The adductor pectoral fin muscle of Micropogonias furnieri (Perciformes: Sciaenidae): a morphological and histochemical study

ABSTRACT The adductor pectoral fin muscle in post-spawning females of the white croaker Micropogonias furnieri (Desmarest, 1823) is described from a morphological, histochemical and morphometric perspectives. A description of the morphological characteristics was conducted after dissections in different layers, down to the deep layer. Five muscles were found: superficial, medial, radial and deep adductors, and dorsal arrector. Their fibers were studied after applying histochemical techniques: succinic dehydrogenase (SDH) to reveal mitochondria, periodic acid-Schiff (PAS) for glycogen, Sudan black for lipids, myosin adenosinetriphosphatase (mATPase) to reveal the types of fibers, and modified mATPase to evidence the capillaries. Fiber diameters were measured and the number of capillaries was counted. Fiber subtypes named small, medium and large were found within red, pink and white fibers, the latter prevailing. Staining homogeneity was observed in white fibers after alkaline pre-incubations. The number of capillaries decreased from red to white fibers. Due to the prevalence of white fibers, the adductor muscle of the pectoral fins appears to be capable of rapid and discontinuous movements, which are important to body stabilization during subcarangiform swimming. The homogenous staining of white fibers observed in this research corresponds to the post-spawning gonad stage studied.

摘要 本研究从形态学、组织化学与形态计量学视角，对福氏白姑鱼（Micropogonias furnieri, Desmarest, 1823）产卵后雌性个体的胸鳍收肌展开了研究。通过分层解剖至深层结构以描述其形态特征，共鉴定出5组肌肉：浅层收肌、内侧收肌、放射状收肌、深层收肌及背侧竖肌。采用多种组织化学技术对肌纤维进行分析：以琥珀酸脱氢酶（succinic dehydrogenase, SDH）标记线粒体、过碘酸-希夫染色（periodic acid-Schiff, PAS）检测糖原、苏丹黑染色显示脂类、肌球蛋白腺苷三磷酸酶（myosin adenosinetriphosphatase, mATPase）鉴定肌纤维类型，以及改良型mATPase染色可视化毛细血管。研究人员测量了肌纤维直径并统计了毛细血管数量。在红、粉、白肌纤维中均发现了小、中、大三型肌纤维亚型，其中白肌纤维占比最高。经碱性预孵育处理后，白肌纤维呈现均一的染色结果。毛细血管数量从红肌纤维到白肌纤维依次递减。由于白肌纤维占据主导地位，该胸鳍收肌能够实现快速且不连续的运动，这类运动在亚鲹形游泳过程中对维持身体稳定具有重要意义。本研究中观察到的白肌纤维均一染色特征，与本次研究所针对的产卵后性腺阶段相匹配。