A bizarre broadbase tunicate (Cnemidocarpa finmarkiensis) was found on a dive that has three siphons instead of the usual two. I have not seen this variation before and was very surprised when I noticed this small filter feeding animal clinging to a wall at around fifty feet of depth. Tunicates usually have two siphons; one to draw water in which is then gleaned of nutrients, and another exhalent siphon to get rid of waste water.
Gretchen Lambert is a west coast expert on tunicates and she hypothesizes that…
“Very unusual Cnemidocarpa finmarkiensis; I’ve never seen one with 3 siphons. In this case the oral (incurrent) siphon is the one that is doubled. It probably resulted from an injury when it was very young, like perhaps a bite taken out of it. There is a graduate student at Tel Aviv Univ. working on regeneration in Polycarpa, a tropical genus in the same family as Cnemidocarpa (Styelidae). Polycarpa’s powers of regeneration are amazing. The student can chop off the entire top of a large Polycarpa, including both siphons, and it will just sit there, the wound gradually closes, and in about a month it has 2 new siphons. In the case of this Cnemidocarpa, the injury was probably just to the oral siphon and it then grew an extra one.”