Parmentier E, Gennotte V, Focant B, Goffinet G, Vandewalle P
Laboratory of Functional and Evolutive Morphology, Institut de chimie, Bâtiment B6, University of Liège, 4000 Liège, Belgium.
Proc Biol Sci. 2003 Nov 7;270(1530):2301-8. doi: 10.1098/rspb.2003.2495.
Sound production in carapid fishes results from the action of extrinsic muscles that insert into the swim bladder. Biochemical, histochemical and morphological techniques were used to examine the sonic muscles and compare them with epaxial muscles in Carapus acus. Sonic fibres are thicker than red and thinner than white epaxial fibres, and sonic fibres and myofibrils exhibit an unusual helicoidal organization: the myofibrils of the centre are in a straight line whereas they are more and more twisted towards the periphery. Sonic muscles have both features of red (numerous mitochondria, high glycogen content) and white (alkali-stable ATPase) fibres. They differ also in the isoforms of the light chain (LC3) and heavy chain (HC), in having T tubules at both the Z-line and the A-I junction and in a unique parvalbumin isoform (PAI) that may aid relaxation. All these features lead to the expression of two assumptions about sound generation: the sonic muscle should be able to perform fast and powerful contractions that provoke the forward movement of the forepart of the swim bladder and the stretching and "flapping" of the swim bladder fenestra; the helicoidal organization allows progressive drawing of the swim bladder fenestra which emits a sound when rapidly released in a spring-like manner.
线口鳗科鱼类的发声是由插入鳔的外在肌肉的作用产生的。运用生物化学、组织化学和形态学技术对线口鳗科鱼类的发声肌肉进行了检测，并将其与尖吻线口鳗的轴上肌进行了比较。发声肌纤维比红色轴上肌纤维粗，比白色轴上肌纤维细，且发声肌纤维和肌原纤维呈现出一种不寻常的螺旋状结构：中央的肌原纤维呈直线排列，而越靠近外周则扭曲程度越大。发声肌肉兼具红色纤维（线粒体众多、糖原含量高）和白色纤维（碱稳定ATP酶）的特征。它们在轻链（LC3）和重链（HC）的同工型、在Z线和A-I连接处均有T小管以及拥有一种可能有助于舒张的独特小白蛋白同工型（PAI）方面也存在差异。所有这些特征引出了关于发声的两种假设：发声肌肉应该能够进行快速而有力的收缩，从而引发鳔前部的向前运动以及鳔孔的拉伸和“拍打”；螺旋状结构使得鳔孔能够逐渐拉伸，当以类似弹簧的方式快速释放时便会发出声音。
