocoon, finally dropping from the cocoon on silk lines, and starting the cycle all over again.

So, I'll bet that inside the cocoon with no extension at its bottom there's a dead female filled with eggs and/or developing larvae. The cocoon with the amber exuvia protruding through a hole at its bottom is that of a male who in the fall went looking for a female.

And that's how you learn the story behind a bag hanging on a tree.

*****

GREEN PARAMECIUM
In a fishbowl of Dry Frio River water on the windowsill a diffuse blob of greenness about the size of a mouse's eye floated at the water's surface. The blob proved to consist of millions of one-celled, greenish, highly mobile organisms. Beneath the microscope, amidst this galaxy of shifting green points appeared a much larger, egg-shaped being, like a lumbering elephant in a field of nervous rabbits. You can see the whole thing, with the elephantine blob being about 0.13mm long, at http://www.backyardnature.net/n/14/140209bp.jpg.

With its body enveloped in hairlike cilia, this has to be a ciliate protozoan. Doing an image search on the keywords "freshwater ciliate protozoans," I was surprised when a match turned up under the name PARAMECIUM BURSARIA, sometimes known as the Green Paramecium. I thought I knew the paramecium pretty well, having been introduced to it back in high school in the 1960s, as an example of a one-celled animal that reproduced by "conjugation." But the paramecium I remembered was more slender, especially at the top, and wasn't at all green.

My high school paramecium had been Paramecium caudatum, so it had been a different species. Our current Paramecium bursaria is in some ways much more interesting. It also undergoes conjugation -- where compatible mating types get side-by-side and exchange genetic material -- but its amazing feature is the presence of those green items inside it.

Each of those green items is a one-celled green alga called Zoochlorella. In the wild sometimes Paramecium bursaria containing no Zoochlorella can be found, but most do have them, and the Zoochlorella seem to like the arrangement, for they reside within numerous protozoan and invertebrate species other than Paramecium bursaria. However, Paramecium bursaria is the only algae-hosting paramecium.

It's a classic symbiotic relationship: The algae occupy the paramecium cell's fluid contents -- its cytoplasm -- providing the cell with photosynthesized food, while the paramecium provides the algae with movement and protection, as well as nitrogen and carbon dioxide. It's been shown that algae-bearing Paramecium bursaria can grow better than those not containing algae.

Paramecia in general feed on micro-organisms like bacteria, algae, and yeasts. Their cilia sweep food and water into the cell mouth, the food continues into the gullet, and when enough food has collected at the gullet's bottom it breaks away and forms a food vacuole -- a little bubble of food that drifts throughout the cell. As it moves about, enzymes from the cytoplasm enter the vacuole and digest it. The digested food then diffuses into the cytoplasm as the vacuole grows smaller and smaller. When the vacuole reaches the anal pore the remaining undigested waste is removed.

Paramecia no longer are regarded as one-celled animals. During most of my life they've been regarded as members of the Kingdom Protista, whose members often have little in common with one another besides their being very small and simply organized. Protista is still recognized by many specialists, but now some experts assign paramecia to the newly erected Kingdom Chromalveolata. His kingdom already is drawing fire because it seems to embrace several unrelated groups.

In other words, science can't really make up its mind what kind of being Paramecium is, and having Paramecium bursaria with algae living inside it probably doesn't make understanding them any easier.

Paramecium bursaria commonly occupies many freshwater habitats in North America and Eurasia, and possibly elsewhere.

*****

MILLING-ABOUT ALGAE
In the diffuse blob of greenness about the size of a mouse's eye floating at the water's surface in the fishbowl of Dry Frio River water on the windowsill, what where the tiny algae among whom the much larger Green Paramecium grazed? The algae are shown at http://www.backyardnature.net/n/14/140209ch.jpg.

The paramecium was about 0.13mm long, but those algae cells are only about 0.01mm in length, a size taxing the magnification capacity of our light microscope. Still, certain identification features are apparent. The algae are unicellular instead of consisting of various cells organized into a filament or a blob. They are slightly egg-shaped, or elongate, instead of spherical. Some display a single, slightly red spot, or "eye." Also, something not shown in the picture is that they were all in constant motion, not traveling in straight lines, but rather just milling about. This movement suggests that they must have had a means of propulsion, like the paramecium's cilia, or else hairlike "flagella," though I couldn't see any.

Thousands of alga species must fit this description, though the barely visible "red eye" is something special. Still, when I browse images of unicellular freshwater algae, one species turns up looking like ours, and that's CHLAMYDOMONAS REINHARDTII. Moreover, that species has a light-sensitive, red eye-spot, and is very common worldwide, in both freshwater and soil, even melting snow. Among its freshwater environments are temporary pools and low-oxygen (eutrophic) ponds and lakes. In other words, this is a species to be expected in a fishbowl of water from a stream.

On the Internet many pictures of Chlamydomonas reinhardtii taken through light microscopes also fail to show appendages the species might use for swimming. However, under certain light conditions or with an electron microscope two hairlike flagella, which propel the cell forward when wiggled, do show up.

Chlamydomonas chloroplasts are cup-shaped and inside each cell there is a starch-synthesizing organelle called a pyrenoid. These features might explain the irregular zones of greenness and transparencies displayed by some of the cells.

Chlamydomonas reinhardtii is much used in labs as a study organism because it's so easy to grow, reproduces both sexually and asexually, can live on nothing but a soup of inorganic salts and light, or else in total darkness in a simple carbon medium such as acetate.

Really, Chlamydomonas reinhardtii is an amazing species, so effectively living under so many growing conditions throughout so much of the world. It seems to have reached a kind of perfection as an organism few other species have.

*****

BIRDBATH ALGA
While scanning through the galaxy of green Chlamydomonas cells I came upon a cluster of reddish items looking very much like red blood cells, or erythrocytes, as shown at http://www.backyardnature.net/n/14/140209ha.jpg.

Once again I had to resort to the identification technique of browsing thumbnail images summoned through Google's image-search feature, this time using the keywords "algae unicellular freshwater reddish." Though amateurish, this technique can be surprisingly useful. Within seconds a good match appeared, a picture of HAEMATOCOCCUS PLUVIALIS.

Haematococcus pluvialis commonly occurs worldwide, except in Antarctica, and is found mostly in temporary pools of freshwater, so it's to be expected in our fishbowl of water from the Dry Frio River. Often the species may occur in a pool beside a stream but be absent from the stream itself. Most authors when describing the species' various temporary habitats don't fail to mention that "If you have a birdbath with water that has turned red you may find the green algae Haematococcus pluvialis." The species hasn't acquired a common name, so here we'll file it under "Birdbath Alga."

You might recall that the world of algae is divided into large groupings such as the green algae, brown algae, diatoms and red algae. Our Birdbath Alga, despite its reddish color in our picture, is a green alga, which means it's a member of the Division Chlorophyta. Its chloroplasts often turn red when conditions become unfavorable, so apparently our cells feel stressed in the windowsill fishbowls. I read that they don't like bright like, so that may be what's turning them red.

As with the smaller, greener Chlamydomonas algae surounding our Birdbath Alga's cells, Birdbath Alga cells are equipped with two hairlike flagella which when wiggled enable the cells to move about, but -- also as with the Chlamydomonas -- under our light microscope the flagella remain invisible.

If you Google Haematococcus pluvialis you'll find many pages of companies selling extracts made from it. That's because the species contains high concentrations of the strong antioxidant astaxanthin, which is especially important in aquaculture (as fish feed), and cosmetics. The reddish tint of shrimp, salmon, crawfish, crabs and lobster is caused by astaxanthin. In living organisms, because of its antioxidant properties, astaxanthin may play a key role in the protection of cell membranes against free radical attack.

In Amazon.com's online "Health & Personal Care Department," you can buy a bottle of 120 Softgel pills labeled as Astaxanthin and containing astaxanthin extracted from Birdbath Alga. It costs $18.95.

*****

PLACIDIUM LICHEN
About three miles up the canyon where the gravel road fords the little Dry Frio River there's a roadcut through a terrace of anciently deposited mud, gravel and fair-sized limestone rocks. A textbook-size portion of the roadcut's vertical face is shown at http://www.backyardnature.net/n/14/140209pl.jpg.

The ancient mud, rich in calcium carbonate from our area's limestone, now has hardened into caliche, a kind of natural cement typical of hot, arid zones. It's hard to pry rocks from the wall because they're cemented in place by the caliche. In the picture you can see that the caliche is covered with a grainy crust. The crust mostly is composed of a complex mixture of lichens, mosses and cyanobacteria. At the picture's bottom, right, notice the egg-size colony of brown lichens whose small, fingernail-like bodies, or thalli, grow flush with the caliche's vertical face. A close-up of the colony is at http://www.backyardnature.net/n/14/140209pm.jpg.

When that picture was taken I doubted that I could identify the lichen because the thalli bear no cuplike, spore-producing bodies, or apothecia. However, with a little browsing on the Internet the little, brown lichen revealed itself as somewhat famous. It's a Placidium lichen, Placidium being a genus name embracing several species.

Probably it's PLACIDIUM SQUAMULOSUM -- "probably," because in our area Placidium squamulosum is one of two nearly identical species, the other being P. lacinulatum, and they occupy similar habitats. The only essential difference between them is that the thalli of P. lacinulatum produce rootlike "rhizines" while P. squamulosum doesn't. I looked closely for rhizines, even soaking the area beneath the lichen with water after reading that dry rhizines might break off and go unnoticed, but I found none. You can see a thallus cross section with no rhizines beneath it, perched atop a toothpick tip, at http://www.backyardnature.net/n/14/140209po.jpg.

That picture is interesting for other reasons than showing an absence of rhizines. First, notice that inside the flat thallus's brown skin there's a green layer on top with a white layer below it. The top, green layer is where most of the photosynthesizing algal cells with their green chlorophyll concentrate, while the lower level, where less sunlight penetrates, consists mostly of non-photosynthesizing fungal hyphae.

Also interesting is the wet, spongy-looking mass below the two-colored lichen thallus. That's a dense network of fungal hyphae known as the "weft." Soil particles intermingle with weft hyphae, so one service the weft provides is to help anchor the thallus in the soil. Also the weft retains water like a ball of wet cotton.

When I wetted part of a lump of soil on which several Placidium Lichen thalli grew, it was surprising to see that within a minute or so the wet thalli turned green while they dry ones remained brown. You can see this at http://www.backyardnature.net/n/14/140209pn.jpg.

Placidium squamulosum mostly occurs on soil, especially soil with a high calcium content, like ours, worldwide.

With regard to Placidium Lichen being somewhat famous, part of the fame is based on what the LichenPortal.org website says: "Together with Placidium lacinulatum, P. squamulosum is the most common species in the Sonoran region," the Sonoran region being the Sonoran Desert of the US Southwest, and northern Mexico. The species is so abundant, and important, because it often contributes to the "biological soil crust" covering vast portions of desert.

More about that, below...

*****

BIOLOGICAL SOIL CRUST
In the above picture of the colony of Placidium Lichen on a vertical roadcut face, at http://www.backyardnature.net/n/14/140209pl.jpg we see a kind of granular-looking crust coating the roadcut's exposed dirt and small gravel. In many of the world's arid zones, that kind of humble-looking crust is the most important ecosystem. In general terms it's referred to as biological soil crust -- sometimes more technically as "cryptobiotic crust" -- and among its main ecological functions are to retard erosion, produce oxygen through photosynthesis, and contribute organic matter to an otherwise fairly sterile soil. Over vast stretches of desert, organisms in the biological soil crust are the main or only photosynthesizers.

Biological soil crusts are complex communities of interrelating and interdependent species of cyanobacteria, green algae, lichens, mosses, liverworts, and many kinds of microorganisms. The crust community creates a favorable environment for seed germination and for insects and other soil organisms to live in.

Crust organisms such as lichens and dried mosses can be killed even by relatively cool, fast-moving grass fires, but the cyanobacteria often survive, helping grasses, shrubs, and other crust organisms regenerate faster than they would on barren ground.

The bad news is that biological soil crusts are extremely fragile, being susceptible to crushing and trampling. Once damaged, it may take many years to return -- time during which several feet of sediment may be washed or blown away. Hikers and horseback riders destroy crusts when they leave trails through crust zones, but their destruction is little compared to that caused by grazing livestock, sand buggies and other offroad vehicles.

One of the most dispiriting features of the situation is that -- similar to the belief in this valley that Ashe Junipers are invasive and use so much water that they should be killed -- in many ranching areas biological soil crust is deliberately destroyed because it "competes" with grass desired by cattle, or "prevents" grass from growing.

*****

BUNCH ONIONS
A neighbor in the valley offered a handful of what he called bunch onions, saying that they were taking over a corner of his garden. You can see them at http://www.backyardnature.net/n/14/140209on.jpg.

Probably you know that bunch onions are small "green onions" whose whole bodies are eaten, not just the bulbs, and that the plants grow in clusters. In the picture you can see how stems clump together, each clump developing from a single original plant.

People around here know what you mean when you refer to "bunch onions" but if you look in seed catalogues it's hard to find "bunch onions" looking like ours in the photograph.

For example, this spring's Gurney's seed catalogue offers an "Evergreen White Bunching Onion," but the illustration above that name shows onions with stems much thicker and pulpier than those of ours. They're like little leeks. Gurney's bunching onion appears to be what often is referred to as the Japanese Bunching Onion, Allium fistulosum.

This is a different species from most onion types -- from the big yellow or white slicing onions to regular green onions and shallots -- which are all Allium cepa. Thing is, Allium cepa embraces many cultivars, and the cultivars fall into at least two broad groups, or varieties, one of which produces clumped stems. The "Common Onion Group," is variety cepa, while small onions whose bulbs remain small and whose stems cluster in groups belong to the "Aggregatum Group," variety aggregatum. Shallots are the best known members of this group, but also included are potato onions and other well known cultivars.

So, are our onions bunching onions of Allium fistulosum, or "aggregated" onions of the Common Onion's Aggregatum Group, Allium cepa?

In considering the question it's not to be overlooked that nowadays Allium fistulosum and Allium cepa are caused to hybridize...

Without flowers on the plants shown in the picture, I'm not really sure what we have. "Bunch Onion" is as far as I can go. If I had to guess I'd say that they're one of many cultivars of Allium fistulosum. If after a few weeks of regular watering and fertilizing the stems grow thicker and more succulent, they'll look more like Gurney's bunching onions, Allium fistulosum.

But, if they don't, we'll just hope for flowers, so we can "do the botany."

*****

WAXWINGS & ROBINS
That morning with a cold front blowing in it was a hard ride up the canyon, and I was peddling right into it. Wind howled through trees and tall grass and there was even a little sleet, but I needed to check something at a certain spot. By the time I got there my legs were wobbly, my face and fingers were numb from the cold, and I was sweating beneath my shirt, an unhealthy combination, and probably I'm lucky that I seldom get around people, else after this I'd probably get a cold.

Leaning the bike against a tree before heading to the spot, I heard them: Robins calling all around, dozens of them, their springy, melodious phrases "cheerily, cheeriup, cheerio, cheeriup" repeated again and again like contented babbling of little kids. The mingled voices were so unexpectedly sweet and musical amidst all that blustery darkness that I just stood in the middle of the gravel road listening as wind blew dust in my face.

Motion was everywhere, robins flying up from and back into dense scrub, and smaller, much more numerous birds, Cedar Waxwings, in diffuse clouds drifting from one wind-convulsed treetop to another, generally heading into the wind, visually ornamenting and starkly contrasting with the mellow, stereophonic robin chorus. The effect was so stunning that forgetting my task I lay in weeds beside the road to listen, looking up into leafless, reticulating branches where at least a hundred waxwings perched silhouetted against low-scudding storm clouds like music notes in a score. A few of the waxwings is shown at http://www.backyardnature.net/n/14/140209ww.jpg.

At first I lay thinking how alike the waxwings and I were, both immersed in and charmed by effervescing robin calls but then gradually the tone-bubbling took me back to not long ago, into the hut in the Yucatan where in February Clay-colored Robins similarly serenaded, and I remembered how in that hut at this very robin-singing season sometimes I awaited a friend while Rachmaninoff played on the computer, remembered the raw urgency of the waiting, the beauty of it, the burning feeling in the music, and then the waxwings began drifting away and the robin calling diminished, and a certain bright patch formed amidst the overcast.

So, the waxwings and I were unlike, for no waxwing can ever resonate with such memories of a tropical hut under the spell of singing robins, and the waiting for a friend amidst searing, minor-key strains of Rachmaninoff.

And yet, who am I to say what waxwings think or what feelings move them? For, see how they obsessively cluster together with a sense of community I shall never experience. See how they address the storm from the highest limbs, facing directly into the wind, while I shelter among weeds on the ground. Something within them makes their approach seem right to them, just as something within me directs me into shelter among low weeds.

How astonishing that all this takes place in an obscure little canyon in a fairly random corner of the world, where on a certain morning nothing is happening other than a cold front moving through, bringing dark clouds and wind.

*****

FEATURED ESSAYS FROM THE PAST:

"Tenting" from the August 7, 2011 Newsletter, at http://www.backyardnature.net/n/p/110807.htm

"Stumpy Meadows" from the August 14, 2005 Newsletter, at http://www.backyardnature.net/n/p/050814.htm

*****

Best wishes to all Newsletter readers,

Jim

All previous Newsletters are archived at http://www.backyardnature.net/n/.