Comb jellies?

[drbill]

The irridescence is what most divers see when they encounter ctenophores and is, as was pointed out, due to the interference created when light strikes the ctenes or combs of the ctenophore. The bioluminescence can be observed at night of course.

There are some ctenophores that prey on other ctenophores as well as predation by some jellies, Mola mola, etc.

 

[rcohn]

The cilia bands on most of them are also iridescent, which is what you are talking about. This is "in addition to" not "instead of" bioluminescence in most ctenophores. The iridescence appears as rainbow bands of pulsating colors. The pulsating of the colors is due to the motion of the cilia in the comb rows. As you said this is merely reflection of ambient light and you cannot see this effect in the dark. The blue bioluminescence can only be seen in the dark.

Technical point - it is not correct to say the iridescence is "merely reflection of ambient light." Riather the cilia form a diffraction grating and diffract the light producing colors that change with the illumination and observation angles, as well as cilia angles and spacing. This diffaction is the same phenomena that produces colors observed in light scattering from the pits in a compact disk's or DVD's surface.

Any as an aside, I earned an M.S. in O.E. from URI, a long time age.

Ralph

 

[RIOceanographer]

Technical point - it is not correct to say the iridescence is "merely reflection of ambient light." Riather the cilia form a diffraction grating and diffract the light producing colors that change with the illumination and observation angles, as well as cilia angles and spacing.

Yup you're right, bad wording on my part. Great explanation on your part.

Any as an aside, I earned an M.S. in O.E. from URI, a long time age.

I just finished my Ph.D. in Bio Oceanography at URI last year, then got a job right across the street at the NOAA lab, it seems there is no escaping the Bay Campus for me.