Oikopleura is a genus of Tunicata (sea-squirts) in the class Appendicularia. It forms a every four hours at 20 degrees Celsius. This house has a coarse mesh to keep out big particles, and a fine mesh that collects the small particles, down to the nanoplankton that includes (pelagic) bacteria. Species of Oikopleura have the smallest genomes in the animal kingdom, only about 75Mb. Oikopleura contains bioluminescent species. About half of Oikopleura species are bioluminescent.