Proc. Arthropod. Embryol. Soc. Jpn. 47, 1–4 (2012)Ⓒ 2012 Arthropodan Embryological Society of Japan
ISSN 1341–1527

OBITUARY: KOICHI SEKIGUCHI1

OBITUARY

Koichi Sekiguchi(1919–2012)
Dr. Koichi Sekiguchi, an honorary fellow of the Arthropodan Embryological Society of Japan, died of aortic dissection on
February 1st, 2012, at age 92.
He also was a Professor Emeritus of University of Tsukuba, honorary fellows of the Zoological Society of Japan, of theJapanese Society of Systematic Zoology, and of the Arachnological Society of Japan, the first honorary president of theJapanese Society of Preservation of Horseshoe Crabs, and an honorary citizen of Kazo City, Saitama, Japan.
Koichi Sekiguchi was born in Kisai Town (present Kazo City), Saitama Prefecture, on December 20th, 1919, as the firstson of three sons of Ryosaku and Take Sekiguchi. He lost his father early at his age of 10, and thereafter he and his younger
brothers were brought up all by their mother. He was educated at the Ko-guki village elementary school and the Saitamaprefectural Fudo-Oka junior high school. He went on to the Higher Teachers College of Tokyo (present University ofTsukuba) in 1938 and was admitted to the Department of Biology in Tokyo Bunrika University (present University ofTsukuba) in 1941. After receiving his Bachelorʼs degree in 1943, he was selected as a special research fellow of zoology inTokyo Bunrika University. In 1945, he was placed as Assistant of Zoology of Tokyo Bunrika University, appointed to AssistantProfessor of Zoology in 1947, and transferred to Assistant Professor of Tokyo Kyoiku University (present University ofTsukuba) in 1951.
In 1941, Koichi Sekiguchi began to study experimental embryology of spiders in the laboratory of Professor Hidemiti
Oka (1902–1982) and received his PhD from Tokyo Kyoiku University in 1957. Dr. Sekiguchi was promoted to Associate
Professor of Tokyo Kyoiku University in 1962, to Professor in 1973, and transferred to Professor of University of Tsukuba in
1974. He retired from University of Tsukuba in 1983 (Professor Emeritus in 1991). In 1983, he was invited to be Professor of
Biology in Jobu University, and was in the post until 1991.
In 1957, Dr. Sekiguchi inherited the study on experimental embryology of horseshoe crabs from Professor H. Oka.
Afterwards Dr. Sekiguchi developed this study deeply and widely through his life. He devised a method of artificial
insemination for horseshoe crab eggs. He collected paired horseshoe crabs at Oe-Hama beach, Kasaoka Bay, Okayama
Prefecture, facing the Inland Sea of Japan, artificially inseminated their eggs in his laboratory of Tokyo Kyoiku University, andobtained a large number of embryos and larvae of the same developmental stage. He used some of these embryos and larvae

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for the study, and planted the rest in their home beach at the end of every study season. In 1980, he was honoured with the
Zoological Society of Japan Award for his studies on experimental embryology of horseshoe crabs.
Dr. Sekiguchi not only accomplished his own study, but also led a number of students to research on horseshoe crabs
and arachnids. At first he used only the Japanese horseshoe crab, Tachypleus tridentatus, for his and his studentsʼ studies, butlater, used all of the four living species including T. gigas and Carcinoscorpius rotundicauda in Southeast Asia and Limulus
polyphemus in east coasts of USA. In summer seasons of 1974 and 1975, Dr. Sekiguchi stayed at the Marine Laboratory ofDuke University, USA, obtained a large number of embryos of L. polyphemus by his artificial insemination method, andbrought the embryos into his laboratory of Tokyo Kyoiku University. He and his students compared embryonic and larval
development of T. tridentatus and L. polyphemus. In 1975 to 2000, he and his students frequently surveyed distributions andbreeding conditions of three Asian horseshoe crab species in beaches of Southeast Asian Countries, and obtained fresh
female and male specimens for the intra- and interspecific insemination.
Dr. Sekiguchi edited three tomes: “Biology of Horseshoe Crabs” in Japanese (1984), an enlarged English edition of thebook (1988), and a more enlarged Japanese edition of the book (1999). In 2008, Handbuch der Zoologie (HDZ), one of the mostauthorized zoological library, entrusted Dr. Sekiguchi with writing some parts of the chapter of the horseshoe crabs for the
newly revised edition. Despite his great age, Dr. Sekiguchi took on the work with his students, and by the end of 2011, thefinal deadline, Dr. Sekiguchi and his students mostly completed their manuscripts. Unfortunately, Dr. Sekiguchi suddenly
died before the publication of the revised edition of HDZ, but his students are making efforts to publish the final work of Dr.
Sekiguchi.
In 1970s, horseshoe crabs of the Kasaoka Bay were threatened with extinction by water pollution and a massive
reclamation of beaches and mud flats, including Oe-Hama beech. In 1978, Professor Sekiguchi founded the Japanese Societyof Preservation of Horseshoe Crabs with his students, some local volunteers, and about 700 members from many parts ofJapan, and served as the first president of the Society until 2003, and then was elected as the honorary president of theSociety. He appealed for the preservation of horseshoe crabs and of the natural environment for the horseshoe crabs and forour own at every annual meeting of the Society, through every number of the annual bulletin of the Society, “Kabuto-Gani(the horseshoe crab)”, and at every other opportunity. He also collected records of living and breeding conditions of thehorseshoe crabs in coasts of the Inland Sea and of the northern Kyushu, Japan, and edited two tomes: “The Present Conditionsof Japanese Horseshoe Crabs (in Japanese)” (1989) and an enlarged edition of the book (in Japanese)(1993).
Koichi Sekiguchi lived all his life at the house where he was born. In this house, he married, and Koichi and Tatsue
Sekiguchi had two daughters and a son. He loved his family and his hometown, Kisai, Saitama Prefecture. After hisretirement, Dr. Sekiguchi forwarded the preservation of natural environment of his hometown as expert members of thecommittees in Kisai Town and Saitama Prefecture. He also taught schoolchildren the natural history of his hometown. In
2007, he was selected as an honorary citizen of Kisai Town (present Kazo City).
Koichi Sekiguchi was a kind, warm-hearted and broad-minded person, and was loved by his many friends, students andneighbors. They will remember him forever.
Toshiki Makioka
Professor retired,
University of Tsukuba
Tsukuba,Japan

OBITUARY: KOICHI SEKIGUCHI

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SELECTED LIST OF PUBLICATIONS OF KOICHI SEKIGUCHION EMBRYOLOGY AND BIOLOGY OF ARACHNIDS AND HORSESHOE CRABS
Sekiguchi, K. (1952) On a new spinning gland found in geometric spiders and its functions. Annotationes Zoologicae
Japonenses, 25, 394–399.
Sekiguchi, K. (1955a) Differences in the spinning organs between male and female adult spiders. Science Report of Tokyo
Kyoiku Daigaku, Section B, 8, 23–32.
Sekiguchi, K. (1955b) The spinning organs in sub-adult geometric spiders and their changes accompanying the last moulting.
Science Report of Tokyo Kyoiku Daigaku, Section B, 8, 34–40.
Sekiguchi, K. (1957) Reduplication in spider eggs produced by centrifugation. Science Report of Tokyo Kyoiku Daigaku, Section
B, 8, 187–280.
Sekiguchi, K. (1960) Embryonic development of the horseshoe crab studied by vital staining. The bulletin of the Marine
Biological Station of Asamushi, Tôhoku University, 10, 161–164.
Sekiguchi, K. (1966) Determination in the development of the horseshoe crab. Japanese Journal of Experimental Morphology,
20, 84–89.
Sekiguchi, K. (1970) On the embryonic moultings of the Japanese horseshoe crab, Tachypleus tridentatus. Science Report ofTokyo Kyoiku Daigaku, Section B, 14, 34–40.
Sekiguchi, K. (1973) A normal plate of the development of the Japanese horseshoe crab, Tachypleus tridentatus. Science
Report of Tokyo Kyoiku Daigaku, Section B, 15, 153–162.
Yamamichi, Y. and K. Sekiguchi (1974) Embryo and organ cultures of the horseshoe crab, Tachypleus tridentatus. Development,
Growth & Differentiation, 16, 295–304.
Sugita, H. and K. Sekiguchi (1975) Heterogeneity of minimum functional unit of hemocyanins from the spider (Argiope
bruennichii), the scorpion (Heterometrus sp.), and the horseshoe crab (Tachypleus tridentatus). Journal of Biochemistry,78, 713–718.
Nakamura, K., T. K. Sen, H. Sugita and K. Sekiguchi (1976) Morphological variation and distribution of a horseshoe crab,
Tachypleus gigas, from the Bay of Bengal and the Gulf of Siam. Proceedings of the Japanese Society of Systematic Zoology,(12), 13–20.
Sekiguchi, K., S. Nishiwaki, T. Makioka, S. Srithunya, S. Machjajib, K. Nakamura and T. Yamasaki (1977) A study on the egglaying habits of the horseshoe crabs, Tachypleus gigas and Carcinoscorpius rotundicauda, in Chonburi area, Thailand.
Proceedings of the Japanese Society of Systematic Zoology, (13), 39–45.
Shishikura, F. and K. Sekuguchi (1977) Two types of hemocytes in localization of clottable protein in Japanese horseshoe
crab, Tachypleus tridentatus. Journal of Experimental Zoology, 201, 303–308.
Shishikura, F. and K. Sekuguchi (1978) Comparative study on horseshoe crab coagulogen. Journal of Experimental Zoology,
206, 241–246.
Sekiguchi, K., K. Nakamura, and H. Seshimo (1978) Morphological variation of a horseshoe crab, Carcinoscorpius
rotundicauda, from the Bay of Bengal and the Gulf of Siam. Proceedings of the Japanese Society of Systematic Zoology, (15),24–30.
Sugita, H. and K. Sekiguchi (1979) Protein components in the perivitelline fluid of the embryo of the horseshoe crab,
Tachypleus tridentatus. Developmental Biology, 73, 183–192.
Itow, T. and K. Sekiguchi (1979) Induction of multiple embryos with NaHCO3 or calcium free sea water in the horseshoe crab.
Wilhelm Roux’s Archives of Developmental Biology, 187, 245–254.
Itow, T. and K. Sekiguchi (1980) Morphogenetic movement and experimentally induced decrease in number of embryonicsegments in the Japanese horseshoe crab, Tachypleus tridentatus. Biological Bulletin, 153, 324–338.
Sekiguchi, K. and H. Sugita (1980) Systematics and hybridization in the four living species of horseshoe crabs. Evolution, 34,
712–718.
Sugita, H. and K. Sekiguchi (1980) Amino acid composition of hemocyanin monomers from the horseshoe crab, Tachypleus
tridentatus. Experientia, 36, 1027–1028.
Sugita, H. and K. Sekiguchi (1981) Swelling mechanism of the embryo of the Japanese horseshoe crab, Tachypleus tridentatus.
Zoological Magazine, 90, 271–282.
Sugita, H. and K. Sekiguchi (1981) Immunological comparison among hemocyanin monomers from the four species ofhorseshoe crabs, Tachypleus tridentatus, T. gigas, Carcinoscorpius rotundicauda, and Limulus polyphemus. In Lamy J. and
J. Lamy (eds.), Invertebrate Oxygen-binding Proteins, pp. 247–255. Marcel Dekker Inc., NY & Basel.
Shishikura, F., S. Nakamura, T. Takahashi, and K. Sekiguchi (1982) Horseshoe crab phylogeny based on amino acid sequenceof the fibrinopeptide-like peptide C. Journal of Experimental Zoology, 223, 89–91.
Sekiguchi, K., Y. Yamamichi, and J. D. Costlow (1982) Horseshoe crab developmental studies I. Normal embryonicdevelopment of Limulus polyphemus compared with Tachypleus tridentatus. In Bonaventura, J., C. Bonaventura and S.
Tesh (eds.), Physiology and Biology of Horseshoe crabs, pp. 53–73. Alan R. Liss Inc., NY.
Sugita, H. and K. Sekiguchi (1982) Horseshoe crab developmental studies II. Physiological adaptation of horseshoe crab
embryos to the environment during embryonic development. In Bonaventura, J., C. Bonaventura and S. Tesh (eds.),
Physiology and Biology of Horseshoe crabs, pp. 75–82. Alan R. Liss Inc., NY.
Shishikura, F., S. Nakamura, T. Takahashi and K. Sekiguchi (1983) Coagulogens from the four living species of horseshoe

4T. MAKIOKA

crabs (Limulidae): Comparison of their biochemical and immunochemical properties. Journal of Biochemistry, 94, 1279–
1287.
Sugita, H. and K. Sekiguchi (1983) The developmental appearance of paternal form of lactate dehydrogenase and malate
dehydrogenase in hybrid horseshoe crabs. Biological Bulletin, 165, 436–443.
Yamamichi, Y., H. Sugita and K. Sekiguchi (1983) Morphological characterization of first instar larvae of Asian horseshoe
crabs and their hybrids. Development Growth & Differentiation, 25, 271–280.
Itow, T. and K. Sekiguchi (1984) Acid mucopolysaccharide in embryos of the horseshoe crab, Tachypleus tridentatus(Chelicerata, Arthropoda). Zoological Science, 1, 463–470.
Sugita, H. and K. Sekiguchi (1984) Lactate dehydrogenase of the horseshoe crabs and their hybrids. Zoological Science, 1,
421–426.
Miyazaki, J., K. Sekiguchi and T. Hirabayashi (1986) Tissue specificity of tropomyosin from a horseshoe crab, Tachypleus
tridentatus. Comparative Biochemistry and Physiology, 3, 679–685.
Itow, T. and K. Sekiguchi (1987) Formation of nervous system and alimentary canal in normal and separate embryos ofhorseshoe crab, Tachypleus tridentatus. Proceedings of Arthropodan Embryological Society of Japan, (23), 17–20.
Miyazaki, J., K. Sekiguchi and T. Hirabayashi (1987) Application of an improved method of two-dimensional electrophoresis
to the systematic study of horseshoe crabs. Biological Bulletin, 172, 212–224.
Sekiguchi, K. (ed.) (1988) Biology of Horseshoe Crabs. Science House, Tokyo.
Sekiguchi, K. (1988) History of the study. In Sekiguchi, K. (ed.) Biology of Horseshoe Crabs, pp. 1–9. Science House, Tokyo.
Sekiguchi, K. (1988) Biogeography. In Sekiguchi, K. (ed.) Biology of Horseshoe Crabs, pp. 22–49. Science House, Tokyo.
Sekiguchi, K. (1988) Ecology. In Sekiguchi, K. (ed.) Biology of Horseshoe Crabs, pp. 50–68. Science House, Tokyo.
Sekiguchi, K., Y. Yamamichi, H. Seshimo and H. Sugita (1988) Normal development. In Sekiguchi, K. (ed.) Biology ofHorseshoe Crabs, pp. 133–195. Science House, Tokyo.
Sekiguchi, K. (1988) Experimental embryology, I. Effects of electro-cauterization. In Sekiguchi, K. (ed.) Biology of Horseshoe
Crabs, pp. 225–242. Science House, Tokyo.
Sekiguchi, K. and Y. Yamamichi (1988) Experimental embryology, III. Embryo and organ culture. In Sekiguchi, K. (ed.)
Biology of Horseshoe Crabs, pp. 225–242. Science House, Tokyo.
Sekiguchi, K. and Y. Yamamichi (1988) Experimental hybridization, II. External morphology of normal and hybrid larvae. In
Sekiguchi, K. (ed.) Biology of Horseshoe Crabs, pp. 302–308. Science House, Tokyo.
Iwasaki, Y., T. Iwami and K. Sekiguchi (1988) Karyology. In Sekiguchi, K. (ed.) Biology of Horseshoe Crabs, pp. 309–314.
Science House, Tokyo.
Sugawara, K., H. Yonekawa, Y. Tagashira and K. Sekiguchi (1988) Biochemistry, IV. Mitochondrial DNA polymorphisms. In
Sekiguchi, K. (ed.) Biology of Horseshoe Crabs, pp. 375–382. Science House, Tokyo.
Miyazaki, J., K. Sekiguchi and T. Hirabayashi (1988) Biochemistry, VI. Protein constitution of hearts. In Sekiguchi, K. (ed.)
Biology of Horseshoe Crabs, pp. 396–407. Science House, Tokyo.
Sekiguchi, K. (1988) General discussion, I. Evolution of horseshoe crabs. In Sekiguchi, K. (ed.) Biology of Horseshoe Crabs,
pp. 408–410. Science House, Tokyo.
Sekiguchi, K. (1988) General discussion, II. Distribution pattern of horseshoe crabs. In Sekiguchi, K. (ed.) Biology ofHorseshoe Crabs, pp. 410–414. Science House, Tokyo.
Sekiguchi, K. (1988) General discussion, III. Phylogeny of horseshoe crabs. In Sekiguchi, K. (ed.) Biology of Horseshoe Crabs,
pp. 414–419. Science House, Tokyo.
Ishijima, S., Y. Hiramoto and K. Sekiguchi (1988) Comparative study of the beat patterns of American and Asian horseshoe
crab sperm: Evidence for a role of the central pair complex in forming planer waveforms in flagella. Cell Motility and theCytoskeleton, (9), 264–270.
Kawakatsu, M., I. Oki, S. Tamura and K. Sekiguchi (1988) Karyological and taxonomic studies of ectoparasitic marine triclads
collected from the four extant species of horseshoe crabs. Fortschritte der Zoologie, 36, 117–121.
Seshimo, H., H. Sugita and K. Sekiguchi (1988) Post-embryonic development of the horseshoe crab. Biological Bulletin, 174,
337–345.
Kawakatsu, M., K. Sekiguchi, K. Miyazaki and T. Makioka (1989) The egg-capsules of ectoparasitic marine triclads collectedfrom the four extant species of horseshoe crabs. Bulletin of the Department of Management and Information Science, Jôbu
University, 1, 15–29.
Miyazaki, J., K. Sekiguchi and T. Hirabayashi (1989) Comparative study of horseshoe crab tropomyosin. Comparative
Biochemistry and Physiology, 93B, 681–687.
Kawakatsu, M. and K. Sekiguchi (1989) Redescription of an ectoparasitic marine triclad Bdelloura candida (Girard, 1850)(Turberallia, Tricladida, Maricola) collected from the American horseshoe crab, Limulus polyphemus. Bulletin of the
Biogeographical Society of Japan, 44, 183–198.
Itow, T., T. Masuda and K. Sekiguchi (1990) Formation of ganglions and stomodaeum in normal and separate embryos ofhorseshoe crab, Tachypleus tridentatus. Zoological Science, 7, 287–295.
Sekiguchi, K. (1994) Adaptive strategies and speciation in the horseshoe crabs. Kaseki (Fossils), 56, 47–50. (in Japanese).
Botton, M. L., C. N. Shuster Jr., K. Sekiguchi and H. Sugita (1996) Amplexsus and mating behavior in the Japanese horseshoe
crab, Tachypleus tridentatus. Zoological Science, 13, 151–159.