This highly invasive solitary ascidian is commonly found in large aggregations on artificial structures. It is transparent white, and has an elongated cylindrical body. It has opaque longitudinal lines on its siphons, and only very subtle colouration on the siphon rims. These siphon features distinguish it from the other invasive Ciona species, C. intestinalis and C. savignyi, as does the red-tipped sperm duct, visible through the atrial siphon.
