July 4, 1999
From: Nishina Masayoshi
I believe that you probably know that the Sea Slug ID book has been released here in Japan. I've already got it and it's all color photo book.
it's so nice and beautiful. It's originally made for diver so it's not expensive so easy to get it. However it only has Sea Slugs from around Okinawa, I believe that I can find a most of kind of Sea Slug live in this area, so this might enough, but I hope you
to release world wide version one day.
I am also not sure where to send topics to the Forum.
I have often wondered how you can tell species apart? Does it depend on color and size? Do you sometimes check DNA?
email@example.comMasayoshi, N., 1999 (Jul 4) How are species recognised?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1014
I guess the book you are talking of is Atsushi Ono's on Kerama Is. I haven't seen it yet and look forward to receiving a copy. If you have questions, animals you can't identify, observations or photos I am happy for you to send them to the Sea Slug Forum. Anything to do with sea slugs is welcome. In this way we can all help to build up a 'worldwide book' on sea slugs for everyone to consult.
You can either send messages and photos by using the SEND NEW MESSAGE button on the Messages Page or by sending me an email message with photos attached. If you have trouble scanning photos you could post them to me by airmail and I would return them to you after scanning.
Now to your question about how do we decide what is a species?
The general philosophical question - What is a species? - will be debated whenever two biologists meet! For practical purposes we tend to define 'a species' as being a unique group of interbreeding organisms with a unique set of genetic information. Usually we consider that a species is unable to breed with any other closely related species. However at this point the debate begins!
For practical purposes we tend to define a species as a group of organisms with a unique combination of characters. These characters can include anatomical features, colour patterns, behaviour, food preference, reproductive behaviour, egg masses, larval development etc.
If you look at the messages I have just put on the Forum from Yoshi Hirano, you will see that slight colour differences, differences in penis shape, and differences in the egg mass and larval development all helped to show him that he had two quite distinct species of the aeolid genus Facelina.
Once we have found a combination of characters which make a species distinct we then need to try and find some simple 'indicator' characters so that we can identify the species easily. If the only characters we have to identify a species are internal parts of the anatomy, then its very difficult for a field naturalist to identify the species. After all we can't do ecological studies if we have to kill and dissect every specimen to identify it.
An example would be the red-spotted chromodorids in southeastern Australia. Have a look at my message where I explain why there are so many species there with very similar colour patterns. In southeastern Australia many species have red spots, so it is necessary to look at other features of the colour pattern, such as colour of gills or rhinophores to find useful characters to identify living animals in the field.
There is of course a difference between identifying a named species, and deciding a particular animal is a new species. Deciding which differences are important enough to justify considering an animal a distinct species needs a broad knowledge of related species. It also needs access to a good library so all the past descriptions of related animals can be checked so that we can see if the animal already has a name. For example, when I find an animal in Australia which I am unfamiliar with, I need to look at all the descriptions of similar animals from all parts of the Indian and Pacific Oceans, from east Africa and the Red Sea, to Japan and Hawaii, because it is possible that the species lives throughout this vast region and someone else has found and named it somewhere else.
It is also important to realise there is a lot we don't know about opisthobranchs. There are still many examples of 'species' or 'variations' which we are unable to be sure about at this stage. An example here in the Forum is a red-spotted Chromodoris from eastern Australia which I suspect is a geographic colour form of the widespread Chromodoris fidelis. It is possible that it should be considered a distinct species but at this stage there is no clear way to decide one way or the other.
Another example would be the orange-spotted species of Nembrotha from the Philippines. Until the anatomy of these three animals is studied we cannot say whether we have one, two or three species. We can't even be sure they are all species of Nembrotha.
At this stage I know of no use of DNA comparisons to determine nudibranch species. Comparisons of enzymes by gel electrophoresis has been used a few times but techniques, such as DNA analysis, are too expensive for most of us to contemplate.
I hope this is of some help,
Sea slug eats own brain??
From: Charles Stenholm, March 18, 2010
Sea slug eyes
From: Erwin Kodiat, January 18, 2007
How many noses does a slug have?
From: Emma, October 3, 2003
The fastest Sea slug?
From: J.Van Doorslaer, February 24, 2003
Sea Slugs in general
From: Rachel Wierenga, September 11, 2002
Need some information
From: Maria Bernamudez, May 14, 2002
Do nudibranchs taste?
From: Jeanette McInnes, February 12, 2002
Re: Where do nudibranchs sleep?
From: Brian Penney, January 31, 2002
Where do nudibranchs sleep?
From: Jeanette McInnes, January 25, 2002
What does cf mean?
From: Elianny Dominguez, September 21, 2001
Where do sea slugs live?
From: Patty, July 17, 2001
What is the family name for the sea slug?
From: Patrick O'Connor, June 11, 2001
RE: What do var, cf. etc mean?
From: Nishina Chikako, June 8, 2001
What do var, cf. etc mean?
From: Nishina Chikako, May 21, 2001
What does 'nudibranch' mean?
From: David James, April 25, 2001
From: Maggie, April 22, 2001
Are sea slugs harmful to people
From: Heidi Colonnese, March 10, 2001
What are sea slugs importance to man?
From: Sarah, January 8, 2001
General information on sea slugs
From: Nick, December 30, 2000
Nudibranch that eats algae?
From: Eric Sterns, October 23, 2000
From: Jennifer, October 19, 2000
Information about slugs
From: Kathleen, October 2, 2000
More information on sea slugs
From: Jennifer & Kate, October 2, 2000
Protection from Dryness
From: Jacob Benveniste, September 30, 2000
Do nudibranchs have eyes?
From: Anonymous, May 10, 2000
Re: Nudibranch Information
From: Anne Dupont, March 15, 2000
Information on adaptations
From: Ross Sinclair, March 13, 2000
Information on Sea Slugs
From: M.C.M, March 13, 2000
Information for a School Project
From: Emilee Bucholz, March 5, 2000
Information for Sigrid, Caroline & Ashlee
From: Bill Rudman, February 19, 2000
What do they eat?
From: Samantha , February 16, 2000
How do nudibranchs breathe?
From: Lillie Hetze, January 21, 2000
Interesting facts about Sea slugs
From: Hartzell, June 9, 1999
From: K. Rabinoiwtz, May 24, 1999
Re: Nudibranch questions
From: Christian Desprez, May 19, 1999
From: Christian Desprez, May 3, 1999
on rhinophores, cerata, and how many species?
From: Carlo Magenta, March 15, 1999
Nudibranch info needed
From: Steve, February 20, 1999
Re: Nudibranch Questions
From: Beth Kyd, February 16, 1999
Sea Slug questions
From: Dale Kyd, February 12, 1999
Information on nudibranchs
From: Ross Tetreault, February 11, 1999
Why study nudibranchs?
From: Brehan Miller, February 9, 1999
Sea Slug metabolism
From: Sean Wise, February 5, 1999
Information on Nudibranch biology
From: Christian Desprez, January 28, 1999
From: Kathie Bryant, December 4, 1998