Histopathology and molecular characterization of the skeletal tissues of golden pompano(Trachinotus ovatus) larvae under temperature stress

【Objective】 This study was conducted to investigate the histopathological effects and molecular regulatory characterization of bone development of golden pompano(Trachinotus ovatus) larvae under different breeding temperatures, and to provide support for further elucidations of the internal molecular mechanisms of bone development and malformation in fish.【Method】 Skeletal tissues of the head and spine of the larvae were observed using hematoxylin-eosin (HE) staining after a week of farming at 24℃, 28℃, and 32℃. In situ hybridization was used to observe the expression of bone development-related genes.【Result】 With an increase in temperature, enlarged chondrocytes and increased cartilage matrix were observed in the head. At the highest temperature, 32℃, more larval notochords transformed into spine and more spinal cartilaginous tissues were formed. The in situ hybridization signals of BMP2, BMP4, RUNX2, MMP9, MMP13 and OCN in the head were enhanced with an increase in water temperature. In the spine, the in situ hybridization signals of BMP2 and BMP4 were enhanced with an increase in water temperature, while the differences of RUNX2, MMP9 and OCN were not obvious between the different treatment groups. The signal of MMP13 was the strongest in the middle temperature group.【Conclusion】 The increase in water temperature may promote the development of bone in the head of the larvae by changing the expression of bone-related genes, and inhibit the mineralization of the spine while promoting the development of the spinal cartilaginous tissues.