That beautiful animalcule: Andrew Pritchard on Volvox

Pritchard figure

Plate from Pritchard 1834. Image from Google Books.

Andrew Pritchard’s 1834 book The Natural History of Animalcules includes several species he classifies as Volvox. Most of them were probably not Volvox, but his Volvox globator certainly was. His description of Volvox begins on page 39. A scanned version is available online at The Biodiversity Heritage Library, but I have used the slightly higher quality scan in Google Books for the plate above.

The animalcules belonging to this genus are of a globular form, and revolve in the water. Some of the species are so large as to be discerned by unassisted vision, while others are very diminutive. Ehrenberg has not demonstrated their digestive organization; but in a note to his table, conceives they ought to follow the monads. In this genus is included that beautiful animalcule, called the Volvox globator, which forms so interesting a spectacle in the Solar and Gas Microscopes.

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Zombie Volvox on PhysOrg

Ueki & Wakabayashi Fig. 4A-C

Figure 4A-C from Ueki and Wakabayashi 2018. Ca2+-dependent changes in the direction of axonemal beating. (A) Experimental setups for observation of live or demembranated spheroids in a chamber. (B) Frames from high-speed recordings of regions near the anterior (Top) and posterior (Bottom) poles of a live spheroid. The observation using setup A was under stationary conditions in continuous light (Left) and after photostimulation (Right). (Scale bar: 100 μm.) (C) Typical sequential flagellar waveforms in a single beating cycle under each condition. Waveforms recorded as in B were traced (time interval of 1/500 s). (Scale bar: 10 μm.).

Last month, I reported on mad scientists Noriko Ueki and Ken-ichi Wakabayashi’s reanimation of dead (demembranated) Volvox rousseletii spheroids. PhysOrg is also carrying the zombie Volvox story:

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How did I miss this?

Volvox Group Limited

Volvox Group Limited:

Volvox Group Limited manufactures and distributes automotive lighting and electrical products in the United Kingdom. It distributes its products to transport industries, workshops, leisure, and the industrial consumables market. Volvox Group Limited also involves in delivering mains power in vehicles from the 12v battery to developing eco-friendly wind-up torches, as well as offers automotive bulbs and industrial tools. Volvox Group Limited was incorporated in 2005 and is based in Leeds, United Kingdom. The company is a former subsidiary of Ring Lamp Company Ltd.

Incorporated in 2005 means there’s no chance I ever had a Volvox light bulb in my ’77 MGB.

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More evidence for co-option in the evolution of soma

One of the reasons Volvox was developed as a model organism was that it has the minimum number of cell types something with cellular differentiation can have: two. This property focuses investigations of cellular differentiation in a way that an organism with many cell types could not. In describing their move from studying avian and mammalian models to studying Volvox, Marilyn and David Kirk said,

The thing that appealed to us most about V. carteri – in addition to the genetic accessibility that Starr (1970) had already demonstrated – was the fact that it presented the germ-soma dichotomy in such a clear and simple form. Each asexual adult (or “spheroid”) of V. carteri contains only two cell types: small, biflagellate somatic cells, and large asexual reproductive cells, called gonidia (figure 1). The somatic cells are mortal; once they have provided the organism with motility for a few days they die. The gonidia, in contrast, are potentially immortal; each mature gonidium acts as a stem cell, dividing to produce a juvenile organism containing a new cohort of gonidia and somatic cells. No one has ever found a way to make wild-type somatic cells divide, but the only way to prevent gonidia from dividing is by withholding energy or poisoning them. Who could ask for a clearer presentation of one of the central issues of developmental biology: how are cells with extremely different phenotypes produced from the progeny of a single cell?

Kirk & Kirk 2004 Fig. 1

Figure 1 from Kirk & Kirk 2004. A young adult spheroid of V. carteri consists of thousands of small, biflagellate somatic cells that are embedded at the surface of a transparent sphere of extracellular matrix, and about 16 large asexual reproductive cells, called gonidia, that are located just internal to the somatic cells.

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The Essential Tension

The Essential Tension

When I ran across The Essential Tension by Sonya Bahar, my first thought was that it sounded very much like something my PhD advisor could have written:

‘The Essential Tension’ explores how agents that naturally compete come to act together as a group. The author argues that the controversial concept of multilevel selection is essential to biological evolution, a proposition set to stimulate new debate.

The subtitle is Competition, Cooperation and Multilevel Selection in Evolution, which is more than vaguely reminiscent of the ‘cooperation and conflict’ framework Rick Michod has built over the last twenty years.

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Two new gene expression studies in Volvox

One of the most remarkable things about multicellular organisms is the differentiation of genetically identical cells into functionally specialized cell types. It’s difficult to say exactly how many cell types a given species has, since we would first have to say how different two cells need to be to count as different types. Nevertheless, it’s clear that there’s a wide range among different multicellular groups. Within animals, for example, placozoa have around five cell types, mammals over a hundred.

Amazingly, all of these very different cell types share a genome: your liver cells are pretty much genetically identical to your brain cells (and your skin cells, your kidney cells, your muscle cells…). The dramatic differences in form and function among all these cell types are mainly a result of differences in gene expression.

Volvox has just two cell types: a dozen or so big cells that are responsible for reproduction and one or two thousand smaller cells that bear the flagella that colonies use to swim:

Matt & Umen Fig 1A

Figure 1A from Matt & Umen 2017. Micrographs of an intact adult Volvox carteri spheroid with fully mature somatic and gonidial cells (left), isolated somatic cell (top right), and isolated gonidial cell (bottom right).

This was one of the main attractions for the researchers who developed Volvox as a model organism. With only two cell types, Volvox retains something close to its original form of cellular differentiation, making questions about how such differentiation evolved much more tractable.

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Volvox meeting posters

I thought I had already done this, but if so I can’t find it. Here are the full-resolution versions of all four Volvox meeting posters:

  • First International Volvox Meeting (Volvox 2011, Tucson, Arizona) pdf jpg
  • Second International Volvox Meeting (Volvox 2013, Fredericton, New Brunswick) pdf jpg
  • Third International Volvox Meeting (Volvox 2015, Cambridge, U.K.) pdf jpg
  • Fourth International Volvox Meeting (Volvox 2017, St. Louis, Missouri) pdf jpg (there wasn’t really a poster for this one; this is the cover of the abstract booklet)

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The Two Jakes

The organizers of the Volvox 2017 meeting put together a Volvox trivia quiz, and one of the questions had to do with a 1990 movie in which Volvox had had a cameo appearance. I was stumped. I knew Europa Report was much more recent. I probably didn’t know what Volvox was in 1990, and I don’t think I had seen the movie in question, which turned out to be The Two Jakesa sequel to 1974’s Chinatown

The Two Jakes

Because that’s how dedicated I am, I rented and watched both videos and screen captured the clip in question. Sorry there’s no sound. [somewhat important spoiler below the fold]

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