Volvox 2015: biophysics

In a session chaired by Ray Goldstein, we heard about recent advances in the biophysics of Volvox and Chlamydomonas. Over the last decade or so, Volvox has proven to be an experimentally tractable model system for several questions in hydrodynamics and flagellar motility. Volvox colonies can be grown in large numbers (even by physicists!), clonal cultures have relatively little among-colony variation, and they are large enough to be manipulated in ways that most single-celled organisms can’t. Furthermore, their simple structure accommodates the kind of simplifying assumptions physicists are fond of, leading Kirsty Wan (among others at the meeting) to refer to them as “spherical cows.”

In a series of papers, Douglas Brumley and colleagues have explored flagellar dynamics in Volvox carteri. Amazingly, these studies have shown that the synchronized beating of V. carteri‘s ~1000 pairs of flagella is entirely due to hydrodynamic coupling. In other words, in spite of the apparent high degree of coordination among the flagella of separate cells within a colony, no actual coordination among cells takes place. Synchronization emerges from indirect interactions mediated by the liquid medium. An elegant demonstration of this is shown in Brumley et al.’s 2014 eLife paper, in which somatic cells were physically separated from a colony and held at various distances from each other. Despite there being no direct physical connection between the cells, they beat synchronously when close together, with a phase shift that increased with increasing cell to cell distance:

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Volvox 2015: evolution

This is taking much longer than I ever expected; hopefully I can get through blogging about Volvox 2015 before registration opens for Volvox 2017!

The final session on day 1 (August 20) was chaired by Aurora Nedelcu from the University of New Brunswick. Dr. Nedelcu’s introduction emphasized some of the basic questions in evolutionary biology, aside from the origins of multicellularity and sex, on which volvocine research has provided insights: the evolution of morphological innovations, the relative importance of cis-regulatory changes vs. protein-coding changes, kin vs. group selection as competing explanations for the evolution of altruism, the evolution of soma and of indivisibility, the genetic basis of cellular differentiation, and the role of antagonistic pleiotropy (my hastily scribbled notes seem to say “antagonistic pleiotropy of olsl.” Is that supposed to be rls1? This is the cost of waiting too long to write. Maybe Aurora can clarify.).

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Excess of vigilance


Fierce Roller gets a lot of spam comments, like several a day (I assume this is normal). If you are looking for cheap Ray-Ban glasses or NFL jerseys, I can hook you up. At some point in the last week or so I apparently hit “select all” before marking some new comments as spam, accidentally consigning all comments ever to spam purgatory. I have now restored all legitimate comments.

By the way, my (informal and subject to change) policy on comments is that I approve all of them unless they are straight up spam. I haven’t ever blocked a comment for any other reason.

Volvox 2015: development

Replica of Antonie van Leeuwenhoek's microscope.

Ray Goldstein‘s working (!) replica of Antonie van Leeuwenhoek’s microscope.

At the start of the Development session, I asked for a show of hands of people who self-identify as developmental biologists. About four went up. That’s not quite fair, since there’s some ambiguity in the question (primarily? exclusively?), but my point was that what all of us who are interested in the evolution of multicellularity study is the evolution of development. In fact, it might fairly be said that the origin of multicellularity is the origin of development.

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Volvox 2015: me and my horsy and a quart of beer


Licensed to Ill

When I was a senior in high school, I gave my friend Arthur Malpere a ride to school in my ’77 MGB just about every day (well, every day it was running). I had a cassette of the then fairly new Licensed to Ill, and Art insisted that we listen to it every damn day. The ride to school was on the order of ten minutes, so we would listen to ten minutes on the way to school, then pick up where we left off, usually mid-song, on the way home (for those of you too young to remember cassettes, it wasn’t trivial to return to the beginning of a song). Of all the outstanding songs on that album, possibly my favorite was “Paul Revere,” a sort of old-west style automythology of the band’s origin (in spite of the casual misogyny, I still do like it pretty well).

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Volvox 2015: cell differentiation

One of the most studied aspects of Volvox development is the differentiation of its 2000 or so cells into two types: a few (usually 12-16) large reproductive cells (germ) and the rest small, biflagellate cells that provide motility (soma). The main genes controlling this differentiation have long been known, but the details of how they work are still being worked out.

Erik Hanschen (left) with Cristian Solari, David Smith, and Jillian Walker

Erik Hanschen (left) with Cristian Solari, David Smith, and Jillian Walker

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Volvox 2015: hunting the wild Volvox

We spent Wednesday afternoon sampling some ponds around Cambridge, looking for Volvox and related algae. Dr. Hisayoshi Nozaki, whose lab has described a substantial proportion of the known species, led the effort, but somehow we failed to locate our quarry.


Thomas Pröschold checking an algae-filled pond.

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Volvox 2015: all about sex

I believe that sex is one of the most beautiful, natural, wholesome things that money can buy.

–Steve Martin

Volvox, and the volvocine algae in general, are well known as a model system for the evolution of multicellularity and cellular differentiation, but they are also an outstanding model for the evolution of sex and mating types. Volvocine algae are facultatively sexual, with haploid vegetative colonies reproducing asexually through mitosis but occasionally entering a sexual cycle that usually results in a diploid, desiccation-resistant zygote or ‘spore.’ Most of the small colonial species and unicellular relatives are isogamous, that is, the gametes are of equal size. Nevertheless, each species has two self-incompatible mating types, usually designated as ‘plus’ and ‘minus.’ In some of the larger species, the gametes have diverged into a small, motile form that we call sperm and a large, often immotile form that we call eggs. Across the eukaryotic domain, it is gamete size, not form of genitalia, fancy plumage, or receding hairline, that define males and females.

The volvocine algae span a wide range of mating systems, making them a useful (and I think underutilized) system for comparative studies of the evolution of sex. As I’ve already mentioned, both isogamous (equal-sized gametes) and oogamous (sperm and eggs) species exist, and there is good reason to suspect that oogamy has evolved independently in two separate lineages:

Isogamy and oogamy

Isogamy and oogamy (Kirk 2006. Curr. Biol., 16:R1028.)

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Volvox 2015

Today is day one of the Third International Volvox Conference in Cambridge, U.K. I arrived yesterday via Chicago, Ottowa, and a bus from Heathrow. Apparently there is a direct flight from Chicago to Heathrow; why I didn’t take that is a mystery. The accommodations at Wychfield are quite comfortable, although many of us have had the usual troubles figuring out English plumbing.

Last night was a pub dinner with half or so of the attendees; I had some very good fish & chips (good, but not as good as Go Fish).

Pub dinner with Stephanie Höhn, one of the organizers, in the foreground.

Pub dinner with Stephanie Höhn, one of the organizers, in the foreground.

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Fierce Roller will be offline next week

Missouri River Breaks

The Upper Missouri River National Monument in Montana. Photo by Bureau of Land Management.

I’ll be leaving Sunday morning for the Epic Canoe Trip on the Upper Missouri River (Coal Banks Landing to Kipp Recreation Area). We’ll be paddling, hiking, and camping in the White Cliffs of the Missouri and the Missouri River Breaks, a total of 107 miles. I’ll be totally offline; no cell service and no email. Don’t cry for me.