title: Seasonal changes in infection with trematode species utilizing jellyfish as hosts: evidence of transmission to definitive host fish via medusivory.
abstract: In the Seto Inland Sea of western Japan, metacercariae of three species of trematodes, Lepotrema clavatum Ozaki, 1932, Cephalolepidapedon saba Yamaguti, 1970, and Opechona olssoni (Yamaguti, 1934), were found in the mesoglea of the jellyfish Aurelia aurita s.l., Chrysaora pacifica, and Cyanea nozakii. Moreover, these jellyfish frequently harbored juveniles of the fish species Psenopsis anomala, Thamnaconus modestus, and Trachurus japonicus. The former two fish species are well-known medusivores. We investigated seasonal changes in the prevalence and intensity of these metacercariae in their host jellyfish from March 2010 to September 2012 and presumed that infection by the trematodes of the definitive host fish occurs through these associations. The mean intensity of metacercariae in A. aurita s.l. clearly showed seasonality, being consistently high in June of each year. The intensity of metacercariae in C. nozakii was highest among all jellyfish hosts and appeared to be enhanced by medusivory of this second intermediate, and/or paratenic host. Trophic interactions between jellyfish and associated fish were verified using both gut content and stable isotope analyses. The detection of trematodes and nematocysts in the guts of P. anomala and T. modestus juveniles, in addition to stable isotope analysis, suggests that transmission of the parasites occurs via prey-predator relationships. In addition, the stable isotope analysis also suggested that P. anomala is more nutritionally dependent on jellyfish than Th. modestus and Tr. japonicus.
authors.affiliation: Takehara Marine Science Station, Seotuchi Field Science Center, Graduate School of Biosphere Science, Hiroshima University, 5-8-1 Minato-machi, Takehara, Hiroshima 725-0024, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kondo
authors.affiliation: Takehara Marine Science Station, Seotuchi Field Science Center, Graduate School of Biosphere Science, Hiroshima University, 5-8-1 Minato-machi, Takehara, Hiroshima 725-0024, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Ohtsuka
authors.affiliation: Takehara Marine Science Station, Seotuchi Field Science Center, Graduate School of Biosphere Science, Hiroshima University, 5-8-1 Minato-machi, Takehara, Hiroshima 725-0024, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hirabayashi
authors.affiliation: Takehara Marine Science Station, Seotuchi Field Science Center, Graduate School of Biosphere Science, Hiroshima University, 5-8-1 Minato-machi, Takehara, Hiroshima 725-0024, Japan.
authors.forename: Shoma
authors.initials: S
authors.lastname: Okada
authors.affiliation: Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka 237-0061, Japan.
authors.forename: Nanako O
authors.initials: NO
authors.lastname: Ogawa
authors.affiliation: Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka 237-0061, Japan.
authors.forename: Naohiko
authors.initials: N
authors.lastname: Ohkouchi
authors.affiliation: 10486-2 Hotaka-Ariake, Azumino, Nagano 399-8301, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Shimazu
authors.affiliation: School of Marine Science and Technology, Tokai University, 3-20-1, Orido, Shimizu-ku, Shizuoka-shi, Shizuoka 424-8610, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Nishikawa
mesh_terms: D000818:Animals; D004197:Disease Reservoirs; D004199:Disease Vectors; D005260:Female; D005393:Fish Diseases / Q000469:parasitology* / Q000635:transmission; D041981:Gastrointestinal Tract / Q000469:parasitology; D006790:Host-Parasite Interactions; D007411:Intestinal Diseases, Parasitic / Q000469:parasitology / Q000635:transmission / Q000662:veterinary*; D008297:Male; D010140:Pacific Ocean; D011235:Predatory Behavior; D037401:Scyphozoa / Q000469:parasitology*; D012621:Seasons; D014200:Trematoda / Q000033:anatomy & histology / Q000254:growth & development / Q000302:isolation & purification / Q000502:physiology*; D014201:Trematode Infections / Q000469:parasitology / Q000635:transmission / Q000662:veterinary*