Unraveling vasotocinergic, isotocinergic and stress pathways after food deprivation and high stocking density in the gilthead sea bream

Abstract

The influence of chronic stress, induced by food deprivation (FD) and/or high stocking density (HSD), was assessed on stress, vasotocinergic and isotocinergic pathways of the gilthead sea bream (Sparus aurata). Fish were randomly assigned to one of the following treatments: (1) fed at low stocking density (LSD-F; 5kg·m); (2) fed at high stocking density (HSD-F, 40kg·m); (3) food-deprived at LSD (LSD-FD); and (4) food-deprived at HSD (HSD-FD). After 21days, samples from plasma, liver, hypothalamus, pituitary and head-kidney were collected. Both stressors (FD and HSD) induced a chronic stress situation, as indicated by the elevated cortisol levels, the enhancement in corticotrophin releasing hormone (crh) expression and the down-regulation in corticotrophin releasing hormone binding protein (crhbp) expression. Changes in plasma and liver metabolites confirmed a metabolic adjustment to cope with energy demand imposed by stressors. Changes in avt and it gene expression, as well as in their specific receptors (avtrv1a, avtrv2 and itr) at central (hypothalamus and pituitary) and peripheral (liver and head-kidney) levels, showed that vasotocinergic and isotocinergic pathways are involved in physiological changes induced by FD or HSD, suggesting that different stressors are handled through different stress pathways in S. aurata.

Allostatic Load and Stress Physiology in European Seabass (Dicentrarchus labrax L.) and Gilthead Seabream (Sparus aurata L.)

“…The expression of glucocorticoid receptors and heat shock proteins is altered when seabass are chronically stressed by high rearing density ( 71 , 73 ). Changes in the expression of stress-related genes have also been reported in seabream exposed to different rearing densities ( 33 ) or to unpredictable chronic low intensity stress in the early stages of life ( 74 ).…”

“…These species constitute the largest portion (approximately 90–95%) of the Mediterranean aquaculture production, and have high economic and societal value. They, however, show often enigmatic differences in their physiology ( 27 ), especially the responsiveness and susceptibility to stress ( 28 ) and react differently to an acute stressor, when previously exposed to chronic (crowding) stress ( 29 – 33 ). Moreover, seabream seems more resilient than seabass in terms of growth under stress ( 31 , 32 , 34 ).…”

Impact of Air Exposure on Vasotocinergic and Isotocinergic Systems in Gilthead Sea Bream (Sparus aurata): New Insights on Fish Stress Response

“…Furthermore, Avt and Crh sinergize to stimulate Acth release in trout pituitary in vitro , suggesting a role of Avt in the central regulation of the HPI axis. Moreover, previous studies in S. aurata highligthed a possible role of vasotocinergic and isotocinergic systems in chronic stress situations produced by high stocking densities (Mancera et al, 2008 ; Skrzynska et al, 2018 ), hyper- and hypo-osmotic transfers (Martos-Sitcha et al, 2013 , 2014a ), cortisol treatment (Kalamarz-Kubiak et al, 2014 ; Cádiz et al, 2015 ), or food-deprivation and refeeding (Skrzynska et al, 2017 ). In our present study, gene expression profiling of both hypothalamic Avt and It precursors ( avt and it , respectively) and their specific receptors ( avtrv1, avtrv2 , or itr ) were assessed in control and air-exposed sea breams.…”

“…Different endocrine and metabolic pathways have been previously studied in gilthead sea bream ( Sparus aurata ) under different chronic stress situations (Tort et al, 2011 ; Martos-Sitcha et al, 2016 ). The involvement of Avt and/or It, under different stocking densities, fasting conditions or salinity challenges, has been shown for this fish species (Sangiao-Alvarellos et al, 2006 ; Mancera et al, 2008 ; Martos-Sitcha et al, 2013 , 2014a ; Skrzynska et al, 2017 , 2018 ), as well as in others teleosts (Fryer and Leung, 1982 ; Haruta et al, 1991 ; Gilchriest et al, 2000 ). In addition, the physiological role of several endocrine players has also been assessed in different fish species under acute stressors, including air exposure, handling, or hypoxia (Arends et al, 1999 ; López-Patiño et al, 2014 ; Vera et al, 2014 ; Martos-Sitcha et al, 2018 ).…”

Myrcia sylvatica essential oil in the diet of gilthead sea bream (Sparus aurata L.) attenuates the stress response induced by high stocking density

“…Furthermore, some studies demonstrated the lack of a direct relationship between primary and secondary responses (Iversen et al., ; Park et al., ), and under long‐term stressful conditions, other hormones could exert both stress and metabolic regulation. Arginine vasotocin (Avt), a neurohypophysial hormone in non‐mammalian vertebrates that presents a pleiotropic function in both stress and metabolic pathways of teleosts, may be another important player mediating metabolic and stress adaptation (Martos‐Sitcha, Wunderink, Gozdowska, Mancera, & Martínez‐Rodríguez, ; Sangiao‐Alvarellos et al., ; Skrzynska, Martos‐Sitcha, Martínez‐Rodríguez, & Mancera, ; Skrzynska et al., ), as the hypothalamic neurons responsible for the synthesis and release of Avt also innervate the adenohypophyseal cells from the HPI axis (Moons, Cambre, Batten, & Vandesande, ). In addition to increasing lactate levels in the control group, HD also reduced hepatic glycogen storage in all diets tested, indicating the activation of glycogenolytic processes to increase the supply of glucose due to energy expenditure resulting from HD condition.…”