Underwater fieldwork with nudibranchs, 2022

Photographing nudibranchs and the many other astonishing creatures of the ocean is an element of my ongoing multi-species fieldwork in Raja Ampat. In eleven segments below, I showcase the amazing, queer, and diverse world of nudibranchs and their companion species based on photos taken while doing underwater fieldwork.

#1

This is an  inornate headshield slug (Mariaglaja inornata). Until recently, it was classified in the genus Chelidonura. But molecular phylogenetic data in 2017 revealed that it belonged to a new genus, named Mariaglaja after the mother of one of the scientists. 

This is a good example of the ongoing rush of scientific discovery of new species and genera of nudibranchs.  Over 3,000 species of nudibranchs are known and described in the scientific literature, but new species are added to this catalogue all the time.  In fact, there might be twice as many species out there!  Western dive tourists love nudibranchs for their colorful photogenicity, and dive tourist interest is a key driver in these new discoveries.  In Beser, one of the several local languages in Raja Ampat, all nudibranchs are called taráir. And unless they happen to be one of the now many expert local dive guides, the Beser-speaking people of Raja Ampat that I know do not care much about nudibranchs.  In fact, they find dive tourists’ interest in nudibranchs either puzzling or vaguely suspicious. What does this interest really hide, they ask themselves (and me).  Local, touristic, and scientific interest in biodiversity rarely line up neatly!

#decolonizetheocean

#2

This is a Flabelina exoptata, I think, one of many species of aeolid nudibranchs.  The cerata on its back are used to breathe but also as defence.  They contain poisonous nematocysts that the nudibranch has acquired from its prey called hydroids, larvae of Hydrozoas, small stinging animals related to jellyfish.

#chemicalocean

#3

The dotted nudibranch (Jorunna funebris) feeds only on barrel sponges (Xestospongia sp), accumulating its toxins in the bronchial plume as a defence against predators.

#symbioticocean

#4

A Phyllida varicose, I think. Juveniles of Graeffe's sea cucumber (Pearsonothuria graeffei) are brightly colored blue and yellow to mimic this nudibranch and trick predators into avoiding it because this nudibranch like all others are toxic to fish and invertebrates.

#mimicryocean

#5

One of many still unnamed nudibranch species of the genus Tenellia.  This species is, I believe, just called Tenellia sp. 50.

#unknownocean

#6

Phyllidiella pustulosa. This is one of the most common nudibranchs and one of the first to be described by Western scientists in the early 1800s.

#studytheocean

#7

Philinopsis gardineri...another widespread species in the Indo-Pacific

#diverseocean

#8

A slightly blurry image of a Chromodoris annae. Notice the yellow branchial plume on the back. This plume is the reason for the name nudibranch which literally means “naked gills”.  The Chromodoris breathes through the plume which also holds high concentrations of a toxin called Latrunculin A. The nudibranch accumulates the toxin, which is poisonous to fish, from the sponges on which it feeds. Latrunculin A is currently being studied as a potential drug in the treatment of cancer.

#cleverocean

#9