Mobilization of energetic substrates in the endangered catfish Steindachneridion parahybae (Siluriformes: Pimelodidae): changes in annual reproductive cycle in captivity

Abstract

This study aimed at analyzing the energetic substrate (ES) in the main storage tissues of Steindachneridion parahybae, throughout the reproductive cycle in captivity. Differently from wild, in captivity, feeding is not interrupted during the reproductive period, the females do not spawn spontaneously, and they are sedentary. Adult females were sampled monthly and based on their histology and gonadosomatic index (GSI), ovaries were classified into: previtellogenic (PRV), vitellogenic (VTG), and regression (REG) stages. Ovaries at the VTG stage showed higher protein and lipids levels than at the PRV stage with a positive correlation between these substrates and the GSI. Muscle was the main source of proteins transferred to the ovaries, according to the negative correlation between these organs. Lipids remained unchanged in the liver, which is an important supplier in vitellogenesis, a pattern that probably occurs due to the continuous feeding. Muscular glycogen levels were higher at the VTG and REG than at the PRV stages. Plasma triglycerides were also higher during REG, while glucose levels were more elevated during the VTG stage. These results suggest that with constant food supply, the pattern of deposition of ES in S. parahybae is different from that described for other wild potamodromous species.Keywords: Glycogen, Lipids, Metabolic substrate, Protein, Reproductive cycle.O objetivo deste estudo foi analisar a composição do substrato energético (SE) nos principais tecidos de armazenamento de Steindachneridion parahybae, durante todo o ciclo reprodutivo em cativeiro. Diferentemente do ambiente natural, em cativeiro, a alimentação desses animais não é interrompida durante o período reprodutivo, as fêmeas não desovam espontaneamente, e são sedentárias. Fêmeas adultas foram amostradas mensalmente e baseada na histologia e no índice gonadossomático (IGS), os ovários foram classificados: estádios pré-vitelogênico (PRV), vitelogênico (VTG) e regressão (REG). Os ovários no estádio VTG apresentaram uma maior concentração de lipídeos e proteínas em relação ao estágio PRV. Esses substratos correlacionaram-se positivamente com o IGS. O músculo foi a principal fonte de proteína transferida aos ovários, como foi confirmado pela análise de correlação negativa entre esses órgãos. Os lipídeos mantiveram-se inalterados no fígado, considerado um importante órgão fornecedor de lipídeos para a vitelogênese, padrão que possivelmente ocorreu devido à contínua alimentação. A concentração do glicogênio muscular foi mais elevada durante os estágios VTG e REG em relação ao PRV. A concentração de triglicerídeos plasmática apresentou maiores valores no estádio REG enquanto a concentração de glicose no plasma foi maior durante os estádios VTG. Esses resultados sugerem que com alimentação constante, as fêmeas de S. parahybae apresentam um distinto padrão de mobilização dos substratos energéticos em relação ao que já foi descrito para outras espécies potamódromas de ambiente natural. Palavras-chaves:Ciclo reprodutivo, Glicogênio, Lipídeos, P...

Dynamics of ovarian maturation during the annual reproductive cycle of the endangered fish Steindachneridion parahybae (Siluriformes: Pimelodidae) in captivity

“…Cortical alveoli oocytes are identified by spherical vacuoles that appear as empty structures, with this stage being commonly called endogenous vitellogenesis (Bobe and Labbé, 2010;Baldisserotto et al, 2020;Grier et al, 2009). In addition, as was observed by Tolussi et al (2018), in this stage, an increase in the lipid content was observed in the ovaries of these same animals (a concurrent study), also suggesting that these spherical vacuoles may have lipid content, as observed in several teleost fish (Baldisserotto et al, 2020).…”

“…In addition, as was observed by Tolussi et al . (2018), in this stage, an increase in the lipid content was observed in the ovaries of these same animals (a concurrent study), also suggesting that these spherical vacuoles may have lipid content, as observed in several teleost fish (Baldisserotto et al ., 2020).…”

“…Sampling was conducted monthly (except for June, July and August, winter months in South America). The authors chose not to handle the animals in the fishponds during these months to avoid the stress and emergence of diseases, such as the one caused by the ciliate Ichthyophthirius multifiliis , avoiding the known risks of mortality during these months (Tolussi et al ., 2018). Females were randomly sampled (four animals/pond/mouth; eight in total), transported to the CESP laboratory and anaesthetized with 0.1% benzocaine (ethyl‐ p ‐aminobenzoate), and their biometrical parameters were recorded (Table 1).…”

The role of energy reserves in common carp performance inferred from phenotypic and genetic parameters

“…HSI is a commonly used indicator of energy reserves in other fishes (e.g., Htun-Han, 1978;Chellappa et al, 1995;Lambert and Dutil, 1997;Binder et al, 2015), but knowledge about the composition and mutual rate of individual nutrients is missing. In an endangered catfish, Steindachneridion parahybae, HSI was phenotypically positively correlated with hepatic glycogen, and negatively correlated with hepatic protein (Tolussi et al, 2018). Similar strong relationship between HSI and hepatic glycogen was observed by Crespel et al (2013).…”

Seasonal Changes in Plasma Hormones, Sex-Related Genes Transcription in Brain, Liver and Ovary during Gonadal Development in Female Rainbow Trout (Oncorhynchus mykiss)

“…Throughout the reproductive cycle, seasonal changes in tissue biochemical composition are related to gonadal weight, especially in females, in which the hepatic metabolism are stimulated during vitellogenesis [3]. Hence, monthly variations in the gonadosomatic index (GSI) helps to determine the breeding season of the fish, and study of the hepatosomatic index (HSI) is also important because the liver is a key organ in fish for production of vitellogenin which plays a significant role in the development of eggs [4,5].…”