This image shows a stained specimen of a young salp, which belongs to a group of tunicates that contains only six genera, most of which are found in tropical and semitropical waters.  Salps differ from sea squirts in having their incurrent and excurrent siphons at the opposite ends of the body.  This arrangement allows them to use the water passing through them not only to obtain food and oxygen but also for locomotion using a  type of "jet propulsion".  Some small forms are brilliantly luminescent while others range in size to over 3 meters!