Study of the Mandibular Bone Microstructure and Blood Minerals Bioavailability in Rainbow Trout (Oncorhynchus mykiss, Walbaum 1792) from Freshwater

Abstract

Farmed salmonids show alterations in bone structure that result in skeletal deformities during formation, repair, and regeneration processes, with loss of mineralization at the level of the axial skeleton, mainly the head and spine, affecting their quality of life and even causing death. Despite improving factors, such as farming conditions, diets, and genetics, bone alterations appear more frequently in farmed fish than in wild fish. Thus, we used SEM-EDX, and TGA-DSC to study bone mineralization in farmed and wild rainbow trouts. As expected, we found significant differences in the nutritional parameters of farmed and wild fish (p < 0.05). Microstructural analyses indicated that farmed fish have a more robust mineral structure (p < 0.05), confirming the differences in mineralization and microstructure between both groups. However, the mechanisms regulating absorption and distribution in the organism and their effect on bone mineralization remain to be known. In our study, the combined use of techniques such as SEM-EDX and TGA-DSC allows a clearer assessment and detailed characterization beneficial to understanding the relationship between diet control and bone microstructure.

Physicochemical Analysis Techniques: An Alternative for the Study of Bone Deformations in Salmonids

“…The elemental analysis obtained by TXRF (Table 2) differs comparatively to that of the SEM-EDX; the latter also shows the presence of carbon, a factor that constitutes an indicator of the organic component of bone (Table 1). This indicator has been reported to reflect a structural compensation mechanism [5,6] and in normal fish its value is lower than that observed in deformed fish. Regarding the presence and quantification of minerals, the percentages exhibited by both techniques showed higher values, given the homogenization by reduction by the pulverization process.…”

“…In addition, with both techniques it was possible to detect the presence of other metals such as iron and aluminum [7]. The zones most affected by the mineralization corresponded to the areas of interest with greater porosity or presence of microfractures [5]. The porosity and surface area analysis showed a slightly larger pore size, while the available surface area was found to be much smaller (Table 3), indicating that the control fish were less likely to develop microfractures [5].…”

“…As a consequence, X-ray images have generally been used as complementary studies [4]. Although these protocols provide a panoramic view that allows us to observe the bone condition of the fish, this approach does not provide quantitative data on the loss of mineralization and does not allow detailed visualization of possible superficial damage to the bone structure, such as the presence of micro-fractures and porosity [5]. In this regard, the incorporation of physicochemical analysis techniques offers a quantifiable alternative, without the need to decalcify the bone tissue, making use of the same sample through a complete microstructural analysis by Variable Pressure Scanning Electron Microscopy coupled to an Energy Detector…”

Osteogenic and microstructural characterization in normal versus deformed jaws of rainbow trout (Oncorhynchus mykiss) from freshwater

“…Salmonids, such as trout, can spend seasons without feeding, and their physiological state tends to be normal (Godoy et al, 2022).…”

“…The dried sample was adhered to the sample holder with double-sided carbon tape. The quantification element was coupled to the X-ray energy dispersive spectroscopy detector (EDX), and three quantification points were chosen for each region of interest (ROI), as has been described previously by Godoy et al (2022). The acquisition was performed under the following parameters: an applied energy of 15 KV, a pressure of 20 Pa, and a WD of 10 mm, using a scanning electron microscope (HITACHI SU3500, Tokyo-Japan) coupled to an XFlash ® Detector 410 and a Quantax ESPRIT 1.8.1 software controller (Bruker, Germany).…”