New review of green algal sex

Hiroyuki Sekimoto from Japan Women’s University has published a review of sexual reproduction in the volvocine algae and in the Charophyte Closterium in the Journal of Plant Research. In addition to a brief description of the Chlamydomonas sexual cycle, it includes a succinct review of the genetics of sex and sex determination. Unfortunately, the article is paywalled, and my inquiry to the author has so far gone unanswered.

Figure 1 from Sekimoto 2017. The life cycle of Chlamydomonas reinhardtii. Vegetative cells (V) di erentiate into mt+ and mt− gametes (G) during nitrogen starvation (−N). Mating types are restricted by mating-type loci (+ and −). When gametes are mixed, the plus and minus agglutinin mol- ecules on their agellar surfaces adhere to each other, and this adhe- sion results in increased intracellular cAMP levels. The signal trig- gers gamete cell wall release and mating-structure activation. Cells then fuse to form binucleate quadri agellated cells. Zygotes with thick cell walls germinate in response to light and nitrogen supple- mentation, and undergo meiosis to release four haploid vegetative cells

Figure 1 from Sekimoto 2017. The life cycle of Chlamydomonas reinhardtii. Vegetative cells (V) differentiate into mt+ and mt− gametes (G) during nitrogen starvation (−N). Mating types are restricted by mating-type loci (+ and −). When gametes are mixed, the plus and minus agglutinin molecules on their flagellar surfaces adhere to each other, and this adhesion results in increased intracellular cAMP levels. The signal triggers gamete cell wall release and mating-structure activation. Cells then fuse to form binucleate quadriflagellated cells. Zygotes with thick cell walls germinate in response to light and nitrogen supplementation, and undergo meiosis to release four haploid vegetative cells.

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Convergence falsifies evolution, according to Cornelius Hunter

Xerus princeps

Xerus princeps, the mountain ground squirrel.

Before I saw the light and switched to studying Volvox, I studied squirrels. With apologies to Iris Vander Pluym, squirrels are cool. If you grew up in the squirrel-deprived eastern U.S., you might not realize that there are over a hundred species. Chipmunks are squirrels. Marmots are fat squirrels. Prairie dogs are adorable squirrels.

Most of my squirrel work, and some of my Volvox work, has focused on understanding the evolutionary relationships among species. This fits in the subfield of evolutionary biology known as phylogenetics. Phylogenetics results are often visualized as trees and published in journals like Cladistics, Molecular Phylogenetics and Evolution, and Systematic Biology. Phylogenetics is a vast subfield, with a huge number of papers devoted to developing methods that are theoretically and empirically sound.

Cornelius Hunter understands none of this. In a recent post over at Evolution News and Science Today (which used to be Evolution News and Views…when did that change?), he argues against the whole idea of common descent, the very foundation of phylogenetics. Dr. Hunter argues that convergence, similarities among distantly related species, falsifies evolution. The nature of his arguments shows pretty conclusively that he doesn’t understand the basic logic of what he’s criticizing.

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As a frequent Amtrak rider, I appreciate this

I have ridden the Empire Builder, the Capitol Limited, the Cardinal, the Sunset Limited, the Crescent, and once as a child the Auto Train all the way from Virginia to Florida. Amtrak doesn’t own most of the rails for these long-haul routes, so freight trains always get priority. Since there’s often only one track, I’ve spent a good bit of time pulled over on a siding and waiting for a freight train to go by in the other direction.

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Counting my millions

Breaking Bad Money

Photo Credit: Lewis Jacobs/AMC

I’m at a net loss from blogging so far. My net income for two years (here and on the old fierceroller.com site) has been $21.54, while I’ve paid around a hundred bucks for domain name registration and stuff like that. That’s fine; I don’t do it for the money. I have a lot of other reasons for doing this, and there have been lots of benefits both intangible and tangible. The blog was partly responsible for me being invited to write the meeting review for the 2015 Volvox meeting, and I’m working on another manuscript inspired by an exchange that played out on Fierce Roller. Still, the main reason I do this is that I like to.

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Algae porn

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.

“…much that was human and natural found no expression.”

Fall of Giants
I discovered Ken Follet only recently, historical fiction not normally being my cup of tea. Right now I’m reading Fall of Giants after enjoying The Pillars of the Earth and World Without End. Follet has, I think, a bit of Stephen King’s ability to make you care what happens to his characters, and he plays the long game, with subplots sometimes taking taking generations to play out. Religion plays an important role in his writing, as it must given the setting. His characters include skeptics and true believers, who are inspired by their beliefs to do evil as often as good. Anyway, I thought the last part of this quote might resonate with the godless heathens that frequent this site:

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Rediscovered after two thirds of a century: Pleodorina sphaerica

Pleodorina sphaerica

Figure 1 from Nozaki et al. 2017. Pleodorina sphaerica.

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.

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Dissent on Bangiomorpha

Bangiomorpha pubescens

Figure 5 from Butterfield 1990. Bangiomorpha pubescens.

In my post on Bangiomorpha, I said

…Bangiomorpha was probably a red alga. This conclusion seems to be accepted by most everyone in the field. In fact, I don’t know of any dissenters, and that kind of consensus is rare for fossils this old.

I guess I didn’t look hard enough, because reader not the FTB Stewart commented

Cavalier-Smith dissents (dissented?) from the consensus
https://books.google.co.uk/books?id=lE6r5q5op94C&pg=PA63&lpg=PA63#v=onepage&q&f=false

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