Abstract
Anatomical study was conducted to reveal the arrangemental principle of the main ventral muscles in the abdomen of the kuruma prawn Penaeus japonicus. The musculature consisted of five components: 1) anterior oblique muscle having anterior and posterior trunks, 2) central muscle, 3) posterior oblique muscle, 4) transverse muscle, and 5) oblique transverse muscle. Their dis-tribution was observed, and their arrangement was described, except 5), of which tracing was dif-ficult. The functions of these main ventral muscles and especially of the anterior oblique muscle which showed a specifically twisted structure are discussed.
