I track the #Volvox hashtag on Twitter, which is how I find out about a lot of the off-label uses of the name Volvox, like DJ Volvox, Volvox the ship, and Volvox the art gallery. Every now and then, it even turns up something related to Volvox the little rolling algae. The other day, @QuintaSwinger tweeted the following video with #Volvox:
The Twitter handle is about just what you think it is; apparently volvocine sex puts someone in mind of polyamory. I suppose I can see that: when a sperm packet enters a colony, it gets busy with all the ova. The video was uploaded to YouTube by Dr. Donald Ott from the University of Akron.
I think the algae in the video are not actually Volvox, though. Certainly the still photo at the beginning is Volvox. Probably not section Volvox (too few cells), and probably not Developmental Program 2 (germ cells too small in the one on the lower right). If I had to guess, I’d say V. aureus, but that’s largely a Bayesian bet because they’re so common. Maybe Alexey Desnitskiy or Hisayoshi Nozaki can comment.
The colonies in the video, though, look more like Pleodorina to me. Not P. sphaerica, since the somatic cells are all in the front, but without more information I can’t narrow it down more than that.
There really aren’t enough people looking for volvocine algae. There’s a suspicious tendency for the geographical centers of volvocine diversity — southern Africa, central North America, southeast Asia — to include the home institutions of phycologists studying volvocine diversity — Mary Pocock, Richard Starr, Hisayoshi Nozaki, respectively. I find it much more likely that this is an artifact of sampling effort than that, for example, central Africa and Central and South America are depauperate of volvocine algae.
A new paper in Oceanological and Hydrobiological Studies reports a massive bloom of Pleodorina indica in a reservoir in central Poland. Piotr Knysak and Joanna Żelazna-Wieczorek sampled the reservoir on the Olechówka River in Łódź during the summer of 2015 and found that P. indica made up ~95% of the algae collected.
Stephanie Höhn and Armin Hallmann have published a detailed study of the developmental process of inversion in Pleodorina californica. Pleodorina is one of the two genera we usually refer to as ‘partially differentiated’ (the other is Astrephomene), meaning that some of their cells are specialized for motility and never reproduce (soma) and some perform both motility and reproductive functions. P. californica is pretty big, up to about 1/3 of a millimeter, easily visible to the naked eye (though you’d need better vision than mine to make out any details).
Like all members of the family Volvocaceae, P. californica undergoes complete inversion during development:
After the completion of the cell division phase and before inversion, the embryos of Gonium, Pandorina, Eudorina and Pleodorina consist of a bowl-shaped cell sheet, whereas the embryonic cells of Volvox form a spherical cell sheet. With exception of the genus Astrephomene, all multicellular volvocine embryos face the same “problem”: the flagellar ends of all the cells point toward the interior of the bowl-shaped or spherical cell sheet rather than to the exterior, where they need to be later to function during locomotion. [References removed]
I spent a year in graduate school trying to cross male and female strains of the volvocine green alga Pleodorina californica. A year. I did some other stuff in that time, but I spent an awful lot of it trying to convince these algae to get busy. I threw everything I could think of at them: four different mating media, different temperatures, different lighting conditions…nothing worked. I never recovered a single viable zygote. I needed to cross them to generate some genetic variation for an ambitious artificial selection study, my ‘official’ dissertation project. Eventually, my advisor suggested I ask Hisayoshi Nozaki for advice.
There is little doubt that Dr. Nozaki is the world’s leading expert on volvocine biodiversity, having described about half of the known species (see for example New Volvox Species, Volvox ovalis, and African Volvox in Montana). He responded that the strains of Pleodorina californica I had been failing to breed had been collected many years ago and had probably lost the ability to reproduce sexually (a problem I mentioned in Why don’t we revise volvocine taxonomy?). I had been spinning my wheels, never realizing that I had no hope of success. I should have contacted Dr. Nozaki about eleven months earlier.
Pretty much what the title says: the meeting review from Volvox 2015 is online early at Molecular Ecology. That only took six months! This is the final, published version. Thanks for a great meeting, and thanks to everyone who read earlier drafts!
The meeting review for the Third International Volvox Conference is now available online at Molecular Ecology (doi: 10.1111/mec.13551). The editors warned me ahead of time that the challenge for this paper would be to make it of broad interest to the readership of Molecular Ecology, so there is a lot of background information that will be old news to members of the Volvox community.