| 1. |
- Kotrschal, Alexander, et al.
(författare)
-
The mating brain : early maturing sneaker males maintain investment into the brain also under fast body growth in Atlantic salmon (Salmo salar)
- 2014
-
Ingår i: Evolutionary Ecology. - : Springer Science and Business Media LLC. - 0269-7653 .- 1573-8477. ; 28:6, s. 1043-1055
-
Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that mating behaviours require high levels of cognitive ability. However, since investment into mating and the brain both are costly features, their relationship is likely characterized by energetic trade-offs. Empirical data on the subject remains equivocal. We investigated if early sexual maturation was associated with brain development in Atlantic salmon (Salmo salar), in which males can either stay in the river and sexually mature at a small size (sneaker males) or migrate to the sea and delay sexual maturation until they have grown much larger (anadromous males). Specifically, we tested how sexual maturation may induce plastic changes in brain development by rearing juveniles on either natural or ad libitum feeding levels. After their first season we compared brain size and brain region volumes across both types of male mating tactics and females. Body growth increased greatly across both male mating tactics and females during ad libitum feeding as compared to natural feeding levels. However, despite similar relative increases in body size, early maturing sneaker males maintained larger relative brain size during ad libitum feeding levels as compared to anadromous males and females. We also detected several differences in the relative size of separate brain regions across feeding treatments, sexes and mating strategies. For instance, the relative size of the cognitive centre of the brain, the telencephalon, was largest in sneaker males. Our data support that a large relative brain size is maintained in individuals that start reproduction early also during fast body growth. We propose that the cognitive demands during complex mating behaviours maintain a high level of investment into brain development in reproducing individuals.
|
|
| 2. |
- Shao, Yi Ta, et al.
(författare)
-
Androgen feedback effects on LH and FSH, and photoperiodic control of reproduction in male three-spined sticklebacks, Gasterosteus aculeatus
- 2013
-
Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 182, s. 16-23
-
Tidskriftsartikel (refereegranskat)abstract
- Sexual maturation in the stickleback is controlled by photoperiod. The aim of this study was to find out whether changes in feedback effects exerted by sex steroids could mediate the photoperiodic effect, which is regarded to be of an all-or-nothing character. To that end, males were castrated and treated with different doses of testosterone (T) and in one experiment also with the aromatase inhibitor fadrozole (AI) and kept under different photoperiods. In control fish, long day (LD 16:8) stimulated maturation, associated with more hypertrophied kidneys (a secondary sexual character) and higher levels of pituitary lhb and fshb mRNA than under short day conditions (LD 8:16). Under LD 8:16, low doses of T suppressed both lhb and fshb mRNA levels. However, with the use of high doses of T and/or longer photoperiods the inhibitory effects on lhb and fshb mRNA levels became less clear or instead positive effects were observed. Under intermediate photoperiod conditions, the negative feedback effect of a low dose of T on fshb was more prominent with shorter photoperiods, whereas no such shift was observed for lhb mRNA. The inhibitory effect of the low dose of T on lhb mRNA levels under LD 8:16 was abolished by AI, whereas the stimulatory effect of the high dose of T was not. The negative feedback effects were more marked under short days than under long days, whereas positive feedback effects were more marked under long days. The suppression of both fshb and lhb mRNA levels by low androgen levels, especially under short days, may inhibit maturation completely unless a rise of androgens above threshold levels would allow complete maturation.
|
|
| 3. |
- Shao, Yi Ta, et al.
(författare)
-
Schistocephalus solidus infections increase gonadotropins and gonadotropin releasing hormone (GnRH3) mRNA levels in the three-spined stickleback, Gasterosteus aculeatus
- 2012
-
Ingår i: Parasitology international. - : Elsevier BV. - 1383-5769 .- 1873-0329. ; 61:3, s. 470-474
-
Tidskriftsartikel (refereegranskat)abstract
- Parasites often impair the reproduction of their hosts, one well known case being the cestode Schistocephalus solidus which is a common parasite in three-spined sticklebacks. Gasterosteus aculeatus. One of the possible ways that this could be exerted is by suppression on the brain-pituitary-gonadal (BPG) axis. In this study, mRNA levels of FSH-beta and LH-beta and of GnRH2 (cGnRH II) and GnRH3 (sGnRH) were measured via Q-PCR in infected and uninfected fish sampled from the field a few weeks before the onset of breeding. The pituitary mRNA levels of both FSH-beta and LH-beta were higher in infected males than in uninfected males. Also in females, FSH-beta mRNA levels were higher in infected individuals than in others, whereas there was no significant difference found in LH-beta expression. Brain mRNA levels of GnRH3 were higher in infected fish than in uninfected fish in both sexes, but no difference was found in GnRH2 mRNA levels. Thus, infection by S. solidus was able to alter the expressions not only of gonadotropins (GtHs), but also of GnRH which has not been observed previously. However, the effects are opposite to what should be expected if the parasite suppressed reproduction via actions on the brain-pituitary level. The gonads are perhaps more likely to be impaired by the parasites in other ways, and changed feedbacks on the BPG axis could then lead to the increases in GtHs and GnRH.
|
|
| 4. |
- Trombley, Susanne, 1979-, et al.
(författare)
-
Effects of androgens on the leptin system in immature male Atlantic salmon parr
- 2018
-
Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 257, s. 122-129
-
Tidskriftsartikel (refereegranskat)abstract
- Leptin modulates all levels of the reproductive endocrine axis in mammals, and in turn, both leptin and the leptin receptor are regulated by sex steroids. The aim of this study was to investigate if sex steroids regulate the leptin system also in fish. Immature one-year old male Atlantic salmon parr were implanted with Silclear capsules that were either empty or filled with 11-ketoandrostenedione (11 KA) or testosterone (T) and the effects of 35-days treatment were investigated on measures of maturation, gene expression of leptin (lepa1, lepa2), leptin receptor (lepra1) and circulating plasma leptin. Both 11-KA and T stimulated the reproductive axis by increasing testes weight and up-regulated pituitary lh-beta mRNA levels and for T also fsh-beta. T up-regulated transcription levels of lepa1 and lepra1 in the pituitary, while 11-KA had no effect. Leptin receptor expression in the testis was unaltered by either androgen. T up-regulated lepa1 mRNA levels significantly also in the liver, but had no effect on lepa2, and 11 KA did not affect hepatic gene expression of either lepa1 or lepa2. Plasma leptin levels did not differ significantly between treatments. The results indicate that androgens regulate gene expression of leptin and the leptin receptor in different tissues in fish and that the effects of leptin might be tissue specific considering plasma levels remained unaltered. Overall, the results suggest a role for leptin in fish reproduction, where sex steroids are able to regulate components of the leptin system differentially in liver and important tissues of the reproductive axis. (C) 2017 Elsevier Inc. All rights reserved.
|
|
| 5. |
- Trombley, Susanne, et al.
(författare)
-
Effects of long-term restricted feeding on plasma leptin, hepatic leptin expression and leptin receptor expression in juvenile Atlantic salmon (Salmo salar L.)
- 2012
-
Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 175:1, s. 92-99
-
Tidskriftsartikel (refereegranskat)abstract
- Leptin is a pleiotropic hormone and plays a key role in body weight regulation, energy homeostasis and lipid store utilization in mammals. In this study, we investigated the effect of feed-restriction on leptin genes (lepa1 and lepa2), leptin receptor (lepr) gene expression and plasma leptin levels in juvenile Atlantic salmon parr. Feed restriction was performed from late April to mid-June, in order to gain insight into the role of the leptin system in energy balance regulation and adiposity in juvenile salmon. A significant increase in lepa1 expression as well as higher levels of plasma leptin was found in feed-restricted fish in June compared to fully fed controls, while lepa2 gene expression decreased in both groups during the treatment period. Lepa2 was, however significantly higher in the feed-restricted group in June. Leptin receptor expression was up regulated during the period of enhanced growth and lipid deposition in the fully fed control, indicating a seasonal effect on the receptor expression in the brain. Both lepa1 and lepa2 genes very mainly expressed in the liver in juvenile salmon, while lepr was expressed in the brain but showed also considerable expression in various peripheral tissues. The study provides evidence that the leptin system is sensitive to the metabolic status of the fish as both season and restricted feeding affect lepa1 and lepa2 gene expression in the liver and brain leptin receptor expression, however, for lepa1 expression and leptin plasma level in an opposite way as that observed in the mammalian system. (C) 2011 Elsevier Inc. All rights reserved.
|
|
| 6. |
|
|
| 7. |
- Trombley, Susanne, et al.
(författare)
-
Leptin in fish : possible role in sexual maturation in male Atlantic salmon
- 2013
-
Ingår i: Fish Physiology & Biochemistry. - : Springer Science and Business Media LLC. - 0920-1742 .- 1573-5168. ; 39:1, s. 103-106
-
Tidskriftsartikel (refereegranskat)abstract
- Leptin plays an important role in energy homeostasis and reproductive function in mammals, while its function in fish is still poorly understood, especially its role in reproduction. In the present study, leptin gene expression and circulating leptin plasma levels were measured during sexual maturation in male Atlantic salmon parr. In maturing male salmon, higher hepatic leptin (lepa1) gene expression levels were observed during mid-spermatogenesis compared to immature fish. An upregulation of leptin during sexual maturation has also been observed in a few other teleost species. The physiological significance of elevated leptin levels during the maturational process in teleosts remains to be explored.
|
|
| 8. |
- Trombley, Susanne, 1979-
(författare)
-
Regulation of Leptin by Sexual Maturation and Energy Status in Male Atlantic Salmon (Salmo salar L.) Parr
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Leptin is a peripheral adiposity signal and a key hormone in energy balance regulation in mammals, acting as a link between nutritional status and the endocrine reproductive axis. If this is also the role of leptin in fish is not fully understood. This thesis investigates how different components of the leptin system are affected by sexual maturation and seasonal changes in energy balance in male Atlantic salmon (Salmo salar L.) parr under fully fed and feed-restricted conditions. Moreover, the role of sex steroids as being one of the possible mechanisms by which sexual maturation interacts with leptin is explored.The salmon leptin-a genes, lepa1 and lepa2, were expressed mainly in liver and the leptin receptor (lepr) in brain and ubiquitously in peripheral tissues. Seasonal characterization of the lepa genes and lepr during the growth and reproductive season in one-year old males showed that hepatic lepa1 and lepa2 mRNA levels and plasma leptin levels were down-regulated concomitantly with an increase in weight and body fat. Feed restriction up-regulated hepatic leptin, and pituitary lepr expression as well as plasma leptin levels. Correlation between leptin levels and body lipid stores were either lacking or negative. These findings show that leptin and lepr are sensitive to changes in energy balance, but that leptin might not reflect adiposity in juvenile salmon.Hepatic lepa1 and lepa2, and testicular lepr expression increased during mid- to late spermatogenesis in early maturing males. This up-regulation was preceded by rapid gonadal growth and elevated pituitary follicle-stimulating hormone gene expression levels, whereas peak leptin levels coincided with peak pituitary luteinizing hormone expression and the presence of running milt in the testes. The sex steroids testosterone (T), 11-ketotestosterone and 17-β estradiol stimulated lepa1 and lepa2 gene expression in Atlantic salmon hepatocytes in vitro differentially depending on developmental stage. T was also able to stimulate hepatic lepa1 and pituitary lepa1 and lepr gene expression in immature male salmon in vivo. These results suggest that leptin plays a role in male fish reproduction during later stages of the maturational process and that the elevation of leptin expression during spermatogenesis could be caused by androgen stimulation.
|
|
| 9. |
- Trombley, Susanne, et al.
(författare)
-
Regulation of the seasonal leptin and leptin receptor expression profile during early sexual maturation and feed restriction in male Atlantic salmon, Salmo salar L., parr
- 2014
-
Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 204, s. 60-70
-
Tidskriftsartikel (refereegranskat)abstract
- In mammals, leptin acts as an adiposity signal and is a crucial link between nutritional status and the reproductive axis. So far the link between leptin and energy balance during sexual maturation in teleosts has been poorly investigated. In this study, seasonal gene expression changes in two leptin genes (lepa1 andlepa2) and the leptin receptor were investigated during early sexual maturation in male Atlantic salmon parr under fully fed (control) and feed restricted conditions from April through September. Both Atlantic salmonlepa1 and lepa2 in the liver and lepr in the brain were significantly down-regulated in non-maturing control males in early spring, coinciding with the start of the growth and fat accumulation. In maturing control males, hepatic leptin expression increased during mid-spermatogenesis and lepa1 and lepa2 mRNA levels were up-regulated by 7.7 and 49 times respectively during final maturation. For the first time in a fish species, a significant up-regulation of lepr expression was observed in the testis throughout mid to late spermatogenesis. Feed restriction decreased the incidence of sexual maturation by 53% and highly up-regulated both leptin genes in the liver and the leptin receptor in the pituitary. This study shows that hepaticlepa1 and lepa2 expression and lepr expression in the testis is affected by early sexual maturation in male Atlantic salmon parr. Fast growth and high fat stores are associated with low leptin levels while feed restriction has a stimulatory effect on hepatic leptin and leptin receptor gene expression in the pituitary, suggesting a role for leptin other than that as an adiposity signal.
|
|
| 10. |
|
|
