Use of common salt affects aggressiveness in matrinxã larvae (Brycon amazonicus)

Aggressiveness is potentiated during the production of fish of commercial interest due to the densification and confinement, and this may affect the welfare and health of these animals. We compared the effect of salinity on aggressiveness, locomotor activity and body cortisol level in matrinxã larvae (Brycon amazonicus) submitted to three experimental treatments: 0, 2 and 4 g of common salt/L. For each treatment, the larvae were collected at 24, 36, 48, 60 and 72 HAH (hours after hatching) and then transferred to 5‐L aquariums for 30 min to analyse behavioural categories. The use of common salt increased the frequency of aggressive interaction, cannibalism, mortality and locomotion in all observation periods. Body cortisol levels did not differ between treatments until 48 HAH, but showed a significant increase at 72 HAH in the 4 g salt/L. There was a positive correlation between aggressive interactions and locomotor activity. Negative correlation was observed between these parameters and cortisol up to 60 HAH; however, they were positively correlated at 72 HAH. We concluded that the use of common salt stimulates the display of aggressive behaviour and locomotor activity and that the effect of salt is dependent on the developmental phase of the larvae of B. amazonicus.     

Mitochondrion-rich cells distribution,Na<Superscript>+</Superscript>/K<Superscript>+</Superscript>-ATPase activity and gill morphometry of the Amazonian freshwater stingrays (Chondrichthyes: Potamotrygonidae)

Detailed measurements of gill area and constituent variables (total filament number, total filament length and mean filament length), and immunolocalization of the α-subunit of Na⁺/K⁺-ATPase and Na⁺/K⁺-ATPase activity were performed on both hemibranchs of all five arches of freshwater potamotrygonid stingrays (Paratrygon aiereba and Potamotrygon sp.). Both species exhibit similar mass-specific gill area, 89.8 ± 6.6 and 91.5 ± 4.3 mm² g⁻¹ for P. aiereba and Potamotrygon sp., respectively. The density of Na⁺/K⁺-ATPase-rich MRCs and Na⁺/K⁺-ATPase activity was higher in the 4th gill arch in both species. The Na⁺/K⁺-ATPase activity was positively correlated to the Na⁺/K⁺-ATPase-rich (Na⁺/K⁺-ATPase rich) mitochondrion-rich cell (MRC) distribution among the gill arches of P. aiereba but not in Potamotrygon sp. The levels Na⁺/K⁺-ATPase activity were not correlated to the gill surface area among the arches for both rays’ species. Considering that the Na⁺/K⁺-ATPase-rich MRC is the main site for active ion transport in the gill epithelia and Na⁺/K⁺-ATPase activity plays a crucial role in osmoionoregulatory function, we suggesting that 4th gill arch is more relevant for osmoregulation and ion balance in these potamotrygonids.     

Dietary lysine requirements of Colossoma macropomum (Cuvier, 1818) based on growth performance,hepatic and intestinal morphohistology and hematology

Veterinary Research Communications - This study aimed to determine the dietary lysine requirements of juvenile Colossoma macropomum tambaqui based growth performance, hepatic and intestinal...