Slime Molds on the Move

Q: I’ve heard slime molds are neither plant nor animal, and that despite being single-celled they can move and even navigate a maze! How can this be? Are there slime molds in the Bay Area? [Michele, a frequent visitor from Toronto]

A: Strolling through a local redwood forest years ago, I came across a huge, bright yellow mass of a slime mold. I vaguely recalled reading that you could grow slime molds on a medium of oatmeal. I brought a bit of the yellow goo home and tried it. My experiment failed miserably; the slime mold shriveled and died horribly. My calling as a pet owner was finished.

Slime molds are weird, but not uncommon. There are two types in the Bay Area. The plasmodial slime molds are nothing more than gigantic single-celled life forms with thousands of nuclei. They develop when tens of thousands of single cells, all with a whip-like appendage called a flagellum, throng together and fuse into one giant cell with a single membrane. Worldwide there are about 500 species; they are often orange or yellow and are probably the easiest single-celled organisms to see with the unaided eye. They can be several inches across and cruise around on the forest floor like giant amoebas engulfing microorganisms such as bacteria and yeast. They also devour decaying vegetation, but apparently not oatmeal!

There are only about 65 species of the cellular slime molds. They are also single cells, but microscopic—they do not form huge plasmodia. They too feed amoeba-like, engulfing mostly living bacteria found in the leaf litter. When they exhaust the local food supply a remarkable event occurs: A chemical signal released by several of the cellular slime molds causes all the surrounding ones to stream together to form a larger colonial organism. Slug-like in appearance, this new mass moves toward sunlight; then fruiting bodies pop up and bear spores. These mature and are released, enabling the slime molds to drift to a new promised land, hopefully full of more edible bacteria. Yummy…

Slime molds’ spore-based reproduction strategy first led biologists to lump them with fungi, along with familiar household molds. But things are not so simple: Slime molds behave like animals when they are feeding and growing, and then more like plants or fungi when in the immobile, reproductive phase. So now they are classified in the kingdom Protista. This diverse group includes many “leftover” organisms that just do not fit into other kingdoms. They are mostly single-celled, like amoebas and dinoflagellates, but also include the multicellular seaweeds.

So on your next winter walk in any deep, damp forest, watch for bright yellow or orange blobs. Just don’t try to feed them oatmeal.

Michael Ellis – Ask the Naturalist- Bay Nature Magazine

The Paranoid Jay

Q: A blue jay has been flying against the windows of our house and poking at them. I thought it might be territorial, but I put out rice that the jay ate peacefully with another jay! Why is the jay doing this? What can I do to deter it? [Venkat, Union City]

A: I get a variation on this question every year. First, the jay that you are referring to, while its dominant color may be blue, is not a “blue jay.” Blue jays are common to the eastern United States but do not normally cross the Rockies, though they are expanding their range into Washington and Idaho. In the Bay Area, we have two widespread species of jays. Look for scrub jays (mostly blue and gray) in suburban yards, chaparral, and scrubland. Steller’s jays (bluer with a large crest) live in forests and wooded yards.

The behavior you witnessed is clearly related to breeding. These jays are defending their territory. The jay sees an image of itself in your window and assumes that it is a stranger invading his turf. In defense, he attacks. It is usually the male doing this, though in a monogamous pair of birds, the female can also get aggressive. The communal feeding behavior you saw was likely the happy couple sharing resources and reinforcing their pair bond. Mating could follow. The same thing happens in humans. A nice dinner out followed by . . . .

The only way to prevent the bird’s attacks is to do away with the reflections. That’s more easily said than done. Putting a paper covering or perhaps a silhouette of a falcon or accipiter hawk on the window may work. Eventually the testosterone will wear off and the bird will cease that behavior at the end of the breeding season. And hopefully both the bird and your window will still be intact.

Michael Ellis – Ask the Naturalist Column- Bay Nature Magazine

Why are some leaves red

Q: How does photosynthesis occur in plants that are not obviously green, such as ornamental plum trees with deep purple-colored leaves? [Paul, Santa Cruz]

A: Photosynthesis (which literally means “light” “put together”) is that very elegant chemical process that jump-started life as we know some 4 billion years ago. So to answer your question, we’ll have to do a short chemistry lesson. Basically six molecules of water (H2O) plus six molecules of carbon dioxide (CO2) in the presence of light energy produce one molecule of glucose sugar (C6H12O6) and emit six molecules of oxygen (O2) as a by-product. That sugar molecule drives the living world. Animals eat plants, then breath in oxygen, which is used to metabolize the sugar, releasing the solar energy stored in glucose and giving off carbon dioxide as a by product. That’s life, in a nutshell.

All photosynthesizing plants have a pigment molecule called chlorophyll. This molecule absorbs most of the energy from the violet-blue and reddish-orange part of the light spectrum. It does not absorb green, so that’s reflected back to our eyes and we see the leaf as green. There are also accessory pigments, called carotenoids, that capture energy not absorbed by chlorophyll. There are at least 600 known carotenoids, divided into yellow xanthophylls and red and orange carotenes. They absorb blue light and appear yellow, red, or orange to our eyes. Anthocyanin is another important pigment that’s not directly involved in photosynthesis, but it gives red stems, leaves, flowers or even fruits their color.

Many plants are selected as ornamentals because of their red leaves—Japanese plums, Norway maples, and purple smoke bush, to name just a few. Obviously they manage to survive quite well without green leaves. At low light levels, green leaves are most efficient at photosynthesis. On a sunny day, however, there is essentially no difference between red and green leaves in trapping the sun’s energy. I have noticed the presence of red in the new leaves of many Bay Area plants as well as in numerous tropical species. The red anthocyanins apparently prevent damage to leaves from intense light energy by absorbing ultraviolet light. There is also evidence that unpalatable compounds are often produced along with anthocyanins, which may be the plant’s way of advertising its toxicity to potential herbivores. So red-leaved plants get a little protection from ultraviolet light and send a warning to leaf-eating pests, but they lose a bit of photosynthetic efficiency in dimmer light.

Botanists have been wondering about red versus green leaves for the past 200 years and there is still much research to be done in this arena. So you are in good company, Paul.

Michael Ellis – Ask the Naturalist Column – Bay Nature Magazine
Send your questions to atn@baynature.org.

Swarming Dragonflies

Q: Last October, while hiking on Mount Tamalpais, near Laurel Dell, I saw numerous swarms of dragonflies. Could you tell me more about this phenomenon? Is it seasonal? Or triggered by weather or courtship? [Khiem, San Jose]

A: Those dragonflies were most likely congregating to hunt, catch, and eat abundant insects that were also swarming. This is indirectly weather-related, because dragonflies are active only on warm days. Most need an air temperature of at least 63 degrees to get moving.

Dragonflies and damselflies belong to an ancient insect group called the odonata, some of the earliest flying creatures on our planet. Dragonflies are big, strong fliers. They have very large eyes and hold their wings out straight when resting. Their cousins, damselflies, are smaller and have a weak, fluttery flight. Damselflies have small eyes and rest with their wings held up directly over their thorax.

While driving through the Central Valley near Williams last August, I encountered thousands, maybe millions, of common green darners, our state’s second-largest dragonfly. As far as I could scan through binoculars in every direction for miles and miles, the air was filled with them. These iridescent giants were in constant flight, hunting insects breeding in the standing water and irrigation ditches so prevalent in this fertile agricultural land. On Mount Tamalpais I have seen swarms of common greens but also of the variegated meadowhawk. I suspect the latter may be what you saw. This widespread dragonfly, which grows to about two inches long and varies in color from pink to tan to dull gray, can be active year-round in the Bay Area, even in winter.

The swarming you saw probably had nothing to do with mating. There are over 60 kinds of dragonflies in California and more than 28 in the Bay Area, so mating strategies vary quite a bit among species. In some species, males wait and pounce on females as they fly by, and there is little color difference between males and females. The males of other species, like the western pondhawk, establish territories over a patch of prime real estate (rich with insect prey—freshwater ponds, lakes, streams, rivers, even poorly maintained hot tubs) and chase off rival males and attempt to copulate with every female that comes into their range. These species sometimes show a marked difference between females and males; the males are brilliantly colored with more vibrant facial patterns, which make it easier for them to tell potential mates from rivals.

Two great references are Kathy Biggs’s self-published pocket-size guide Dragonflies of California (Bigg’s Wildlife Pond) and Tim Manolis’s UC Press field guide Dragonflies and Damselflies of California (UC Press).

Santa Rosa-based naturalist Michael Ellis leads nature trips around California and throughout the world with Footloose Forays.

Native Snails

Q: What native land snails live in the Bay Area? Where do the common garden snails come from, and what’s the status of our native snail populations? [Erica, Mountain View]

A: If you are a gardener like me, you eventually come to despise snails with a passion, even if you’re a kind, gentle, loving person. And while you would not dream of actually torturing them, you have few qualms about ending their slimy little mollusk lives.

Our wet and relatively mild Bay Area winters are peak time for land mollusks. The snail that most of us encounter is the European garden snail (Helix aspersa). These animals were brought to California over 100 years ago, allegedly as a food resource. So when you collect them in your garden, you might as well eat them. They are about 15 percent protein, 3 percent fat, and the rest water. Dipping them in garlic butter will greatly improve the flavor and add quite a few calories. But make sure to properly prepare these snails, which must be purged before it’s safe to eat them (search “snail’s pace” at Matt Bites for details).

So much for nonnatives. I remember the first native snail I ever saw in the Bay Area. Hiking in Muir Woods in early winter, I found a lovely specimen. The shell was very dark and not as tall as the common garden snail. The flesh had beautiful, subtle shades of purple. It was Monadenia infumata, or the Monadenia land snail, and simply gorgeous.

The most common native land snails are the shoulderbands in the genus Helminthoglypta. They can be easily confused with garden snails. But instead of the broad, somewhat fuzzy brown pigment of the European snails, these natives have a very distinct single dark band that wraps around the shell at the “shoulder.” There are over 60 species in California, including the Morro shoulderband snail or banded dune snail (Helminthoglypta walkeriana) and the Coast Range shoulder-band snail (Helminthoglypta nickliniana), among others. Mostly our native snails can be found in relatively undisturbed native ecosystems.

Another snail that is commonly overlooked is called Haplotrema minimum, the California lancetooth. This species not only feeds on plant material but also hunts and eats other snails and slugs.

Dr. Barry Roth compiled the “Checklist of the Land Snails and Slugs of California,” available from the Santa Barbara Museum of Natural History, and he is generally considered our local snail and slug expert. He says there is no indication that the introduced European garden snails and other exotic land mollusks are affecting our native snail populations. The introduced species live in areas with significant habitat modification, where the natives are already long gone. Apparently as long as the habitat is intact, the native snails will do fine.

Santa Rosa-based naturalist Michael Ellis leads nature trips around California and throughout the world with Footloose Forays.

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