Ascidian

Ascidians (Ascidia) begin their lives as a several millimetres long larva living freely in the oceans and resembling a tadpole. After completing larval growth, it changes (metamorphoses) into an adult. The process of metamorphosis is very complicated and lasts for several days. The body of a sedentary living adult is coved by a tunic (hard outer layer). Branchial orifice leads to a pharynx that fills more than half of entire body volume and is perforated by thousands of tiny slits. Pharynx´s slits catch tiny particles of food that are covered by slime and transported by cilia to the mouth. Digestion system continues further to oesophagus, stomach and guts. Ascidians have the hearth and veins, one blood circle lasts several minutes. Each ascidian has males and females reproductive organs. Self-fertilization doesn´t happen because male reproductive cells mature and are released from the body earlier than females eggs. Colonially living species can reproduce asexually by germination. Ascidians live only in oceans. Many species are very brightly and vividly coloured yellow, red, blue or purple.