Tag Archives: color

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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Open letter to produce managers re: yams

Dear Produce Manager,

If you want to sell more orange-fleshed sweet potatoes, craft your labels with “yams” in parentheses, like this:

Sweet potatoes (“yams”)

Because you are a produce manager, you undoubtedly know that a yam is a completely unrelated thing, so using quotation marks will indicate to ignorant shoppers that you are not actually selling yams. As you also surely know, “yam” is regional slang used by some (generally older folks) to refer to a sweet potato that has orange flesh. But if you only have “yams” on label, some shoppers might get flustered and leave for another store that labels sweet potatoes as “sweet potatoes.” Still others are looking for a specific variety of orange-fleshed sweet potato (Beauregard, Jewel, etc.), so list that, too. E.g.,

‘Beauregard’ sweet potatoes (“yams”)

That’s a lot of text, but different varieties are good for different recipes, and some of your customers are over-educated foodies who care deeply about such details. Ideally, cut one in half and cover in plastic wrap to convince skeptical shoppers that it does, indeed, have orange flesh.

Colin Purrington

These are sweet potatoes

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Sweet potato flesh can reduce yam confusion

So I have a silly, futile goal of reducing the confusion over sweet potatoes and yams in the United States. If you are a grocery store manager and are on board with this silly, futile goal, please consider displaying the flesh inside the different sweet potato varieties you sell. Doing that will reduce reliance on the strange habit of calling orange-fleshed sweet potatoes “yams.” You can easily show the insides of your sweet potatoes by chopping one in half and wrapping the cut end in plastic wrap, then placing back into the display shelf — you can even use a Sharpie to write stuff on the plastic (I’ve never seen this done … but I’m sure it would work). Or you can make signage that has a photograph of flesh. If you also add some thoughts on how to use them in cooking, even better. Below are two examples of ‘Nancy Hall’ and ‘Beauregard’ sweet potatoes that I cooked over the weekend.

Labels for sweet potatoesNote that the word “yam” does not appear on the sign. If you are the type that says, “What?? You idiot. That sure looks like a yam to me!” … please have look over my “Yams versus sweet potatoes” page. It probably won’t change your opinion, but you’ll at least know what a yam looks like.

On a side note, my ‘Nancy Hall’ sweet potatoes turned out great. I partially cooked them in the oven (coat with bacon fat first) and then sauteed the diced flesh with butter and hickory bark syrup. I used the ‘Beauregard’ to make biscuits. It turns out that biscuits are good with Chessmen cookie butter. Just saying.

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Sweet potatoes and yams

Some photographs to get you excited about starches on Thanksgiving.  If you’re curious about the difference between yams, sweet potatoes, and potatoes, please refer to my page, “Yams and sweet potatoes are not potatoes.”

colin purrington photography: plants &emdash; yam-display-at-ethnic-grocer
The bin of “#1 American yams” is filled with sweet potatoes. The labeling mistake is a common one. The white yam and yellow yams are actual yams.
colin purrington photography: plants &emdash; purple-yams
Okinawan sweet potatoes label as yams. They are not yams.
colin purrington photography: plants &emdash; oriental-sweet-potato
Oriental sweet potatoes. Note that sweet potatoes are not potatoes.
colin purrington photography: plants &emdash; potatoes
Potatoes are unrelated to sweet potatoes.


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Masked robin

Mutant robin (Turdus migratorius) with mask of white plumage. I suspect the leucism  was congenital because the patches were located on several parts of the body (injury and parasites can sometimes cause regrowth to be white).  Regardless of cause, it’s a good look. Spotted on the campus of Swarthmore College, Swarthmore, Pennsylvania.

Colin Purrington Photography: Birds &emdash; Leucistic American robin
Robins seem to be famous for leucism (Gross 1965), as a Google image search will confirm.  If you’d like to see some even stranger birds, check out this page from Cornell University.

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