| 1. |
- Handeland, S. O., et al.
(författare)
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Long-term effects of photoperiod, temperature and their interaction on growth, gill Na+, K+-ATPase activity, seawater tolerance and plasma growth-hormone levels in Atlantic salmon Salmo salar
- 2013
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112. ; 83:5, s. 1197-1209
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Tidskriftsartikel (refereegranskat)abstract
- This study was undertaken to examine the long-term effects of photoperiod, temperature and their interaction on growth, gill Na+,K+-ATPase (NKA) activity, seawater tolerance and plasma growth-hormone levels in Atlantic salmon Salmo salar pre-smolts and smolts. The fish (mean +/- s.e. initial body mass=159 +/- 04g) were reared on two photoperiods (continuous light, LL, and simulated natural photoperiod, LDN, 60 degrees 25 N) and two temperatures (83 and 127 degrees C) from June to May of the following year. Mean body mass was affected by photoperiod, temperature and their interactions. Both temperature groups on LL developed peak levels in gill NKA activity from October to November, 4-5months prior to the natural season for the parr-smolt transformation. Fish at 12 degrees C showed peak levels in NKA activity 4-6weeks before the fish at 8 degrees C. Fish in all four experimental groups showed maximum NKA activity within a similar size range (113-162g). The present findings further indicate that smoltification in S. salar is to some extent driven by size, and that S. salar will develop smolt characteristics, e.g. a marked increase in NKA activity, within a similar size range. Faster-growing S. salar will, thus, reach this size threshold at a relatively younger age. (C) 2013 The Fisheries Society of the British Isles
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| 2. |
- Handeland, S. O., et al.
(författare)
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Physiology during smoltification in Atlantic salmon: effect of melatonin implants
- 2013
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Ingår i: Fish Physiology and Biochemistry. - : Springer Science and Business Media LLC. - 0920-1742 .- 1573-5168. ; 39:5, s. 1079-1088
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Tidskriftsartikel (refereegranskat)abstract
- Melatonin implants were used to override natural melatonin rhythm in groups of juvenile Atlantic salmon, Salmo salar, raised at simulated natural photoperiod (SNP) and constant light (LL) from mid-March until end of August. The experiment contained also both sham control (with non-melatonin implants) and control (no implants). No differences were found in the experimental variables between these two control groups. Growth and food intake were negatively affected by melatonin implantation. Overall, higher GH levels were observed in the SNP melatonin-implanted group, whereas no differences in GH levels were seen between the SNP control, LL control, or the LL melatonin-implanted groups. Highest food intake was seen in the LL control group. No differences in food intake were recorded between the LL melatonin-implanted and SNP control groups. Gill Na+, K+, ATPase (NKA) activity was influenced by time as well as the interaction between photoperiod and time. No differences in gill NKA activity or plasma chloride levels following transfer to seawater were seen between the groups with melatonin implants and their controls. Based on the present results, it seems apparent that melatonin does play a role in regulating food intake and growth in Atlantic salmon smolts.
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| 3. |
- Handeland, S. O., et al.
(författare)
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Seawater adaptation and growth of post-smolt Atlantic salmon (Salmo salarnext term) of wild and farmed strains
- 2004
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Ingår i: Aquaculture. - 0044-8486. ; 220:1-4, s. 367-384
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Tidskriftsartikel (refereegranskat)abstract
- previous termAtlantic salmon smolts (Salmo salarnext term L.) of wild (Namsen) and farmed (AquaGen) strains were transferred to full-strength previous termseawaternext term (33‰) for 0 (initial control group), 0.5, 1, 2, 4, 8, 14, 30, 42 and 60 days at three different temperatures (4.3, 9.4 and 14.3 °C). Freshwater temperature in each tank was adjusted to test conditions 10 days prior to transfer. Physiological previous termadaptationnext term was monitored as changes in plasma previous termgrowthnext term hormone levels, gill Na+,K+-ATPase activity, plasma chloride levels and survival in previous termseawater.next term Overall, previous termsmoltsnext term from the wild strain were better able to tolerate transfer to previous termseawater than smoltsnext term from the hatchery strain. A delay in the osmotic disturbance and a prolonged period of osmotic stress were observed at the low temperature. Circulating GH levels increased transiently in all groups during the first 12–48 h in previous termseawaternext term and long-term GH levels were positively correlated with previous termseawaternext term temperature. previous termGrowthnext term rates were influenced by temperature and strain, with the farmed previous termsmoltsnext term showing a higher previous termgrowthnext term than the wild previous termsmolts.next term Food Conversion Efficiency (FCE) was higher in previous termsmoltsnext term from the farmed strain, whereas no differences in daily food consumption were observed. Optimum temperature for FCE was calculated to be 10.5 °C, whereas the optimal temperature for previous termgrowthnext term in previous termseawaternext term was calculated to be 13.0 °C. We suggest that the observed differences in previous termseawaternext term tolerance, previous termgrowthnext term and food conversion probably are genetic and may reflect the fact that the hatchery fish have been bred for rapid previous termgrowthnext term for several generations.
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| 4. |
- Nilsen, Tom Ole, et al.
(författare)
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EFFECTS OF ANDROGENS AND CORTISOL ON GILL ION TRANSPORTERS AND OMSMOREGULATORY CAPACITY IN ATLANTIC SALMON (SALMO SALAR)
- 2014
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Ingår i: ICBF 2014, Edinburgh.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Sex steroids have been reported to compromise ion homeostasis in teleosts, yet there is limited and somewhat contradicting knowledge about the mechanisms through which androgens impact osmoregulatory capacity in salmonids. Immature Atlantic salmon post-smolts in seawater (SW) were injected with 11-ketoandrostenedione (OA; 25 µg/g BW), cortisol (F; 25 µg/g BW), F+OA (25 µg/g BW) and sham control (CON). After 8 days treatment, androgen treated fishdemonstrated a striking transcriptional increase in freshwater (FW)-type of ion transporters (NKA α1a ) , concurrent with no apparent ion perturbations, or down regulation of SW gill ion-transporters (NKA α1b). F treated post-smolts displayed increased gill NKA α1a transcription, with an additive effect of F+OA.. Moreover, F also resulted in decreased transcription of NKA α1b whilst fish treated with combinations of F and OA experienced severe ion perturbations and mortalities in SW, while no mortality occurred when only F was administered. Our findings suggests that androgens have, either directly or indirectly, a role in remodelling the gill epithelia for FW entry, rather than leading to osmoregulatory dysfunction in SW acclimated post-smolts. Moreover, maturing post-smolts may be sensitive to stress since combinations of elevated androgens and cortisol levels may have detrimental effects on homeostasis and fish welfare.
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| 5. |
- Bakke-McKellep, A. M., et al.
(författare)
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Effects of dietary soybean meal and photoperiod cycle on osmoregulation following seawater exposure in Atlantic salmon smolts
- 2006
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 69:5, s. 1396-1426
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Tidskriftsartikel (refereegranskat)abstract
- Atlantic salmon Salmo salar juveniles were fed either fishmeal-based diets (FM) or diets in which soybean meal (SBM) partly replaced the FM from first feeding on. The fish were kept at continuous daylight during the juvenile stage. During the last 3 weeks before reaching 100 g body mass, all fish were subjected to 12L:12D. Starting at 100 g body mass, groups of 60 fish from each feeding background were subjected to continuous light for 12 weeks (short winter), or a square-wave photoperiod cycle to stimulate parr to smolt transformation with 8L:16D during the first 6 weeks, and then continuous light during the last 6 weeks (long winter). After the 12 weeks, 20 fish from each treatment were subjected to 0, 24 or 96 h seawater exposure at a water salinity of 34. Hypo-osmoregulatory ability at seawater exposure was assessed by mortality, intestinal pathology, plasma ion concentrations and osmolality, gill Na+/K+-ATPase activity and element concentrations in the cytoplasm of distal intestinal enterocytes using X-ray microanalysis. The hypo-osmoregulatory capacity was higher in fish kept at short winter than at long winter, apparently due to more rapid development of gill Na+/K+-ATPase activity. Fish fed SBM suffered typical soybean meal-induced histological alterations of the distal intestine and apparent reductions in digestive function in the more proximal gastrointestinal regions. The net osmoregulatory capacity of these fish was maintained, as indicated by higher gill Na+/K+-ATPase activity and lower plasma Na+, Ca2+ and osmolality compared to the FM-fed fish. Thus, feeding SBM did not impair the hypo-osmoregulatory ability of the Atlantic salmon following seawater exposure.
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| 6. |
- Björnberg, Jakob, 1983, et al.
(författare)
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Random Walk on Random Infinite Looptrees
- 2015
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Ingår i: Journal of statistical physics. - : Springer Science and Business Media LLC. - 0022-4715 .- 1572-9613. ; 158:6, s. 1234-1261
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Tidskriftsartikel (refereegranskat)abstract
- Looptrees have recently arisen in the study of critical percolation on the uniform infinite planar triangulation. Here we consider random infinite looptrees defined as the local limit of the looptree associated with a critical Galton-Watson tree conditioned to be large. We study simple random walk on these infinite looptrees by means of providing estimates on volume and resistance growth. We prove that if the offspring distribution of the Galton-Watson process is in the domain of attraction of a stable distribution with index then the spectral dimension of the looptree is 2 alpha/(alpha+1).
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| 7. |
- Ebbesson, L. O.E., et al.
(författare)
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Propylthiouracil-induced hypothyroidism in coho salmon, Oncorhynchus kisutch : Effects on plasma total thyroxine, total triiodothyronine, free thyroxine, and growth hormone
- 1998
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Ingår i: Fish Physiology and Biochemistry. - 0920-1742. ; 19:4, s. 305-313
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Tidskriftsartikel (refereegranskat)abstract
- Thyroid hormones transiently increase during parr-smolt transformation in coho salmon, Oncorhynchus kisutch, and are believed to trigger morphological, physiological, behavioural, and neural changes. The effectiveness of propylthiouracil (PTU) to induce hypothyroidism in smolting coho salmon was determined by immersing coho salmon, Oncorhynchus kisutch, in 30 mg 1-1 PTU from May 1, two weeks prior to the consistent annual total thyroxine (TT4) peak in mid-May, until the last sampling date. Plasma was obtained at two sampling dates from control and PTU -treated coho salmon: May 15, during the plasma TT4 peak; and May 26, after the TT4 peak. Radioimmunoassays were used to measure plasma TT4, total triiodothyronine (TT3), free thyroxine (FT4), and salmon growth hormone (sGH). The PTU -treatment inhibited the natural smoltification-related increases in plasma TT4, TT3 and GH levels compared with controls, but PTU-treatment did not affect these hormone levels when they were low. PTU -treatment increased FT4 and decreased TT3 and sGH levels in the May 26 sample. In the May 15 sample, FT4 levels were unaffected by PTU-treatment, whereas TT4 levels were decreased. These data demonstrate the ability of PTU to induce hypothyroidism in salmonids as shown by the decrease in TT4 and TT3. These data demonstrate that PTU treatment by immersion can induce hypothyroidism in salmonids as shown by: (1) the inhibition of the natural increases of TT4 and TT3; (2) the increase in FT4 levels corresponding to the lowered TT3 levels, suggesting an inhibition of thyroxine 5′-monodeiodinase activity. We also show for the first time that PTU treatment can lower plasma GH levels in salmonids. This lowering of plasma GH level is associated with the decrease in TT3 levels and the increase in FT4 levels. Lhe PLU induced lowering in GH levels may contribute to the observed changes in FT4 and TT3, since GH is known to increase thyroxine 5′-monodeiodinase activity.
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| 8. |
- Einarsdottir, Ingibjörg, 1951, et al.
(författare)
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Plasma growth hormone-binding protein levels in Atlantic salmon Salmo salar during smoltification and seawater transfer
- 2014
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112. ; 85:4, s. 1279-1296
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Tidskriftsartikel (refereegranskat)abstract
- Specific growth hormone (GH)-binding protein (Ghbp) was purified from Atlantic salmon Salmo salar and rainbow trout Oncorhynchus mykiss plasma with immunoprecipitation and characterized in cross-linking studies using autoradiography and western blots. The size of the Ghbp was estimated to be c. 53 kDa. A radioimmunoassay was established to measure Ghbp in salmonids, using antibodies specific against the extracellular segment of the S. salar growth hormone receptor 1 (grh1; GenBank AY462105). Plasma Ghbp levels were measured in S. salar smolts in fresh water and after transfer to seawater (SW; experiments 1 and 2), and in post-smolts kept at different salinities (0, 12, 22 and 34) for 3 months (experiment 3). A transient increase in plasma Ghbp, which lasted for 1 month or less, was noted in smolts after transfer to SW. Concomitantly, plasma GH and gill Na+-K+-ATPase activity increased during smoltification (in experiment 2). No difference in plasma Ghbp was evident between post-smolts kept at different salinities, although the fish kept at salinity 34 had higher plasma GH than the group kept at salinity 22 and higher hepatic ghr1 expression than post-smolts kept at salinity 12. This suggests that plasma Ghbp regulation may respond to salinity changes in the short term. The lack of correlation between Ghbp, plasma GH and hepatic ghr1 expression in the long-term post-smolt experiment indicates that Ghbp levels may be regulated independently of other components of the endocrine GH system in salmonids.
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| 9. |
- Imsland, A.K, et al.
(författare)
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Temperature and salinity effects on plasma insulin-like growth factor-1 concentrations and growth in juvenile turbot (Scophthalmus maximus).
- 2007
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486. ; 271:1-4, s. 546-552
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Tidskriftsartikel (refereegranskat)abstract
- The effects of temperature and salinity on plasma IGF-I levels and its interrelationship with growth, daily feed intake and feed conversion of juvenile turbot (initial mean weight 14 g) were investigated by rearing fish at 10, 14, 18 and 22 °C and 15, 25 and 33.5‰ for 3 months. The plasma IGF-I levels increased with increasing temperatures reaching a plateau around 18 °C. Further, both temperature and salinity had a significant effect on growth, daily feed intake and feed conversion efficiency in juvenile turbot. Growth, food consumption, and food conversion efficiency were highest at 18 °C and 15‰, and lowest at 10 °C and 33.5‰. Although there was a high variation between IGF-I values within all groups there was a positive relationship between IGF-I levels and specific growth rates and daily feed intake. The levels of IGF-I were almost three times higher for fish with higher growth rates than for those with lower growth. In addition, the results show evidence for an increased appetite in fish with high plasma IGF-I levels. Interestingly, there was no correlation between environmental salinity and IGF-I levels, although decreased salinity improves growth and feed conversion efficiency.
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| 10. |
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