EXPERIMENTALLY PRODUCED ABNORMAL COILING AND ANALYSIS OF GROWTH IN GASTROPODS - ROLE OF DEVELOPMENTAL CONSTRAINT IN EVOLUTION -

以涡旋螺为研究对象，研究了牡蛎附着等环境干扰对螺壳正常生长的影响。在这个项目中，硅橡胶球被用作障碍物。一到两年后，大多数个体成功地保持了生长，并诱导了以下模式作为对依恋的反应。橡胶球附着在前一螺孔重叠区的上部（顶端侧），壳的生长由向下变化，经过障碍物后又恢复向上。当橡胶球附着在孔径重叠区的下部（自适应侧）时，壳体的向前生长停止，而孔径向外扩展。这两种对障碍物的反应模式表明，头脚接触对孔径边界有一定的影响。为了验证接触对壳体形态发生的作用，对涉及孔缘头足接触的壳体形态发生模型进行了计算机模拟。该模型的计算机模拟结果如下：最流行的卷取模式是规则卷取和紧卷取，即使没有卷取壳的固有性质，也只能通过孔缘上的头脚接触来产生。头-脚/孔接触机制可以模拟天然蜗牛对附着在前一个螺杆上的障碍物的反应。所有的实验和计算机模拟都表明，头足接触机制对壳盘绕的演化施加了发育约束。

Samples of Turbo cornutus were used to investigate how snail reacts to environmental disturbance like attachment of Oyster which blocks the normal course of the shell growth. In this project, silicon rubber balls were used as an obstacle. After one or two years, most of individuals succeeded in keeping their growth and the following patterns were induced as reaction to the attachment.1. With the rubber ball attached in upper part (on abapical side) of aperture overlap zone on the previous whorl, the shell growth changes downward and then returns back to upward after passing by the obstacle.2. With the rubber ball attached in lower part (on adapical side) of aperture overlap zone, the forward growth of the shell stops for a while the aperture expands outwards.These two patterns of the reaction to the obstacle suggest a certain role of the head-foot contact on the aperture margin. In order to test the role of the contact on the shell morphogenesis, a computer simulation has been performed for the shell morphogenetic model involving the head-foot contact on the aperture margin. Results of computer simulation of this model are as follows.1. Most popular model of coiling, regular and tight coiling, can be produced only by the head-foot contact on the aperture margin even if there is no intrinsic nature of coiled shell.2. The head-foot/aperture contact mechanism can simulate the reaction of the natural snail to the-obstacle attached on the previous whorl.All the experiments and computer simulations indicates that the head-foot contact mechanisms imposes the developmental constraints on the evolution of the shell coiling.