Fig. 2.

Fig. 2.

Hypertrophy of intermuscular bones following contusions. (A) Boxed areas represent the contusion sites. (B) Injury timeline, similar to that for pectoral fin injuries but resulting in hypertrophy of intermuscular (IM) bones. (C-F) Alizarin Red-stained caudal peduncle regions of wild-type fish. (G-J) Alizarin Red-stained thoracic regions of wild-type fish. Scale bars: 500 µm. (C,D) Uninjured caudal peduncle sites showing the intermuscular bones (arrows). Epineurals are dorsally located and epipleurals are ventrally located. (E) Injured caudal peduncle site, 1 month later, showing hypertrophied hypurals and parahypural (arrows). (F) Injury site showing hypertrophied intermuscular bones (arrows). (G) Uninjured thoracic region showing normal epineural intermuscular bones (arrows). The absence of epipleurals in the thoracic region can be noted. (H,I) Injured thoracic region, 1 month later, showing hypertrophied intermuscular bones (arrows). (J) Hypertrophied neural spines in an injured fish (arrows). (K) Comparison of intermuscular bone size between the uninjured and injured side (n=12 bones/group from four fish), with significantly larger intermuscular bones observed on the injured side (y-axis is in μm²). Boxes show the interquartile range, whiskers show the highest and lowest value, and the median is marked with a line. ***P<0.0001 (two-tailed unpaired t-test).