A few years back, I invited Dr. Hisayoshi Nozaki to visit the University of Montana, and to my surprise, he came. In fact, five Japanese researchers came to Missoula for the better part of a week: Dr. Nozaki, Dr. Noriko Ueki, Dr. Osami Misumi, and two undergraduate researchers. We found a species, Volvox capensis, which had previously only ever been found in South Africa, in Ninepipe Reservoir (about an hour north of Missoula).
Now Ryosuke Kimbara and colleagues have reported another apparent long-distance traveller. In a new paper in PLoS One, they report finding Volvox rousseletii, previously reported only in Africa, in Lake Sagami in Japan. Volvox rousseletii is a member of the group of species known as Volvox section Volvox (also sometimes referred to as Euvolvox), which includes the largest species (in terms of cell number) and evolved independently of the other species in the genus Volvox.
Figure 1 from Kimbara et al. 2019. Light microscopic features of asexual spheroids in culture of Volvox rousseletii strain v-sgm-17 from Lake Sagami, Japan. (A) Mature spheroid showing daughter spheroids (d). (B-D) Part of spheroids. (B) Top view of individual sheaths (asterisks) of somatic cells stained with methylene blue. (C) Top view of somatic cells with thick cytoplasmic bridges (b). (D) Side view of elongate-ellipsoidal, anterior somatic cell with stigma (s) and pyrenoid (p) in the chloroplast. (E) Developing embryo just after inversion, showing gonidia (g) of the next generation.
The species identity was confirmed by comparison of the DNA sequences of several genes with existing Volvox rousseletii sequences. This is not only the first record of Volvox rousseletii but of any dioecious section Volvox species in Japan.
Figure 4 from Kimbara et al. 2019. Phylogenetic position of Volvox rousseletii originating from Japan within Volvox section Volvox, based on maximum likelihood (ML) analysis of the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA (rDNA) (ITS-1, 5.8S rDNA, and ITS-2). Branch lengths are proportional to the evolutionary distances that are indicated by the sale bar. Numbers in left and right sides at branches represent bootstrap values (50% or more) based on 1000 replications of ML and posterior probabilities (0.85 or more) by Bayesian inference, respectively.
The researchers also found morphologically similar, monoecious Volvox colonies in Lake Sagami, which they refer to only as Volvox sp. Sagami (see Fig. 4 above). Nozaki and colleagues reported this strain, a close relative of Volvox ferrisii, in a previous paper, which I wrote about back in 2016 (What is a (Volvox) species?).
Kimbara and colleagues conclude that
…more data are needed to resolve the biogeographical significance of the morphological and genetic variability within this species.
and
Additional dioecious species of Volvox sect. Volvox with intercontinental distribution and/or new species of this section may be revealed in further studies using both field-collected and cultured materials of this section growing in various freshwater habitats worldwide.
I couldn’t agree more. Far too little work has been done on the biogeography of the volvocine algae to draw general conclusions about their distributions. As I’ve said before,
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.
There has also been too little effort, in my opinion, devoted to quantifying and understanding genetic and morphological variability within species of volvocine algae. This type of data would contribute to our understanding of the population genetic and biogeographic processes that drive volvocine distributions and evolution. More data are indeed needed!
Stable links:
Kimbara, R., Isaka, N., Matsuzaki, R., Kawai-toyooka, H., Kawachi, M. and Nozaki, H. 2019. Morphological and molecular identification of the dioecious “African species Volvox rousseletii (Chlorophyceae) in the water column of a Japanese lake based on field- collected and cultured materials. PLoS One, 14: e0221632. doi: 10.1371/journal.pone.0221632
Nozaki, H., N. Ueki, N. Isaka, T. Saigo, K. Yamamoto, R. Matsuzaki, F. Takahashi, K. Wakabayashi, and M. Kawachi. 2016. A new morphological type of Volvox from Japanese large lakes and recent divergence of this type and V. ferrisii in two different freshwater habitats. PLoS One. doi: 11:e0167148.
Nozaki, H., N. Ueki, O. Misumi, K. Yamamoto, S. Yamashita, M. D. Herron and F. Rosenzweig. 2015. Morphology and reproduction of Volvox capensis (Volvocales, Chlorophyceae) from Montana, USA. Phycologia 24:316-320. doi: 10.2216/15-14.1
Hi Matt,
I have a comment. In 2010, Noriko Ueki et al. published a paper on phototaxis in Volvox rousseletii:
Ueki N, Matsunaga S, Inouye I, Hallmann A (2010) How 5000 independent rowers coordinate their strokes in order to row into the sunlight: phototaxis in the multicellular green alga Volvox. BMC Biol 8:103. doi:10.1186/1741-7007-8-103
The alga was isolated from different Japanese location and the molecular identification of species was also made.
It is a bit strange that Ueki’s paper (2010) was not cited in the new Volvox rousseletii paper (2019).
Best regards,
Alexey
Based on a quick BLAST search of the Dr. Ueki’s rbcL sequence, I believe the strain she analyzed was either Volvox ferrisii or Volvox sp. Sagami. Neither had been described in 2010, so it makes sense that they would have called the strain Volvox rousseletii, since the closest available sequences would have been from that species.
Thanks, I think that it is a wonderful explanation. However, I am sad to see that no explanation of this situation was included into the last paper about Volvox rousseletii in Japan.