How do I start to identify a Nudibranch

[Waja]

Took this picture of a nudibranch in Anilao. These were very small and I had no idea of what I was taking a picture of at the time. My guild had a pointer that sometimes took me forever to find in the the viewfinder. I follow to the end of the pointer, focus and shoot. A lot.  What are these? I shot with a Canon 5D MkIII, 100mm macro, Saga +10 diopter.

 

[jlaity]

The Gosliner book is the standard for nudi ID. Also available as an app if you prefer, but I'm not sure the app is as thorough or up-to-date. You'll find a copy at most resorts and liveaboards that cater to divers. 

 

The faster way is to say "I think it's XXX YYYY" and wait for someone here to correct you. Should be IDed in a few minutes. ;)

[Chris Ross]

A number of approaches - the easy way is to use google lens, feed it the image and it will come back with suggestions.  I tried it and it suggests this is Mexichromis trilineata.  You can post it to one of the Facebook Nudi groups, Nudibase or Nudibranch Central ( read the rules first - they'll delet your post if you don't provide the right info).  Lastly buy Nudibranch & Sea slug identification Indo Pacfic  by Gosliner, Valdes and Behrens.

 

It often pays to try a number of avenues, some species are difficult to ID or are undescribed so don't have an official name.  Google lens even if it doesn't provide a correct hit first up often will get you to right family to start looking in your guide book.  Be careful it is a slippery slope to nudi obsession😂

[Waja]

Almost bought the book, but then realized this is one of those things that my kids like to find on my wishlist.

Thanks!

[Kraken de Mabini]

Neville Coleman's "Nudibranchs Encyclopedia", while a bit old, is an excellent book, well worth having together with Gosliner's books.

Thosee by Helmut Debelius are also well worth having.

 

I found that the more books I have on sea life, the more I enjoy them, they are an excellent investment.  Their authors have done us all lovers of sea life a huge favor by gathering and publishing their knowledge, we owe them a huge debt of gratitude.  

 

Through my late dive buddy Capt Jim Black, an expert nudibranch aficionado, I had the opportunity to meet several of these authors, and they were a pleasure to be with. Their books are on my desktop as I write this. 

Amazon offers an excellent variety of books on reef life: 

https://www.google.com/search?q=amazon.com+nudibranch+reef+life+books&sca_esv= 

Edited September 26 by Kraken de Mabini

[Luko]

On 9/26/2024 at 8:56 PM, Kraken de Mabini said:

Neville Coleman's "Nudibranchs Encyclopedia", while a bit old, is an excellent book, well worth having together with Gosliner's books.

Thosee by Helmut Debelius are also well worth having.

Problem is that the nudibranch taxonomy is continuously evolving (I won't even mention the disagreements between different "schools" and various attempts at categorizing nudibranch families) if you ever compare older books like the ones you mention from Coleman or Debelius (first published 20 years ago or so) with newer ones (say NSSI2 Gosliner, Valdes, Behrens, published some 5-6 years ago) it's completely different, you won't find the same names, even the families are completely different. Hence the older Nudi Id. books are outdated and somehow useless now.

 

I guess the awaited NSSI3 will correct some errors, allocate new names to unnamed sp. nudibranches (about 20% of the nudibranches illustrated inside NSSI2 only get a family name with a sp. number, say Goniobranchus sp.25 for instance) or even propose new families (like Bermudella or Ceratodoris which are already in use but missing in NSSI2).

 

My recommendation would be select some good Websites that are updated to new species names, some of my favorites (but there are many more, depending on your location) :

Erwin Koehler's multi location http://www.medslugs.de/E/Pac-W/select.htm

S&J Johnson from Kwajalein for Pacific slugs https://www.underwaterkwaj.com/nudi/nudi.htm

For Indian Ocean, Ph.Bidgrain's http://seaslugs.free.fr/nudibranche/a_intro.htm

 

There are also excellent Facebook groups like Nudibase where any nudi will be identified by marine biologists.

 

Re- the initial question these are Mexichromis trillineata.

Edited September 28 by Luko

[Kraken de Mabini]

[Kraken de Mabini]

Yes, these two nudibranchs do remind one of a Mexichromis trilineata, but I am not able to take it any further.  

Maybe you can ask Terry Gosliner or Mike Miller for their expert opinion.

Edited September 29 by Kraken de Mabini

[Chris Ross]

On 9/28/2024 at 6:18 PM, Luko said:

Problem is that the nudibranch taxonomy is continuously evolving (I won't even mention the disagreements between different "schools" and various attempts at categorizing nudibranch families) if you ever compare older books like the ones you mention from Coleman or Debelius (first published 20 years ago or so) with newer ones (say NSSI2 Gosliner, Valdes, Behrens, published some 5-6 years ago) it's completely different, you won't find the same names, even the families are completely different. Hence the older Nudi Id. books are outdated and somehow useless now.

 

I guess the awaited NSSI3 will correct some errors, allocate new names to unnamed sp. nudibranches (about 20% of the nudibranches illustrated inside NSSI2 only get a family name with a sp. number, say Goniobranchus sp.25 for instance) or even propose new families (like Bermudella or Ceratodoris which are already in use but missing in NSSI2).

 

My recommendation would be select some good Websites that are updated to new species names, some of my favorites (but there are many more, depending on your location) :

Erwin Koehler's multi location http://www.medslugs.de/E/Pac-W/select.htm

S&J Johnson from Kwajalein for Pacific slugs https://www.underwaterkwaj.com/nudi/nudi.htm

For Indian Ocean, Ph.Bidgrain's http://seaslugs.free.fr/nudibranche/a_intro.htm

 

There are also excellent Facebook groups like Nudibase where any nudi will be identified by marine biologists.

 

Re- the initial question these are Mexichromis trillineata.

All true, however if you enter the species from these outdated books into Google, it will often point you to the new name.  The Facebook groups are very good, though there are many entries that are ignored in my experience.  The experts do a good job on there , but it's not like they are getting paid. 

 

In a great many cases of re-classification the specific name (second part of name) remains the same (apart from gender changes due to it being in Latin)  but the generic name (first part of name) changes indicating placement into a different genera .  For example the Australian slug Chromodoris splendida became Goniobranchus splendidus.  If you google the first name the first entry popping up for me is the new name.  I have heard though that some of the names in the Kuiter and Debelius book are just completely wrong.  Then of course you will find some slugs that are completely un-described.  The Seaslug forum site is full of old names but to me is still quite useful as it has a great many images so you can thee variations within the same species.

 

[Kraken de Mabini]

On second thought, the dorsal three white lines and the white mantle's edge tell us these nudis are a Mexichromis trilineata couple.

The white may be replaced with a light color depending on the nudi's diet.  Nice photo, thanks for posting it!

[RickMo]

There's also a good set of phone apps published by Gary Cobb, who is the hard-working mod of the FB nudibranch ID group.  There are six collections, broken down by region, and don't require an internet or cell connection.

[bvanant]

One problem with even Terry's books is that they have annoyingly changed some sp numbers from edition to edition. So if you give an ID you need to like Unidentia sp2 you have to tell what edition you are quoting.  Many of our southern Cal nudis have changed genus a few have changed species (Hermissenda crassicornis now Hermissenda opalescens. 

 

There are a few groups around doing DNA work but even interpreting that is complex.

 

Bill