The influence of stocking density and food deprivation in silver catfish (Rhamdia quelen): A metabolic and endocrine approach

Abstract

The influence of stocking density and food deprivation on energy metabolism, stress processes and the pituitary endocrine system of silver catfish (Rhamdia quelen) was investigated after a period of 14 days, in which plasmatic and hepatic parameters and the mRNA expression of prolactin (PRL), growth hormone (GH) and somatolactin (SL) were assessed. The fish were subjected to four experimental conditions: (1) fed under high stocking density (32 kg/m 3 , HSD); (2) fed under mean stocking density (16 kg/m 3 , MSD); (3) fed under low stocking density (8 kg/m 3 , LSD); and (4) food-deprived under low stocking density (8 kg/m 3 , LSD-FD). After 14 days, plasma and liver samples were obtained to analyze the metabolite levels and enzymatic activities related to metabolism, and pituitary glands were obtained to analyze hormone expression (PRL, GH and SL). Liver weight and the hepato-somatic index (HSI) revealed that specimens maintained at HSD and/or MSD had higher hepatic stores, which were observed in the triglyceride and glycogen levels in this tissue, than animals submitted to the LSD and LSD-FD groups. Triglyceride levels in the plasma and liver revealed the consumption of fatty acid reserves in the fasting group. Enzymatic activities, such as glutamate dehydrogenase (GDH), phosphorylase (GPase), pyruvate kinase (PK), aspartate transaminase (AST) and glycerol-3-phosphate dehydrogenase (G3PDH), indicated an increase in gluconeogenic pathways in the HSD group and an increase in glycolitic metabolism in the LSD groups. The expression of PRL was not affected by stocking density and/or food deprivation and GH decreased with increased density and increased in fasting conditions. A negative effect of density and fasting was observed on the expression of SL. Overall, the data suggested that juvenile silver catfish reared at stocking densities of 16 to 32 kg/m 3 were better maintained than those maintained at the lowest density.

Rhamdia quelen (Quoy & Gaimard, 1824), submitted to a stressful condition: effect of dietary addition of the essential oil of Lippia alba on metabolism, osmoregulation and endocrinology

“…High plasma cortisol levels were observed in the control group, demonstrating that the stocking density and the limited space of the 60 L tanks of the present experiment was stressful for R. quelen as previously indicated by Barcellos et al (2004) and Menezes et al (2015). According to Barcellos et al (2001) .…”

“…A recent study demonstrated that feeding R. quelen with different levels of dietary EOLA for 60 days does not affect growth, but alters some metabolic parameters and improves the antioxidant status (Saccol et al, 2013). However, it is not known whether the effect of EOLA on anesthesia and antioxidant status may induce any protective effect in R. quelen exposed to non-optimal culture situations, as at a stocking density of 10.6 kg m -3 , which is considered stressful for this species when fish are maintained in a limited space (tanks or cages around up to 300-400 L) (Barcellos et al, 2004;Menezes et al, 2015). Consequently, the aim of this study was to evaluate metabolic, osmoregulatory and endocrinological parameters of R. quelen fed with a diet containing different levels of EOLA and submitted to a stressful situation.…”

Influence of stocking density on growth, metabolism and stress of thick- lipped grey mullet (Chelon labrosus) juveniles

“…2). In addition, the same kind of cortisol response in specimens held at the lowest stocking density has been recently demonstrated in specimens of the silver catfish (Rhamdia quelen) (Menezes et al, 2015), suggesting that this hormone is also species-dependent regarding the stocking density and the proper nature of the specimens. Moreover, the concordance about the enhancement of plasma cortisol and glucose observed in the LD group, together with the stimulation of hepatic glycogenolytic and glucose export capacity demonstrated in this tissue ( Fig.…”

Effects of stocking density on growth performance and welfare‐related physiological parameters of Atlantic salmon S almo salar L. in recirculating aquaculture system

“…Compared with Cl − and GLU, other serum parameters TG, TCH and TP in salmon were not affected by stocking density in this study, a finding that agrees with other density trials in European sea bass and silver catfish Rhamdia quelen (Di Marco et al . ; Menezes, Ruiz‐Jarabo, Martos‐Sitcha, Toni, Salbego, Becker, Loro, Martínez‐Rodríguez, Mancera & Baldisserotto ).…”