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.

Piscivory of the Japanese giant box jellyfish <i>Morbakka virulenta</i>

“…Many fish are known to be associated with jellyfish mainly for the reasons of antipredation and/or feeding (Mansueti 1963, Arai 1988, 2005, Ates 1988, Bonaldo et al 2004, Ohtsuka et al 2009. Some medusivorous fish, such as filefish, seem to consume not only scyphomedusae, but also cubomedusae, as food (Arai 1988, 2005, Ates 1988, Purcell & Arai 2001, Bonaldo et al 2004, Masuda 2009b, Miyajima et al 2011, Kondo et al 2016. Our observation of the feeding behavior by Thamnaconus modestus on M. virulenta clearly confirmed that cubomedusae were eaten by the fish.…”

Occurrence and effect of trematode metacercariae in two endangered killifishes from Greece

“…Therefore, we assume that this 293 spatial variation in the parasite prevalence could be related to a spatial variation of the primary host 294 (gastropod) densities, as well as of that of the definitive host. Parasite prevalence also remained 295 high throughout the year, a range similar to that reported elsewhere for Posthodiplostomum cuticula 296(Ondráčková et al 2004a) or other digeneans(Mbokane et al 2015;Kondo et al 2016). Maximum 297 prevalence (100%) was observed in autumn, and then prevalence decreased in winter, due to the 298 presence of both juvenile and adult metacercariae-free fish.…”

DNA sequencing demonstrates the importance of jellyfish in life cycles of lepocreadiid trematodes

“…Trachurus species are a main prey item of Arripis trutta in south-eastern Australia (Hughes et al, 2013). Trachurus species are known to associate with jellyfish (Masuda et al, 2008;Kondo et al, 2016) and, thus, seem a likely pathway for O. kahawai to reach S. lalandi and species of Arripis.…”