We documented the regeneration of longitudinal muscle bands in the sea cucumber, Apostichopus ja-ponicus. The longitudinal muscle bands at the rear of the abdominal cavity were severed with scissors. The sea cucumbers were then reared in sea water containing antibiotics (100 IU/mL penicillin and 100μg/mL streptomy-cin), and the structural changes of the regenerated longitudinal muscle bands were documented using morpho-logical and histological methods. Morphological analysis revealed a gap of 0.5-1 cm around the broken muscle bands caused by contraction of the longitudinal muscle after surgery. Ivory and flocculent tissue (muscle precur-sors) were observed at the trauma site 15 d after the operation. The muscle precursor thickened 30-45 d after in-jury and the ends of the severed muscle were reconnected. The muscle precursor gradually transformed into mus-cle bands that were half the thickness of the normal longitudinal muscle 60-90 d after surgery. The regenerated longitudinal muscle bands grew further, and were only slightly smaller in diameter 110-130 d after surgery. The longitudinal muscle bands were completely regenerated 150 d after surgery, and there was no significant difference from undamaged muscle fibers. Histological analysis revealed that the muscle precursor was composed of connec-tive tissue and individual muscle fibers 15 d after surgery. At 30-45 d, the number of new muscle cells increased significantly, and there was evidence of“bridged’ connections between thickening muscle precursors and the body wall. At 60-90 d, the thickening muscle precursor was largely replaced by muscle fibers, and could be classified as longitudinal muscle bands. Concurrently, the number of“bridged’ connections increased. At 110-130 d, the num-ber of new muscle fibers increased significantly and the number of“bridged”connections decreased. At 150 d, the longitudinal muscle bands had regenerated completely and the “bridged” connections had disappeared. Our ob-servations suggest that the longitudinal muscle bands have a strong ability for regeneration and the new muscle cells are derived from the connective tissue cells in the body wall and the coelomic epithelium.%采用人工创伤的方法剪断仿刺参(Apostichopus japonicus)体腔背部的纵肌带,然后缝合切口处的体壁,将其在添加抗生素(100 IU/mL的青霉素和100μg/mL的链霉素)的海水中继续饲养。通过形态学和组织学方法对仿刺参纵肌带再生过程中的结构变化进行了观察。形态学结果显示,创伤后0 h,由于纵肌带的收缩,断端出现0.5~1 cm的间隙；创伤15 d,创伤处出现乳白色絮状组织,暂命名为肌前组织；创伤30~45 d时,肌前组织逐渐增厚并将断端肌肉组织连接起来；创伤60~90 d,肌前组织已转化成纵肌带,并且其厚度增至正常纵肌带的1/2；创伤后110~130 d,新生纵肌带进一步增粗,形态上与未创伤处组织没有区别,只是直径略小一些；创伤150 d,再生的纵肌带厚度同正常状态。组织学结果显示,创伤后15 d,在损伤处出现结缔组织及单个的肌纤维,形成一条不规则的细长条带,即肌前组织；创伤后30~45 d,肌前组织中肌细胞数量大量增加,并与体壁间形成一些“桥状”连接；创伤后60~90 d,肌前组织几乎被肌纤维占据,且“桥状”连接数量增加,此时肌前组织已转化为肌肉带(纵肌带)；创伤后110~130 d,新生肌纤维数量大量增加,和体壁相连的“桥状”连接数量减少,创伤150 d,新生的纵肌带基本达到正常的结构,且“桥状”连接消失。分析认为仿刺参纵肌带具有较强的再生能力,且新生的肌细胞来源于体壁结缔组织细胞和体腔上皮细胞。
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