Among zooplankton we can find many animals in a larval stage. Larval appearance often completely differs to that of the adult and species can be very difficult to recognize. Sometimes we find only eggs which are much more difficult to identify. Some of them may be tunicate eggs which, if they have been fertilized and if you conserve them in a favorable environment, larvae will hatch and begin their development.
Tunicate growth includes metamorphosis which is very intriguing to observe.
Ascidians are amazing marine animals often called 'sea squirts', because they spit water when they are disturbed. Their adult appearance may be sometimes a little repelling. Ascidians filter sea water into a double layered envelope. The thick external wall is called the tunic and the inside layer is pierced by gill slits which circulate water. Nutrients are captured and brought into the stomach by the endostyle, which is a mucus secreting structure above the slit layer.