Figure 1

Developmental characteristics and visualization of cross sections from four key Intermuscular bone (IB) developmental stages in M. amblycephala. (A–D) represent ossification process of IBs stained with ARS from S1, S2, S3, and S4, respectively. (A) S1. Body Length ≈ 11 mm (17 dph), the IBs have not emerged in the tail part; (B) S2. Body Length ≈ 16mm (24 dph), several small IBs have ossified in the tail part; (C) S3. Body Length ≈ 21 mm (29 dph), more IBs gradually ossified in the tail part with immature form; (D) S4. Body Length ≈ 32 mm (42 dph), all the IBs ossified in the tail part with mature morphology. Blue arrows indicate IBs; scale bars = 200 μm. (E–H) represent histological structures of the tail part with alizarin red S staining from S1, S2, S3, and S4, respectively. (I–L) represent histological structures of the tail part with alcian blue staining from S1, S2, S3, and S4, respectively. Blue arrows indicate IBs and black arrows indicate notochord sheath. The notochord sheath and vertebra were magnified in the lower left corner in (I–L). Scale bars = 100 μm.