This paper reviews the author’s studies on sibling species of estuarine nereidid polychaetes in taxonomy and related fields over the past 46 years. First, the case of the genus Hediste, on which the author started to study earliest, is reviewed with the following 10 topics: 1) Fine structure of sperm-egg interaction during fertilization; 2) Finding of two forms (small- and large-egg forms) with markedly different life-history characteristics in “H. japonica”, which was believed to be the only species of Hediste in Japan; 3) Evidence for the presence of two sibling species by electrophoretic analysis of allozymes; 4) Finding of the presence of the third form (Ariake form) with specialized morphology in parapodia and chaetae; 5) History of the taxonomic studies on Japanese Hediste species; 6) Descriptions of two new species and a redescription of H. japonica sensu strict; 7) Karyotypes; 8) Feeding habits; 9) Worldwide distributions of currently known species; 10) A hypothesis of the speciation. Next, studies on the other sibling species complex of Nectoneanthes and Potamonereis are briefly reviewed.

The oldest fish specimens in Japan include those taken over from the Museum under the jurisdiction of the Home Ministry into the Imperial Museum (later Tokyo Imperial Household Museum; now Tokyo National Museum) in 1889 and those transferred from the Tokyo Education Museum (now National Museum of Nature and Science) to the Imperial Museum in 1890. Most of these early specimens are now at the National Museum of Nature and Science; however, it was known that some of these specimens were kept in Gakushuin Boys’ Senior and Junior High School, Tokyo, yet detailed information on the specimens in the school was unclear. We examined the early specimens of the school, comprised of 14 stuffed specimens and two fluid preserved specimens representing 16 species in 16 families. No extant stuffed fish specimens previously stored in the Tokyo Imperial Household Museum are known, except for those kept in the school, and thus 13 of the 14 stuffed specimens (one is an Australian lungfish) are found to be the oldest stuffed Japanese fish specimens held in Japan. Details about specimen identifications and the specimen transfer history are clarified.

Leeches in the order Hirudinida comprise approximately 700 species that are distributed worldwide and occupy diverse habitats, including freshwater, marine, and terrestrial habitats. Leeches have traditionally been classified into two main groups, Rhynchobdellida and Arhynchobdellida, on the basis of the presence or absence of a proboscis. However, recent molecular analyses using large datasets have suggested that Rhynchobdellida is a paraphyletic group, and this has led to calls for a new classification that better reflects phylogeny. In addition, recent studies have clarified the previously unresolved phylogenetic relationships among leeches and two leech-like worms, Acanthobdellida and Branchiobdellida. Here, we discuss recent trends in the higher-level phylogenetic relationships and classification of leeches.

We examined feather mites on stuffed specimens of the South Polar Skua Stercorarius maccormicki Saunders, 1893 and the Laysan Albatross Phoebastria immutabilis (Rothschild, 1893) preserved in the National Institute of Polar Research and the Museum Park of the Ibaraki Prefectural Museum of Nature and Science, Japan, respectively. We detected the feather mite Zachvatkinia stercorarii Dubinin, 1952 from the South Polar Skua, which was first detected in Japanese Antarctic research. We also detected Z. trouessarti (Bonnet, 1924) from the Laysan Albatross, the second report of this mite species in waters around Japan.