粘虫蛾飞行肌超微结构的研究

ULTRASTRUCTURE OF THE FLIGHT MUSCLE OF ADULT ORIENTAL ARMYWORM,MYTHIMNA SERATA(WALKER)

应用电子显微镜对粘虫雌蛾Ｍｙｔｈｉｍｎａｓｅｐａｒａｔａ（Ｗａｌｋｅｒ）飞行（背纵）肌的研究结果表明，其肌原纤维由５００～７００根肌球蛋白丝（粗丝）组成，每根粗丝由６根肌动蛋白丝（细丝）环绕排列成六角形，每根细丝精确地位于两根粗丝间１／２处，从而使粗丝和细丝的比为１：３。肌节较短，长度约２．２—２．６μｍ。肌原纤维之间充满着线粒体和横管。每个肌节约有线粒体三个，横管二根。线粒体约占肌纤维体积的４０％，而横管为７％。每根横管准确地位于肌节的１／４、３／４处，或Ｚ线和中隔的中央，并与肌质网交接形成二位体（ｄｙａｄｓ）或三位体（ｔｒｉａｄｓ）。肌质网相当不发达，约占肌纤维体积的２．５％。但其分布很有特色，即除了紧贴于肌原纤维周围的由单层液泡组成的肌质网以外，在中隔处还有一层横穿于肌原纤维的肌质网。和其它同步飞行肌的结构和功能分析比较的结果还表明，粘虫蛾飞行肌具有较善于飞行的结构。

Ultrastructure of the indirect flight muscles of a migratory moth, Orientalarmyworm Mythimna separata (Walker) was examined with electron microscope'Incross section, the polygonal, close-packed elliptical myofibrils each has a diameter of0.8--1.0μm and consists of 500 ￣ 700 myosin filaments。 Thick and thin filamentsform a hexagonal lattice with the thin filaments midway between the adjacent thickfilaments with ratio actin and myosin in 3:l' In longitudinal section, myofibrils exhibitregular, well aligned sarcomeres (sarcomere length about 2.2 -- 2.6μm, A--bandabout 2.0 -- 2.3μm) divided by homogeneous and continuous Z lines. Mitochotidria are intercalated between myofibrils and completely filled the interstices between them.There are usually 3 mitochondria and 2 T--tubes along each sarcomere. Mitochondriaand T--system are estimated to be about 40% and 7% respectively of the fiber'stotal volume. T--tubes situate at midway between Z lines and middle of eachsarcomere and make contacts with sarcoplasndc reticulum (SR) to form dyads andtriads wherein. The SR is lesser in quantity as compared with the T--system andoccupies ohly about 2.5% of the fibers total volume' The characteristic feature of theSR is that there is a layer of SR cisternae transversely penetrating myofibril halfwaybetween Z lines in every sarcomere. Ultrastructure of the flight muscle fiber of M'separata moth is similar to those of fast acting insect muscle fiber in many aspectseven though it may show some variations as the moth's age changes'