Larvae plankton - Tunicata
The group Tunicata is systematically placed between evertebrata and vertebrata because of the planctonic larvae which has a chorda in the back region. The chorda is lacking in adults. The Tunicata group is big and have a lot of species in sea water, most of them are bottom living animals.
The larvae is planktonic and have a shape like a tadpole. They are filter feeders. The video shows a larva from the undergroup called Appendicularia where the genus Oikopleura belong. In this undergroup the larvae and adults are planktonic all the life.
The larvae is enclosed by a mucilaginous house. When beating the tail the larvae set up a water stream through the house and in the opening is a net which filters small plankton organisms (nanoplankton) and bacteria as food for the larvae. When the net is clogged the larvae makes a new one.
Length 2-8 mm.
Video of a subgenus called Oikopleura.