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.

[Read more…]

Don’t dump and run

In the December issue of EMBO ReportsMatheus Sanitá Lima and David Roy Smith argue that biologists utilizing next-generation sequencing data should include detailed methods with their submissions to the Sequence Read Archive (the paper is paywalled at the publisher site but available here):

For those who are unfamiliar with it, the SRA is an international public online archive for next-generation sequencing (NGS) data, which was established about a decade ago under the guidance of the International Nucleotide Sequence Database Collaboration (INSDC)…Once there, you will find yourself at a sequencing-read superstore.

Sanitá Lima & Smith

[Read more…]

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.

[Read more…]

Some responses to “A cautionary tale on reading phylogenetic trees”

PLoS ONE logo

Back in September, I complained that a PLoS ONE article purporting to provide “valuable insight into the evolution of eukaryotes” contained substantive problems that should have been caught during the peer review process (“A cautionary tale on reading phylogenetic trees“). The problems are so serious that, in my opinion, they render the bulk of the results invalid.

There were also numerous problems with the interpretation of those results, mainly stemming from misunderstandings about what kinds of information phylogenetic trees represent:

Some of these problems are just rhetorical, but some of them are substantive, and this is the real problem. A failure to understand that phylogenies represent sister group relationships has led to incorrect interpretations of evolutionary relationships, such as that the outgroup is more closely related to one ingroup clade than another, that the sister of one clade is a ‘link’ to another clade, and that a single branching event can have a bunch of different divergence times.

I later admitted, in response to criticism from a reader, that I may have been overly pedantic in pointing out some of the rhetorical problems (“A valid point“). In this post, though, I’m going to focus on the substantive problems and respond to a couple of comments to the original post.

[Read more…]

Chlamydomonas monograph

Chlamydomonas monograph cover

There’s a new Microbiology Monograph on ChlamydomonasChlamydomonas: Molecular Genetics and Physiology, edited by Michael Hippler. It’s actually cheaper to buy it directly from the publisher, but still $149 for an e-book.

This Microbiology Monographs volume covers the current and most recent advances in genomics and genetics, biochemistry, physiology, and molecular biology of C. reinhardtii. Expert international scientists contribute with reviews on the genome, post-genomic techniques, the genetic toolbox development as well as new insights in regulation of photosynthesis and acclimation strategies towards environmental stresses and other structural and genetic aspects, including applicable aspects in biotechnology and biomedicine.

[Read more…]

Sonic weapons on Skeptoid


Photo credit: Aexandre Meneghini/Reuters/Newscom.

I’ve been meaning to get back to the absurd claims of Cuban “sonic weapons” for a while now (Sonic stupidity; It may seem the stuff of sci-fi novels; More acoustic credulity; No means, no motive, and no suspectCuba’s “magical sci-fi sound gun”; More Cuban science fiction), but Brian Dunning has beaten me to it. The latest episode of Skeptoid is all about the alleged attacks on the U.S. embassy, and it leaves the administration’s claims in tatters:

Beginning in early 2016, American diplomats stationed in Cuba began reporting a mysterious illness. They believed they were under attack by what they described as a sonic weapon. No culprit could be identified, no such weapons were found, no clear motive could be established…

[Read more…]

Volvox 2017: Vexed Volvocines

Zach Grochau-Wright

Zach Grochau-Wright

Zach Grochau-Wright has kindly given me permission to print the haiku he presented at the Volvox 2017 meeting in St. Louis. Zach may be the most prolific artist in the obscure sub-genre of volvocine poetry, having previously written and performed “Volvocine rap” at the Volvox 2015 meeting. Here it is in its barely-longer-than-his-name entirety:

[Read more…]

Chlamy 2018 dates and venue announced

Chlamydomonas zygotes

The dates and location have been announced for the 18th International Conference on the Cell and Molecular Biology of Chlamydomonas:

The 18th International Conference on the Cell and Molecular Biology of Chlamydomonas will be held from June 17-21, 2018 in Washington DC. We look forward to seeing all of you there, so please keep those dates open. The venue will be the historic Carnegie Institution headquarters located in the heart of DC at 1530 P Street NW. To learn more about the venue go to More information will be posted concerning the conference over the next couple of months.

I’ll keep you posted as more information becomes available.