Researcher Information

KAKUI Keiichi


Diversity in invertebrates

Department of Biological Sciences, Biodiversity


Taxonomy and biology of marine invertebrates, especially the crustacean order Tanaidacea

FieldSystematic zoology, Reproductive biology, Morphology, Zoology
KeywordMarine invertebrates, Arthropoda, Crustacea, Tanaidacea, Benthos, Taxonomy, New species, Molecular phylogeny, Reproduction, Sexual mode, Morphology, Life cycle, Evolution

Introduction of Research

I am interested in the taxonomy, phylogeny, reproductive biology, morphology, and evolution of invertebrate animals. The main focus of my research is the order Tanaidacea, a group of tiny aquatic crustaceans, with around 1400 species. However, past or ongoing collaborative projects in taxonomy and phylogeny have dealt with animal groups other than tanaidaceans, including isopods, amphipods, decapod, ostracods, copepods, mite, sea spider, nematodes, entoproct, nemertean, feather star, and xenoturbelid.

Various tanaidaceans
A parasitic copepod (arrow) on a tanaidacean
A tanaidacean which can self-fertilize
A deep-sea tanaidacean with a wide distributional range spanning at least 3700 km (cf. Kakui et al. 2020)
A tanaidacean described by my student, one collaborator, and me (cf. Okamoto et al. 2020); there is a breeding season, from May to October, in the Oshoro Bay population (cf. Kakui et al. 2017)
A hermit-crab-like tanaidacean (cf. Kakui 2019)

Representative Achievements

Kakui K, Nomaki H, Komatsu H, Fujiwara Y (2020) Unexpected low genetic differentiation between Japan and Bering Sea populations of a deep-sea benthic crustacean lacking a planktonic larval stage (Peracarida: Tanaidacea). Biological Journal of the Linnean Society 131: 566–574.
Okamoto N, Oya Y, Kakui K (2020) A new species of Zeuxo (Crustacea: Peracarida: Tanaidacea) from Japan, with remarks on carapace pigmentation as a potentially useful taxonomic character. Marine Biology Research 16: 411–422.
Kakui K, Fujita Y (2020) Paradoxapseudes shimojiensis sp. nov. (Crustacea: Tanaidacea: Apseudidae) from a submarine limestone cave in Japan, with notes on its chelipedal morphology and sexual system. Marine Biology Research 16: 129–136.
Kakui K (2019) Shell-exchange behavior in a hermit-crab-like tanaidacean (Crustacea: Malacostraca). Zoological Science 36: 468–470.
Kakui K, Hayakawa Y, Katakura H (2017) Difference in size at maturity in annual and overwintering generations in the tanaidacean Zeuxo sp. in Oshoro Bay, Hokkaido, Japan. Zoological Science 34: 129–136.
Academic degreePh.D.