Nudibranchs/Sea Slugs Identification - Neville Coleman

Nudibranch / Sea Slugs Defence Systems

Nudibranchs / Sea Slugs - Reproductive Biology

Often referred to as "butterflies of the sea" nudibranchs and their kin certainly deserve this apt description. 

Their gaudy colours, intricate patterns, bizarre shapes, myriad lifestyles and cryptic natures make them one of the world's most fascinating marine animal groups.
With over 3000 species currently recorded and hundreds more yet to be described, they capture the imaginations of all who make their acquaintance.

The Spanish Dancer Hexabranchus   sanguineus is one of the largest and well-known nudibranchs.
It ranges from the Red Sea to the South Pacific and can grow up to 250mm. 

Thirty years ago few divers had ever heard of a nudibranchs.  Most early divers were interested in spearing fish, collecting souvenirs from wrecks, or catching shellfish to eat or sell. 
Today, with the emphasis on scuba diving as an educational, conservation based, adventure activity there are hundreds of thousands of divers all over the planet and nudibranchs are the single most popular sea creature divers look for, and a "must see" on every dive.

Sometimes scientific names appear to be confusing. The  Minor Notodoris
Notodoris minor  grows to over 100mm and is the largest species in its genus. 
However, the original specimen described in 1904 must have been a very small specimen?

My love affair with nudibranchs has been going on for over 40 years and during that time I have found and photographed around 800 species of opisthobranch including 216 new species.

Pioneering underwater visual identification, my Australian Coastal Marine Expedition (1969 to 1973) traversed much of the diveable coastline of Australia, during which I photographed, collected and preserved thousands of specimens which were donated to Australian museums.  Amongst these were over 1,000 nudibranch specimens, most of which went to the Victorian Museum where my good friend Bob Burn (one of Australia's leading opisthobranch taxonomists) identified them.  His interest encouraged my endeavours with feedback on how many new species I had sent back in the last parcel from wherever I happened to be at the time.

This was extremely exciting to me at the time as there was little encouragement towards my endeavours from any other source.
Discovering new species gave me a sense of being a real explorer and few people in the entire world could (in 1973) lay claim to having found 216 new species of nudibranchs underwater.

Bolland's Phyllodesmium, Phyllodesmium sp. was first discovered by Bob Bolland at Okinawa
in 1989, yet it took divers in the Philippines and Papua New Guinea over 20 years
to find it in these areas, as it was so well camouflaged.

Scientific Taxonomy

Nudibranchs cast their birth shell off when they are veligers and from then on (over their short lives) remain soft-bodied, with no external or internal skeleton.  They can really only be seen while they are in salt water. Once they are removed their soft bodies collapse into jelly-like mush, leaving little to be identified by visual means. Even scientific specimens preserved in 70% alcohol shrink into unrecognizable blobs, losing their patterns and colours.

Although common throughout it's range from Mabul to the Philippines and across
to the east coast of Australia, this very characteristic mauve-gilled Hypselodoris
Hypselodoris sp. is still awaiting description.

In those early days the only way for a scientific taxonomist to determine species identification from a preserved specimen was to anatomically dissect it under a microscope and mount the animal's radula (a multi-toothed ribbon-like process the nudibranch uses to rasp bits off its prey) onto a microscope slide. Penis characteristics were also sketched along with other anatomical features, and descriptions noted.  Once all this was accomplished it was then necessary to compare all the descriptions from all the known species published in scientific papers in order to get a name, or to declare it a new species.  This was an enormous job often taking a long time before identification could be made.

Nudibranch photography - advanced science

In the 1950s the few shell books available often displayed a few plates of painted nudibranchs.  Over the next 10 years marine photographers took pictures of nudibranchs in aquaria and scientific photography followed suit.

By the late 1960s underwater photography had emerged and once I had managed my first nudibranch picture I realised that if scientific knowledge was to be available to the average diver then the future was in visual identification.  If I could produce a visual identification system based on a colour photograph and a preserved specimen, then surely it would make nudibranch identification much simpler.  Instead of needing a PhD to taxonomically determine a species, six-year-olds could do it!

Discovered at Milne Bay in Papua New Guinea in 2004 we have yet to find an expert
who can even put this Rusty 'Phidiana' Phidiana sp.
(a new species) into a genus. It appears to belong to the family Facelinidae.

In 1969 my Australasian Marine Photographic Index was developed, and in 1984 I published the first Australian book on nudibranch identification, Nudibranchs of Australasia, authored with Dr Richard Willan.  Nudibranchs of Australasia did not inspire the world of diving, nor did it sell many copies, but as a self-published quality publication it proved a point; underwater photography could be of great assistance to knowledge and science.

Since then, it has been my pleasure to see a number of nudibranchs books published, all over the world. With at least six excellent books on the market in several languages, every enthusiast now has the opportunity to learn and take part in the exploration of their favourite dive sites by identifying nudibranchs and adding to our knowledge.

My newest addition to the visual identification of opisthobranchs is NUDIBRANCHS ENCYCLOPEDIA Catalogue of Asia/Indo-Pacific Sea Slugs. With over 3000 images and  80,000 words it is one of the most comprehensive publications of its kind in the world.

Discovering Nudibranchs

Even though there are nudibranch taxonomists in several countries it appears that there are so many new ones awaiting description that hundreds still remain unnamed.

Despite all the efforts of science and scientists, the Asia/Indo-Pacific region just keeps turning out new ones and us divers are responsible for finding them.  This is what makes diving such an exciting adventure activity.  Everybody with a camera is an underwater explorer and with the wealth of new species still awaiting discovery, everybody can contribute to the greatest adventure of allÉincreasing knowledge and learning more about those fantastic soft-bodied slugs we call nudibranchs.

Certainly one of the most bizarre new species to be found in Milne Bay is this Donut Doto,
Doto sp.  It lives on hydroids in strong current and grows to 25mm.

Nudibranchs can be found in almost every habitat in the ocean. The brightly coloured ones are easy to see, but those cryptically marked species and the really small ones are often difficult to find.  However, once a diver realizes that almost every sessile invertebrate seen on a dive may be the food of some kind of opisthobranch the search becomes easier.

There are places (such as Milne Bay in Papua New Guinea) where over the last few years we have discovered an incredible number of new species. On one trip alone over 35 species of undescribed nudibranchs were found.  However, most of these are often very cryptic, very small or nocturnal, and only seen on night dives.

How do you know you've found a new species?

Divers are continually asking me this question, but there is no easy answer.  Nothing of consequence is ever easy.  For me to keep up on what has been found, I must try and keep all the ones I have met before or researched in books in my head, as a visual reference library.  Due to having 40 years and over 14,000 dives experience and dedicating my life to underwater exploration this ability at visual retention was just another thing I had to teach myself over the years.  Of course, I haven't seen every species (far from it) but I keep abreast of what I can and if I get stumped and need verification I can rely on my expert friends who will give me good advice.

Another small species (20mm) is this Samauri Trinchesia Trinchesia sp.that belongs in the
family Tergepedidae.  So far only one specimen has been found in Milne Bay
living at 20metres on a hydroid in strong current.

How are nudibranchs named?

If a diver suspects they have a new species (because they have checked their reference books and are unable to find a similar one to their photograph or observation) they can always send it to me at , worldofwater@nevillecoleman.com.au

It isn't impossible to get a new species you have discovered named after you, but it generally takes a lot of work and lots of patience to pursue all that is required. There are no rules regarding selection of names by publishing taxonomists, it all depends on the situation at the time and the individual preference of the author.  Some taxonomist authors will often select a person to name the species after, others only select a Latin name based on distinguishing features of the animal, or where it came from. Although I have donated thousands of species to Australian museums including hundreds of new species, of all those that have been described only a small number (15) include a reference to my name in them.

A diver that is interested in taking their photography further would be well advised to contact or work with a marine scientist from a museum or university of the country they belong to.  In this way if something of significance is discovered it can be registered in a local institution and the scientist can offer advice or even make contact with other scientists overseas on the possibility of having the discovery researched and published.  However, one must have patience.

Some of my new marine species have taken 15 years to eventually be published.  However, my new pygmy seahorse Hippocampus colemani only took two years to be described and published because my friend, taxonomist Rudie Kuiter offered to do the work.  The NSW national parks manager and NSW Fisheries agreed to grant me the required permit to collect two from the Lord Howe Island Marine Park, which was the "type" locality.

Belonging to the family Dorididae the Scribbly  Paradoris, Paradoris sp.
was found at Loloata Island, Port Moresby, Papua New Guinea. 
It is also known from Japan and appears to be nocturnal.

Marine Parks and reserves

Some places I dive in are marine parks and to carry out a fauna survey one must obtain permission from the park manager and State fisheries before any specimen might be removed for scientific purposes.
Many dive resorts have self-imposed rules regarding divers behavior in not handling the animals at their dive sites. Where large numbers of divers form several different operators visit the same sites on a regular basis this is always a good practice. One must also keep in mind that the dive guides often earn a percentage of their wages by showing customers special "critters".  Should the animals become too disturbed they may leave the area and then everybody loses!

This also applies to collecting specimens. Divers need to get permission from the operators who have to balance losing one of their part time attractions against gaining excellent publicity if the species is a new one. Remember, most nudibranchs only live for three months, and die soon after mating and laying their eggs.

An undescribed species I discovered at Milne Bay Papua New Guinea in 2002 this
Sand-speckled Rostanga Rostanga sp. mimics the colour of its host sponge and
even the sand grains which often cover the sponge in rough weather.

ACKNOWLEDGEMENTS

My ability to publish books and information in an effort to advance our knowledge of Asia/Indo - Pacific opisthobranchs would have been a lot less without the friendship and assistance of Bob Burn, one of Australia's pioneer workers on opisthobranchs. His understanding of opistobranch taxonomy and biology and his dedicated work for over 50 years has resulted in a wealth of species and his efforts and assistance over 30 years on my behalf are most appreciated.

Many thanks BOB, the results speak for themselves.

Dr. Richard Willan Curator of Molluscs at the Northern Territory Museum has also contributed greatly with opisthobranch identifications for AMPI and with many publications. Richard played a significant part in the production of "Nudibranchs of Australasia"which we combined efforts on in 1984 to bring out the first four colour book on Australian Nudibranchs. Due to his assistance it has allowed publication of many species in "Nudibranchs Encyclopedia" that otherwise would have been without accurate identification at the time of publication and I thank him very much for his efforts and dedication.

Nudibranch / Sea Slugs Defence Systems

Nudibranchs / Sea Slugs - Reproductive Biology