Symmetry variation in the heart‐descending artery system of the parthenogenetic marbled crayfish
Symmetry variation in the heart‐descending artery system of the parthenogenetic marbled crayfish
复制标题
孤雌生殖大理石螯虾心降动脉系统的对称性变异
作者：
G. Vogt;C. S. Wirkner;S. Richter
淡水螯虾的内部解剖结构是严格两侧对称的，除了垂直定向的降动脉（胸骨动脉），它起源于心脏并终止于神经下动脉。对133只孤雌生殖淡水螯虾幼虾的连续切片观察发现，降动脉两侧对称的占4.5%，右侧不对称的占45.1%，左侧不对称的占50.4%。两侧对称型的心脏有两个分支，分别从左心室和右心室发出，环绕后肠，并在后肠下方融合;不对称型的心脏只有一个背侧分支，环绕后肠的左侧或右侧。心脏的其他结构，如成对的触角动脉和肝胰腺动脉以及口或不成对的前、后动脉，没有显示对称性变化。由于实验动物的遗传特性及其在相同环境条件下的培养，观察到的降动脉对称性的变化被解释为发育变异的结果。我们建议，大理石纹螯虾被认为是调查的后生机制负责的维护和打破双边对称后生动物。J. Morphol.，2009.© 2008 Wiley利斯公司
The internal anatomy of freshwater crayfish is strictly bilaterally symmetric, with the conspicuous exception of the vertically oriented descending artery (sternal artery), which originates from the heart and terminates in the subneural artery. Serial sectioning of 133 juveniles of the parthenogenetic marbled crayfish revealed that the descending artery was bilaterally symmetric in 4.5% of the specimens, right asymmetric in 45.1%, and left asymmetric in 50.4%. In the bilaterally symmetric variant two branches arise from the left and right chambers of the bulbus of the heart, run laterally around the hindgut, and fuse underneath it. The asymmetric variants have only one dorsal branch, which loops around the hindgut on either the left or the right side. Other structures of the heart, such as the paired antennary and hepatopancreatic arteries and the ostia or the unpaired anterior and posterior aortae, showed no symmetry variation. Because of the genetic identity of the experimental animals and their culture under identical environmental conditions, the variation in symmetry of the descending artery observed is interpreted as the result of developmental variation. We recommend that the marbled crayfish be considered for investigation of the epigenetic mechanisms responsible for the maintenance and breaking of bilateral symmetry in metazoans. J. Morphol., 2009. © 2008 Wiley‐Liss, Inc.