The name nudibranch means “naked gills.” Many types of nudibranchs have developed external gills to absorb oxygen from the water. These feathery, ribbon-like organs can be very beautiful, and make it easy for a diver to distinguish nudibranchs from other kinds of underwater slugs. External gills “crown” the nudibranch above, called Chromodoris elizabethina (presumably named after the queen). The external gills can be clearly seen in the left portion of the photo. Divers might spot this nudibranch munching on coral polyps.
A Brilliant Blue Nudibranch With Red Gills
Some Nudibranchs Use External Gills to Breathe
Chromodoris elizabethina is an example of a nudibranch with external gills. This nudibranch's gills form the bright red "crown" pictured above.
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