Naked Gills

(December 3, 2017)

Nudibranchs, often referred to as “sea slugs”, are this underwater photographer’s favorite subject.  They come in a wide range of shapes, sizes, and most importantly – color.  In fact, nudibranchs are some of the most colorful creatures on earth.  They can be red, yellow, blue, green, black, white, brown, orange, purple, lavender, pink, or any combination of these colors.  They can be solid, stripped, dotted, or streaked. The icing on the cake – they typically move very slowly, if at all. 

When you first encounter a nudibranch, it is difficult to know which end is which because they don’t have discernable eyes, nose or mouth.  But once you understand the anatomy of a nudibranch, it is much easier to know which is the front end and which is the back end (I have many “nudi-butts” from my early years in photography). 

Nudibranch rhinosphores

At one end of the nudibranch, are a pair of horn-like appendages called rhinosphores which are used for smelling.  Like the nudibranch, the rhinosphores come in a variety of shapes, sizes and colors – but there are always two of these at one end. 

Nudibranch branchial plume

At the opposite end of most nudibranchs is the branchial plume, commonly in a contrasting color to the body of the nudibranch.  The branchial plume surrounds the creature’s anus, and are actually external gills – which is how the nudibranchs breath.  The name nudibranch is derived from this particular piece of anatomy – the Latin word “nudus” meaning “naked” and Greek word “brankhia” meaning “gills”. 

On our most recent trip to Wakatobi (October 2017), I was able to photograph more types of nudibranchs and flatworms than I have in all my previous years of diving.  We saw tiny, juvenile nudis, large nudis (over 8 inches), long, thin, curly nudis, flat nudis, bulbous nudis, smooth nudis, semi-transparent nudis and warty nudis.  And even with all of the creatures that I saw, I did not come close to photographing the more than 2300 species of nudibranchs. 

I hope you enjoy viewing the photos below as much as I enjoyed shooting them. 

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