- The Brain-Pituitary-Gonad Axis in the Atlantic Salmon

2015 ◽  
pp. 119-134
Keyword(s):  
Atlantic Salmon ◽  
The Brain

Multiple changes in the brain of Atlantic salmon, Salmo salar, during photoperiodically-induced parr-smolt transformation

Aquaculture ◽  
1994 ◽  
Vol 121 (1-3) ◽  
pp. 289-290 ◽  
Author(s):  
Pierre-Philippe Morin ◽  
J.Geoffrey Eales ◽  
Toshiaki J Hara ◽  
Svante Winberg ◽  
Göran E Nilsson
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Atlantic Salmon Salmo Salar ◽  
The Brain

Development, survival, and structural alterations of embryos and alevins of Atlantic salmon, Salmo salar L., continuously exposed to alkaline levels of pH, from fertilization

1980 ◽  
Vol 58 (3) ◽  
pp. 369-377 ◽  
Author(s):  
P. G. Daye ◽  
E. T. Garside
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Hydrogen Ions ◽  
Gradual Decline ◽  
Cumulative Mortality ◽  
Zona Radiata ◽  
Atlantic Salmon Salmo Salar ◽  
Branchial Epithelium ◽  
The Brain ◽  
Degree Of Severity

Embryos of the Atlantic salmon, Salmo salar L., were incubated continuously from fertilization at pH 6.8 (control) and pH 9.0 and 9.5, initially at 6.7 °C but with a gradual decline in the first 5 weeks to 5.0 °C for the remaining 10 weeks of exposure. Subsequently, the alevins were maintained in these environments for 50 days after hatching. Developmental processes and hatching were not affected by these levels of pH. Percentage cumulative mortality of treated embryos, 8%, was approximately that in the controls. Alevin mortality in the control lots was 1.2 and 1.3%. At pH 9.0, cumulative mortality was 0.4%, but at pH 9.5 there was an accelerating increase to 18%, at the termination of observation.Sublethal changes in embryos were confined mostly to cell necrosis and sloughed rudimentary epidermis. Some metaplasia of the brain stem occurred at pH 9.5. Sites and intensity of alterations increased in alevins at pH 9.5, following the loss of the zona radiata. In addition to ongoing injury of epidermis, including mucous cells, deleterious alterations occurred in branchial epithelium, erythrocytes, myocardium, blood vessels of the viscera, liver, brain, and optic lenses. In general, sublethal changes caused by hydroxylions are similar to those caused by excessive hydrogen ions but are somewhat less extensive in the structures affected or in their degree of severity.

scholarly journals Salinity and photoperiod modulate pubertal development in Atlantic salmon (Salmo salar)

2013 ◽  
Vol 220 (3) ◽  
pp. 319-332 ◽  
Author(s):  
Michelle C Melo ◽  
Eva Andersson ◽  
Per Gunnar Fjelldal ◽  
Jan Bogerd ◽  
Luiz R França ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Plasma Levels ◽  
Pubertal Development ◽  
Mrna Levels ◽  
Treatment Groups ◽  
Timing Of Puberty ◽  
The Brain ◽  
Spermatogonial Proliferation ◽  
Stimulation Of

The Atlantic salmon shows substantial life cycle plasticity, which also applies to the timing of puberty. While it is characterized by the activation of the brain–pituitary–gonad axis, many morphophysiological aspects of puberty and the influence of environmental conditions, such as water salinity, are not well understood in fish. Here, 12-month-old Atlantic salmon coming from an out-of-season smoltification regime in December were exposed to freshwater (FW) or seawater (SW) at 16 °C to stimulate puberty under a 24-h constant light (LL) or 12 h light:12 h darkness (LD) photoperiod. These four treatment groups (FWLL, SWLL, FWLD, and SWLD) were studied from January to March. Next to 11-ketotestosterone (11-KT) plasma levels, the expression of pituitary genes (gnrhr4, fshb, and lhb) and spermatogenesis was quantified. When spermatogonial proliferation started, fshb mRNA levels increased steeply and began to decrease when spermatogonial mitosis approached completion and most germ cells had reached meiotic or post-meiotic stages. Conversely, lhb mRNA levels increased progressively during spermatogenesis. Most males in all treatment groups matured, but exposure to SW resulted in the strongest stimulation of the onset of spermatogenesis and elevation of pituitary gnrhr4 and fshb mRNA levels. Later on, the LD photoperiod accelerated, irrespective of the salinity, the completion of spermatogenesis, associated with higher lhb mRNA and 11-KT plasma levels than in the LL groups. We find that both salinity and photoperiod modulated different aspects of spermatogenesis, and resulted in a differential activation of pituitary and testis functions; SW stimulating the onset and the shorter photoperiod the completion of spermatogenesis.

Exophiala salmonis. [Descriptions of Fungi and Bacteria].

1983 ◽  
Author(s):  
B. L. Brady
Keyword(s):  
Atlantic Salmon ◽  
Leaf Litter ◽  
Geographical Distribution ◽  
Salmo Salar ◽  
Giant Cells ◽  
Salvelinus Namaycush ◽  
Granuloma Formation ◽  
Swim Bladder ◽  
Second Year ◽  
The Brain

Abstract A description is provided for Exophiala salmonis. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS AND SUBSTRATA: Salmo clarkii, S. salar, Salvelinus namaycush; Acacia karroo (leaf litter), Araucaria sp. (wood). GEOGRAPHICAL DISTRIBUTION: Widespread. DISEASE: The three epidemics in fish hatcheries described by Carmichael in S. clarkii and Salvelinus 'namaycush' involved infection of the head only, apparently commencing in the brain and spreading to neighbouring tissue. The lesions were of the chronic granulomatous type. Severe losses were caused. The outbreak described by Richards et al. (1978) was in Atlantic salmon, Salmo salar, second year smolts introduced from a hatchery into sea-cages. Fish exhibited abdominal swelling due to kidney enlargement; the posterior kidney was infected in all fish and lesions were sometimes also present in the heart, liver, spleen, pancreas and muscle. Granuloma formation occurred in all affected organs, the amount of fungus present bore little relation to the extent of granuloma formation. Giant cells were present throughout the lesions. In contrast to Carmichael's description, no lesions were found in the brain, nor in the swim bladder or intestines. PATHOGENICITY AND TRANSMISSION: Carmichael (1966) was unable to obtain infection by injection or by allowing fish to swim in water heavily contaminated by the fungus. Richards et al. (1978) noted that in adjacent cages of fish in seawater only one cage was affected by the disease and suspected that infection was via the commercial food supplied.

scholarly journals Environment-dependent plasticity and ontogenetic changes in the brain of hatchery-reared Atlantic salmon

2016 ◽  
Vol 301 (1) ◽  
pp. 75-82 ◽  
Author(s):  
J. Näslund ◽  
M. H. Larsen ◽  
S. T. Thomassen ◽  
K. Aarestrup ◽  
J. I. Johnsson
Keyword(s):  
Atlantic Salmon ◽  
Ontogenetic Changes ◽  
Dependent Plasticity ◽  
The Brain

scholarly journals Long-term feeding of Atlantic salmon in seawater with low dietary long-chain n-3 fatty acids affects tissue status of the brain, retina and erythrocytes

2016 ◽  
Vol 115 (11) ◽  
pp. 1919-1929 ◽  
Author(s):  
N. H. Sissener ◽  
B. E. Torstensen ◽  
I. Stubhaug ◽  
G. Rosenlund
Keyword(s):  
Fatty Acids ◽  
Atlantic Salmon ◽  
Effect Of Temperature ◽  
Production Cycle ◽  
Tissue Concentrations ◽  
Tissue Levels ◽  
Feeding Trials ◽  
The Brain ◽  
Long Chain

AbstractIn two long-term feeding trials in seawater, Atlantic salmon were fed EPA+DHA in graded levels, from 1·3 to 7·4 % of fatty acids (FA, 4–24 g/kg feed) combined with approximately 10 % 18 : 3n-3, at 6 and 12°C. Dietary EPA appeared to be sufficient in all diet groups, as no differences were seen in polar lipid tissue concentrations of either the brain, retina or erythrocytes. For DHA, a reduction in tissue levels was observed with low dietary supply. Effects on brain DHA at ≤1·4 % EPA+DHA of dietary FA and retina DHA at ≤2·7 % EPA+DHA of dietary FA were only observed in fish reared at 6°C, suggesting an effect of temperature, whereas tissue levels of n-6 FA increased as a response to increased dietary n-6 FA in both the brain and the retina at both temperatures. DHA levels in erythrocytes were affected by ≤2·7 % EPA+DHA at both temperatures. Therefore, DHA appears to be the limiting n-3 FA in diets where EPA and DHA are present in the ratios found in fishmeal and fish oil. To assess the physiological significance of FA differences in erythrocytes, the osmotic resistance was tested, but it did not vary between dietary groups. In conclusion, ≤2·7 % EPA+DHA of FA (≤9 g/kg feed) is not sufficient to maintain tissue DHA status in important tissues of Atlantic salmon throughout the seawater production cycle despite the presence of dietary 18 : 3n-3, and effects may be more severe at low water temperatures.

Early enrichment effects on brain development in hatchery-reared Atlantic salmon (Salmo salar): no evidence for a critical period

2012 ◽  
Vol 69 (9) ◽  
pp. 1481-1490 ◽  
Author(s):  
Joacim Näslund ◽  
Kim Aarestrup ◽  
Søren T. Thomassen ◽  
Jörgen I. Johnsson
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Brain Size ◽  
Early Period ◽  
Structural Complexity ◽  
Brain Growth ◽  
Atlantic Salmon Salmo Salar ◽  
Rearing Methods ◽  
External Feeding ◽  
The Brain

In hatcheries, fish are normally reared in barren environments, which have been reported to affect their phenotypic development compared with wild conspecifics. In this study, Atlantic salmon ( Salmo salar ) alevins were reared in conventional barren hatchery trays or in either of two types of structurally enriched trays. We show that increased structural complexity during early rearing increased brain size in all investigated brain substructures. However, these effects disappeared over time after transfer to barren tanks for external feeding. Parallel to the hatchery study, a group of salmon parr was released into nature and recaptured at smoltification. These stream-reared smolts developed smaller brains than the hatchery reared smolts, irrespective of initial enrichment treatment. These novel findings do not support the hypothesis that there is a critical early period determining the brain growth trajectory. In contrast, our results indicate that brain growth is plastic in relation to environment. In addition, we show allometric growth in brain substructures over juvenile development, which suggests that comparisons between groups of different body size should be made with caution. These results can aid the development of ecologically sound rearing methods for conservational fish-stocking programs.

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