Ecological studies - procedures and methodologies

Authorship details
Rudman, W.B., 2000 (April 1) Ecological studies - procedures and methodologies. [In] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

Re: Freeze-branding slugs

February 11, 2004
From: Jessica Marsh

Dear Bill,
Thanks for your comments. I will be working off the coast of Maine. Dendronotus frondosus is very common in this area, and is one of the few nudibranchs seen in my particular area of study. I don't think I'll have any problems with identification, but thank you for the heads up, I'll keep you posted with my findings.
Thanks again,
Jay Marsh

Marsh, J., 2004 (Feb 11) Re: Freeze-branding slugs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Jay,
As you'll see from the other messages concerning Dendronotus on the Forum, it is probably worth keeping an eye out for 'consistent anomalies'. There still seems to be enough uncertainty surrounding just how many species there are in the Atlantic, for you to cover your options. You don't want to discover at the end of a long ecological study that you had two or more cryptic species mixed up in your sampling. I guess if you start to find consistent colour or morphological differences and can match them to a food choice or a different egg mass then you would have a trigger to consider looking at the anatomy, or getting someone else to. You may be quite correct in thinking you have only one species, but it is always worth keeping alert to the possibility you may have more than one species.

See Dendronotus frondosus and Dendronotus cf. frondosus Atlantic - Nth America Pages and the attached messages.
Good Luck
Bill Rudman

Rudman, W.B., 2004 (Feb 11). Comment on Re: Freeze-branding slugs by Jessica Marsh. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Freeze-branding slugs

February 5, 2004
From: Jay Marsh

Dear Bill,
I am doing a senior thesis on Dendronotus frondosus in a fouling community. I'm currently looking into tatto ink, and I've heard of freeze branding, but I don't know what it is. Any suggestions on marking and tracking these guys?

Marsh, J., 2004 (Feb 5) Freeze-branding slugs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Jay,
I have given a reference to tattoo marking in an earlier message and I mentioned there that I remember reading of someone marking slugs by using a freeze drying technique. From memory it destroyed the melanin producing cells and left a colourless mark. Unfortunately I can't find a reference but hopefully someone will let us know.

You don't say where you are doing your studies or what youn plan to study. Am I right in suspecting you will be working on the east coast of Nth America? If you have a look at the other messages on this page you will see there is still some confusion identifying Dendronotus in that part of the world, so it would be worth keeping a record, preferably with photos, of the colour forms or variation in colour you find in your population. You would also need to consider comparing the anatomy of animals with different colour forms to see if you are dealing with one or more species. Please let us know how things go
Best wishes
Bill Rudman

Rudman, W.B., 2004 (Feb 5). Comment on Freeze-branding slugs by Jay Marsh. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Behaviour of Triopha catalinae

January 22, 2002
From: Ryan Murphy

Dear Bill,
This is Ryan again, a year or so after my first message. I ended up writing a paper on shade preference in five species of subtidal dorids, but not Triopha catalinae .

My report is at:

I studied Archidoris montereyensis, Anisodoris nobilis, Diaulula sandiegenesis , Cadlina luteomarginata and Acanthodoris hudsoni.
Thanks again for your help.

Murphy, R., 2002 (Jan 22) Behaviour of Triopha catalinae. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Ryan,
Thanks for getting back to me. It's always nice to get some feedback. I hope your exams went well. I've had a look at your report and it certainly raises some interesting questions on whether these animals prefer shade. I guess the other point it raises is just how difficult it is to design experiments to study specific aspects of an animal's behaviour. As you have found, and thoughtfully considered, it is very difficult to isolate one particular item in an animal's behavioural repertoire and at the same time isolate one of the multiplicity of environmental factors which may have some effect on that behaviour.

Good Luck with your future studies.
Bill Rudman

Rudman, W.B., 2002 (Jan 22). Comment on Behaviour of Triopha catalinae by Ryan Murphy. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

When does a nudi become an adult?

January 19, 2002
From: Andrea Bradley

Dear Bill,
I don't know how answerable this question is, but how big does a nudibranch (specifically chromodorids & phyllidiids)have to be to be considered an adult? I have a lot of size data from a survey I did with Operation Wallacea but am unsure what to do with it.
Andie Bradley

Bradley, A., 2002 (Jan 19) When does a nudi become an adult?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Andrea,
The first thing an ecologist will say to you is that it is vital to plan how you are going to collect your data before you start your investigation. It is also important to have at least a general idea on whether there is any point in collecting the data in the first place. In general collecting work it is valuable to record size, colour, depth, and information on food (or probable food), egg masses etc. All this helps in the longterm to build some basic background knowledge about the species.

If you are interested in lifecycles, growth rates or other specific ecological information then it is very necesary to plan out how you are going to study this and what are the most appropriate methods to employ. I am afraid the size at which an animal will reach sexual maturity differs with different species. We also know that in some species that have been studied, nutrition plays an important role in growth, and so an animal can reach sexual maturity at quite different sizes depending on whether it is well fed or not. In other examples, temperature can affect growth rates, so again size of sexual maturity can also differ.

Another complicating factor is that in some species the male reproductive system matures weeks or months before the female system, so you have the phenomenon of very small animals (functional males) mating with much larger animals.

Data on size, such as yours, may give us some maximum size information, and may possibly give us some clues to life histories, if it is collected for long enough, but basically it needs to be treated with considerable caution.
Best wishes,
Bill Rudman

Rudman, W.B, 2002 (Jan 19). Comment on When does a nudi become an adult? by Andrea Bradley. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

About the ecology of nudibranchs

April 2, 2000
From: Phanor Montoya

dear Bill,
I would like to know if nudibranchs have a diel pattern, like migrations to deeper waters at night or any similar behavior. Also, is there a way to do a mark/recapture study with them?

Phanor Montoya


Montoya, P., 2000 (Apr 2) About the ecology of nudibranchs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Phanor,
If you use the SEARCH button and search for diurnal you will get some information on some sea hares and a chromodorid. I am sure many tropical nudibranchs hide during the day, emerging only at night, apparently as a predator avoidance measure. In act phylldiids, with very distasteful mantle scretions, are often the only commonly seen nudibranchs on show during the day in the tropics.

Perhaps someone can suggest some references. The only one I can suggest on diurnal rhythms is:
•Johnson, S. (1989): Temporal patterns of nudibranch mollusk activity on a subtidal Hawaiian reef. The Veliger 32(1): 1-7.

Mark & recapture studies usually means tagging. Tagging Sea Slugs is quite difficult as they can quite quickly move the tag to the edge of their parapodia or mantle edge and discard the tag. There is a paper on using tattoo ink, which I list below, and I am sure I have read of someone successfully freeze-branding slugs.
•Kiest,K (1990): Tattoo ink as a tag for nudibranchs. The Veliger 33(4, 1 October), 416.

If anyone has references on either topic I would be grateful for them. Apart from helping Phanor, it would be good to set up reference pages for both topics.

Bill Rudman.

Rudman, W.B., 2000 (Apr 2). Comment on About the ecology of nudibranchs by Phanor Montoya. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from