Abstract
Lower jaw deformity (LJD) is a skeletal anomaly affecting farmed triploid Atlantic salmon (Salmo salar L.) which leads to considerable economic losses for industry and has animal welfare implications. The present study employed transcriptome analysis in parallel with real-time qPCR techniques to characterise for the first time the LJD condition in triploid Atlantic salmon juveniles using two independent sample sets: experimentally-sourced salmon (60 g) and commercially produced salmon (100 g). A total of eleven genes, some detected/identified through the transcriptome analysis (fbn2, gal and gphb5) and others previously determined to be related to skeletal physiology (alp, bmp4, col1a1, col2a1, fgf23, igf1, mmp13, ocn), were tested in the two independent sample sets. Gphb5, a recently discovered hormone, was significantly (P < 0.05) down-regulated in LJD affected fish in both sample sets, suggesting a possible hormonal involvement. In-situ hybridization detected gphb5 expression in oral epithelium, teeth and skin of the lower jaw. Col2a1 showed the same consistent significant (P < 0.05) down-regulation in LJD suggesting a possible cartilaginous impairment as a distinctive feature of the condition. Significant (P < 0.05) differential expression of other genes found in either one or the other sample set highlighted the possible effect of stage of development or condition progression on transcription and showed that anomalous bone development, likely driven by cartilage impairment, is more evident at larger fish sizes. The present study improved our understanding of LJD suggesting that a cartilage impairment likely underlies the condition and col2a1 may be a marker. In addition, the involvement of gphb5 urges further investigation of a hormonal role in LJD and skeletal physiology in general.
Highlights
Lower jaw deformity (LJD) is a skeletal anomaly affecting the lower jaw of farmed Atlantic salmon (Salmo salar L.)
Among the eleven genes tested in individuals displaying a normal lower jaw or a LJD, only col2a1 and gphb5 showed the same consistent pattern of differential expression, being down-regulated in LJD affected fish in both independent sample sets
This result implies that, in contrast to other genes found differentially expressed between traits either in one sample set or in another, col2a1 and gphb5 are reliable indicators of the mechanisms underlying LJD
Summary
Lower jaw deformity (LJD) is a skeletal anomaly affecting the lower jaw of farmed Atlantic salmon (Salmo salar L.). Lower Jaw Deformity in Triploid Atlantic Salmon (Salmo salar L.). LJD has been frequently observed and identified in both freshwater and seawater phases of production in all countries producing Atlantic salmon at/ with different prevalence between years and populations [3,4,5,6,7,8,9]. LJD can occur in diploid populations at very low prevalence, LJD was linked to triploid Atlantic salmon in all recent studies cited above. LJD affected triploid fish represent a considerable loss of production because they have lower growth rates and cannot be sold whole due to their visual unattractiveness [5, 7, 11]. Fish affected by skeletal anomalies usually require hand-grading which is an expensive process and adds further cost [12, 13]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
