Distribution and abundance of the digenean parasites Monascus filiformis and Opechona sp. on hydromedusae from the Southwestern Atlantic Ocean.

DIAZ BRIZ, L. M; RODRIGUEZ C.S:; MARTORELLI SERGIO R; GENZANO, G. N; MIANZAN, H. W

Mar del PLata

Simposio; Third International Jellyfish Blooms Symposium; 2010

INIDEP-UNMdP,

It is well-known that some digenean parasites of fishes use medusae as secondary hosts. The studies of parasite-host interactions and the trophic relationships involved among the hosts during the transmission of these parasites, would improve the knowledge about the marine food webs structure. As part of a proyect with Medusozoa from southwestern Atlantic Ocean (33º - 55ºS), two species of digenean Monascus filiformis and Opechona sp. were analyzed on the most abundants and frequents hydromedusae species:  Liriope tetraphylla,  Eucheilota ventricularis, Clytia hemisphaerica and Proboscidactyla mutabilis. A total of 31.569 medusae specimens were analyzed, 2.211 had parasites (total prevalence= 7 %). Although, both parasites were found in the four hydromedusa species, M. filiformis parasited the most of the specimens (67%), contrarily to Opechona sp. (35%). The highest values of mean abundances of M. filiformis and Opechona sp. were observed in C. hemisphaerica and E. Ventricularis; lower values were found in  L.  tetraphylla and P. mutabilis.  The area with the highest abundances, prevalences and intensities of both parasites and the highest abundances of their medusa hosts coincided with the Rio de la Plata estuarine zone and Península Valdés. So, the high values of parasitism found as well as the presence of the  first intermediate hosts (mollusks) of these parasites in such areas, suggest that them would complete their life cycles there, when their medusa host are consumed by the final hosts (fishes). Consequently, our finding would support the posibility of use these parasites as biological tags in  these particular environment since trophic relationship between medusae and fish are necessary to complete the life histories of these parasites.