Hypoxia Is Like An Ethiological Factor In Vertebral Column Deformity Of Salmon

Aquaculture 316 (2011) 13–19

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Aquaculture
j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / a q u a - o n l i n e

Hypoxia is like an ethiological factor in vertebral column deformity of salmon (Salmo salar)
Rodrigo Castro Sánchez ⁎, Eduardo Bustos Obregón, Mariana Rojas Rauco
Programa de Anatomía y Biología delDesarrollo, ICBM, Facultad de Medicina, Universidad de Chile, Santiago de Chile, Avenida Independencia 1027, Santiago de Chile, Código postal 8380453, Chile

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In Chilean salmonicultures, vertebral column deformity (VCD) is a common pathology that lowers the quality and commercialization of the product. Hypoxia has been related to other musculoskeletaldeformities in fishes, but not to VCD. The notochord has a structural and functional role in vertebral morphogenesis and in mature fish resulting in mechanical support in swimming motility. This work analyzes the morphology of the vertebral column and notochord of Salmo salar alevins starting free life (950 Accumulated Temperature Units, ATU) cultured under hypoxia (60% O2 saturation in the water tanks)for different time periods after hatching (2, 4, 6 and 8 days). These are compared with their normoxic control (100% O2 saturation). Using histological, histochemical and morphometric techniques, it was found that there is an association between VCD and the time of exposure to hypoxia (Pearson X2(5) = 60.1050 Pr = 0.0001). The time of exposure to hypoxia is inversely proportional to the bodylength, mineralization to the vertebral body, notochord diameter and thickness of its sheath. Hypoxia decreases collagen type II in the notochord sheath and up regulation of collagen type I. The organic response to hypoxia was quantified by immunohistochemistry for HIF-1α as the sensor of hypoxia. Its expression increased significantly (p b 0.05) in the experimental groups that exhibit VCD. Althoughethiology for VCD is probably multifactorial, this study allows to conclude that hypoxia by itself, produces VCD. © 2011 Elsevier B.V. All rights reserved.

Article history: Received 22 February 2011 Accepted 9 March 2011 Available online 21 March 2011 Keywords: Vertebral column Deformity Hypoxia Salmon

1. Introduction The controlled culture conditions in the modern salmoniculture have weakenednatural selection. Thus an increase in uncommon diseases has emerged (Sadler et al., 2001). One group of relevant diseases is musculoskeletal deformities that affect the quality of the final product and diminishes its commercial value (Gjerde et al., 2005), such as jaw deformities (Venegas et al., 2003), gills and opercular anomalies that are being studied in our laboratory and more recentlyvertebral column deformity (VCD). VCD exhibits major deviations in the column curvature (Gavaia et al., 2002; Lewis et al., 2004; Silverstone and Hammell, 2002; Sullivan et al., 2007) and morphological anomalies in the vertebral bodies (Fjelldal et al., 2007a,b; Witten et al., 2006) as well as less weight,

Abbreviations: VCD, vertebral column deformity; ATU, accumulated temperature units. ⁎Corresponding author at: Avenida Portugal 71 Dep. 84, Santiago de Chile, Código Postal 8330034, Chile. Tel./fax: +56 2 7237488. E-mail addresses: rocavet@gmail.com (R.C. Sánchez), ebustos@med.uchile.cl (E.B. Obregón), mrojas@med.uchile.cl (M.R. Rauco). 0044-8486/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2011.03.012

lower survival, erratic swimming, decreasedbody length and increased susceptibility to other stressors and diseases (Boglione et al., 2001; Gjerde et al., 2005). VCD was first reported in 1981 (McKay and Gjerde, 1986), and associated to economic loss in the middle '90s (Vagsholm and Djupvik, 1998), but its ethiopatogenia is not yet elucidated (Fjelldal et al., 2007a,b). Sick fishes have lower weights (Gjerde et al., 2005), low survival...