Loss of Fshr Prevents Testicular Maturation in Atlantic Salmon (Salmo salar L.)

Early puberty poses a significant challenge for male Atlantic salmon in aquaculture due to its negative impact on growth and welfare. The regulation of puberty in vertebrates involves 2 key reproductive hormones: follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and their gonadal receptors. In male mice lacking FSH receptor, testes size is reduced, but fertility is maintained, while medaka and zebrafish with a disrupted fshr gene exhibit near normal testis size and fertility. In these fishes both Fsh and Lh are present during puberty and Lh may rescue fertility, while in salmonid fish only Fsh is present in the circulation during puberty. Using CRISPR-Cas9, we produced crispants with a high prevalence of fshr mutations at the target site, which remained fertile, although more than half showed a testis development deviating from wild-type (wt) males. Crossing out these F0 crispants to each other produced a viable F1 generation showing frameshift (fshr−/−) or in-frame mutations (fshrif/if). Nearly all wt males matured while all fshr−/− males remained immature with small testes containing A spermatogonia as the furthest developed germ cell type and prepubertal plasma androgen levels. Also, the pituitary transcript levels of gnrhr2bba and lhb, but not for fshb, were reduced in the fshr−/− males compared with maturing males. More than half of the fshrif/if mutant males showed no or a delayed maturation. In conclusion, Atlantic salmon show the unique characteristic that loss of Fshr function alone results in male infertility, offering new opportunities to control precocious puberty or fertility in salmon

Ploidy elicits a whole-genome dosage effect: growth of triploid Atlantic salmon is linked to the genetic origin of the second maternal chromosome set

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Structural and micro-anatomical changes in vertebrae associated with idiopathic-type spinal curvature in the curveback guppy model

Background: The curveback lineage of guppy is characterized by heritable idiopathic-type spinal curvature thatdevelops during growth. Prior work has revealed several important developmental similarities to the human idiopathicscoliosis (IS) syndrome. In this study we investigate structural and histological aspects of the vertebrae that areassociated with spinal curvature in the curveback guppy and test for sexual dimorphism that might explain a femalebias for severe curve magnitudes in the population.Methods: Vertebrae were studied from whole-mount skeletal specimens of curved and non-curved adult males andfemales. A series of ratios were used to characterize structural aspects of each vertebra. A three-way analysis of variancetested for effects of sex, curvature, vertebral position along the spine, and all 2-way interactions (i.e., sex and curvature,sex and vertebra position, and vertebra position and curvature). Histological analyses were used to characterize microarchitecturalchanges in affected vertebrae and the intervertebral region.Results: In curveback, vertebrae that are associated with curvature demonstrate asymmetric shape distortion,migration of the intervertebral ligament, and vertebral thickening on the concave side of curvature. There is sexualdimorphism among curved individuals such that for several vertebrae, females have more slender vertebrae than domales. Also, in the region of the spine where lordosis typically occurs, curved and non-curved females have a reducedwidth at the middle of their vertebrae, relative to males.Conclusions: Based on similarities to human spinal curvatures and to animals with induced curves, the concaveconvexbiases described in the guppy suggest that there is a mechanical component to curve pathogenesis incurveback. Because idiopathic-type curvature in curveback is primarily a sagittal deformity, it is structurally more similarto Scheuermann kyphosis than IS. Anatomical differences between teleosts and humans make direct biomechanicalcomparisons difficult. However, study of basic biological systems involved in idiopathic-type spinal curvature incurveback may provide insight into the relationship between a predisposing aetiology, growth, and biomechanics.Further work is needed to clarify whether observed sex differences in vertebral characteristics are related to the femalebias for severe curves that is observed in the population

The metabolic basis of adolescent idiopathic scoliosis: 2011 report of the “metabolic” workgroup of the Fondation Yves Cotrel

OBJECTIVE: The purpose of this review is to elucidate the metabolic processes involved in the pathogenesis of adolescent idiopathic scoliosis (AIS) in light of research by the present authors as well as current literature. METHODS: Pathogenetic mechanism

The pattern of the lower jaw dentition in farmed Atlantic salmon (Salmo salar): a tool to study mechanisms of tooth replacement?

We investigated the tooth pattern on the lower jaw of adult farmed Atlantic salmon (Salmo salar L.) to elucidate whether this pattern is more regular, with less variations, than that observed in wild Atlantic salmon studied previously. A highly regular and predictable tooth pattern, in combination with the availability of Atlantic salmon in near unlimited numbers, should provide us with an ideal model to test the hypothesis whether field or local control regulates the process of tooth replacement. In 30 animals a tooth was damaged, or partially or nearly completely extracted. The animals were sacrificed after a recovery period varying between 1 and 12 weeks. X-rays were taken prior to and at various time points after manipulation. After sacrifice, dissected jaws were cleared and stained. Surprisingly, farmed Atlantic salmon do not display a regular pattern of tooth replacement and rather resemble the marine life stage of wild Atlantic salmon. While the irregularity of the tooth replacement pattern speaks against general (field) regulation of the replacement process, it impedes its use as a tool with which the nature of this control mechanism can be studied experimentally. Our observations nevertheless provide the first preliminary data on tooth growth and turnover in Atlantic salmon

Vertebral deformities in farmed Atlantic salmon (Salmo salar L.) : etiology and pathology

The present review sums up and discusses the current literature on occurrence, causation and pathology of vertebral deformities in farmed Atlantic salmon, and also gives a brief introduction into the normal ontogeny and anatomy of the vertebral column of Atlantic salmon. Skeletal development and growth are sensitive processes that can be affected by many factors. Many of these factors can be manipulated under farming conditions, and are thus regarded as risk factors. Several risk factors that relate to environmental conditions and to feed composition have been identified. Elevated temperatures and photoperiod manipulation to speed up growth are likely the most important environmental factors that cause skeletal deformities. Among the nutritional factors, optimal phosphorus nutrition during specific periods, for example after transfer to sea water, appears to be critical for development of deformity at later stages. More research is needed to understand the interdependency of genetics, development, aging, phosphorus nutrition, temperature and photoperiod, in order to establish the best practice procedures for salmon farming that improve fish welfare

Dietary phosphorus does not reduce the risk for spinal deformities in a model of adjuvant-induced inflammation in Atlantic salmon (Salmo salar) postsmolts

Inflammation is a non-specific protective mechanism towards injury known to affect bone remodelling. This study aimed to investigate the effect of Freunds complete adjuvant (FCA) induced-inflammation on the prevalence of spinal deformities of Atlantic salmon postsmolts fed with two different dietary P levels. Sextuple groups of salmon postsmolts were fed with either a low-phosphorous (6 g kg-1 available P, LP) or a high-phosphorous (9 g kg-1 available P) diet for a period of 101 days. On Day 102, individually tagged fish were subjected to (i) single injection with FCA (0.125 mg kg-1 BW) dissolved in phosphate-buffered saline (PBS) (ii) placebo injection with PBS or (iii) sham injection (insertion of needle only) or (iv) remained untreated. On Day 103, fish were given a common diet for 174 days in seawater. No significant differences in body weight were observed. Injected fish, particularly the FCA group, had more compressions in the injection site than untreated fish. No effect of diet and no interaction between treatment and diet were observed. Severe scoliosis was observed in similar to 7% of FCA-injected individuals, corresponding to a mixture of bone malformations in the tail region. In conclusion, experimentally induced inflammation may be an independent risk factor for bone deformities in Atlantic salmon

Dietary fatty acids and inflammation in the vertebral column of Atlantic salmon, Salmo salar L., smolts : a possible link to spinal deformities

Vegetable oils (Vo) are an alternative to fish oil (Fo) in aquaculture feeds. This study aimed to evaluate the effect of dietary soybean oil (Vo diet), rich in linoleic acid, and of dietary fish oil (Fo diet) on the development of spinal deformities under bacterial lipopolysaccharide (LPS)-induced chronic inflammation conditions in Atlantic salmon, Salmo salar L. Fish [25 g body weight (BW)] were fed the experimental diets for 99 days. On day 47 of feeding (40 g BW), fish were subjected to four experimental regimes: (i) intramuscular injections with LPS, (ii) sham-injected phosphate-buffered saline (PBS), (iii) intraperitoneally injected commercial oil adjuvant vaccine, or (iv) no treatment. The fish continued under a common feeding regime in sea water for 165 more days. Body weight was temporarily higher in the Vo group than in the Fo group prior to immunization and was also affected by the type of immunization. At the end of the trial, no differences were seen between the dietary groups. The overall prevalence of spinal deformities was approximately 14% at the end of the experiment. The Vo diet affected vertebral shape but did not induce spinal deformities. In groups injected with LPS and PBS, spinal deformities ranged between 21% and 38%, diet independent. Deformed vertebrae were located at or in proximity to the injection point. Assessment of inflammatory markers revealed high levels of plasma prostaglandin E-2 (PGE(2)) in the Vo-fed and LPS-injected groups, suggesting an inflammatory response to LPS. Cyclooxigenase 2 (COX-2) mRNA expression in bone was higher in fish fed Fo compared to Vo-fed fish. Gene expression of immunoglobulin M (IgM) was up-regulated in bone of all LPS-injected groups irrespective of dietary oil. In conclusion, the study suggests that Vo is not a risk factor for the development of inflammation-related spinal deformities. At the same time, we found evidence that localized injection-related processes could trigger the development of vertebral body malformations

Can improved nutrition for Atlantic salmon in freshwater increase fish robustness, survival and growth after seawater transfer?

The loss of fish in the seawater (SW) phase of Atlantic salmon farming is high, and a major proportion of this loss occurs in the period just after SW transfer. In the current study, we hypothesize that improvements made to the diet during the freshwater (FW) stage affect fish growth, survival and robustness later in the SW stage. To test this, salmon parr were fed five experimental diets in FW at 12 °C. In addition to a commercial-like control diet, fish were fed a diet with changed FA composition aimed to be more like the natural feed of salmon in FW, a diet with increased concentrations of selected AA/N-compounds (methionine, lysine, threonine and taurine), a diet with increased concentrations of methionine and certain B-vitamins (folate, B12 and B6) and a final diet combining all of these potential improvements. At the time of SW transfer, the robustness of fish fed the different diets was tested by direct transfer to SW at three different temperatures (8, 12 and 16 °C, without prior acclimation), as well as transfer into open net pens, while fed on a common commercial diet. Growth and proximate composition of the fish did not differ between the diet groups. All diet groups seemed to handle transfer to SW well, and while SW transfer elicited a stress response in the fish, this was not significantly different between diet groups. Fish transferred to SW at 8 °C had higher mortality, reduced mucus layer and increased prevalence of scale loss and wounds, but this applied to all diet groups. Hence, direct transfer to SW at a lower temperature than the fish has been acclimated to cannot be recommended. At the two highest temperatures, there were some differences between the groups in the severity of cataracts. Apart from this, none of the health- or welfare related parameters measured showed any difference between the diet groups, indicating that the control diet was already sufficient