正在交配的非洲蜗牛（Achatina fulica）Africa land snails are mating

晚上经常能看到蜗牛在草地，或者小路上爬，以前没怎么在意。今晚饭后散步，偶遇几只蜗牛正在交配，拍了照片，回家后马上搜寻蜗牛相关的知识。
原来本地最常见的是非洲大蜗牛（Achatina fulica），原产于东非，不过现在在世界广泛分布，因为会大量啃食蔬菜和花卉，在很多地方被列入有害的入侵种。
蜗牛是雌雄同体，但是异体交配才能繁殖后代。其生殖器官位于头部右侧长触角稍后处（照片中的白色部位），每一个个体均可产卵繁殖。生殖季节生殖器官处向外突起，两只蜗牛的长触角互相摩擦，身体前端互相交叉，完成异体受精。一般在夜晚交配。
有趣的是，相互交换的精子可以在体内保存两年之久，莫非是因为行动缓慢的蜗牛不容易遇到一个中意的伴侣的缘故？
The Africa land (Achatina fulica) snail is quite common in Singapore. It is native in East Africa, but intruded in many countries and areas. It is considered as a pest in some areas.
The Giant East African Snail is a simultaneous hermaphrodite, but it is allogamy. Instances of self fertilisation are rare, occurring only in small populations.
The most interesting point is the sperm can be stored within the body for up to two years.