Ions levels in the gastrointestinal tract content of silver catfish Rhamdia quelen (Siluriformes: Heptapteridae) are related to the reproduction period

Níveis de íons no conteúdo do trato gastrointestinal de jundiá Rhamdia quelen (Siluriformes: Heptapteridae) são relacionados ao período reprodutivo

ABSTRACT:

The current study tested the hypothesis that an increase in the ionic levels (Na⁺, Cl^-, Ca²⁺, Mg²⁺, and K⁺) in the gastrointestinal tract (GIT), and hepatosomatic index (HSI), gonadosomatic index (GSI), and Fulton’s condition factor (FCF) are associated with the reproduction period of silver catfish (Rhamdia quelen). So, we verified ionic levels of the fluid phase of the different portions of the GIT content, HSI, GSI, and FCF of silver catfish in different seasons in a dam in southern Brazil. The highest Na⁺ and Cl^- levels in GIT were found in spring. The stomach’s Na⁺ and Cl^- values were lower than the other segments. The K⁺ and Ca²⁺ levels in GIT were higher in winter, except in the stomach, where the values increased in summer. The highest K⁺ levels were reported in the anterior intestine. The highest Ca²⁺ levels in winter and spring were reported in the anterior and mid-intestines. In summer, the Mg²⁺ levels in the intestine were lower. The values of GSI and FCF were higher in winter and spring, and those of HSI were higher in winter. In conclusion, ions in the GIT and HSI, GSI, and FCF were higher in the reproduction period (winter for spring).

Key words:
Fulton’s condition factor; gonadosomatic index; Na⁺ ions; Cl^- ions