Metazoan parasites of white croaker, Micropogonias furnieri (Pisces: Scianidae) from coasts of Buenos Aires Province, Argentina.

ALARCOS, A.J.; ETCHEGOIN, J.A; TIMI, J.T.; SARDELLA N.H.

Viterbo, Italia.

Simposio; 7 th International Symposium on Fish Parasites; 2007

Universidad de Roma

The white croaker Micropogonias furnieri (Desmarest, 1823) (Sciaenidae) inhabits coastal waters from México to Argentina. In the Buenos Aires province, Argentina, this species also uses the waters of Mar Chiquita coastal lagoon as nursery ground and feeding area, being targeted by commercial fishermen during all the year. The aim of this work is to know the composition and structure of parasitic communities of this host species in the coasts of Buenos Aires Province, Argentina, and the probable effect of variations in salinity levels on these assemblages. A total of 66 croakers from Mar Chiquita coastal lagoon (37º46'S, 57º27'W, n=41) and coastal area of Mar del Plata (38º08’S- 57°32'W, n=25) collected during January 2004 and June 2006, and October 2006 and March 2007 respectively, were examined for parasites. Fish were either kept fresh or deep frozen in plastic bags at -18ºC until examination. Each white croaker was measured for total length. Fish from brackish waters were significantly smaller than those from open sea. Parasites were collected from the body surface, gills, branchial and body cavities and viscera. A total of 3,205 individual parasites were collected, with a mean abundance of 48.60 parasites/fish. Most croakers (92.43%) were parasitized by at least one parasite species, whereas 27.27% fish harboured monospecific infections. Nineteen species of metazoan parasites were collected (6 Nematoda, 3 Acanthocephala, 2 Monogenea, 2 Digenea, 1 Aspidobothrea, 2 Copepoda and 3 Eucestoda). Abundance of five parasite species increased significantly with fish size. The mean values of the infracommunity indices for the whole sample were: Brillouin´s diversity: 0.58±0.30 (0.07-1.11), species richness: 2.86±1.69 (1-7), evenness: 0.57±0.27 (0.10-1) and total number of parasites per fish 52.54±68.71 (1-270). No relationship was observed between evenness and fish size (r2=0.002, P=0.92), whereas diversity (r2=0.17, P<0.01), species richness (r2=0.43, P<0.01) and number of parasites (r2=0.36, P<0.01) increased significantly with host length. However, after correcting for fish length, no differences were observed between fish caught in brackish waters (smaller) and those catched in open sea (larger), for none of infracommunity descriptors(all P>0.05). Higher levels of parasitism in larger/older hosts is a common feature of fish-parasite systems, due to larger fish having higher feeding rates and/or larger surfaces for parasite attachment, as well as having been exposed to parasites for longer. The access of hosts to different habitats with more potential parasites available can produce changes in parasite community structure. However this is not the case of M. furnieri, for which their incursions in brackish waters do not produce variations in the structure of metazoan assemblages. This is not surprising, because all parasite species found in M. furnieri have a marine origin.