Sikai

The sikai replaced its ancestor the rikaia in tropical coasts. Unlike its ancestor the sikai has undergone major evolutionary changes very beneficial for survival. Sexual reproduction is acquired through the development of some organs and a pair of tubes where entering and exiting gametes for fertilization. But have isogamy gametes because the gametes have the form of ciliognathus, and the species is hermaphroditic. It has a method of coupling consisting tubes together with another individual of the same species facilitating fertilization. After coupling, the individual puts thousands of eggs. The larvae have the same shape as its ancestor, but that is undergoing a metamorphosis. The adult has a more complex nervous system that gets to develop a brain. It has a pair of antennae that detect the vibrations of the external environment. Its eight eyes are more evolved. Its skin has gone to have a grayish tone. It has developed a backbone formed by magnesium. It has also developed six prolegs which have the function of moving in the aquatic environment. It has increased in size.