Thordisa villosa

Images courtesy of Andrew Podzorski
Triton Bay, PNG

Image courtesy of Andrew Podzorski

Thordisa villosa sp. (Alder & Hancock, 1864)

When most of us think about nudibranchs, we think about all those brightly colored flamboyant species. We rarely think about those; well how do I say it with a little compassion - "ugly" cryptic species. That said - when you stop and think about it - the evolution of these species crypsis, is as unique as those color strategies used by flamboyant aposematic species.

When I study this somewhat rare species, I am amazed at its disguise and how it hides on sandy bottoms. This interesting example of crypsis seems to be a combination of mantle tissue colorations and the ability of its conical papillae (which is the feature this species was named for) to hold onto grains of the sand, making this species almost invisible. Maybe that why it is so rare.

I am not sure if the papillae are caryophyllidic (bearing a series of spicules about their base) but his would explain the interesting ability to hold onto flacks of sand. Combined with the black specks on the dorsum they create an amazing costume to hide under.

Joshua Alder & Albany Hancock hit it out of the park when they named this species "villosa", but I am not sure they truly understood the functionality of these very specialized dermal tissues.

Great Photos Andrew and thanks for sharing!


Alder, J. & Hancock, A. (1864). Notice of a collection of nudibranchiate mollusca made in India by Walter Elliot Esq., with descriptions of several new genera and species. Transactions of the Zoological Society of London, 5: 113-147.
Chan, J.M. & Gosliner, T.M. 2007. Preliminary Phylogeny of Thordisa Nudibranchia: Discodorididae) with Descriptions of Five New Species. The Veliger, 48(4): 284-308.

Dave Behrens
Sammamish, WA 98074
Jul., 2022
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Started diving in 1977 with the Jamaica branch of the British Subaqua Club (JSAC). I qualified as a BASC Advanced Diver/CMAS *** in 1978. As a freshwater botanist in the University of the West Indies, I had collaborative projects with the marine labs at Port Royal and Discovery Bay. I had the privilege to be personally taught about Caribbean corals by Nora Goreau. My first underwater photos were taken in Jamaica with a NIkonos 2! It was impossible not to become passionate about reefs with the great people in the JSAC and the marine labs. I left Jamaica in 1980 with some 425 dives and spend a short time diving with the Institute of Marine Affairs in Trinidad. There I helped with research collection of sponges on the north coast of Trinidad, on Chacachacare and in the Grand Boca, and we even found a new species of ahermatypic coral. Moving on from there, I did some freshwater diving in the USA and cold water diving in southern Sweden, snorkeling and free diving in the Galapagos, before returning to reef diving on the west cost of Saudi Arabia, Queensland, the Philippines, Thailand, and quite extensive diving in mid to eastern Indonesia. Quite some time ago I stopped counting dives when I reached 2000, though I take notes, documentary photos and record the profiles of all dives.

With the travel restrictions imposed by Covid, and finding out how little money is donated to charities supporting reef conservation, I decided to use my knowledge and photos to create a website to encourage people to donate to Greenpeace, Sea Shepard, Conservation International etc. Reef Image-Stories - Help save our reefs!

Camera: Nikon D750 with a Nikon 105mm macro objective in a Seacam housing with Seacam Seaflash 100D strobes.

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From left to right, Terry Gosliner, Angel Valdes, Dave Behrens La Jolla, Calif.

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