January 13, 2013

PHOEBE AT THE RIVER'S EDGE
On a sunny but chilly morning a small flycatcher worked along the gravelly edge of the little Dry Frio River behind the cabin. He'd perch awhile, then fly down onto the gravel or maybe zip out and catch something in midair, for on sunny days here we do still have insects buzzing about and ranging across the ground. Grasshoppers flutter from grass, spiderlings balloon through air, and all kinds of gnaty things fly about, so there are things here for a flycatcher to eat.

Usually flycatcher species are so similar to one another that they can be hard to distinguish. However, even with my poor vision I could whittle down the possibilities for this one, for he flipped his tail up and down with quick, jerky motions. In Mexico several overwintering flycatcher species wag their tails, but around here only the phoebes do it.

However, here in southwestern Texas we have three tail-wagging phoebe species: the Eastern; Black, and; Say's Phoebes. The latter two species are western birds, with us at the eastern fringes of their ranges, and we're at the western fringe of the Eastern Phoebe's range.

As soon as our bird's picture was on my laptop screen I could see that it wasn't the black-topped Black Phoebe, or the Say's with its rusty underparts, but rather the Eastern Phoebe, SAYORNIS PHOEBE, as you can confirm at https://www.backyardnature.net/n/13/130113ph.jpg.

A back view of the same bird is at https://www.backyardnature.net/n/13/130113pi.jpg.

Besides being tail waggers, Eastern Phoebes also are recognized by their dark heads without eye rings and their solid black beaks. Beaks of similar-looking wood pewee species display pale lower mandibles.

In most of eastern and central North America Eastern Phoebes are to be seen only during their summer nesting season, retiring to the US southeastern states and much of Mexico during the winter.

During the summer it's always a treat, almost comical, to hear the Eastern Phoebe calling because his call is so unusual and funny sounding, especially coming from such a small, plain-looking bird. In a raspy, almost gruff voice he says, not sings, "fee-be, fee-be," again and again.

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VORTICELLA
Though days are gradually lengthening and there's a decided feeling of springtime in the air, the landscape continues to be void of plants with flowers, and insects, while present, are few. One way I compensate is by taking field trips in drops of water from the little Dry Frio River behind the cabin. Beneath a microscope, a drop of river water is like a vast forest with diverse flora and fauna.

Something new found this week is shown at https://www.backyardnature.net/n/13/130113vo.jpg.

The new discovery is the little, transparent, ball-shaped item at the end of the curvy, hairlike stem cutting diagonally across the image. The heavy, greenish, dark band horizontal in the picture's center is a strand of filamentous alga. The diameter of both the alga filament and the ball-like item is about 70 microns. The width of an average human hair is about 100 microns.

The ball-shaped thing caught my attention as it slowly moved across the field of vision, taking up slack in its slender, wavy stem. Once the stem was straight and taut, the ball remained in one place for a couple of seconds, then so suddenly that I didn't see it happen it disappeared, reappearing closer to where its stem apparently was attached, the stem itself once again looking curvy and loose. Then again the ball moved away from its stem base, maybe for fifteen or twenty seconds, until its stem was straight again, and then suddenly again the ball jerked back closer to the root, and again began its journey outward, this time in a slightly different direction.

Remembering this organism from biology class decades ago, I realized that the "ball" had an opening opposite its point of attachment with its stem, or peduncle. Tiny, hairlike cilia sweep food such as bacteria through the hole into the spherical body, where it's digested.

This is a Vorticella, described as being common and worldwide of distribution, found especially on leaves and roots of submerged vegetation, but also on shells of animals such as snails and turtles.

Though behaving like animals, usually Vorticellas are regarded as neither plants nor animals, but rather protozoans of the Kingdom Protista. However, as greater understanding of evolution develops, many say that the "kingdoms" of organisms (there's the Plant Kingdom, the Animal Kingdom, etc.) sometimes overlap -- and that the whole concept of "kingdom" is misleading -- so Vorticellas may be protozoans but also very primitive animals. Estimates of the number of species of the genus Vorticella vary from 15 or so to over a hundred, depending on your expert.

I'd known from school that Vorticellas exist, but only now am I realizing that they're part of my life here along the little Dry Frio River, and if you have standing, unpolluted water near you, they're probably in your life, too. They prey on bacteria and other tiny organisms and are preyed on themselves by tiny aquatic animals and by critters such as snails who graze the surfaces of aquatic plants.

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CHRYSALIS BENEATH A SOTOL LEAF
Butterflies undergo complete metamorphosis, so their life cycle consists of egg --> caterpillar --> pupa --> adult. The word chrysalis is a special term applied to the butterfly's pupa. Usually a chrysalis with its tough but thin shell is tucked in some obscure spot so that the incredible transformation the larva must undergo during its metamorphoses into a butterfly can take place without botheration from the outside world.

Sotol is an agave-like, card-table size plant with tough, spiny-edged blades mostly found in the desert but also growing here in cobblestone flats along the river.

So, the other day I noticed a chrysalis attached to the lower surface of a Sotol leaf by two silk threads, as shown at https://www.backyardnature.net/n/13/130113cy.jpg.

The chrysalis was about 1¼ inches long (3cm) and with such a distinctive shape that I figured volunteer identifier Bea in snowy Ontario might enjoy trying to identify it.

Bea was pretty sure it was a Pipevine Swallowtail chrysalis, though chrysalises of other swallowtail species are very similar. Moreover, she thought she saw a story in that picture.

She guessed that the chrysalis had been parasitized by something, maybe a wasp that upon emergence created the hole clearly visible in the side near the bottom. Bea thinks that the butterfly never emerged from the chrysalis, especially because there's no opening at the chrysalis's top where the adult would have emerged. She sent a link to a butterfly-fancier's forum where folks were complaining about losing their Pipevine chrysalises to parasitic wasps.

It took Bea a couple of days of noticing details in the photo and thinking about it all, but, in the end -- as always is the case in nature study -- paying attention paid off with an interesting insight.

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CYPRESS
In rural western Kentucky I grew up near Cypress Creek. The cypresses along Cypress Creek were swamp-loving Baldcypresses, however, and Baldcypresses aren't the cypresses most of the world think of when they hear the word "cypress." Taxonomically the word "cypress" designates only species of the Cypress genus Cupressus in the Cypress Family, the Cupressaceae. Baldcypresses are a whole other thing in a completely different family.

Features separating cypresses from other members of the Cypress Family -- which includes junipers, arbor-vitae, Incense-Cedar and others -- include these:

Therefore, the main features distinguishing cypresses from all other kinds of gymnosperms appear in the reproductive parts, not the vegetative ones. That's the case with most kinds of plants. Especially it's the case with cypresses, because the trees' stems and scale-like leaves look very much like those of the junipers so abundant around us. You can confirm this by first looking at the stems and woody cones of a non-native cypress someone has planted near the cabin I'm staying in, at https://www.backyardnature.net/n/13/130113jr.jpg.

In that picture, the pale items at the tips of many branches are pollen-producing male cones. A close-up of stems and scale-like leaves is at https://www.backyardnature.net/n/13/130113jq.jpg.

Now look at an Ashe Juniper's very similarly structured stems and leaves but profoundly different, fleshy cones at https://www.backyardnature.net/n/w/ashe-jun.htm.

The property's owner says that the cypress beside the cabin is a planted Arizona Blue Cypress. Botanically this ornamental cultivar is known as CUPRESSUS ARIZONICA 'Blue Pyramid.' Naturally occurring trees of this species are known as Arizona Cypresses. Naturally occurring Arizona Cypresses are found mostly in arid upland Mexico, though a few scattered populations occur in southern California, southeast Arizona, southwest New Mexico, and in Texas's Big Bend National Park.

You can compare the branch color of our Arizona Blue Cypress with that of our native Ashe Junipers in the background at https://www.backyardnature.net/n/13/130113jo.jpg.

One feature distinguishing Arizona Cypresses from many other cypress species is that each triangular leaf bears on its outer surface a pitlike gland that produces a drop of resin, as shown at https://www.backyardnature.net/n/13/130113js.jpg.

Arizona Cypresses are highly adapted for fire-prone areas. The hard, woody cones in the picture may remain closed for many years. In Nature they open only after the parent tree has been killed in a wildfire, thereby allowing the seeds to colonize bare ground exposed by the fire. The trunk of our tree is armored with large, loose plates, as shown at https://www.backyardnature.net/n/13/130113jp.jpg.

The cultivar "Arizona Blue Cypress" is noted for its drought-tolerance and its fragrant foliage. It's a prettily shaped tree and -- important in our area -- it's deer-resistant.

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CARTILAGE LICHEN
An eye catching, unusually large, fruticose lichen commonly seen in our area dangling from fairly thick tree limbs is shown at https://www.backyardnature.net/n/13/130113li.jpg.

Actually several lichen species appear in that photo. The one we're looking at now displays numerous, vertically hanging, slender, three-inch-long (8cm) blades. The blades bear many mushroom-shaped growths on their outward-facing surfaces. A close-up of some of these stalked items is at https://www.backyardnature.net/n/13/130113lj.jpg.

To get a fix on what those mushroom-shaped growths are, remember that lichens are composite organisms comprising two, or maybe even three, completely different kinds of organisms. Every lichen is part fungus. Usually the other species it's made of is a photosynthesizing alga, but sometimes it can be a photosynthesizing bacterium known as a cyanobacterium. In this mutualistic relationship the alga or cyanobacterium photosynthesizes, thus producing food for the lichen body, while the fungus mainly provides the lichen with a distinctive form and a reproductive system. The fungus produces fungal spores that must land next to an appropriate alga or cyanobacterium, germinate and wrap its hyphae around it. As the lichen grows, the fungus produces more mycelium and the alga or cyanobacterium keeps pace reproducing itself.

So, the mushroom-shaped growths are apothecia, which are the reproductive structures of fungi belonging to a certain fungus phylum, the Ascomycota. Across each apothecium's top there are jillions of microscopic, sac-like structures called asci (singular ascus). In this species eight spores are reproduced in each ascus. You can see our diagram of a typical apothecium with its asci at https://www.backyardnature.net/f/funclass.htm#a.

Sometimes the lichen in our photo is known by the name of Cartilage Lichen. It's RAMALINA CELASTRI, and it's widely distributed in tropical and cool temperate regions in the Southern Hemisphere as well as southern North America and Central America. The genus Ramalina contains over 240 species. You might enjoy admiring variations on a Ramalina theme at the Ramalina of North America page at http://lichens.digitalmycology.com/macrolichens/Ramalina.html.

A compound called parietin has been isolated from Ramalina celastri and demonstrated antiviral activity against certain arena viruses.

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FROST CRYSTALS ON A FENCEPOST
On a frosty morning this week the rising sun produced such a sparkly landscape that I went out with the camera. A thick crust of ice topped my neighbor's concrete fencepost so, with the sun backlighting the frost, I photographed the frost, as you can see at https://www.backyardnature.net/n/13/130113xt.jpg.

When that image first appeared on my computer screen I was astonished to see that the crystals looked like long-stemmed wine glasses -- open bowls atop slender stems. Examining other images I decided that the crystals were cylindrical, not merely solid tubes of ice. You can see this yourself at https://www.backyardnature.net/n/13/130113xu.jpg.

In chemistry class we learned how the hydrogen and oxygen atoms of water, H20, combine into three-cornered molecules with a positive charge on one side of the lopsided molecule and a negative on the other. Then pairs of the bipolar water molecules align with one another, weakly held together by the negative and positive ends of each molecule in the pair being attracted to the opposite charges of their partner molecule. These pairs of three-cornered molecules form six-cornered, or hexagonal, latticeworks. Ice crystals begin with these simple hexagonal cores. That's why snowflakes have six arms. But this doesn't explain why our fencepost crystals look the way they do.

Browsing the Internet I learn that ice crystals grow by adding more and more hexagonal pairs of water molecules. Once a firm hexagonal prism is formed it branches out into more complicated patterns. Since the faces of a crystalline prism are smooth, it's difficult for new atoms to attach there. The corners are much easier to attach to, so crystals branch out from there. How the crystals grow depends on the temperature, how much water vapor is present to work with, air turbulence and other environmental features. Sometimes the prisms only grow from the top and the bottom, leading to long, thin columns. At other times, new hexagonal latticeworks develop at each corner of the prism, then they branch out providing new corners to branch from, and so on until very complicated patterns develop.

However, that still doesn't explain how cylindrical frost crystals might form.

Browsing more, I find that cylindrical ice crystals do exist but they don't look like ours. But I do stumble upon a page describing many kinds of snowflakes, where snowflakes called "hollow columns" at first glance may appear to be cylindrical but actually are solid, hexagonal tubes with shallow, cone-shaped depressions at their ends. You can see what "hollow columns" look like -- second line from the top -- at http://www.its.caltech.edu/~atomic/snowcrystals/class/snowtypes4.jpg.

Assuming that the crystals in our photos are "hollow columns," why would they melt near their bases, converting the solid part of the column into the long-stemmed wine glass' slender stem, but not melt the top, hollow, cup part? Maybe it's simply because the fencepost was warmer than the surrounding air, so the part of the crystal closest to the post melted before the top part did.

These are just guesses, and I still don't know why cone-shaped depressions might form in a long, slender ice crystal. Whatever the deal, there's magic here merely in the fact that on a fencepost right beside the cabin such amazing crystals can form with no fanfare or particular reason

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FROST DAMAGE IN PLANTS
The frosty morning producing the crystals examined above sneaked up on me. The forecast had been for night temperatures well above freezing, so I'd left some plants out who got hurt.

The interesting thing was seeing that some plants were seriously damaged, while others didn't seem to suffer at all. For instance, two pots of different kinds of mint remained outside, both very similar vegetatively but smelling different. One mint suffered only minor damage but the other lost every leaf. Also, outside my door there's a colony of Yarrow with its overwintering green leaves forming rosettes that laced with frost looked very pretty. You can see a frost-covered Yarrow leaf at https://www.backyardnature.net/n/13/130113xv.jpg.

The Yarrows suffered no visible damage at all.

Studies show that it's not cold temperature that injures plants but rather ice formation inside and between the plant's cells. Ice crystals forming inside plant cells puncture cell membranes and generally disrupt the protoplasm's architecture and function. Damage caused by ice crystals between cells and forming on the plant's surface is thought to work by a more subtle mechanism.

There's a concept in thermodynamics referred to as "saturation vapor pressure," and it's too complicated to be dealt with here. Saturation vapor pressure is lower over ice than over liquid water, so when there's ice just outside a plant cell, water passes from inside the cell, through its semipermeable cell membranes, to gather on those ice crystals outside the cells -- as frost. This removal of water from inside the cells stresses the cells just as if they were suffering through a drought. In fact, drought-tolerant plants normally also display freeze tolerance.

By gradually exposing certain plant species to lower and lower temperatures over a period of nights, often the plants can be "hardened" to survive mild freezing. One way hardening works is that the gradually lowering temperatures cause an accumulation of sugars or sugar alcohols in the protoplasm, which lowers the protoplasm's freezing point. Other hardening mechanisms are known as well. Whatever the mechanism, though, typically a few days and nights without cold weather typically undo the hardening, and plants become vulnerable again.

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FEATURED ESSAYS FROM THE PAST:

"On the Gift of Cold, Rainy Days," from the February 15, 2004 Newsletter, at https://www.backyardnature.net/n/p/040215.htm

"On the Merest Hints of Scents & Hues," from the August 14, 2011 Newsletter, at https://www.backyardnature.net/n/p/110814.htm

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Best wishes to all Newsletter readers,

Jim

Visit Jim's backyard nature site at https://www.backyardnature.net