Tag Archives: photosynthesis

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

 

Posted in Biology, Photography, Science | Tagged , , , , , , , , , , , , , , , , , , | 1 Comment

Signs of mistletoe

Below are three photographs of mistletoe seeds I took at La Selva Research Station in Costa Rica. Seeds were most likely deposited by birds perching on the signs, but I’m not sure whether the birds scraped off the seeds (which can be extremely sticky, due to presence of viscin threads) or simply pooped them. If the latter was the case, the bulk of the poop is long gone, but it rains enough in the tropics for that to happen. There are threads visible on the top photograph, so I’m going to guess that the seeds were attached to the birds somehow, and the birds scraped them off onto the sign.

By the way, mistletoe are parasitic plants … which is why it’s amusing (to me) that they were on a sign. Although they are clearly green and can photosynthesize, they’ll eventually need the water (and other xylem contents) from a host. Under those adhesive pads there is (or will soon be) a haustorium that will attempt  to burrow into the substrate in hopes of finding host xylem. If I lived at the station I’d naturally record how long these beasties survived, but staff probably clean off the seedlings every few weeks just so it doesn’t look to nasty. Some species can apparently last a year as self-sufficient seedlings.

Colin Purrington Photography: Parasitic plants &emdash; Mistletoe germinating on sign

Colin Purrington Photography: Parasitic plants &emdash; Mistletoe seeds germinating on pole and sign

Colin Purrington Photography: La Selva, Costa Rica &emdash; mistletoe-seedling-close-up

Posted in Biology, Education, Graphic design, Photography, Science | Tagged , , , , , , , | Leave a comment

Indestructible water molecules?

When you’re chaperoning a school trip, you notice things.  Annoying things.  Shown below is a sign at Philadelphia’s Fairmount Water Works Interpretive Center that makes the claim that all the water molecules on Earth are never, ever destroyed — they are immortal entities. If you teach biology, you’ll be instantly outraged, especially when you think of the hundreds of thousands (millions?) of kids who’ve absorbed the contents of this signage as fact.  Details below the image, but see if you can figure out the flaw before you jump.

photosynthesis, water, split, molecule, science, biology, signage, error

The sign is wrong partly because of photosynthesis, which usually involves the splitting of water molecules (to generated electrons).  That little trick evolved about 3,500,000,000 years ago, so I’d wager that most if not all the water originally present on the planet has been replaced by new molecules produced from combustion (including respiration). That’s just a guess, though…I couldn’t find a calculation on the internet.  Download this photograph and use in your lectures to introduce the ideas of photosynthesis and respiration.  If you lecture on science center signage, you can use this to highlight the value of getting a few scientists to proof the graphics.  Or a few 7th graders.

Posted in Biology, Graphic design, Science | Tagged , , , | 1 Comment