Seasonal characterization of metazoan parasite assemblages associated with Mugil liza juveniles on Cassino beach (Rio Grande-RS)

Author: Yorleys Tatiana Diaz Navarro (Currículo Lattes)
Supervisor: Dr Joaber Pereira Junior
Co-supervisor: Dr Rogério Tubino Vianna


In this work, the composition and seasonal variation of metazoan parasites associated with juvenile mullet, Mugil liza from coastal streams at Praia do Cassino, in Rio Grande do Sul were studied. Monthly collections (n ​​= 40) were carried out for one year, from January to December 2012, totaling 480 fish. The hosts were taken to the laboratory, stunned by cerebral concussion and necropsied to collect endo and ectoparasites. The parasites were fixed (formalin or AFA) and kept in 70% alcohol. Representative specimens were selected to mount slides that allowed identification to the lowest possible taxonomic level. The results are presented in two chapters, namely: 1) Ectoparasites associated with Mugil liza juveniles from the region of Rio Grande, RS;2) Endoparasites associated with Mugil liza juveniles from the region of Rio Grande, RS. In both cases, the parasitological prevalence rates (P%), average intensity of infection (IMI) and average abundance (AM) were calculated for each of the sampled rates / month and, seasonally. Parasitological indices were compared using the program “Quantitative Parasitology 3.0” and the effect of “Crowding” (CRD) was verified for each species. In the first chapter, four species were reported: a) Gyrodactylus sp. present in all seasons and presenting the highest P% (17.5 and 16.7) and IMI (4.14 and 1.90) values ​​in autumn and winter, respectively; b) Polyclithrum sp. it only occurred in the spring with P% of 4.2% and IMI of 3.60; c) Ligophurus sp. was present in all seasons and its highest P% (59.2) and IMI of 36,70 occurred in the spring; d) Solostamenides platyorchis was absent in the summer and its highest P% (16.70) and IMI (2.05) occurred in the spring. Gyrodactylus sp. and Polyclithrum sp. were located on the body surface (fins) and showed a uniform distribution pattern throughout the year according to parasitological indexes. 11 Ligophorus sp. showed a uniform distribution pattern for autumn and aggregated in other seasons. Solostamenides platyorchis demonstrated a uniform distribution pattern. These last two parasites were located in the gills, where it was also possible to observe the presence of Gyrodactylus sp. with low P%. II the liver and intestine form the organs where the presence of parasites has been observed. In the liver, unidentified metacercariae (NI) were found, which remained absent in the spring.In other seasons, autumn was where there was the highest P% (64.2) and IMI (12.34) for NI. NI showed a uniform distribution in winter and summer and aggregate in autumn. Ascocotyle cysts (Phagicola) longa showed very discrete P% during all seasons and their highest parasitological indices were P% (6.7) for summer and IMI (8.2) for autumn. Its distribution pattern was uniform in all seasons. Three species were found in the intestine: a) Hemiuridae (Gn. Sp.) Was present in spring and summer with moderate values ​​of P% (8.3) and IMI (1.90); b) Dicrogaster fastigata, in its adult and metacercaria form, were present throughout the year, with its highest P% (84.2 and 70.8) and IMI (25.93 and 11.09) observed for the winter and spring, respectively. c) Scolex spleuronectis,development of many organisms including parasites. Wild or captive fish can be heavily infested/infected. Quantitative and qualitative temporal variations for parasites depend, for example, on the host species, the life cycle of the parasites and environmental conditions. The results reported in this study should be expanded, especially with larger time series, but offer relevant information for the control of parasitic diseases in aquaculture.