The Experts below are selected from a list of 1272 Experts worldwide ranked by ideXlab platform
Krista M Nichols - One of the best experts on this subject based on the ideXlab platform.
-
rna seq reveals differential gene expression in the brains of juvenile resident and migratory smolt rainbow trout oncorhynchus mykiss
Comparative Biochemistry and Physiology Part D: Genomics and Proteomics, 2016Co-Authors: Matthew C Hale, Garrett J Mckinney, Frank P Thrower, Krista M NicholsAbstract:Abstract Many migratory traits are heritable, but there is a paucity of evidence identifying the molecular mechanisms underlying differentiation in alternative migratory tactics, or in linking variation in gene expression to migratory behaviors. To that end, we examined differential gene expression in the brain transcriptome between young steelhead trout that had undergone the Smoltification process, and resident rainbow trout ( Oncorhynchus mykiss ) from Sashin Creek, Alaska. Samples were sequenced from two time points: immediately before (at 20 months of age) and during (2 years of age) the presumed peak of Smoltification. Smolt and resident individuals came from two genetic crosses, one where both parents were migratory, and another where both parents were residents. A total of 533 (1.9%) genes were differentially expressed between crosses, or between smolt and resident samples. These genes include some candidate migratory genes (such as POMC ), as well as genes with no previous known involvement in the migratory process. Progeny from resident parents showed more upregulated genes than progeny from migrant parents at both time points. Pathway analysis showed enrichment in 227 biological pathways between cross type, and 171 biological pathways were enriched between residents and smolts. Enriched pathways had connections to many biofunctions, and most were only enriched in one contrast. However, pathways connected to phototransduction were enriched between both cross type and migratory tactics in 11 out of 12 contrasts, suggesting there are fundamental differences in how smolts and residents process light in the brain. The genes and pathways described herein constitute an a priori candidate list for future studies of migration in other populations of O. mykiss , and other migratory species.
-
Divergence in Expression of Candidate Genes for the Smoltification Process Between Juvenile Resident Rainbow and Anadromous Steelhead Trout
Marine Biotechnology, 2014Co-Authors: Benjamin C. Hecht, Frank P Thrower, Madeline E. Valle, Krista M NicholsAbstract:Rainbow and steelhead trout ( Oncorhynchus mykiss ), among other salmonid fishes, exhibit tremendous life history diversity, foremost of which is variation in migratory propensity. While some individuals possess the ability to undertake an anadromous marine migration, others remain resident in freshwater throughout their life cycle. Those that will migrate undergo tremendous physiological, morphological, and behavioral transformations in a process called Smoltification which transitions freshwater-adapted parr to marine-adapted smolts. While the behavior, ecology, and physiology of Smoltification are well described, our understanding of the proximate genetic mechanisms that trigger the process are not well known. Quantitative genetic analyses have identified several genomic regions associated with Smoltification and migration-related traits within this species. Here we investigate the divergence in gene expression of 18 functional and positional candidate genes for the Smoltification process in the brain, gill, and liver tissues of migratory smolts, resident parr, and precocious mature male trout at the developmental stage of out-migration. Our analysis reveals several genes differentially expressed between life history classes and validates the candidate nature of several genes in the parr-smolt transformation including Clock1α , FSHβ , GR , GH2 , GHR1 , GHR2 , NDK7 , p53 , SC6a7 , Taldo1 , THRα , THRβ , and Vdac2 .
Stephen D. Mccormick - One of the best experts on this subject based on the ideXlab platform.
-
Functional divergence of thyrotropin beta-subunit paralogs gives new insights into salmon Smoltification metamorphosis
Scientific Reports, 2019Co-Authors: Mitchell S. Fleming, Gersende Maugars, Jocelyn Rancon, Romain Fontaine, Rasoul Nourizadeh-lillabadi, Elena Santidrian Yebra-pimentel, Ron Dirks, Anne-gaëlle Lafont, Finn-arne Weltzien, Stephen D. MccormickAbstract:Smoltification is a metamorphic event in salmon life history, which initiates downstream migration and pre-adapts juvenile salmon for seawater entry. While a number of reports concern thyroid hormones and Smoltification, few and inconclusive studies have addressed the potential role of thyrotropin (TSH). TSH is composed of a α-subunit common to gonadotropins, and a β-subunit conferring hormone specificity. We report the presence and functional divergence of duplicated TSH β-subunit paralogs ( tshβa and tshβb ) in Atlantic salmon. Phylogeny and synteny analyses allowed us to infer that they originated from teleost-specific whole genome duplication. Expression profiles of both paralogs in the pituitary were measured by qPCR throughout Smoltification in Atlantic salmon from the endangered Loire-Allier population raised in a conservation hatchery. This revealed a striking peak of tshβb expression in April, concomitant with downstream migration initiation, while tshβa expression remained relatively constant. In situ hybridization showed two distinct pituitary cell populations, tshβa c ells in the anterior adenohypophysis, and tshβb cells near to the pituitary stalk, a location comparable to the pars tuberalis TSH cells involved in seasonal physiology and behaviour in birds and mammals. Functional divergence of tshβ paralogs in Atlantic salmon supports a specific role of tshβb in Smoltification.
-
environmental endocrinology of salmon Smoltification
General and Comparative Endocrinology, 2011Co-Authors: Bjorn Thrandur Bjornsson, Sigurd O Stefansson, Stephen D. MccormickAbstract:Smolting is a hormone-driven developmental process that is adaptive for downstream migration and ocean survival and growth in anadromous salmonids. Smolting includes increased salinity tolerance, increased metabolism, downstream migratory and schooling behavior, silvering and darkened fin margins, and olfactory imprinting. These changes are promoted by growth hormone, insulin-like growth factor I, cortisol, thyroid hormones, whereas prolactin is inhibitory. Photoperiod and temperature are critical environmental cues for smolt development, and their relative importance will be critical in determining responses to future climate change. Most of our knowledge of the environmental control and endocrine mediation of smolting is based on laboratory and hatchery studies, yet there is emerging information on fish in the wild that indicates substantial differences. Such differences may arise from differences in environmental stimuli in artificial rearing environments, and may be critical to ocean survival and population sustainability. Endocrine disruptors, acidification and other contaminants can perturb smolt development, resulting in poor survival after seawater entry.
-
endocrine systems in juvenile anadromous and landlocked atlantic salmon salmo salar seasonal development and seawater acclimation
General and Comparative Endocrinology, 2008Co-Authors: Tom Ole Nilsen, Stephen D. Mccormick, Lars O E Ebbesson, Björn Th. Björnsson, Steffen S Madsen, Pia Kiilerich, Sigurd O StefanssonAbstract:Abstract The present study compares developmental changes in plasma levels of growth hormone (GH), insulin-like growth factor I (IGF-I) and cortisol, and mRNA levels of their receptors and the prolactin receptor (PRLR) in the gill of anadromous and landlocked Atlantic salmon during the spring parr-smolt transformation (Smoltification) period and following four days and one month seawater (SW) acclimation. Plasma GH and gill GH receptor (GHR) mRNA levels increased continuously during the spring Smoltification period in the anadromous, but not in landlocked salmon. There were no differences in plasma IGF-I levels between strains, or any increase during Smoltification. Gill IGF-I and IGF-I receptor (IGF-IR) mRNA levels increased in anadromous salmon during Smoltification, with no changes observed in landlocked fish. Gill PRLR mRNA levels remained stable in both strains during spring. Plasma cortisol levels in anadromous salmon increased 5-fold in May and June, but not in landlocked salmon. Gill glucocorticoid receptor (GR) mRNA levels were elevated in both strains at the time of peak Smoltification in anadromous salmon, while mineralocorticoid receptor (MR) mRNA levels remained stable. Only anadromous salmon showed an increase of gill 11β-hydroxysteroid dehydrogenase type-2 (11β-HSD2) mRNA levels in May. GH and gill GHR mRNA levels increased in both strains following four days of SW exposure in mid-May, whereas only the anadromous salmon displayed elevated plasma GH and GHR mRNA after one month in SW. Plasma IGF-I increased after four days in SW in both strains, decreasing in both strains after one month in SW. Gill IGF-I mRNA levels were only increased in landlocked salmon after 4 days in SW. Gill IGF-IR mRNA levels in SW did not differ from FW levels in either strain. Gill PRLR mRNA did not change after four days of SW exposure, and decreased in both strains after one month in SW. Plasma cortisol levels did not change following SW exposure in either strain. Gill GR, 11β-HSD2 and MR mRNA levels increased after four days in SW in both strains, whereas only the anadromous strain maintained elevated gill GR and 11β-HSD2 mRNA levels after one month in SW. The results indicate that hormones and receptors of the GH and cortisol axes are present at significantly lower levels during spring development and SW acclimation in landlocked relative to anadromous salmon. These findings suggest that attenuation of GH and cortisol axes may, at least partially, result in reduced preparatory upregulation of key gill ion-secretory proteins, possibly a result of reduced selection pressure for marine adaptations in landlocked salmon.
-
molecular mechanisms of continuous light inhibition of atlantic salmon parr smolt transformation
Aquaculture, 2007Co-Authors: Sigurd O Stefansson, Tom Ole Nilsen, Lars O E Ebbesson, Björn Th. Björnsson, Anna Wargelius, Steffen S Madsen, Stephen D. MccormickAbstract:Atlantic salmon (Salmosalar)rely onchangesin photoperiodfor thesynchronization ofthe developmental eventsconstituting the parr–smolt transformation. In the absence of photoperiod cues, parr–smolt transformation is incomplete, and such ‘pseudo-smolts’ normally fail to adapt to seawater. The present study addresses the endocrine and molecular mechanisms controlling the development of hypo-osmoregulatory ability and how artificial photoperiod can disrupt these changes. Juvenile Atlantic salmon reared under constant light (LL) from first feeding, were separated into two groups, and exposed to either LL or simulated natural photoperiod (LDN) from October, eight months prior to the expected completion of Smoltification. Juveniles reared on LL grew well, but failed to show the smolt-related reduction in condition factor in spring. Gill mRNA levels of Na + ,K + –ATPase (NKA) isoform α1a decreased in LDN fish through completion of parr–smolt transformation, while levels remained unchanged in the LL group. In contrast, α1b expression increased 6-fold in the LDN group between February and May, again with no change in the LL group. Further, Na + ,K + , 2Cl − co-transporter (NKCC) showed a transient increase in expression in smolts on LDN between February and May, while no changesinmRNAlevelswereseeninjuvenilesunderLL.Consequently,gillNKAactivityandNKA αandNKCCproteinabundance were significantly lower in juveniles on LLthan in smolts onLDN. LL fish in spring had lower circulating levels ofthyroid hormones (THs), growth hormone (GH) and cortisol. Gill GH-receptor mRNA levels, determined by quantitative PCR, were less than 50% of controls. In contrast, circulating levels of IGF-1 and gill IGF-1 receptor expression, were comparable to controls. Our findings show thatcontinuouslightpreventsthecompletionofparr–smolttransformationataverybasiclevel,disruptingthenaturalup-regulationof key elements of the endocrine system involved in the regulation of the parr–smolt transformation, and consequently inhibiting the Smoltification-related increase in expression, abundance and activity of gill ion transport proteins. © 2007 Elsevier B.V. All rights reserved.
Steffen S Madsen - One of the best experts on this subject based on the ideXlab platform.
-
corticosteroid regulation of na k atpase α1 isoform expression in atlantic salmon gill during smolt development
General and Comparative Endocrinology, 2011Co-Authors: Pia Kiilerich, Karsten Kristiansen, Sara H Pedersen, Steffen S MadsenAbstract:Abstract The proposed mineralocorticoid-like signalling axis in teleost fish, consisting of the hormone 11-deoxycorticosterone (DOC) and a mineralocorticoid receptor (MR), has recently challenged our conception of cortisol being the only osmoregulatory corticosteroid in teleost fish. This paper aimed at comparing the osmoregulatory role of DOC with that of cortisol during the pre-adaptive development of SW-tolerance, Smoltification, in Atlantic salmon. Using an in vitro gill block incubation system, the effect of DOC and cortisol in the gill was investigated from January to September, using Na + ,K + -ATPase α-subunit isoforms α-1a and α-1b mRNA levels as targets for regulation by the hormones. Cortisol and DOC both conferred significant up-regulation of α-1a and α-1b mRNA levels at specific time-points during Smoltification. However, the effect of cortisol and DOC on α-subunit isoforms varied seasonally between isoforms and hormones. The maximum induction of α-1a was 3- to 4-fold compared to controls whereas a 2-fold induction was observed for α-1b. The pattern and capacity of stimulation of α-1a through Smoltification were similar for cortisol and DOC, whereas cortisol had an enhanced capacity to stimulate α-1b as compared to DOC. Even though there was no demonstrable change in cortisol or DOC sensitivity in the gill, the magnitude of the hormonal effects were seasonally dependent. This is the first report of DOC-induced effects on osmoregulatory targets in fish, thus indicating a role for DOC and MR signalling in osmoregulation.
-
endocrine systems in juvenile anadromous and landlocked atlantic salmon salmo salar seasonal development and seawater acclimation
General and Comparative Endocrinology, 2008Co-Authors: Tom Ole Nilsen, Stephen D. Mccormick, Lars O E Ebbesson, Björn Th. Björnsson, Steffen S Madsen, Pia Kiilerich, Sigurd O StefanssonAbstract:Abstract The present study compares developmental changes in plasma levels of growth hormone (GH), insulin-like growth factor I (IGF-I) and cortisol, and mRNA levels of their receptors and the prolactin receptor (PRLR) in the gill of anadromous and landlocked Atlantic salmon during the spring parr-smolt transformation (Smoltification) period and following four days and one month seawater (SW) acclimation. Plasma GH and gill GH receptor (GHR) mRNA levels increased continuously during the spring Smoltification period in the anadromous, but not in landlocked salmon. There were no differences in plasma IGF-I levels between strains, or any increase during Smoltification. Gill IGF-I and IGF-I receptor (IGF-IR) mRNA levels increased in anadromous salmon during Smoltification, with no changes observed in landlocked fish. Gill PRLR mRNA levels remained stable in both strains during spring. Plasma cortisol levels in anadromous salmon increased 5-fold in May and June, but not in landlocked salmon. Gill glucocorticoid receptor (GR) mRNA levels were elevated in both strains at the time of peak Smoltification in anadromous salmon, while mineralocorticoid receptor (MR) mRNA levels remained stable. Only anadromous salmon showed an increase of gill 11β-hydroxysteroid dehydrogenase type-2 (11β-HSD2) mRNA levels in May. GH and gill GHR mRNA levels increased in both strains following four days of SW exposure in mid-May, whereas only the anadromous salmon displayed elevated plasma GH and GHR mRNA after one month in SW. Plasma IGF-I increased after four days in SW in both strains, decreasing in both strains after one month in SW. Gill IGF-I mRNA levels were only increased in landlocked salmon after 4 days in SW. Gill IGF-IR mRNA levels in SW did not differ from FW levels in either strain. Gill PRLR mRNA did not change after four days of SW exposure, and decreased in both strains after one month in SW. Plasma cortisol levels did not change following SW exposure in either strain. Gill GR, 11β-HSD2 and MR mRNA levels increased after four days in SW in both strains, whereas only the anadromous strain maintained elevated gill GR and 11β-HSD2 mRNA levels after one month in SW. The results indicate that hormones and receptors of the GH and cortisol axes are present at significantly lower levels during spring development and SW acclimation in landlocked relative to anadromous salmon. These findings suggest that attenuation of GH and cortisol axes may, at least partially, result in reduced preparatory upregulation of key gill ion-secretory proteins, possibly a result of reduced selection pressure for marine adaptations in landlocked salmon.
-
molecular mechanisms of continuous light inhibition of atlantic salmon parr smolt transformation
Aquaculture, 2007Co-Authors: Sigurd O Stefansson, Tom Ole Nilsen, Lars O E Ebbesson, Björn Th. Björnsson, Anna Wargelius, Steffen S Madsen, Stephen D. MccormickAbstract:Atlantic salmon (Salmosalar)rely onchangesin photoperiodfor thesynchronization ofthe developmental eventsconstituting the parr–smolt transformation. In the absence of photoperiod cues, parr–smolt transformation is incomplete, and such ‘pseudo-smolts’ normally fail to adapt to seawater. The present study addresses the endocrine and molecular mechanisms controlling the development of hypo-osmoregulatory ability and how artificial photoperiod can disrupt these changes. Juvenile Atlantic salmon reared under constant light (LL) from first feeding, were separated into two groups, and exposed to either LL or simulated natural photoperiod (LDN) from October, eight months prior to the expected completion of Smoltification. Juveniles reared on LL grew well, but failed to show the smolt-related reduction in condition factor in spring. Gill mRNA levels of Na + ,K + –ATPase (NKA) isoform α1a decreased in LDN fish through completion of parr–smolt transformation, while levels remained unchanged in the LL group. In contrast, α1b expression increased 6-fold in the LDN group between February and May, again with no change in the LL group. Further, Na + ,K + , 2Cl − co-transporter (NKCC) showed a transient increase in expression in smolts on LDN between February and May, while no changesinmRNAlevelswereseeninjuvenilesunderLL.Consequently,gillNKAactivityandNKA αandNKCCproteinabundance were significantly lower in juveniles on LLthan in smolts onLDN. LL fish in spring had lower circulating levels ofthyroid hormones (THs), growth hormone (GH) and cortisol. Gill GH-receptor mRNA levels, determined by quantitative PCR, were less than 50% of controls. In contrast, circulating levels of IGF-1 and gill IGF-1 receptor expression, were comparable to controls. Our findings show thatcontinuouslightpreventsthecompletionofparr–smolttransformationataverybasiclevel,disruptingthenaturalup-regulationof key elements of the endocrine system involved in the regulation of the parr–smolt transformation, and consequently inhibiting the Smoltification-related increase in expression, abundance and activity of gill ion transport proteins. © 2007 Elsevier B.V. All rights reserved.
-
hormone receptors in gills of smolting atlantic salmon salmo salar expression of growth hormone prolactin mineralocorticoid and glucocorticoid receptors and 11β hydroxysteroid dehydrogenase type 2
General and Comparative Endocrinology, 2007Co-Authors: Pia Kiilerich, Karsten Kristiansen, Steffen S MadsenAbstract:Abstract This is the first study to report concurrent dynamics in mRNA expression of growth hormone receptor (GHR), prolactin receptor (PRLR), gluco- and mineralocorticoid receptor (GR and MR) and the 11β-hydroxysteroid dehydrogenase type-2 enzyme (11β-HSD2) in Atlantic salmon ( Salmo salar ) gill during Smoltification. Transcript levels were analysed by quantitative PCR in fresh water (FW) fish and after a 24-h salt water (SW) challenge. GHR transcript levels increased concurrent with gill Na + , K + -ATPase activity in FW fish consistent with the SW-adaptive role of GH. SW-transfer induced an increased GHR expression levels in the early stages of Smoltification but a decrease in expression at the peak of Smoltification. PRLR transcript levels decreased steadily during Smoltification in agreement with the recognized hyper-osmoregulatory role of PRL. Surprisingly, PRLR levels increased after SW transfer during the course of Smoltification. GR mRNA levels were low early on during Smoltification but increased at the peak of Smoltification and remained high during de-Smoltification, indicative of increased cortisol signalling at this point. Coherently, SW transfer increased GR levels to smolt levels prior to the Smoltification peak. 11β-HSD2 levels increased at the Smoltification peak and MR levels increased during de-Smoltification, suggesting a need for protection of MR from cortisol signalling during Smoltification. This is supported by the fact that SW-transfer results in a profound up-regulation of 11β-HSD2, whereas SW transfer down-regulates MR levels. The study concludes that GR and MR may have distinctive roles in developing hypo- and hyper-osmoregulatory mechanisms during Smoltification and de-Smoltification, respectively.
-
17 β estradiol and 4 nonylphenol delay smolt development and downstream migration in atlantic salmon salmo salar
Aquatic Toxicology, 2004Co-Authors: Steffen S Madsen, Soren Skovbolling, Christian Nielsen, Bodil KorsgaardAbstract:Abstract The effect of 17-β estradiol (E2) and 4-nonylphenol (4-NP) on Smoltification and downstream migration of Atlantic salmon was studied in an integrated laboratory and field study. In a stock of hatchery-raised 1-year-old salmon, Smoltification progressed from February until late May as judged by increased gill Na+,K+-ATPase activity and 24 h sea water (SW)-tolerance. Starting late March, three groups of 150 fish were each given 6 serial injections over 20 days of 2 μg/g body weight E2, 120 μg/g 4-NP dissolved in peanut oil or peanut oil (4 μl/g) as control. After the last injection, all fish were individually tagged (Passive Integrated Transponder tags) and a non-lethal gill biopsy was taken. Two days later (8 April), 100 fish per group were transported to the field site and released into a small stream. Smolt migration was registered by measuring arrival time at a trap downstream of the release site. Serum vitellogenin levels increased several-fold in both male and female E2- and 4-NP-treated fish. Overall, E2- and 4-NP-treatment impaired smolting as judged by elevated condition factor, reduced gill Na+,K+-ATPase activity and α-subunit Na+,K+-ATPase mRNA level, reduced muscle water content and increased mortality following 24 h SW-challenge. After release, control fish initiated downstream migration immediately, with 50% of the total number of migrants appearing in the trap within 10 days. E2- and 4-NP-treated fish appeared in the trap with a delay in comparison to controls of 6 and 8 days, respectively. After the smolt run, no fish were registered by electro-fishing upstream of the trap. The total number of fish reaching the trap and thus post-release survival was in the order control (81%), E2 (53%), 4-NP (12%). Representatives from all treatment groups held under simulated natural conditions in the laboratory survived 100% through the migration period, suggesting that a combination of behavioural and in-stream factors (predation by herons) may contribute to the differential mortality. The study indicates that short-term exposure to natural and environmental estrogens may impair smolt development and survival and delay subsequent downstream migration in Atlantic salmon.
Sigurd O Stefansson - One of the best experts on this subject based on the ideXlab platform.
-
environmental endocrinology of salmon Smoltification
General and Comparative Endocrinology, 2011Co-Authors: Bjorn Thrandur Bjornsson, Sigurd O Stefansson, Stephen D. MccormickAbstract:Smolting is a hormone-driven developmental process that is adaptive for downstream migration and ocean survival and growth in anadromous salmonids. Smolting includes increased salinity tolerance, increased metabolism, downstream migratory and schooling behavior, silvering and darkened fin margins, and olfactory imprinting. These changes are promoted by growth hormone, insulin-like growth factor I, cortisol, thyroid hormones, whereas prolactin is inhibitory. Photoperiod and temperature are critical environmental cues for smolt development, and their relative importance will be critical in determining responses to future climate change. Most of our knowledge of the environmental control and endocrine mediation of smolting is based on laboratory and hatchery studies, yet there is emerging information on fish in the wild that indicates substantial differences. Such differences may arise from differences in environmental stimuli in artificial rearing environments, and may be critical to ocean survival and population sustainability. Endocrine disruptors, acidification and other contaminants can perturb smolt development, resulting in poor survival after seawater entry.
-
effects of acidic water and aluminum exposure on gill na k atpase α subunit isoforms enzyme activity physiology and return rates in atlantic salmon salmo salar l
Aquatic Toxicology, 2010Co-Authors: Tom Ole Nilsen, Lars O E Ebbesson, Ole G Kverneland, F Kroglund, Bengt Finstad, Sigurd O StefanssonAbstract:Abstract Na+, K+-ATPase (NKA) is involved, through its role as a major driving force for electrochemical gradients, in a range of transmembrane transport processes. Maintenance of homeostasis in anadromous salmonids requires modulation of several gill ion secretory proteins as part of the preparatory adaptation and acclimation to marine life. Atlantic salmon smolts were exposed to combinations of low pH and inorganic aluminum (acid/Ali) in freshwater (FW) and were then transferred to seawater (SW) for studies of post-smolt performance. Gill mRNA levels of four NKA-α isoforms (α1a, α1b, α1c and α3) of the catalytic NKA subunit and NKA enzyme activity were measured. Moderate acid/Al treatment (MOD, pH 5.9 ± 0.3, 15 ± 9 μg l−1 Ali) prevented the FW preparatory increase in NKA activity observed in control (CON, pH 6.9 ± 0.1, 8 ± 3 μg l−1 Ali) smolts, while high acid/Al treatment (SEV, pH 5.6 ± 0.2, 30 ± 7 μg l−1 Ali) caused a rapid and persistent reduction in NKA activity. Correspondingly, a 3.3-fold increase in plasma glucose levels in the SEV groups concurrent with a decrease in plasma chloride levels suggest that acid/Al exposed fish were stressed and experienced problems maintaining ion homeostasis. Gill NKA activities in acid/Al exposed groups were re-established after 28 days in SW. Both long (9 days) and short-term (2.5 days) treatments had significant impact on isoform-specific Na+, K+-ATPase α-subunit mRNA abundance in the FW period. Acid/Al exposed groups lacked the preparatory increases in all NKA-α isoform mRNA levels seen in the CON group, except for α1a. In contrast to the other isoforms measured, α1a mRNA abundance decreased sharply upon SW transfer, supporting the hypothesis of isozyme shifting as a mechanism of altering the gill from an ion absorbing to an ion excreting tissue during Smoltification and SW exposure. Adult return rates to the Imsa river were significantly reduced both in short-term (78% of controls) and long-term (55% of controls) acid/Al exposures, emphasising the physiological and ecological consequences of acid/Al exposure during Smoltification.
-
endocrine systems in juvenile anadromous and landlocked atlantic salmon salmo salar seasonal development and seawater acclimation
General and Comparative Endocrinology, 2008Co-Authors: Tom Ole Nilsen, Stephen D. Mccormick, Lars O E Ebbesson, Björn Th. Björnsson, Steffen S Madsen, Pia Kiilerich, Sigurd O StefanssonAbstract:Abstract The present study compares developmental changes in plasma levels of growth hormone (GH), insulin-like growth factor I (IGF-I) and cortisol, and mRNA levels of their receptors and the prolactin receptor (PRLR) in the gill of anadromous and landlocked Atlantic salmon during the spring parr-smolt transformation (Smoltification) period and following four days and one month seawater (SW) acclimation. Plasma GH and gill GH receptor (GHR) mRNA levels increased continuously during the spring Smoltification period in the anadromous, but not in landlocked salmon. There were no differences in plasma IGF-I levels between strains, or any increase during Smoltification. Gill IGF-I and IGF-I receptor (IGF-IR) mRNA levels increased in anadromous salmon during Smoltification, with no changes observed in landlocked fish. Gill PRLR mRNA levels remained stable in both strains during spring. Plasma cortisol levels in anadromous salmon increased 5-fold in May and June, but not in landlocked salmon. Gill glucocorticoid receptor (GR) mRNA levels were elevated in both strains at the time of peak Smoltification in anadromous salmon, while mineralocorticoid receptor (MR) mRNA levels remained stable. Only anadromous salmon showed an increase of gill 11β-hydroxysteroid dehydrogenase type-2 (11β-HSD2) mRNA levels in May. GH and gill GHR mRNA levels increased in both strains following four days of SW exposure in mid-May, whereas only the anadromous salmon displayed elevated plasma GH and GHR mRNA after one month in SW. Plasma IGF-I increased after four days in SW in both strains, decreasing in both strains after one month in SW. Gill IGF-I mRNA levels were only increased in landlocked salmon after 4 days in SW. Gill IGF-IR mRNA levels in SW did not differ from FW levels in either strain. Gill PRLR mRNA did not change after four days of SW exposure, and decreased in both strains after one month in SW. Plasma cortisol levels did not change following SW exposure in either strain. Gill GR, 11β-HSD2 and MR mRNA levels increased after four days in SW in both strains, whereas only the anadromous strain maintained elevated gill GR and 11β-HSD2 mRNA levels after one month in SW. The results indicate that hormones and receptors of the GH and cortisol axes are present at significantly lower levels during spring development and SW acclimation in landlocked relative to anadromous salmon. These findings suggest that attenuation of GH and cortisol axes may, at least partially, result in reduced preparatory upregulation of key gill ion-secretory proteins, possibly a result of reduced selection pressure for marine adaptations in landlocked salmon.
-
molecular mechanisms of continuous light inhibition of atlantic salmon parr smolt transformation
Aquaculture, 2007Co-Authors: Sigurd O Stefansson, Tom Ole Nilsen, Lars O E Ebbesson, Björn Th. Björnsson, Anna Wargelius, Steffen S Madsen, Stephen D. MccormickAbstract:Atlantic salmon (Salmosalar)rely onchangesin photoperiodfor thesynchronization ofthe developmental eventsconstituting the parr–smolt transformation. In the absence of photoperiod cues, parr–smolt transformation is incomplete, and such ‘pseudo-smolts’ normally fail to adapt to seawater. The present study addresses the endocrine and molecular mechanisms controlling the development of hypo-osmoregulatory ability and how artificial photoperiod can disrupt these changes. Juvenile Atlantic salmon reared under constant light (LL) from first feeding, were separated into two groups, and exposed to either LL or simulated natural photoperiod (LDN) from October, eight months prior to the expected completion of Smoltification. Juveniles reared on LL grew well, but failed to show the smolt-related reduction in condition factor in spring. Gill mRNA levels of Na + ,K + –ATPase (NKA) isoform α1a decreased in LDN fish through completion of parr–smolt transformation, while levels remained unchanged in the LL group. In contrast, α1b expression increased 6-fold in the LDN group between February and May, again with no change in the LL group. Further, Na + ,K + , 2Cl − co-transporter (NKCC) showed a transient increase in expression in smolts on LDN between February and May, while no changesinmRNAlevelswereseeninjuvenilesunderLL.Consequently,gillNKAactivityandNKA αandNKCCproteinabundance were significantly lower in juveniles on LLthan in smolts onLDN. LL fish in spring had lower circulating levels ofthyroid hormones (THs), growth hormone (GH) and cortisol. Gill GH-receptor mRNA levels, determined by quantitative PCR, were less than 50% of controls. In contrast, circulating levels of IGF-1 and gill IGF-1 receptor expression, were comparable to controls. Our findings show thatcontinuouslightpreventsthecompletionofparr–smolttransformationataverybasiclevel,disruptingthenaturalup-regulationof key elements of the endocrine system involved in the regulation of the parr–smolt transformation, and consequently inhibiting the Smoltification-related increase in expression, abundance and activity of gill ion transport proteins. © 2007 Elsevier B.V. All rights reserved.
Matthew C Hale - One of the best experts on this subject based on the ideXlab platform.
-
rna seq reveals differential gene expression in the brains of juvenile resident and migratory smolt rainbow trout oncorhynchus mykiss
Comparative Biochemistry and Physiology Part D: Genomics and Proteomics, 2016Co-Authors: Matthew C Hale, Garrett J Mckinney, Frank P Thrower, Krista M NicholsAbstract:Abstract Many migratory traits are heritable, but there is a paucity of evidence identifying the molecular mechanisms underlying differentiation in alternative migratory tactics, or in linking variation in gene expression to migratory behaviors. To that end, we examined differential gene expression in the brain transcriptome between young steelhead trout that had undergone the Smoltification process, and resident rainbow trout ( Oncorhynchus mykiss ) from Sashin Creek, Alaska. Samples were sequenced from two time points: immediately before (at 20 months of age) and during (2 years of age) the presumed peak of Smoltification. Smolt and resident individuals came from two genetic crosses, one where both parents were migratory, and another where both parents were residents. A total of 533 (1.9%) genes were differentially expressed between crosses, or between smolt and resident samples. These genes include some candidate migratory genes (such as POMC ), as well as genes with no previous known involvement in the migratory process. Progeny from resident parents showed more upregulated genes than progeny from migrant parents at both time points. Pathway analysis showed enrichment in 227 biological pathways between cross type, and 171 biological pathways were enriched between residents and smolts. Enriched pathways had connections to many biofunctions, and most were only enriched in one contrast. However, pathways connected to phototransduction were enriched between both cross type and migratory tactics in 11 out of 12 contrasts, suggesting there are fundamental differences in how smolts and residents process light in the brain. The genes and pathways described herein constitute an a priori candidate list for future studies of migration in other populations of O. mykiss , and other migratory species.