Category Archives: Biology

Green slime mold

Plasmodial slime molds (class Myxogastria) come in many colors (yellow, purple, orange, blue, red), but rarely in green, so this find at a local park intrigued me. I found it February 23 under the bark of a decaying pine tree in Springfield, Pennsylvania. There were no fruiting bodies. 

I’m curious what species it is (let me know, if you know, please), but would love to know why it’s green. Here are three possibilities (I have more, if they fail): (1) the slime mold has formed an association with an algae or cyanobacteria, (2) the green pigment replaces the yellow pigment under some conditions, and (3) this is a species of slime mold that’s green but not frequently encountered so not part of books and online keys. The latter two are most likely, but the first was interesting to consider … see below if you have a few minutes.

Colin Purrington Photography: Slime molds &emdash; Green slime mold

(1) In regards to algal associations, I looked into this option first because the green appeared so exactly like that of alga. Of course, I’d never, ever heard of algal/myxomycetes symbiosis, so I looked into this possibility very, very quietly so people wouldn’t spew coffee out their noses. But I eventually found an article on the topic (Lazo, W. 1961.Growth of green algae with Myxomycete plasmodia. American Midland Naturalist 65:381-383). Here’s the summary from his abstract:

“Three species of Chlorella were able to enter into full associations with Physarum didermoides and Fuligo cinerea, forming green plasmodia in which the algae multiplied in light.”

The above association was under special laboratory circumstances, however, notably using slime molds that he’d purged of their bacterial partners with antibacterials. But even though the conditions might seem artificial, I suspect slime molds have a built-in ability to purge themselves (and surrounding substrate) of bacteria. And algae are easily found growing in soil and on dead trees, so it’s very likely that slime molds and algae come into contact in the wild regularly. And algae (or at least some species like Chlorella) can grow heterotrophically in the dark (e.g., on sucrose) and still remain green. This latter fact is important because I found this slime mold under rather thick bark, and I doubt it received any appreciable light. 

Indeed, some plasmodial slime molds appear to even specialize on the algal biofilms growing on wood (reviewed in Smith 2007). One mentioned by Smith is Barbeyella minutissima, which I Googled and found this:

“In addition to liverworts, Barbeyella is found socialised with monocellular algae. It is assumed that the protoplasmodium phagocytizes either the algae or the bacteria on their surface.”  — Global Fungal Red List Initiative

Smith also mentions that a Didymium iridis plasmodium harbored an alga (Trebouxia sp.) for months in a laboratory culture (Keller and Braun 1999; I couldn’t obtain to read).

So if the above scenario does occur, perhaps it’s similar to the trick noticed in some Dictyostelium spp. (cellular slime molds, in the class Dictyostelia), which known to carry around bacteria, which they can release onto substrates that are favorable for bacteria (i.e., they farm). 

Anyway, I don’t have a microscope to examine the slime mold for algae or cyanobacteria, so the above is just mere speculation. I suppose I could spray it with a good herbicide, but that’s seems cruel.

(2) The green color might simply be a pigment change. I don’t know much about myxogastrid pigments, but apparently moisture, light, starvation and other environmental factors all cause color changes. But I could find only a few papers discussing a green pigment. Here’s the best line from one of them:

“The yellow pigment of P. polycephalum has been found to be an excellent natural pH indicator (Seifriz & Zetzmann, 1935). In a neutral medium, the natural indicator is yellow, in an alkaline medium it is bright green, and in an acid medium it is deep reddish orange.” Seifriz and Russell (1936) [emphasis added]

[The citation of the referenced paper, which I couldn’t obtain in full, is Seifriz, W., and M. Zetsmann. 1935. A slime mould pigment as indicator of acidity. Protoplasma 23:175-179.]

The above fact is really interesting, but don’t know why a decaying pine log would become alkaline. I couldn’t find any good research on the topic, but perhaps I missed it.

The more interesting scenario is that a pigment gene is mutated. Mutations happen, though it’s rare enough that I don’t think it’s likely. 

(3) It’s of course most likely that there’s a species of green slime mold and I’m simply ignorant of its existence. Maybe it’s not even a slime mold.

(4) Or it could be oobleck


Some more pics:

Colin Purrington Photography: Slime molds &emdash; Green slime mold plasmodia

Colin Purrington Photography: Slime molds &emdash; Green slime mold

 

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Snow midge with yellow halteres

Here’s a snow midge I found a few days ago at Hildacy Farm Preserve. I’m not positive about the species, but perhaps Diamesa nivoriunda. I only saw one, but related members of the genus are reported to swarm during the winter. 

What I’d love to know is why the halteres are yellow. They seem to be yellow on majority of diptera I’ve seen, and I’ve never stumbled onto a paper discussing why that is. All I could find was the sentence “Haltere color is often used to distinguish between species” in a Drosophila book .” If you know of a paper, please send link ASAP. Am dying of curiosity.

 Colin Purrington Photography: Insects &emdash; Snow midge (Diamesa nivoriunda)

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Small winter stonefly

I was out looking for the elusive snow fly yesterday but found this, instead: an eastern stonefly (Allocapnia recta), a member of the Capniidae (small winter stoneflies). At least that’s what I think it is. Larvae are active during the winter, and adults can fly and mate even when temperature is in the teens. Pretty incredible to see them flitting around on a cold day when other insects cannot even move. At Hildacy Farm in Media, PA. Probably emerged from the nearby Crum Creek. 

Colin Purrington Photography: Insects &emdash; Eastern stonefly (Allocapnia recta) Colin Purrington Photography: Insects &emdash; Eastern stonefly (Allocapnia recta)

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Trigger warning for creationist visitors to National Zoo

Here’s a photograph I took several years ago at the National Zoo’s “Think Tank” exhibit on primate cognition. Darwin Day is one week so I thought I’d share.

Colin Purrington Photography: Evolution graphics &emdash; Think Tank warning for creationists

The text is a little hard to read so here’s transcription:

“This exhibit is about animal thinking. It contains some things you may agree with, some you may disagree with, and others that may even trouble you. Come explore and see what you think.” 

The warning sign was crafted by Smithsonian staff to cater to snowflake creationists who complained about the “Changes over millions of years have resulted in today’s humans” panel that covered the age of the earth, human evolution, and how natural selection works. 

The “see what you think” part suggests to visitors that the facts presented within are up for debate and thus shouldn’t undermine somebody’s alternative views about human origins or the age of the earth. But, of course, the warning signage undermines the experience for all visitors. I.e., a curious but uninformed visit might assume that the exhibits are just wild guesses about what might have happened. A shameful use of tax dollars, in my opinion.

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Graphopsocus cruciatus

Here’s a photograph of a narrow barklouse (Graphopsocus cruciatus) with a clutch of eggs. I was initially taking a photograph of the domed structure (more on that below), but then examined the photo on my camera’s LCD viewer and saw this tiny insect moving around. Which surprised me — it was December 18th, and cold. It wasn’t freezing, but certainly not a day I’d expect to find an insect out ovipositing. But apparently this group of insects (Stenopsocidae) are known to be active if there’s a random warm day in winter. I might go back in a few weeks to see what’s become of them.

Colin Purrington Photography: Insects &emdash; Narrow barklouse (Graphopsocus cruciatus)

Here’s a closeup of the eggs so you can see the silk that holds them down. I watched her apply this webbing (from labial silk glands) for about 15 minutes. Some species in this group are gregarious and can cover an entire tree in such webbing, which tends to freak out homeowners. I’ve only seen that in Puerto Rico, though. 

Colin Purrington Photography: Insects &emdash; Clutch of narrow barklouse (Graphopsocus cruciatus) eggs

I’m not exactly sure what the egg case is (antmimic spider? ground sac spider?), but I’m wondering whether the barklouse might have positioned her eggs near a potential food source. Barklice are reported to eat fungi, algae, lichens, plant tissue, and pollen, but there doesn’t seem to be much published on the species’ natural history or diet prefereces. I briefly thought the structure might be a slime mold like Enteridium lycoperdon, but then I saw (I think) white embryos or larvae through one of the two holes that seemed roughly chewed through the shell-like exterior. If you recognize the contents, I’d love to hear from you.

Colin Purrington Photography: Insects &emdash; Close-up of hole in egg case

Many thanks to Ross Hill (Meford, Oregon) for identification, and to Edward Mockford (University of Illinois) for helpful references on the species.

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