Susumu Ohtsuka

Last Updated :2024/11/05

Affiliations, Positions
., Professor
E-mail
ohtsukahiroshima-u.ac.jp

Basic Information

Academic Degrees

  • Doctor of Agriculture, The University of Tokyo
  • Master of Science, Kyoto University

Educational Activity

  • [Bachelor Degree Program] School of Applied Biological Science : Department of Applied Biological Science : Integrative Hydrospheric Science Program
  • [Master's Program] Graduate School of Integrated Sciences for Life : Division of Integrated Sciences for Life : Program of Bioresource Science
  • [Doctoral Program] Graduate School of Integrated Sciences for Life : Division of Integrated Sciences for Life : Program of Bioresource Science

Research Fields

  • Agricultural sciences;Applied aquatic science;Aquatic life science

Research Keywords

  • Taxonomy
  • Ecology
  • invertebrate
  • Symbiosis
  • Phylogeny
  • fish
  • Mysids
  • Copepods
  • parasite
  • Jellyfish

Affiliated Academic Societies

Educational Activity

Course in Charge

  1. 2024, Liberal Arts Education Program1, 2Term, Introduction to Field Sciences
  2. 2024, Undergraduate Education, 3Term, Seminar in Field Science
  3. 2024, Undergraduate Education, 4Term, Introduction to Hydrospheric Biodiversity
  4. 2024, Undergraduate Education, Intensive, Practical Work in Hydrospheric Field ScienceII
  5. 2024, Undergraduate Education, Second Semester, Graduation Thesis I
  6. 2024, Undergraduate Education, First Semester, Graduation Thesis II
  7. 2024, Undergraduate Education, Second Semester, Graduation Thesis III
  8. 2024, Undergraduate Education, Intensive, Seminar in Fildwork on Community Coasts
  9. 2024, Undergraduate Education, Intensive, Practice on economic marine invertebrates and seaweeds in the Seto Inland Sea
  10. 2024, Undergraduate Education, Intensive, Practice and Field Work in Fisheries Science
  11. 2024, Undergraduate Education, Year, Special Practice I
  12. 2024, Undergraduate Education, Year, Practical Course in Marine Bioscience and Technology IV
  13. 2024, Undergraduate Education, Year, Practice on East China Sea Study
  14. 2024, Undergraduate Education, Year, Practical Course on Fisheries Science and the Marine Environment I-B
  15. 2024, Undergraduate Education, Year, Practice Course on Fisheries Science and the Marine Environment III
  16. 2024, Undergraduate Education, Year, Practical Course in Marine Bioscience and Technology I
  17. 2024, Undergraduate Education, Year, Practical Course in Marine Bioscience and Technology II
  18. 2024, Undergraduate Education, Intensive, Practice Course on Fisheries Science Data Analysis I
  19. 2024, Undergraduate Education, Intensive, Practice Course on Fisheries Science Data Analysis II
  20. 2024, Undergraduate Education, Second Semester, Practice on Primary Production (Plankton and Benthos) in the Marine Ecosystem
  21. 2024, Graduate Education (Master's Program) , 1Term, Exercises in Bioresource Science A
  22. 2024, Graduate Education (Master's Program) , 2Term, Exercises in Bioresource Science A
  23. 2024, Graduate Education (Master's Program) , 3Term, Exercises in Bioresource ScienceB
  24. 2024, Graduate Education (Master's Program) , 4Term, Exercises in Bioresource ScienceB
  25. 2024, Graduate Education (Master's Program) , Academic Year, Research for Academic Degree Dissertation in Bioresource Science
  26. 2024, Graduate Education (Master's Program) , 2Term, Fisheries Oceanography I
  27. 2024, Graduate Education (Master's Program) , 4Term, Fisheries Oceanography II

Research Activities

Academic Papers

  1. Habitat shift of adult Caligus undulatus (Copepoda: Siphonostomatoida: Caligidae) from host fish to plankton in response to host behavior, DISEASES OF AQUATIC ORGANISMS, 157, 81-94, 20240314
    Link to Paper Search Results by DOI
  2. First record of Caligus dussumieri Rangnekar, 1957 (Copepoda, Siphonostomatoida, Caligidae) from Malaysia, with notes on caligids found from Malaysia and on host-specificity of caligids on lutjanid fishes, BIODIVERSITY DATA JOURNAL, 12, 20240220
    Link to Paper Search Results by DOI
  3. A new genus and species of oceanic planktonic Tisbidae (Crustacea, Copepoda, Harpacticoida) with enlarged modified eyes, ZOOKEYS, 307-338, 20240215
    Link to Paper Search Results by DOI
  4. Isolation and characterization of bacteria from the gut of a mesopelagic copepod Cephalophanes reflugens (Copepoda: Calanoida), JOURNAL OF PLANKTON RESEARCH, 46(1), 48-58, 20240120
    Link to Paper Search Results by DOI
  5. Morphological Description and Molecular Characterisation of Glyptothoa gen. nov., a Fish Parasitic Deep-sea Cymothoid (Crustacea: Isopoda) from the Indian Ocean, with Four Species, Including One New Species, ZOOLOGICAL STUDIES, 62, 20231026
    Link to Paper Search Results by DOI
  6. Redescription and molecular characterization of Mothocya parvostis Bruce, 1986 (Crustacea: Isopoda: Cymothoidae) parasitic on Japanese halfbeak, Hyporhamphus sajori (Temminck & Schlegel, 1846) (Hemiramphidae) with Mothocya sajori Bruce, 1986 placed into synonymy, ZOOTAXA, 5277(2), 259-286, 20230502
    Link to Paper Search Results by DOI
  7. Are We Ready to Get Rid of the Terms "Chalimus" and "Preadult" in the Caligid (Crustacea: Copepoda: Caligidae) Life Cycle Nomenclature?, PATHOGENS, 12(3), 202303
    Link to Paper Search Results by DOI

Publications such as books

  1. 2016, Diversity and Commonality in Animals Species Diversity of Animals in Japan, Recent advances in our understanding of the biodiversity of copepods in Japanese waters are briefly reviewed. It is noteworthy that the two new species of Platycopioida found in Japan are the first record of this order from the Indo-Pacific. Taxonomic revisions of calanoids in Japanese waters have continued based on both morphological and molecular data. Molecular analyses have revealed the presence of cryptic/sibling species in a common species and of intraspecific variations. Complete mitochondrial DNA sequences from copepods have been analyzed for Tigriopus japonicus, which suggest that copepods are genetically ‘eccentric.’ Molecular tools have helped to clarify the phylogenetic relationships of highly modified symbiotic copepods. Population dynamics, life cycles, and distributions of planktonic copepods have been thoroughly investigated in coastal and oceanic waters. These studies highlighted the influence of the Oyashio/Kuroshio currents on the coast, the high mortality of eggs from predation, adaptive responses to phytoplankton blooms, and niche partitioning by habitat and food. Deep-sea calanoids are highly diverse and specialized for detritivory and carnivory. East Asian planktonic copepods have been introduced to America and Europe via ballast water, although Japan not yet received any alien planktonic copepods. In contrast, parasitic copepods have been introduced to Japan via aquaculture. The life cycle of commercially important sea lice was clarified. Because copepods are one of the most abundant metazoans on Earth, more biological but also biomimetic information should be accumulated., Copepod Biodiversity in Japan: Recent advances in Japanese Copepodology, Alien • Copepod • Indo-West Pacific • Partition • Relict •Zoogeography, Springer, 2016, December, Scholarly Book, Joint work, E, Susumu Otsuka, Shuhei Nishida, 721
  2. 2015/10/08, Marine Protists Diversity and Dynamics, marine protists, Springer, 2015, 10, Scholarly Book, Cocompilation, E, Ohtsuka S, Suzaki T, Horiguchi T, Suzuki N, Not F (eds), 978-4-431-55129-4, 648
    Amazon URL
  3. 1999, Xth JSPS/VCC joint seminar on marine and fisheries sciences, Malacca, Malaysia (Taxonomy and feeding ecology of demersal calanoid copepods collected from Thailand, JSPS/VCC, 1999, Joint work

Invited Lecture, Oral Presentation, Poster Presentation

  1. An account on all copepodid stages of Paramacrochiron tridentatum Ohtsuka, Ha & Thu 2020 (Copepoda: Cyclopoida: Macrochironidae) associated with the rhizostome jellyfish Versurigaana dyoneme with notes on its affinity to the lichomolgoid complex, Yusuke Kondo, Sota Komeda, Susumu Ohtsuka, Panakkool Thamban Aneesh, Tran Manh Ha, Pham The Thu, Sho Toshino, Akane Iida & Jun Nishikawa, Tran Manh Ha, Pham The Thu, Sho Toshino, Akane Iida & Jun Nishikawa, e-International Conference on Copepoda, 2022/07/29, Without Invitation, English, World Association of Copepodologists, Online, The cyclopoid family Macrochironidae has been known to be associated with a variety of invertebrates such as cnidarians, echinoderms and tunicates. The species of the macrochironid genus Paramacrochiron is known to prefer jellyfish, as its host and it has been frequently collected from plankton samples. The genus globally includes 10 species described from the coastal areas of Japan, Southeast Asia, Australia, and India. In the present study, we are describing all the all post-naupliar stages of Paramacrochiron tridentatum Ohtsuka, Ha & Thu, 2020, a species recently described from the rhizostome jellyfish Versurigaana dyoneme obtained from Vietnam. The post-naupliar stages of P. tridentatum were collected from the same host and consisted of six copepodid stages as other copepods generally have. Interestingly, the present study appears to be the first detailed information on all the six copepodid stages of the family Macrochironidae. Further the information on sexual dimorphism and relationships between the Macrochironidae and lichomolgoid complex is also discussed. Sexual dimorphism first appeared in the maxillipeds of copepodid IV. The setation on the antennulary proximal segments and an element on the mandible in copepodid I of P. tridentatum imply close relationships between the Macrochironidae and Rhynchomolgidae.
  2. Seasonal fluctuations in the occurrence of two species of sea lice (Crustacea: Copepoda: Caligidae), Caligus sclerotinosus, and Lepeophtheirus sekii on wild red seabream Pagrus major in the Seto Inland Sea, Japan, Yusuke Nishida, Susumu Ohtsuka, Yusuke Kondo, Sadaharu Iwasaki, e-International Conference on Copepoda, 2022/07/29, Without Invitation, English, World Association of Copepodologists, Online, The parasitic copepods of the family Caligidae, commonly the sea lice, are known to infest many farmed fishes and may cause serious economic losses. In the present study, we discuss the seasonal occurrence of two caligid species on red sea bream Pagrus major collected from the Seto Inland Sea, Japan. The species, Caligus sclerotinosus Roubal, Armitage & Rhode, 1983 was originally described from silver sea bream Pagrus auratus, a fish native to Oceania. In Japan, C. sclerotinosus was first recorded from P. major cultured in Oita Prefecture, in 1999. This species is believed to have been introduced from Oceania to Japan through the international trade of P. auratus. Previous reports showed that heavy infestations of C. sclerotinosus were seen in farmed P. major in Japan and Korea. However, C. sclerotinosus had never been found in wild individuals of P. major. In the present study, we examined 284 wild individuals of P. major collected from the Seto Inland Sea from March 2020 to May 2021. Interestingly, we confirmed the presence of C. sclerotinosus in wild individuals of P. major in the sea for the first time. The prevalence and mean intensity of the species on wild P. major were 41.2% and 2.64 ± 2.3, respectively (highest record: 82.4% in September 2020 and 6.67 ± 3.21 in August 2020). Our results indicate that C. sclerotinosus has already spread over wild P. major entirely in the sea. Apart from C. sclerotinosus, we recovered another caligid Lepeophtheirus sekii Yamaguti, 1936 from the body surface of wild P. major. Prevalence and mean intensity of L. sekii were 43.3% and 2.57 ± 2.1, respectively (highest record: 78.4% in May 2021 and 4.25 ± 4.57 in May 2020). It seems that these two sea lice clearly exhibited seasonal segregation on the same host.
  3. Exploring evolutionary trends within the Pennellidae (Copepoda: Siphonostomatoida) using molecular data., Nanami Yumura, Kenta Adachi, Masato Nitta, Yusuke Kondo, Sota Komeda, Kaori Wakabayashi, Jun Fukuchi, Geoffrey A. Boxshall & Susumu Ohtsuka, Jun Fukuchi & Geoffrey A. Boxshall, e-International Conference on Copepoda, Without Invitation, English, World Association of Copepodologists, Online, Some species of the family Pennellidae have a profound impact on their fish hosts. This family consists of ecto or mesoparasitic copepods that parasitize marine fish. Since members of the family have highly modified bodies and reduced appendages, it is difficult to deduce their exact phylogenetic relationships. The present study aimed to reveal molecular phylogenetic relationships among 8 genera and 13 species of pennellids using 18S and 28S ribosomal DNA sequences. According to our analysis, three clades were generated (Clade-I, Peniculus-Peniculisa; Clade-II, Haemobaphes-Lernaeocera-Phrixocephalus-Exopenna-Lernaeenicus radiatus; Clade-III, Pennella-Lernaeenicus spp.), which were supported by high bootstrap values (> 82%) in Maximum likelihood and posterior probabilities (=1.00) in Bayesian inference. This result supports the morphology-based phylogenetic relationships previously proposed by Boxshall (1986) but did not support a sister group comprising Exopenna, Phrixocephalus, and Pennella. The first offshoot, Peniculus and Peniculisa, is defined as a fin-ectoparasite branch with members exhibiting clear tagmosis. The second and third branches to diverge are characterized by modifications of the anterior and posterior body tagmata to play roles in nutrient absorption/attachment and reproduction, respectively. Most of the species classified within Clade-II are gill parasites that have coiled egg strings that could have evolved in adaptation to the confined spaces within the gill cavities of the host. Phrixocephalus is an eye parasite in Clade-II, which also has coiled egg strings and may have descended from ancestral gill mesoparasites. All species of Clade-III are distinctly characterized by a head region that serves as the anchor, with processes that embed deeply in the host tissues.
  4. New discoveries on the development, life cycle and attachment mechanism of Caligus, Susumu Ohtsuka, Yusuke Nishida, Yusuke Kondo, Danny Tang & Geoffrey A. Boxshall, Danny Tang & Geoffrey A. Boxshall, e-International Conference on Copepoda, 2022/07/26, With Invitation, Japanese, World Association of Copepodologists, Online, The siphonostome genus Caligus Müller, 1785 has been studied intensively, in part because some species cause economic losses of commercially important farmed fishes. Basic data on the biology of caligids are essential to marine aquaculture. In this presentation, we briefly review our new findings concerning the development, life cycle, and attachment mechanism of Caligus occurring in Japan. We have elucidated the development and life cycle of two species: “planktonic” C. undulatus and non-indigenous C. sclerotinosus. The latter is considered to have been introduced from Oceania to Japan. Both species have the same number of developmental stages as in previously known congeners, i.e., 2 naupliar, 1 copepodid, 4 chalimus and the adult stages. We found that all post-naupliar stages of C. undulatus parasitize two species of brackish-water fishes, Sardinella zunasi and Konosirus punctatus. Detachment of the adult from its host to become a member of the plankton community may serve to prevent the release of free swimming naupliar stages in the lowest salinity zones where they would be vulnerable to freshwater. The pelagic mode of life has been independently adopted by members of different species groups within Caligus. Although the involvement of intermediate hosts for C. sclerotinosus has been suggested based on the highly skewed composition of developmental stages (towards the adults) on red sea bream Pagrus major, all post-naupliar stages were found to infect this host in the present study. The reported bias is likely a result of one or a combination of the following factors: (1) the rapid growth rates of chalimi, (2) the longevity of adults, and (3) the limited breeding season. Our discovery of C. sclerotinosus on wild hosts from the Seto Inland Sea, Japan sheds light on the rapid dispersal of this non-indigenous caligid after its introduction. We also report on an undescribed species of Caligus which was found to parasitize the small-sized, anadromous ice goby Leucopsarion petersii (which has only a 1-year life span). Attachment of caligids to host fishes by the main cephalothoracic sucker, assisted by the lunules in Caligus, is critical to their parasitic life. We have found considerable variation in internal cuticular structures (the endocuticle in particular), in different parts of the body of Caligus. The conversion of water flow resulting from simple antero-posterior motions of leg 2 into a mechanism for generating suction involves these highly modified cuticular structures. The endocuticular structure of the lunule of Caligus was unique and is key to our postulated actuating mechanism for the generation and release of suction. The morphological consistency of suckers and lunules across Caligus taxa implies a highly conserved attachment behavior that is effective on mucus-rich surfaces of a wide variety of fishes. In contrast, flexibility for attachment was also observed on the undescribed species of Caligus parasitic on the small ice goby.
  5. Carnivory and detritivory in oceanic calanoid copepods: functional morphological approaches, Susumu Ohtsuka, Sota Komeda & Tomonari Kaji, Tomonari Kaji, e-International Conference on Copepoda, 2022/07/25, With Invitation, English, World Association of Copepodologists, Online, Highly speciose planktonic calanoid copepods in marine ecosystems play pivotal roles in food webs. Based on their feeding habits, they are typically classified as particle feeders, carnivores, and detritivores. The latter two are the predominant groups in oligotrophic oceanic waters. In carnivores, highly specialized structures are found in the antennules and mouthparts. The main function of the maxillae and maxillipeds is grasping prey. Either or rarely both of these appendages are elongated for capture of prey in comparison with those of particle feeders. In some taxa, such as Euchaetidae, the maxillules are also involved in grasping prey. An extraordinary example is shown by four genera of the oceanic family Heterorhabdidae (Heterorhabdus, Paraheterorhabdus, Hemirhabdus, and Neorhabdus), which utilize “venom (or anesthetic)” like viper. In this study, we briefly explain how this venomous system works. “Venom” is produced in the labral glands and injected into prey via the fang-like ventralmost teeth of the mandible in harmony with muscle activity. A molecular phylogenetic analysis of this family revealed that evolution from a primitive particle-feeding genus to these advanced carnivorous genera may correspond to speciation of related families. Detritivorous calanoids are also dominant in the ocean, particularly in deep seas, some of which are sometimes called Bradfordian families. They have highly unique chemosensory and/or optical sensors to detect specific detrital matter. Chemosensory organs were located on the maxillary endopods and are much more complex than previously known. In addition to hundreds of sensory cilia reported by previous studies, cells similar to solitary chemosensory cells (SCCs) and free nerve endings were newly discovered in the chemosensory setae of Scolecitrichidae. These possible sensory cells have not been observed in any arthropod aesthetascs and are similar to vertebrate ones. In vertebrates, cilia and SCCs are known as highly-sensitive and persistent chemosensors, respectively. The combination of various sensory cells may enable multifunctional chemosensory organs. Contrary to Scolecitrichidae mentioned above, Phaennidae had developed cilia to compensate for the absence of SCC-like cells. In addition to these chemosensors, Bradfordian families sometimes had optical sensors with semi-parabolic reflectors or cuticular lenses. Comparative morphology found that chemosensory setae were developed in genera without optical sensors. These genera may have fed on odorous foods because they had various bacteria producing acyl-homoserine lactone in their gut. In contrast, genera with optical sensors had a higher frequency of bioluminescent taxa in their enteric bacterial flora. Bradfordian families may use chemical and/or optical bacterial signals from detrital foods, and seem to have sensory organs adapted to various feeding niches in oligotrophic environments.
  6. Global spread of aquatic parasites via aquaculture, aquarium and game fishing, Susumu Ohtsuka, International Forum on Post COVID Fisheries and Aquaculture Update in Japan, Indonesia and Malaysia, 2021/11/16, With Invitation, Japanese, University Sultan Zainal Abidin, Malaysia, online
  7. Taxonomic review of the copepod family Chondracanthidae Milne Edwards, 1840 (Copepoda, Poecilostomatoida) parasitizing the marine fishes from Indian waters, Ameri Kottarathil Helna1, Panakkool Thamban Aneesh, Appukuttannair Bijukumar, Balu Alagar Venmathi Maran, Susumu Ohtsuka, Ameri Kottarathil Helna1, Panakkool Thamban Aneesh, Appukuttannair Bijukumar, Balu Alagar Venmathi Maran, virtual International Conference on Marine Sciences & Aquaculture, 2022/03/10, Without Invitation, English, University of Malaysia Sabah, Malaysia (online)
  8. Tropical fish parasitic crustaceans: parasitic adaptations and emerging paradigms in research, Panakkool Thamban Aneesh, Ameri Kottarathil Helna, Appukuttannair Bijukumar, Balu Alagar Venmathi Maran, Susumu Ohtsuka, Panakkool Thamban Aneesh, Ameri Kottarathil Helna, Appukuttannair Bijukumar, Balu Alagar Venmathi Maran, virtual International Conference on Marine Sciences & Aquaculture, 2022/03/10, Without Invitation, English, University of Malaysia Sabah, Malaysia (online)
  9. Parasitism of the non-indigenous sea louse Caligus sclerotinosus among wild and farmed Red Sea bream Pagers major in the Seto Inland Sea, Japan, Yusuke Nishida, Susumu Ohtsuka, Ione Madinabeitia, Yusuke Kondo, Kenta Adachi, Hirofumi Yamashita, Sadaharu Iwasaki, Sho Shirakashi, Kazuo Ogawa, virtual International Conference on Marine Sciences and Aquaculture, 2022/03/10, Without Invitation, English, University of Malaysia Sabah, Malaysia (online)
  10. Seasonal occurrence of ctenophores and their parasites in the Seto Inland Sea, Japan E, Yusuke Kondom Dong Hang Li, Susumu Ohtsuka, virtual International Conference on Marine Sciences & Aquaculture, 2022/03/10, Without Invitation, English, University of Malaysia Sabah, Malaysia (online)
  11. Global spread of aquatic parasites via aquaculture, aquarium and game Fishing, Susumu Ohtsuka, virtual International Conference on Marine Sciences & Aquaculture, 2022/03/10, With Invitation, English, University of Malaysia Sabah, Malaysia(online)
  12. Hosts and seasonal occurrence of the planktonic sea-louse Caligus undulates in Japanese waters, Masaki Nawata, Susumu Ohtsuka, Yusuke Kondo, Yusuke Nishida, virtual International Conference on Marine Sciences & Aquaculture, 2022/03/09, Without Invitation, English, University of Malaysia Sabah, Malaysia (online)
  13. What could have happened to the evolution of the highly modified fish parasite Pennellidae: implication of evolutionary trends based on molecular analysis, Nanami Yumura, Kenta Adachi, Masato Nitta, Yusuke Kondo, Sota Komeda, Kaori Wakabayashi, Jun Fukuchi, Geoffrey A. Boxshall, Susumu Ohtsuka, Geoffrey A. Boxshall, virtual International Conference on Marine Sciences and Aquaculture, Without Invitation, English, University of Malaysia Sabah, Malaysia (online)
  14. Impact of jellyfish fisheries on their symbionts, Ohtsuka, Susumu, International Workshop on Emergent Issues of Marine Ecosystems in the Southeast Asia: For Sustainable Use of Marine Ecosystem Services, 2019/09/06, With Invitation, English, Atomsphere and Ocean Research Institute, University of Tokyo, Kashiwa City, Chiba
  15. Impact of jellyfish fisheries on their symbionts, Susumu Ohtsuka, Lecture for students of Universiti Sultan Sainan Abidin, Malaysia, 2018/11/01, With Invitation, English, Universiti Sultan Sainan Abidin, Terengganu, Malaysia
  16. Planktonic phases of symbiotic copepods, with a special reference to Caligidae, Susumu Ohtsuka, International Conference on Agriculture, Animal Sciences, and Food Technology, 2018/10/30, With Invitation, English, Universiti Sultan Zainal Abidin, Terengganu, Malaysia
  17. Symbionts of jellyfish occurred in Thailand, Ohtsuka S, Y. Kondo, International workshop on classification and culture of jellyfish in Thailand, 2018/09/02, With Invitation, English, Burapha University and Department of Marine and Coastal Resources, Thailand, Bangsean, Trat
  18. Population structure of the "hitch-hike" ophiuroid, Ophiocnemis marmorata, associated with jellyfish, Hiruta, SF, Y. Kondo, J Nishikawa, Fed Yusoff, EB Metillo, H Pagliawan, K Srinui, S Ohtsuka, T. Fujita, 16th International Echinoderm Conference, 2018/05/28, Without Invitation, English, Nagoya University, Nagoya City
  19. Morphometric study on feeding appendages of pelagic calanoid copepods: relationship with feeding mode, habitat depths and stable isotopes, S. Sota,H. Tamura,Y. Abe, M.N. Aita,F. Hyodo,S. Ohtsuka,R.R. Hopcroft,A. Yamaguchi, A. Yamaguchi, 33th International symposium on the Okhotsk Sea and Polar Oceans, 2018/02/21, Without Invitation, Japanese
  20. Symbiotic biology and fisheries of jellyfish in southeastern Asia, Susumu Otsuka, 2nd International symposium on marine and fisheries research, 2017/07/24, With Invitation, English, Universities Gadjah Mada, Youyakarta
  21. Trophic interactions between bacteria and Bradfordian families, Katsushi Hirano, Susumu Otsuka, Kentaro Takada, Hideo Fukushima, Kentaro Takada, Hideo Fukushima, 13th International Conference on Copepoda, 2017/07/20, Without Invitation, English, World Association of Copepodologists, California, USA
  22. Morphometric study on the feeding appendages of planktonic calanoid copepods: relationships with feeding modes, habitat depth ,and stable isotopes, Sota Komeda, Hiroaki Tamura, Yoshiyuki Abe, Maki Noguchi Aita, Fujio Hyodo, Susumu Otsuka, Russel R. Hopcroft, Atsugi Yamaguchi, Atsugi Yamaguchi, 13th International Conference on Copepoda, 2017/07/20, Without Invitation, English, World Association of Copepodologists, California, USA
  23. Ecological studies on Panaietis yamaguchi that infect the buccal cavity of horned turbo, Turbo cornets, Hayato Uchiumi, Yusuke Kondo, Susumu Otsuka, 2017/07/19, Without Invitation, English, World Association of Copepodologists, California, USA
  24. Functional morphology of the cephalothoracic sucker of Callous, Taiki Fuji, Susumu Otsuka, Yusuke Kondo, Tomonori Kaji, Satoshi Yasumi, Tomonori Kaji, Satoshi Yasumi, 13th International Conference on Copepoda, 2017/07/19, Without Invitation, English, World Association of Copepodologists, California, USA
  25. Planktonic phases of symbiotic copepods, Susumu Otsuka, 13th International Confernce on Copepoda, 2017/07/18, With Invitation, English, World Association of Copepodologists, California, USA
  26. Behavioral observations of an undescribed hyperbenthic misophrioid copepod, with supplementary data on DNA sequences, Susumu Otsuka, Hayato Tanaka, Yusuke Kondo, Katsushi Hirano, Dame Jaume, Geoffrey A. Boxshall, Dame Jaume, Geoffrey A. Boxshall, 13th International Conference on Copepoda, 2017/07/18, Without Invitation, English, World Association of Copepodologists, California, USA
  27. Taxonomy and fisheries of commercially harvested jellyfish Crambionella (Scyphozoa) from central Java, Indonesia, Nishikawa J, Ohtsuka S, Mulyadi, Mujiono N, Lindsay DJ, Minamoto H, Nishida S, Asian CORE-COMSEA seminar on coastal ecosystems in southeast Asia, 2016/02/24, Without Invitation, English, University of Tokyo, Kashiwa, Japan
  28. Evolutionary shift from particle-feeding to carnivory in ccalanoid copepods: morphological and molecular evidences, Takeshi Hirabayashi, Makoto Urata, Ko Tomikawa, Susumu Ohtsuka, 12th International Conference on Copepoda, 2014/07/14, Without Invitation, English, World Association of Copepodologists, Seoul, Korea, In calanoid copepods exclusive carnivory is found in some lineages. In oceanic waters a wide variety of families or genera are supposed to be carnivores, whereas in coastal waters restricted members such as Euchaetidae, Pontellidae and Tortanidae are truly carnivorous. In the oceanic family Heterorhabdidae both particle-feeding and carnivorous genera are involved with some intermediate taxa, and the evolutionary shift from particle-feeding to carnivory has already been supported by the morphology-based phylogenetic analyses. The evolution in feeding of this family could have occurred without any addition of novel structure. Our new molecular analysis using nuclear ribosomal DNAs (18S, 28S) strongly enhances the results: the carnivorous Heterorhabdus-Paraheterorhabdus and Neorhabudus-Hemirhabuds clades are a final divergence, while the particle-feeding genus Disseta is basal with offshooting of the intermediate genera between these extremes. In calanoids two basic modes of carnivory are distinguished: chopsticks and scooping. The carnivorous genera of Heterorhabdidae, Candaciidae, Chiridiella and Corunucalanus are supposed to exclusively adopt chopsticks mode, whereas others essentially employ both feeding modes, depending on prey size. The former is characterized by only a few of highly chitinized elements on the maxillae only or maxillae/maxillipeds, while the latter is defined by the formation of feeding basket with the feeding appendages. The morphological and molecular phylogenetic analyses on the Heterorhabdidae propose that chopsticks mode could have divided directly from particle-feeding to carnivory not via scooping mode. We exactly traced the homology of maxillary and maxillipedal segments/elements specific to carnivory, and recognized 11 morphological types in carnivorous calanoids, suggesting that carnivory could have independently evolved many times through the evolution of calanoids.
  29. Complete life cycle of a pennellid Peniculus minuticaudae Shiino (Copepoda: Siphonostomatoida) infecting cultured threadsail filefish, Ismail Norshida, Susumu Ohtsuka, Balu Alagar Venmathi Maran, Satoshi Tasumi, Kassim Zaleha, Hirofumi Yamashita, Balu Alagar Venmathi Maran, Satoshi Tasumi, Kassim Zaleha, Hirofumi Yamashita, 12th International Conference on Copepoda, 2014/07/14, Without Invitation, English, World Association of Copepodologists, Seoul, Korea, Peniculus minuticaudae Shiino is a parasitic copepod infecting the fins of fishes mainly belonging to the family Monachantidae. Recently it seems to have been spreading in fish farms in western Japan and southern Korea. Our study showed the infection occurs all year round with the highest intensity recorded during summer. Based on our finding of all post-embryonic stages together with the post-metamorphic adult females on the fins of threadsail filefish Stephanolepis cirrhifer Temminck and Schlegel　cultured in a fish farm at Ehime Prefecture, Japan, we newly proposed the complete life cycle the P minuticaudae. The hatching stage was observed as an infective copepodid. It metamorphosed into chalimi I to IV after infection on fins. Sex can be differentiated from chalimus I. Adult males were observed frequently in precopulation amplexus with various stages of chalimi, however, copulation occurs only between adults. Fertilized pre-metamorphic adult females carrying paired spermatophores may detach from the host, and settle again on the same host and site to undergo massive differential growth to become post-metamorphic. A comparison in of the life cycle of P. minuticaudae has been made with those of three known pennellids; Lernaeocera branchialis Linnaeus, Cardiodectes medusaeus Wilson and Lernaeenicus sprattae Sowerby. The life cycle of pennellids can be divided into four categories based on the number of hosts and the presence or absence of nauplii. Combinations are as follows: (1) L. branchialis (two hosts, nauplii present); (2) C. medusaeus (two hosts, no nauplii); (3) L. sprattae (single host, nauplii present); (4) P. minuticaudae (single host, no nauplii). In L. sprattae, adult females change infection sites from fins and body surface to eyes of the host for oviposition, whereas in P. minuticaudae all stages including ovigerous females infect fins of the host. In the family blood-suckers may have two hosts, while histophagous taxa may not change host and/or attachment site.
  30. Systematics, morphology and feeding of calanoid copepods, Susumu Ohtsuka, 12th International Conference on Copepoda, Preconference Workshop, 2014/07/08, Without Invitation, English, World Association of Copepodologists, Yosu, Korea, The systematics, morphology and feeding of calanoid copepods are explained in detail, using powerpoint.
  31. Associations of fish juveniles and benthic invertebrates with large-sized jellyfish in Asian waters: key issues in pelagic realms, Susumu Ohtsuka, Yusuke Kondo, Shoma Okada, Jun Nishikawa, Khwanruan Srinui, Ephrime Metillo, Fatimah Md. Yusoff, Nanako O. Ogawa, Naohiko Ohkouchi, Shuhei Nishida, Jun Nishikawa, Khwanruan Srinui, Ephrime Metillo, Fatimah Md. Yusoff, Nanako O. Ogawa, Naohiko Ohkouchi, Shuhei Nishida, 9th International Scientific Symposium (IOC/WESTPAC), 2014/04/22, Without Invitation, English, IOC/WESTPAC, Nha Trang, Vietnam, Large-sized jellyfish harbor a wide variety of fish and invertebrates as hosts. However their actual interactions are rarely addressed, because of difficulties in assessment of trophic relationships between them and of little information on roles of the host throughout the life cycle of symbionts. We have been intensively investigating these interactions in Asian waters with modern techniques such as stable isotope analyses. In East Asian waters, scyphozoans such as Aurelia aurita s.l., Chrysaora pacifica, Cyanea nozakii and Sanderia malayensis are frequently associated with butterfish juveniles during warm seasons. Essentially the fish utilize jellyfish for commensalism or antipredation, however, the ontogenetic changes in symbiosis are suggested based on the stable isotopic analysis. The fish tends to feed on the host tissues, as it grows. The shrimp Latreutes mucronatus is highly specific to the Netrostoma setouchiana. The highly venomous box jellyfish Morbakak virulenta also shows complex interactions with fish. In southeastern Asian waters two commercially harvested rhizostomes, Rhopilema hispidum and Lobonemoides robustus, play an important role as host for fish juveniles (shrimp scad Alepes djedaba) and invertebrates (cross crab Charybdis feriata and hippolytid shrimp La. anoplonyx). These interactions seem to change with the growth of these symbionts as observed in butterfish in East Asia. In case of sympatric occurrence of these two hosts, shrimp scad juveniles exhibit habitat segregation: larger individuals prefer R. hispidum to Lo. robutus. An association between the ophiuroid Ophiocnemis marmorata and these rhizostomes is broadly observed in tropical Asian waters, corresponding to commensalism. Our results strongly imply that larvae of these benthic animals most likely settle directly on the jellyfish host and then temporarily stay there until the death o f the host. On the other hand fisheries of these edible jellyfish seem to have a great negative impact on the recruitment of these symbionts.
  32. Undescribed species of the commercially harvested jellyfish Crambionella (Scyphozoa) from central Java, Indonesia with remarks on the fisheries, Jun Nishikawa, Susumu Ohtsuka, Mulyadi, Nova Mujiono, Dhugal J. Lindsay, Hiroomi Miyamoto, Shuhei Nishida, Jun Nishikawa, Mulyadi, Nova Mujiono, Dhugal J. Lindsay, Hiroomi Miyamoto, Shuhei Nishida, 9th International Scientific Symposium (IOC/WESTPAC), 2014/04/22, Without Invitation, English, IOC/WESTPAC, An undescribed species of Crambionella is discovered from central Java, Indonesia. The number of lappets per octant (14), presence of foliaceous appendages on oral-arms, absence of tubercles on the velar lappets, and the body colour distinguish this species from three previously-described congeners. In addition, the analysis of partial sequences of the cytochorome c oxides subunit I gene indicated substantial genetic differences from both C. orsini and C. stuhlmani, supporting the validity of this new species. A combination of morphological and genetic approaches determined that the remarkable differences in exumbrellar colors observed in specimens is simply intra-specific variation. Surprisingly, this species has been commercially harvested for more than 20 years and is well-known to the local people in the region, yet it had remained unknown to science until this point. The commercial fisheries targeting this formerly unknown species are also presented in detail.
  33. Functional morphology of calanoids copepods; Evolution of planktonic copepods, Susumu Otsuka, 2003/07, With Invitation, Japanese
  34. Morphology and Systematics of planktonic copepods, Susumu Otsuka, Eighth International Conference on Copepoda (Preconference Workshop), 2002/07, With Invitation, Japanese
  35. Seuxal dimorphism in calanoid copepods-morphology and function, Susumu Otsuka, The World Association of Copepodologists, 1999, With Invitation, Japanese

Awards

  1. 2020/08/21, Early Career Outstanding Posters: Honorable Mention, Deep-Sea Biology Society/DSBS, An undescribed genus and species of the phylum Loricifera from Japanese Waters, Northwest Pacific
  2. 1999/09, Zoological Science Award, 日本動物学会, "学術論文「Platycopia compacta n.sp.,the second species of Platycopioida (Crustacea: Copepoda) in the Indo-Pacific region, wi

Social Activities

History as Committee Members

  1. Executive Council, 2021/04/01, 2022/03/31, World Association of Copepodologists
  2. Vice President, 2021/04, 2024/03, The Plankton Society of Japan
  3. Vice President, 2021/04, 2024/03, The Plankton Society of Japan
  4. Vice President, 2021/04, 2024/03, The Plankton Society of Japan
  5. Associate editor of Marine Biodiversity, 2020/04, 2021/03, Springer
  6. Executive council members, 2018/04, 2019/03, Plankton Society of Japan
  7. Council members of World Association of Copepodologists, 2017/07, 2022/06, World Association of Copepodologists
  8. Council members of World Association of Copepodologists, 2017/07, 2022/06, World Association of Copepodologists
  9. Council members of World Association of Copepodologists, 2017/07, 2022/06, World Association of Copepodologists

Organizing Academic Conferences, etc.

  1. Workshop on jellyfish, member of UNESCO program, 2019/09, 2019/09
  2. Workshop on jellyfish, member of UNESCO program, 0908/, 0911/

Other Social Contributions

  1. 15th International Conference on Copepoda, Executuve and Local Commitee Members (chairman), World Association of Copepodologists, 2022/04/01, 2025/03/31, Hiroshima City, Takehara City, Organizing Member, Meeting or assembly, Scientific organization
    Related URL

History as Peer Reviews of Academic Papers

  1. 2023, Marine Biodiversity, Editor, associate editor, 1
  2. 2021, ZooKeys, Others
  3. 2021, International Journal for Parasitology: Parasites and Wildlife, Others
  4. 2021, Plankton and Benthos Research, Others
  5. 2021, Parasitology International, Others
  6. 2021, Philippine Journal of Systematic Biology, Others
  7. 2021, Life, Others
  8. 2021, Journal of King Saud University-Science, Others
  9. 2021, Journal of Natural History, Others
  10. 2021, Indian Journal of Geo-Marine Sciences, Others
  11. 2021, Ichthyological Research, Others
  12. 2021, Frontiers in Marine Science, Others
  13. 2021, Diseases of Aquatic Organisms, Others
  14. 2021, Crustaceana, Others
  15. 2021, PlosOne, Others
  16. 2021, Marine Biodiversity, Editor
  17. 2019, Regional Studies in Marine Science, Others
  18. 2019, Zootaca, Others
  19. 2019, Scientific Reports, Others
  20. 2019, Crustacean Research, Others
  21. 2019, ZooKeys, Others
  22. 2019, Journal of Asia-Pacific Biodiversity, Others
  23. 2019, Crustaceana, Others
  24. 2019, Marine Environmental Research, Others
  25. 2019, BMC Evolutionary Biology, Others
  26. 2019, Disease of Aquatic Oragnisms
  27. 2019, PeerJ, Others
  28. 2019, Nauplius, Others
  29. 2019, Marine Biodiversity, Editor
  30. 2019, Journal of Crustacean Biology, Others
  31. 2019, Aquaculture, Others
  32. 2019, Diversity, Others
  33. 2015, Species Diversity, Editor, Editor