Comparative Parasitology 67(2) 2000 - Peru State College

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228 COMPARATIVE PARASITOLOGY, 67(2), JULY 2000 Figures 17-19. Cephalic extremities of third-stage larvae of Spiroxys spp., lateral view (scale bars = 25 (Jim). 17, 18. Spiroxys hanzaki collected from experimentally infected copepod, Mesocyclops dissimilis (17), and naturally infected sand loach, Cobitis biwae (18). 19. Spiroxys japonica collected from naturally infected Rana rugosa (tadpole) in Akita, Akita Prefecture, Japan. imentally infected copepods or naturally infected fish. Measurements are stated in Table 1. ADVANCED THIRD-STAGE LARVAE (Figs. 15, 16): Morphology identical with that of the third-stage larvae described above but with much larger body (Table 1). IMMATURE ADULTS: Morphology identical with that of mature adults described in Hasegawa et al. (1998), but much smaller in size: males 10.2-13.3 mm long (« = 5) and females 10.2- 15.5 mm long (n = 5). Discussion Although only a few third-stage larvae were recovered from the experimentally infected copepods, it is apparent that 5. hanzaki utilizes copepods as its intermediate host, like most gnathostomatoids for which life histories have been elucidated (cf. Anderson, 1992). Compared with Spiroxys contortus (Rudolphi, 1819) and S. japonica (cf. Hedrick, 1935; Hasegawa and Otsuru, 1978), S. hanzaki shows some different features in the life history. Hatched larvae are much larger (175-294 long in S. contortus, and 148-207 long in S. japonica). The hatched larva attaches at the bottom, like that of 5. contortus, whereas the larva of S. japonica often swims in the water. Moreover, the period to attain the third stage in the copepods is much longer (10 to 14 days and 6 to 8 days in S. contortus and S. japonica, respectively). The large size of the hatched larva and the slow development may be responsible for the high mortality rate of the infected copepods. Penetration of such a large larva through the alimentary canal wall of the copepod may result in perforation, through which pathogenic organisms could easily invade the hemocoel, as shown by the disseminated infection with flagellates in Copyright © 2011, The Helminthological Society of Washington the present experiment. Meanwhile, it is also probable that the larva in the hemocoel would stimulate some defense mechanism of the copepods to eliminate the invader, because the larvae often died without further development. The worm size and morphology of the thirdstage larvae from the copepods are similar to those of the smallest third-stage larva found in the salamander. This suggests that the third-stage larva developed in copepods could be infective to the final host. However, most of the gnathostomatoids require the second intermediate or paratenic hosts, often fish, in which the thirdstage larva becomes the so-called advanced third stage, that shows significant gain in body size but without essential morphological change (cf. Anderson, 1992). A similar pattern was also postulated for S. hanzaki (Hasegawa et al., 1998). Because the low tolerance of the copepods to the infection in our experiments prevented experimental infection of fish with raised larva, it remains unknown whether the larvae grow to the advanced third stage in fish. In most parasitic nematodes, the fourth stage exists between the infective third stage and fifth (adult) stage. However, the presence of the fourth-stage larva in Spiroxys is doubtful. Hedrick (1935) stated that the third and fourth molts of S. contortus were observed in the definitive host turtles but did not present the morphology of the fourth stage. In the life history study of S. japonica, Hasegawa and Otsuru (1978) could not find any larva that was distinguishable morphologically from the third-stage larva in the experimentally infected definitive host, frogs. Berry (1985) described the larvae of Spiroxys chelodinae Berry, 1985, collected from the stomach ulcers of Australian chelonians, as fourth stage, but the morphology resembles that of third-stage
larvae of 5. contortus or S. japonica. In the present study, the largest third-stage larva from the salamander had nearly the same body size as that of the smallest immature adult. These facts suggest that Spiroxys lacks a fourth larval stage. The presence of the fourth larval stage is also unclear- for other gnathostomatoids. In Gnathostorna spp., there has been no description of the fourth-stage larva. In the life history study of Gnathostoma procyonis Chandler, 1942, Ash (1962) termed the larva of which a cross-section was presented as the fourth stage in the figure caption. However, he did not use this term in the text or describe a stage morphologically different from both the third stage and the adult stage. Moreover, we recently observed that Gnathostoma doloresi Tubangui, 1925, larvae in molting to the adult stage had the cuticle with typical arrangement of cephalic booklets of the third stage (specimens courtesy of Dr. J. Imai). Further careful study is required to determine whether gnathostomatoids molt only once in the definitive host. Acknowledgments Sincere thanks are rendered to Dr. J. Imai, Miyazaki Medical College, Dr. M. Koga, Kyushu University School of Medicine, and Dr. H. Akahane, Fukuoka University School of Medicine, for their kindness in providing invaluable information on the development of Gnathostoma spp. Thanks are also extended to Dr. T. Yoshino, University of the Ryukyus, for his kindness in verifying the scientific names of the fish. This study HASEGAWA ET AL.—LIFE HISTORY OF SPIROXYS HANZAKI 229 was partly supported by the grant-in-aid from the Ministry of Education, Science and Culture, Japanese Government, No. 11640700. Literature Cited Anderson, R. C. 1992. Nematode Parasites of Vertebrates. Their Development and Transmission. C.A.B International, Wallingford, U.K. 578 pp. Ash, L. R. 1962. Migration and development of Gnathostoma procyonis Chandler, 1942, in mammalian hosts. Journal of Parasitology 48:306-313. Berry, G. N. 1985. A new species of the genus Spiroxys (Nematoda: Spiruroidea) from Australian chelonians of the genus Chelodina (Chelidae). Systematic Parasitology 7:59-68. Hasegawa, H., A. Miyata, and T. Doi. 1998. Spiroxys hanzaki n. sp. (Nematoda: Gnathostomatidae) collected from the giant salamander, Andrias japonicus (Caudata: Cryptobranchidae), in Japan. Journal of Parasitology 84:831-834. , and M. Otsuru. 1978. Notes on the life cycle of Spiroxys japonica Morishita, 1926 (Nematoda: Gnathostomatidae). Japanese Journal of Parasitology 27:113-122. Hedrick, L. R. 1935. The life history and morphology of Spiroxys contortus (Rudolphi); Nematoda: Spiruridae). Transactions of the American Microscopical Society 54:307-335. Masuda, H., K. Amaoka, C. Araga, T. Uyeno, and T. Yoshino, eds. 1984. The Fishes of the Japanese Archipelago. Tokai University Press, Tokyo. 456 pp. Ueda, H., T. Ishida, and J. Imai. 1996. Planktonic cyclopoid copepods from small ponds in Kyushu, Japan. I. Subfamily Eucyclopinae with descriptions of micro-characters on appendages. Hydrobiologia 333:5=56. , , and . 1997. Planktonic cyclopoid copepods from small ponds in Kyushu, Japan. II. Subfamily Cyclopinae. Hydrobiologia 356:61-71. Copyright © 2011, The Helminthological Society of Washington
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July 2000 Number 2 Comparative Para
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Table 1. Unidentified diplectanids
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preferences, separation of Lateroca
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ward, 1996). Vincent's sillago, Sil
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(see Johnston and Tiegs, 1922; Murr
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Sphyraena chiysotaenia Klunzinger,
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figures of the internal anatomy (wh
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KRITSKY ET AL.—DIPLECTANIDS FROM
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2)] long, slender, fusiform; greate
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creation of paraphyletic taxa when
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Comp. Parasitol. 67(2), 20(K) pp. 1
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DAILEY AND GOLDBERG—LANGERONIA BU
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Comp. Parasitol. 67(2), 2000 pp. 16
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BOUAMER AND MORAND—OXYUROID GENUS
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Figure 10. Thaparia thaparia thapar
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BOUAMER AND MORAND—OXYUROID GENUS
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Page 41 and 42: Discussion Twelve parasite species
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Page 121 and 122: ANNIVERSARY AWARD 263 laboratory on
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Page 131 and 132: *Edna M. Buhrer * Mildred A. Doss *
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