Lacy Double Take

by Jennifer Frazer on June 25, 2009

The other day I was walking by the coffee table at work and noticed a Science magazine cover that made me do a 180. First, take a look at this. Now examine this:

Credit: George Shepherd. Used with permission; click image for link.

Credit: George Shepherd. Used with permission; click image for link.

Striking, no? And strange as it may seem, neither one of these creatures was the inspiration for the Boston street “grid”. Those Bostonians thought that one up all on their own.

This would be, I believe, another form of our old friend convergent evolution. So what the heck are these two things? Well, the cover of Science is a closeup of a tropical coral called Favia speciosa. I believe the lacy network (scientists would call it “reticulated” or “reticulate”, which is just a fancy Latin term for “net-like”. Gladiators with tridents and nets were called “retiarii”) is the bony calcite skeleton of the coral, the walls between each individual animal or “polyp”. During the night (or whenever they get peckish), they poke their little heads out and filter feed the water with teeny, finger-like tentacles.

The second image is, of course, one of my favorite — and distinctly terrestrial — creatures: a pretzel slime mold, Hemitrichia serpula. This is one of those plasmodial slime molds I get so excited about that starts out as two individual and microscopic amoebae in the soil who meet, have coffee, realize they share the same values, desire for spores, and that all-important “chemistry”, and decide to fuse and grow into a giant, gelatinous, pulsating bag of cytoplasm that goes on an insane bacteria-eating rampage.

When the time has come for the blessed event, instead of making individual bulbous sporangia (places where spores are made) like the slime mold in the photo at the top of this page, H. serpula simply freezes into a netlike structure and subdivides its entire body into a giant spore mass. I believe this structure goes by the beautiful name “aethalium” (pronounced “ee-THAL-ium”. Should name first-born daughter “Aethalia”).

UPDATE 7/23/09: George Shepherd informs me that this reproductive structure is a plasmodiocarp, not an aethalium. I’m working on figuring out the difference between the two, but when I do I’ll post it here.

After drying out, the structure splits open and a fuzzy mass of spores flies out and blows away in the wind. In the photo above, you can see this is already starting to happen.

{ 3 comments… read them below or add one }

ilona July 7, 2009 at 10:40 am

Love the comparison of the pretzel slime mold to the Boston street “grid”! Thanks for introducing me to this life form.

Jennifer Frazer July 7, 2009 at 10:52 am

Of course! Absolutely beautiful, isn’t it? Almost mosaic-esque. : ) Thanks for checking out my site, Ilona!

George Shepherd February 28, 2011 at 3:02 am

Jennifer, you might find the following site of interest since it describes some of the reproductive structures mentioned here (and gives some more info on Hemitrichia serpula, the pretzel slime mold

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