I snorkeled for the first time in my life as part of a marine laboratory course when I was an undergrad. I will never forget the bountiful variety and striking beauty of the marine organisms I saw off Aomori’s coast. Since then, I have been captivated by sea life and have devoted my research to marine invertebrates.
Yamazaki A., Kidachi Y., Yamaguchi M., and Minokawa T. (2014)
Yamazaki, A., Y. Kidachi and T. Minokawa (2012) “Micromere” formation and expression of endomesoderm regulatory genes during embryogenesis of the primitive echinoid Prionocidaris baculosa
Minemura K., M. Yamaguchi and T. Minokawa (2009) Evolutionary modification of T-brain (tbr) expression patterns in sand dollar
Iijima, M., Y. Ishizuka, Y. Nakajima, S. Amemiya, and T. Minokawa (2009) Evolutionary modification of specification for the endomesoderm in the direct developing echinoid Peronella japonica: loss of the endomesoderm-inducing signal originating from micromeres
Nakata, H. and T. Minokawa (2009) Expression patterns of wnt8 orthologs in two sand dollar species with different developmental modes
The Zoological Society of Japan, Japanese Society of Developmental Biologists
Marine Biology, Evolutionary Developmental Biology
Photo 1: Cidaroida 16-cell stage embryo. The arrows point to the smaller blastomeres formed in the vegetal pole, and the arrowhead indicates the animal pole.
I am interested in the evolution and diversity of the developmental mechanism. For the past several years, our group has conducted research focused on the differences between primitive and derivative-type sea urchins, in particular the evolution of micromere formation and functions. Derivative-type sea urchins form four micromeres of the same size in the vegetal pole at the 16-cell stage. On the other hand, little was known about the micromere formation of primitive sea urchins (Cidaroida). We studied Cidaroida embryonic development in detail and found that in this organism, the four same-size micromeres do not form (Photo 1), and the endomesoderm specification mechanism occurring at vegetal hemisphere is vastly different from that of derivative-type sea urchins. Using comparative methodologies, we have been studying the evolutionary changes of the sea urchin developmental mechanism. (Photo 1)
Photo 2: Various sea urchins living in the vicinity of Asamushi: Glyptocidaris crenularis (top left), Strongylocentrotus nudus (top right), Hemicentrotus pulcherrimus (bottom left), Scaphechinus mirabilis (middle bottom), and Strongylocentrotus intermedius (bottom right).
There are variations in the developmental mechanisms of different kinds of sea urchins. These differences are the result of over 200 million years of diversification and evolution. The sea urchins are therefore favorable research subjects in evolutionary development biology. We are conducting research on the evolution of the developmental mechanism using various sea urchins living in the vicinity of Asamushi (Photo 2).