Changes in the Immune System of Coho Salmon (Oncorhynchus kisutch) during the Parr-to-Smolt Transformation and after Implantation of Cortisol

Abstract

The primary immune response of coho salmon (Oncorhynchus kisutch), as assessed by the production of splenic antibody-secreting cells (plaque-forming cells, PFC) after an injection of Vibrio anguillarum O-antigen, decreased during smoltification. This period was marked by increases in gill Na+-K+-adenosine triphosphatase (ATPase) activity and plasma thyroxine and cortisol titers. Numbers of leucocytes relative to erythrocytes in peripheral blood and splenic lymphocytes relative to fish body weight were also reduced. Fish reared at normal hatchery density (approximately 2 fish∙L−1) appeared to have reduced rates of development and higher numbers of PFC than fish reared at one-third normal density. Moreover, in fish changed from normal density to low density 2 wk before sampling, ATPase activity and plasma thyroxine levels were equal to those in fish reared continuously at normal density, but plasma cortisol levels and PFC were equal to those in fish reared at low density. Fish with cortisol implants had higher plasma cortisol titers, reduced numbers of splenic PFC, splenic lymphocytes, and circulating leucocytes, and greater mortality when fish were exposed to V. anguillarum.

The effect of allostatic load on hypothalamic–pituitary–interrenal (HPI) axis before and after secondary vaccination in Atlantic salmon postsmolts (Salmo salar L.)

“…The "stress and vaccine" group experienced two weeks prior to the second vaccination elevated baseline levels of plasma cortisol compared to pre-stress levels, and the secondary vaccination (week 4) seemed just to be the additional stressor that "pushed" the animals in to a chronic stress state or allostatic overload type 2 situation. Similar studies of base-line plasma cortisol have shown that an unstressed fish had a baseline levels as low as 13.8 nM, while chronic stressed fish had a baseline level above 27.5 nM (Maule et al 1987;Pickering and Pottinger 1989;Van Zwol et al 2012). This seemed to be supported by the fact that secondary and tertiary stress responses as plasma chloride, magnesium, fin rot and mortality, were significantly increased in the "stress and vaccine" group compared to the "vaccine and stress" and the control group.…”

Adrenocorticotropic Hormone in Relation to Interrenal Function during Stress in Tilapia (Oreochromis mossambicus)

“…Tilapia species are hierarchal (de Oliveira Fernendez and Volpato, 1993), and therefore we suggest that in our fish differences in hierarchal sta tus (established prior to or during the con finement period) underly the different stress responses. As suggested for other species, this phenomenon might selectively predispose high responders to infectious diseases (Maule et al, 1987), as well as re duce their development and growth rate. Other relevant features include the facts that subordinates generally suffer most from additional stress conditions (Schreck, 1981) and social rank in some fish is asso ciated with interrenal mass (Erickson, 1967) and interrenal cell activity (Noakes and Leatherland, 1977;Schreck, 1981).…”

Variation in adrenal and thyroid hormones with life-history stage in juvenile northern elephant seals (Mirounga angustirostris)

“…Catecholamines, such as epinephrine and norepinephrine, are also released as part of the fight-or-flight response to stress. Together, the suite of hormones activated by this response influence many processes in the body including heart rate, metabolic rate, energy allocation, growth, reproduction, immune response, memory, and behavior, allowing an animal to react appropriately to the stress, which ultimately promotes survival (Breuner et al, 2013;Brilion et al, 1995;Connell and Davies, 2005;Khani and Tayek, 2001;Maule et al, 1987;Romero and Butler, 2007;Tilbrook et al, 2000).…”