Kazuya Nagasawa

Tokyo University of Marine Science and Technology, Tokyo, Tokyo-to, Japan

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Publications (114)62.67 Total impact

  • Hirotaka Katahira, Kazuya Nagasawa
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    ABSTRACT: Five helminths, including a new echinorhynchid acanthocephalan Acanthocephalus longiacanthus n. sp., are described based on specimens from the giant mottled eel Anguilla marmorata Quoy & Gaimard caught in a small river, western Japan. The new acanthocephalan is distinguished from the other congeners in terms of hook arrangement (8-9 longitudinal rows with 5-6 hooks per row) on proboscis, maximum length of hook blade (81-95 μm in male, 150-190 μm in female), lemnisci being longer than proboscis receptacle, and small-sized eggs (80-83 μm). Two monogeneans, Pseudodactylogyrus anguillae (Yin & Sproston, 1948) and P. bini (Kikuchi, 1929), and two acanthocephalans, Acanthocephalus gotoi Van Cleave, 1925 and Southwellina hispida (Van Cleave, 1925), were also found; this new material is described. The monogeneans are notorious as invasive parasites spreading worldwide via anthropogenic transportations of anguillid eels, but in Japanese waters A. marmorata appears to be an indigenous host for these parasites. Anguilla marmorata is a new host record for the acanthocephalans A. gotoi and S. hispida.
    Systematic Parasitology 05/2014; 88(1):91-102. · 1.26 Impact Factor
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    ABSTRACT: This note reviews the work done by Ju-shey Ho, currently Professor Emeritus at California State University, Long Beach, CA, USA, on the systematics of symbiotic copepods from aquatic animals in Japanese waters. Since 1980, he has reported 110 species of symbiotic copepods from Japanese fish and marine invertebrates, including those representing one new family, seven new genera and 41 new species, and has greatly contributed to clarifying the symbiotic copepod fauna of Japan. Research using symbiotic copepods as bioindicators of the phylogeny and evolution of host animals was conducted by him for the first time in Japan. He also made significant contributions to the taxonomy and biology of caligid copepods, a group that poses a serious threat to the aquaculture industry, found on farmed fish in Japan.
    Journal of Natural History 02/2013; 47(5-12):517-527. · 0.78 Impact Factor
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    ABSTRACT: A new species of parasitic copepod, Choniomyzon inflatus n. sp., is described based on specimens collected from the external egg masses of the smooth fan lobster Ibacus novemdentatus Gibbes captured in the North Pacific Ocean off Ainan, Ehime Prefecture, western Japan. The new species differs from its congeners in having a globular to ovoid prosome, in bearing asymmetrically arranged denticles at a rounded apex of both the terminal segment of the antenna and the maxilliped, and in lacking serrate lobes on the basis of legs 1 and 2. The species is similar in size and shape to the host's eggs, which may be interpreted as egg mimicry. The new species is the first member of Choniomyzon Pillai, 1962 from subtropical regions.
    Systematic Parasitology 02/2013; 84(2):157-65. · 1.26 Impact Factor
  • Daisuke Uyeno, Kazuya Nagasawa
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    ABSTRACT: Four new species of the genus Hatschekia Poche, 1902 (Copepoda: Siphonostomatoida: Hatschekiidae) are described based on female specimens collected from pufferfishes (Tetraodontiformes: Tetraodontidae) caught in coastal waters off the Ryukyu Islands, Japan: H. longiabdominalis sp. n. on Arothron hispidus (Linnaeus), H. geniculata sp. n. on A. hispidus (type host) and A. stellatus (Bloch et Schneider), H. ellipsocorpa sp. n. on A. mappa (Lesson), and H. boonah sp. n. on A. nigropunctatus (Bloch et Schneider) (type host) and A. meleagris (Schneider). Hatschekia longiabdominalis sp. n. and H. boonah sp. n. differ from all other congeners by sharing an unusual, projected abdomen and a fusiform trunk with posterior lobes; these two species are differentiated from each other by the shape of the dorsal chitinous frame on the cephalothorax. Hatschekia geniculata sp. n. can be distinguished by the combination of the following morphological characters: a rhomboidal cephalothorax with a pair of lateral conical protrusions, a cylindrical trunk with posterior lobes and a bent abdomen with a dorsal protrusion. Hatschekia ellipsocorpa sp. n. resembles H. pholas (Wilson, 1906) but can be distinguished from the latter by the possession of one distal and one inner setae on the terminal endopodal segment of legs 1 and 2. Hatschekiapholas is also redescribed based on female specimens from the tetraodontid A. stellatus. At present, 44 nominal species of the genus have been reported from Japan, including four new species described in this paper; 38 of them have been described originally from Japan.
    Folia parasitologica 02/2013; 60(1):61-74. · 2.52 Impact Factor
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    ABSTRACT: A redescription of the caligid copepod Lepeophtheirus acutus Heegaard, 1943 is provided based on mature adults of both sexes collected from two new elasmobranch hosts, the Alfred manta Manta alfredi (Krefft, 1868) and the whale shark Rhincodon typus Smith, 1828, held in sea pens off Okinawa-jima Island, Japan. Lepeophtheirus acutus can be distinguished from other congeners by a combination of adult female characters that includes: (1) abdomen about one-third length of cephalothorax; (2) sternal furca with long, apically pointed tines; (3) leg 2 endopod with a row of large denticles and a spiniform projection on the distolateral corner of the first and second segments, respectively; (4) leg 3 endopod with six setae on the distal segment; and (5) leg 4 exopod with an armature of I-0; III. This report also confirms the observation of previous workers that L. acutus is a pathogen of elasmobranchs held in captivity.
    Journal of Natural History 01/2013; 47. · 0.78 Impact Factor
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    Ione Madinabeitia, Danny Tang, Kazuya Nagasawa
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    ABSTRACT: This study describes four new species of Colobomatus Hesse, 1873 and redescribes Colobomatus collettei Cressey, 1977 and Colobomatus pupa Izawa, 1974 based on females collected from the sensory canals of seven finfish species from off the Ryukyu Islands, southern Japan. Colobomatus pteroisi sp. nov. from Pterois volitans is unique in having a mid-lateral pair of cephalic processes; Colobomatus acanthuri sp. nov. from Acanthurus olivaceus possesses a short neck between the head and first pair of thoracic processes and tiny spinules and three claws apically on the cephalic, thoracic and genital processes; Colobomatus gymnocranii sp. nov. from Gymnocranius griseus has an anterior pair of papillose thoracic processes that are twice as long as the posterior pair of spinulose processes; Colobomatus absens sp. nov. from Pterocaesio digramma is unique in lacking a posterior pair of thoracic processes. New host and locality records for C. collettei and C. pupa are also reported herein. http://www.zoobank.org/urn:lsid:zoobank.org:pub:BEB140D5-8936-4B47-B8B9-738BFABF37E1
    Journal of Natural History 12/2012; 47(5-12):563-580. · 0.78 Impact Factor
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    Ione Madinabeitia, Kazuya Nagasawa
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    ABSTRACT: An alternative approach for the recovery of parasitic copepods from finfishes is proposed herein by applying double-netting (DN) after visual scanning (VS). Double-netting consists of double-filtering the dislodged debris after washing and shaking all dissected parts visually scanned previously. During DN, two different sized hand-nets (≤200 μm in mesh size) are used simultaneously. The debris entangled in the first net is recovered by washing the first net in the second one. A total of 1448 copepods were recovered from nine sparid finfish species by applying DN, accounting for 25% of the total. The most abundantly recovered copepods were bomolochids and philichthyids. Our double-sieving method is efficient in recovering overlooked copepods by VS, providing more accurate results in diversity and quantitative studies. Additional advantages of DN include its simplicity (small size and weight), low price (less than US$ 3), and convenience (easy to transport and apply directly in the field).
    Journal of Natural History 12/2012; 47(5-12):529-541. · 0.78 Impact Factor
  • Danny Tang, George W. Benz, Kazuya Nagasawa
    Zoosymposia. 12/2012; 8:7-19.
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    ABSTRACT: With technological improvements in otolith microchemical analysis, the flexible use of habitat from coastal marine to fresh waters has been discovered in Japanese eels Anguilla japonica. We examined the occurrence of 3 congeneric gill monogeneans-Pseudodactylogyrus anguillae, P. bini, and P. kamegaii-on wild Japanese eels, in relation to the host's flexibility. From April 2008 to October 2009, 114 eels were collected from a brackish-water cove and 2 rivers flowing into the cove in Ehime Prefecture, western Japan. Based on otolith microchemical analysis, the eels were discriminated according to the following 4 types of habitat use: freshwater residents (Type I), individuals utilizing low-salinity habitats (Type II), downstream habitat-shifters (Type III), and cove residents (Type IV). P. anguillae occurred mainly on Type I and II eels, while P. bini was primarily found on Type I eels. In contrast, P. kamegaii occurred mainly on Type III and IV eels. Thus, we conclude that species composition and infection levels of Pseudodactylogyrus spp. clearly differed with habitat-use patterns of Japanese eels. Also, since P. anguillae was scarcely found on either Type III or IV eels, this study suggests that previous identifications of monogeneans collected from European brackish-water localities as P. anguillae may require verification.
    Diseases of Aquatic Organisms 08/2012; 100(1):43-9. · 1.73 Impact Factor
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    Takeo Yamauchi, Kazuya Nagasawa
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    ABSTRACT: Nerocila japonica Schioedte & Meinert, 1881 is redescribed based on the holotype and specimens from various localities in Japanese waters. The following fishes are recorded as new hosts: Tribolodon hakonensis (Cyprinidae), Mugil cephalus, Liza affinis, Chelon haematocheilus (Mugilidae), Lateolabrax japonicus, L. latus (Lateolabracidae), Acanthopagrus latus, A. schlegelii schlegelii (Sparidae), Rhyncopelates oxyrhynchus (Terapontidae), Ditrema viride, D. temminckii temminckii (Embiotocidae), Chaenogobius gulosus, Acanthogobius flavimanus (Gobiidae), Pseudolabrus sp. (Labridae) and Aluterus monoceros (Monacanthidae). Specimens previously recorded as 'Nerocila acuminata' from Toyama Bay (the Sea of Japan) were examined, when available, and re-identified as N. japonica. As there has been no reliable record of N. acuminata Schioedte & Meinert, 1881 from off Japan, reports of this species in Japanese waters are considered to represent N. japonica.
    Systematic Parasitology 02/2012; 81(2):147-57. · 1.26 Impact Factor
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    ABSTRACT: A new species of the Macrochironidae Humes & Boxshall, 1996 (Copepoda: Cyclopoida), Pseudomacrochiron aureliae n. sp., is described based on adult specimens extracted from the gastrovacular cavity of the scyphistomae of Aurelia sp. (Cnidaria: Scyphozoa) collected in the Seto Inland Sea and Ise Bay off the coast of Japan. The new species differs from its congeners by having the following combination of characters: a caudal ramus with a length to width ratio of 3.1; an accessory flagellum on caudal setae II, III and VI; three apical setae on the maxillule; only setae I and II on the maxillary basis; two short spines on the female maxilliped claw (endopod); an armature of III, I, 4 on the terminal exopodal segment of leg 3; an armature of I, II, 2 on the terminal endopodal segment of leg 3; an armature of II, I, 4 on the terminal exopodal segment of leg 4; and a short free exopodal segment of leg 5 (length to width ratio of 1.4) armed with a long seta and short spine. P. aureliae n. sp. is the first member of the genus reported from off Japan and from the scyphistomae of its scyphozoan host.
    Systematic Parasitology 02/2012; 81(2):125-34. · 1.26 Impact Factor
  • Frantisek Moravec, Kazuya Nagasawa, Kenji Nohara
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    ABSTRACT: Gravid females of two species of philometrid nematodes (Philometridae) were collected from marine perciform fishes in Japanese waters, mainly from the southern Sea of Japan. Based on light microscopy and scanning electron microscopy examinations, the previously described but poorly known species Philometra cryptocentri Yamaguti, 1961 is redescribed from specimens recovered from the abdominal cavity of Acanthogobius flavimanus (Temminck et Schlegel), Pterogobius elapoides (Günther) and P. zonoleucus Jordan et Snyder (all Gobiidae) (all new host records); the number (14) and arrangement of cephalic papillae in this species are described for the first time. The new species, Philometroides branchiostegi sp. n. from head tissues of Branchiostegus japonicus (Houttuyn) (Malacanthidae), based on a single specimen, is mainly characterized by the embossment of the entire body except for the cephalic end, presence of four submedian pairs of large cephalic papillae of external circle and two small lateral single papillae of internal circle, pair of large papilla-like caudal projections, the oesophagus with a distinct anterior inflation, by a markedly small body (length about 18 mm) and the larvae 306-465 microm long.
    Folia parasitologica 02/2012; 59(1):71-8. · 2.52 Impact Factor
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    ABSTRACT: The loggerhead turtle (Caretta caretta) is listed as an endangered species in the International Union for Conservation of Nature Red List, and this is critical for the maintenance of future genetic diversity. For the conservation of this species, it is important to understand the relationships between sexual selection and gene flow in the evolution of biodiversity. It is, however, virtually impossible to study sexual selection in such an oceanic species in the field. We investigated the relationships between mate preference and genetic relatedness of reproductively active loggerhead turtles (n = 7) kept in a tank at an aquarium using 4 different estimators of pairwise genetic relatedness (r) based on the genotypes at 23 microsatellite loci. Although relationships between total number of courtship behavior and r were not significant in the 4 estimators, there were significant and consistent inverse relationships between cumulative duration of mountings and r in all of the estimators. In addition, significant or marginally significant relationships were found between mean r for each female and number of sires in her successive clutches in 3 of the 4 estimators. However, we found no evidence that more distantly related pairs produced more offspring than the assumption of random mating except for 1 estimator or any relationship between r of parents and their reproductive success (hatchability). Based on these results, the most parsimonious explanation is that loggerhead turtles in the tank tend to prefer their mate(s) according to genetic relatedness but that the extent of female mate selection and the relationship between mate selection and fitness still remain debatable.
    Chelonian Conservation and Biology 01/2012; 11(2):214-222. · 0.74 Impact Factor
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    Journal of Natural History 01/2012; · 0.78 Impact Factor
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    Daisuke Uyeno, Kaori Wakabayashi, Kazuya Nagasawa
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    ABSTRACT: A new species of copepod, Sarcotretes umitakaesp. n., of the siphonostomatoid family Pennellidae is described based on female specimens from the rattail Coelorinchus jordani Smith and Pope (Actinopterygii: Gadiformes: Macrouridae) caught in the East China Sea. This species is characterized by exhibiting the following characters: the large proboscis projects strongly; the head bears paired lateral processes which are bulbous and taper into a slender horn; the twisting neck is significantly longer than the trunk; and the trunk bears an anterior constriction with a reduced abdomen.
    ZooKeys 01/2012; · 0.92 Impact Factor
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    Daisuke Uyeno, Kazuya Nagasawa
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    ABSTRACT: Four new species of splanchnotrophid copepods are described based on specimens collected from 5 species of doridacean nudibranchs from coastal waters of Japan. They belong to 3 genera, one of which, Majimun gen. n., is new. The parasites and their hosts are as follows: Ceratosomicola japonicasp. n. ex Hypselodoris festiva (A. Adams); Splanchnotrophus helianthussp. n. ex Thecacera pennigera (Montagu); Splanchnotrophus imagawaisp. n. ex Trapania miltabrancha Gosliner & Fahey; and Majimun shirakawaigen. et sp. n. ex Roboastra luteolineata (Baba) and Roboastra gracilis (Bergh). Ceratosomicola japonicasp. n. is the fifth species of Ceratosomicola and is characterized by the shape and armature of the prosome in females. Both Splanchnotrophus helianthussp. n. and Splanchnotrophus imagawaisp. n. are differentiated from 4 known congeners by the absence of posterolateral processes or lobes on the prosome in females, and the females of these 2 new species are separated from each other by the shape and armature of the genito-abdomen, the mandible, and the swimming legs. Majimungen. n. is distinguished from other splanchnotrophid genera by the segmentation of the antennule as well as the combination of the following characters in females: 2 postgenital somites and the shape of the antenna, the mandible and the swimming legs.
    ZooKeys 01/2012; · 0.92 Impact Factor
  • Danny Tang, Daisuke Uyeno, Kazuya Nagasawa
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    ABSTRACT: Two new copepod species of the genus Taeniacanthus Sumpf, 1871 (Cyclopoida: Taeniacanthidae) are described from boxfishes (Aracanidae and Ostraciidae) caught in the Indo-West Pacific region: T. larsonae n. sp. from Ostracion nasus Bloch in the Arafura Sea and off Australia and Tetrosomus concatenatus (Bloch) off Japan; and T. thackerae n. sp. from O. immaculatus Temminck & Schlegel off Palau, O. rhinorhynchos Bleeker off Australia, Lactoria cornuta (Linnaeus) and Ostracion sp. off Japan, and Kentrocapros aculeatus (Houttuyn) in the East China Sea. T. larsonae n. sp. differs from its congeners by having several rows of spinules on the large pectinate process of the antenna and by differences in the shape of the sclerotised plates on the rostral area and structure of the maxilliped. T. thackerae n. sp. can be distinguished from its congeners by differences in the shape of the sclerotised plates on the rostral area, the structure of the maxilliped and ornamentation pattern of legs 1-4. Supplemental information for the female of Taeniacanthus ostracionis (Richiardi, 1870) and T. moa (Lewis, 1967), as well as the first description of the male of T. moa, are also provided based on new material collected from ostraciid hosts caught in the Arafura Sea and off Australia, Indonesia and Japan. The four taeniacanthid species reported from boxfishes exhibit variable levels of host-specificity and have broad geographical ranges within the Indo-West Pacific region.
    Systematic Parasitology 10/2011; 80(2):141-57. · 1.26 Impact Factor
  • Hirotaka Katahira, Kazuya Nagasawa
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    ABSTRACT: Echinorhynchus hexagrammi Baeva, 1965 is redescribed on the basis of specimens collected from the saffron cod Eleginus gracilis (Tilesius) in Akkeshi Bay (western North Pacific) off Hokkaido, Japan. Eighteen museum specimens deposited as E. salmonis Müller, 1784 from Japanese coastal waters were also re-examined and re-identified as E. hexagrammi. Hexagrammos stelleri Tilesius, Hemitripterus villosus (Pallas), Podothecus sachi (Jordan & Snyder), Sebastes oblongus Günther and Verasper moseri Jordan & Gilbert are recognised as new hosts for E. hexagrammi. This acanthocephalan can be distinguished from three morphologically similar species, E. gadi Zoega in Müller, 1776, E. laurentianus Ronald, 1957 and E. salmonis, by the possession of the following characters: 12-16 (usually 14) rows of hook on the proboscis, a proboscis width of 170-240 μm in males and 195-270 μm in females, a hook root length of 35-45 μm in males and 40-50 μm in females, and linearly or almost linearly arranged cement glands in males.
    Systematic Parasitology 09/2011; 80(1):35-40. · 1.26 Impact Factor
  • Kazuya Nagasawa, Danny Tang, Tomoyasu Tamego
    Biogeography. 09/2011; 13:41-43.
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    ABSTRACT: We investigated the effects of the order of sequential matings in captive female loggerhead turtles (Caretta caretta) on the paternity of their successive clutches. Paternity analysis revealed that only 3 of the 7 successive clutches were multiply sired, although all egg-laying females were observed to copulate with multiple males prior to egg-laying. In multiply sired, successive clutches of particular females, the relative paternal contributions of different males did not vary, although some potentially successful matings were observed during internesting intervals. Prior to nesting periods, males showed mating in response to the female reproductive cycle in which the cumulative durations of mountings observed by highly sensitive cameras peaked at 21–40 days before any individual female laid her first clutch. A regression line between cumulative duration of mountings and relative parental contributions for 21–40 days before laying the first clutch fit a predictive equation for sperm competition based on the assumptions of a fair raffle. These results suggest that sperm precedence has changed with time over the course of a prenesting period and that male turtles in this study have regulated the timing of copulations in accordance with the patterns of sperm precedence.
    Chelonian Conservation and Biology 07/2011; · 0.74 Impact Factor

Publication Stats

237 Citations
62.67 Total Impact Points

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  • 2013
    • Tokyo University of Marine Science and Technology
      • Graduate School of Marine Science and Technology
      Tokyo, Tokyo-to, Japan
  • 2007–2013
    • Hiroshima University
      • • Department of Bioresource Science
      • • Graduate School of Biosphere Sciences
      Hirosima, Hiroshima, Japan
  • 2012
    • University of the Ryukyus
      • Faculty of Science
      Okinawa, Okinawa-ken, Japan
  • 2011
    • University of Western Australia
      Perth City, Western Australia, Australia
  • 2005
    • California State University, Long Beach
      • Department of Biological Sciences
      Long Beach, CA, United States
  • 2004
    • Southeast Asian Fisheries Development Center (SEAFDEC)
      Iloilo Proper, Western Visayas, Philippines
  • 2002
    • Fisheries Research Agency
      Yokohama, Kanagawa, Japan
    • Academy of Sciences of the Czech Republic
      • Biologické centrum
      Praha, Hlavni mesto Praha, Czech Republic
  • 1996–2001
    • National Research Institute of Far Seas Fisheries
      Sizuoka, Shizuoka, Japan