Cellulose in the house of the appendicularian Oikopleura rufescens

By electron diffraction analysis, highly crystalline cellulose IP was found in the house (a special structure in which the tunicate lives) of the appe ndicularian Oikopleura rufescens. Cellulose microfibrils 20 nm in width wer e observed in a random array or highly organized with rectangular spacing o f 2 to 10 mum in the house. The bundled cellulose microfibrils formed in th e inlet filters, which are highly ordered meshwork structures. This paper p rovides the first account of the existence of cellulose in the house of an appendicularian. Our findings showed that the house and tunic are homologou s tissues among the tunicates, and that the common ancestor of the tunicate s (ascidians, thaliaceans, and appendicularians) already possessed cellulos e-biosynthetic ability.