My studies of zoological taxonomy were initiated using oribatid mites as study objects. I also had the idea of looking into the biology of these mites and eventually, we were the first to discover a pheromone (geranial) produced by oribatid mites. Next, we discovered that one of the substances of the external secretion from oribatid mites serving as a defense against enemies, contains a poisonous component also used by their predator, the poison frog with bioconcentration. Geranial and neral are chemical isomers which are produced and secreted by oribatid mites. The astigmatid mites derived from the oribatid mites share the same substance (neral) as a secretion material. The traditional method of ripening a few kinds of European cheese with astigmatid mites seems to partly impart the lemon flavor of the neral to the cheese.

I have switched my research to the ecology and agricultural use of soil protists in the past, to obtain a position in the research institute of the Ministry of Agriculture, Forestry, and Fisheries. Eventually, however, I focused my research towards zoological taxonomy again, but now for protists and finally, I was also involved in the revision of the eukaryotic classification.

During the study of endangered species, we redescribed the testate amoeba species, Difflugia biwae Kawamura, 1918, in the ancient Lake Biwa in Japan. We also discovered that the feather mite Compressalges nipponiae Dubinin, 1950, which was known to dwell in the wings of the Japanese Crested Ibis, had become extinct along with the Japanese lineage, and re­described the species.

Scolopendra alcyona Tsukamoto & Shimano, 2021, described from the Ryukyu Islands in cooperation with local citizens, is the third semi-aquatic species of the genus Scolopendra Linnaeus, 1758 in the world, and the first species of the genus described in 143 years. Moreover, it is the first centipede species described by Japanese researchers in this giant centipede genus.

Ameronothrus twitter Pfingstl and Shimano, 2021, oribatid mite, was voted by the World Register of Marine Species (WoRMS) as one of the “Ten remarkable new marine species from 2021” as “the Japanese Twitter mite” was described with the help of Twitter, a popular social networking service. It will be essential to incorporate citizen science into zoological systematics and work with the public in scientific endeavors in the future.

Nemertea is one of the spiralian phyla, consisting of about 1350 species from all over the world. Nemerteans are commonly known as ribbon worms, occurring in a wide variety of marine, freshwater, and terrestrial ecosystems. Although about 100 species of nemerteans have been reported from Japan, recent studies in limited areas involving molecular phylogenetic techniques have uncovered high species diversity in the area, suggesting that there are a significant number of yet-to-be-discovered species in the entire Japanese waters. In this paper, I present a step-by-step introduction to collection, observation, and identification of nemerteans principally for systematic studies. In addition, the present paper briefly reviews recent progress in molecular phylogeny and systematics in the Nemertea.

Treatments of species taxonomy for Japanese mammals in “Illustrated Checklist of the Mammals of the World” (CMW) published in 2020 and nine volumes of “Handbook of the Mammals of the World” (HMW) from 2009 to 2019 are compared with those in the second edition of “The Wild Mammals of Japan” (WMJ2) in 2015. Then, the updated taxonomy and current problems of Japanese mammals were discussed. Order Eulipotyphla in CMW and HMW combined orders Soricomorpha and Erinaceomorpha in WMJ2, and Order Cetartiodactyla in CMW joined orders Artiodactyla and Cetacea in HMW and WMJ2; both in reflecting the recent molecular phylogenetic studies. A comparative list of the species names of Japanese mammals between CMW and WMJ2 was made, also with reference to descriptions and literatures in HMW. In CMW, 160 species are found in Japan, and 21 species of them had species names different from WMJ2. Concerning about these species and about species necessary for special consideration in species taxonomy or geographic range, 34 comments were provided for discussion.

The labrid genus Suezichthys Smith, 1958 includes 11 valid species, four of which have been recorded from the Japanese waters. Three specimens (125.2–137.7 mm standard length) of the Northern Rainbow Wrasse Suezichthys notatus (Kamohara, 1958) were collected from Tosa Bay and the East China Sea. These specimens possess the following characters: dorsal-fin rays IX, 11; anal-fin rays III, 10; scale rows above lateral line 2 1/2; lateral-line scales 25, each with unbranched laterosensory canal tube; and dark brownish blotches on head and body above pectoral fin. Suezichthys notatus, distributed in scattered localities of the eastern Indian Ocean and the Pacific Ocean, has been recorded only from Okino-shima island, Kochi Prefecture, on the basis of a holotype in the Japanese waters. Therefore, the present specimens represent the second records of the species from Japan.

A single adult specimen (192.2 mm standard length) of the Malabar Trevally, Platycaranx malabaricus (Bloch and Schneider, 1801) (Teleostei: Carangidae), collected from Sagami Bay was observed in the fish collection of the Department of Zoology, The University Museum, The University of Tokyo. Because the northern limit of the distributional range of the species has been regarded as Mihama Town, Aichi Prefecture, the specimen described in this study represents the northernmost record and first record from Kanagawa Prefecture of P. malabaricus.

An immature cymothoid isopod was found infesting a serranid fish, Sacura margaritacea (Hilgendorf, 1879) (Perciformes: Serranidae), captured off Hiratsuka (Kanagawa Prefecture) in the Sagami Bay along the Pacific coast of central Japan. In molecular analyses, cytochrome c oxidase subunit I and 16S rRNA sequences of the cymothoid specimen shared ≥99% identity with those of Ceratothoa oxyrrhynchaena Koelbel, 1878 in GenBank. The produced anterolateral margins of pereonite 1 and the well-expanded carina at the posterior margin of pereopod 7 basis in the present specimen were in close agreement with the diagnostic characteristics of adult of C. oxyrrhynchaena, corroborating the results of molecular analyses. This finding represents a new host record of C. oxyrrhynchaena.