Slug anesthesia

January 22, 2002
From: Kathleen Archer

Hi Everyone,
I am looking for a way to measure size and weight of my sea slugs over time. I have read in old papers about using "menthol crystals" to anesthetize slugs. This appears to cause them to relax so reasonably accurate length and width measurements are possible. Has any one tried menthol crystals? Can anyone suggest other methods that will not harm the animals?
Thanks for your help,
Kathleen Archer

Archer, K., 2002 (Jan 22) Slug anesthesia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Kathleen,
There is some information on the Forum about anaesthetising slugs and I have had animals recover from treatment with both menthol and magnesium salts but I am afraid it doesn't work every time and there is a very fine line between sleep and death. As long as you can live with a degree of inaccuracy measuring their live crawling length is quite simple. I usually use a pair of old forceps or dividers to make quick 'head to tail' measurements as the animals are crawling along in a dish. Other people have the animals crawling in a glass dish hich is sitting on a page of graph paper so again you can measure the slugs as they are crawling along. Today with digital cameras I guess you could standardise a method so you could record your measurements at leisure. Obviously you wouldn't need to anaesthetise them to weight them.

My advice would be to avoid anesthetising them if possible as you don't know what effect doing this a number of times would have on the animal's physiology, and it would seem to be an unnecesary complication if you are trying to study the algal component as well. Plants may not like the increased magnesium levels or the menthol.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Jan 22). Comment on Slug anesthesia by Kathleen Archer. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

  1. Preservation of colour
    From: Hakan Kabasakal, January 30, 2002
  2. Re: Slug anesthesia
    From: Brian Penney, January 30, 2002

Show factsheet and all related messages