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Thursday, January 10, 2013

Flatworms and Nudibranchs - Snorkeling Raja Ampat

Glorious Flatworm
This past November in Raja Ampat our Oceanic Society snorkeling group was again treated to many macro sightings. Locating these wonderous creatures, flatworms and nudibranchs, was often very challenging. Many are less than 2 inches long, and while vibrantly colored are usually perfectly camouflaged among the sponges, sea squirts, and corals they may be found feeding upon. Much like last years sightings the diversity of what we encountered in this years expedition was often spectacular. The dramatic patterns and colors that these animals utilize is truly fantastic. I am sure that there were countless individuals that we missed, but fortunately we managed to spot quite a few. It was a great help to again have our local guide and expert, Dalton Ambat, searching along with us.
Psychedelic Slug feeding

It was the walls that we snorkeled while spending 2 nights at Alyui Bay in Waigeo Island that presented us with some of the most slug sightings per day. These walls are rich in soft corals and tunicates, both things that the nudibranchs and flatworms like to feed on.  At Alyui Bay there is also a large pearl farm. There are literally thousands of oysters being grown in this bay, perhaps the extra structures and the fact that there is good "flushing" of water through this bay also helps to account for the diversity we see there. The walls that we snorkel along in this area have been a highlight of our trip for the last two seasons. In fact, it is at the pier of the pearl farm where we have our night snorkel. This pier is one of the places in Raja Ampat recognized as an exceptional location to see a wide variety of unusual critters.  To follow is just a small sample of the variety of sea slugs and flatworms that our group saw during this most recent snorkel expedition to Raja Ampat.

Elysia ornata
Brown Margin Glossodoris
Glossodoris sibogae
Linda's Flatworm
Pseudocerous sp.
Bicolor Flabellina
Fabellina rubrolineata
Nembrotha kubaryana
Risbecia tryoni
Pseudoceros goslineri
Red-striped Flatworm - Maritigrella virgulata
Thuridilla lineolata - seen in Sulawesi
To learn about traveling to Raja Ampat for your own snorkel adventure visit Oceanic Society, a non-profit marine conservation organization located outside of San Francisco, specializing in educational marine expeditions throughout the worlds tropical oceans.

A few websites that are great resources for identification help are:

Marine Life Photography - Also their great new iPhone and Ipad app for Hawaii reef life ID
The Sea Slug Forum
Nudi Pixel


  1. Incredible photos and documentation of the marine life there in Raja Ampat. The diversity must be just spectacular. It's interesting that the pearl farming presence in that particular bay could actually be affecting the diversity seen there.

    1. Glad you enjoy the photos, the diversity sure makes it fun to have a camera at the ready. Yes the Pearl Farm would make for a few good Master's projects that is for sure. It may just be that the same qualities that make it a good area for pearl farming also account for the extra helping of critters, but I bet there is more to the story.