The effects of salinity on growth, gill tissue and muscle cellularity in Lophiosilurus alexandri juvenile, a Neotropical freshwater catfish

The present study investigated the effects of salinity on growth, mortality, gill morphology and muscle cellularity in Lophiosilurus alexandri. Fish were submitted to the following salinity for 28 days: 0 (S0), 2.5 (S2.5), 5.0 (S5), 7.5 (S7.7) and 10 (S10) ppt. Growth and protein efficiency ratio (PER) decreased with the increase of salinity. All fish from S10 died between the 16th and 21st day of the experiment. Mortality in S7.5 was 78% at the end of 28 days of salinity exposure. Increased salinity was accompanied by increased vascular congestion, hyperplasia of gill filament epithelium, lamellar fusion and loss of structural integrity of pillar cells. Fish at S2.5 and S5 had higher mucosal cell hyperplasia. Chloride cell quantity was higher in fish in the S2.5 to S7.5. In general, L. alexandri juvenile exposed to treatments of freshwater and S2.5 had similar patterns of muscle cellularity, with high averages for the most of the variables of muscle cellularity evaluated. The large fibre size classes tended to decrease with increasing salinity. L. alexandri juveniles may be cultivated up to 2.5 g of salt/L, and superior concentrations change growth, induce damage to gills and modify muscle cellularity.