DEVELOPMENTAL AND MORPHOLOGICAL OBSERVATION OF INTERMUSCULAR BONES IN MEGALOBRAMA AMBLYCEPHALA

To investigate the emergent periods and morphogenesis of Megalobrama amblycephala intermuscular bones, the modified bone clearing and X-ray transmission methods were conducted to study the number, morphology, distribution and length of intermuscular bone of M. amblycephala with different sizes. The results showed that initial intermuscular bones were ossified at 20 days post hatching (dph) with the body length of 1.33 cm, which first appeared in the tail and then turned toward the head. When the fries were 40 dph with the body length of 2.36 cm, all the intermuscular bones were basically appeared. The average number of intermuscular bones of M. amblycephala was 119 with the range from 108 to 129. The number of intermuscular bones in both body sides was not absolutely equal, although the number of each side was quite close. There were more intermuscular bones in the front dorsal part than rear part, and the number of intermuscular bones was almost equal in rear dorsal and rear abdominal parts. There were 6 kinds of intermuscular bones, including 1 卜 y, one-end-multifork, two-end-multifork, and ( types. Various types of intermuscular bones were evolved from the 1 shape, and more complex shapes were formed in the front part of body. The length of intermuscular bones in front dorsal part was significantly longer than that in tail part (P 0.05), while the intermuscular bones in the front abdominal part were shorter than others. The length of intermuscular bones of M. amblycephala was positively related with the body weight and body length. The emergence and differentiation of intermuscular bones was more related to the body size than to the age in M. amblycephala. The result from this study will contribute to understand the molecular mechanisms of intermuscular bone occurrence and development, the research on the inhibition of the intermuscular bone ossification as well as the breeding of M. amblycephala without intermuscular bone.