Sea Cucumber secretions

June 18, 1998
From: Bruce Livett PhD

Dear Bill,
Following up the question by Andrea Stephenson about defence mechanisms, I would be interested in information (or sources) about the chemical nature of the defence secretions of sea slugs. When I was snorkelling with a Quicksilver marine biology "discovery trip" out from Port Douglas on the Great Barrier Reef some years back I was handed a large black sea slug (with white spots I think) by the marine biologist taking the trip and she handed it to me in such a way that I stimulated the secretory glands. The result was that my hands were covered with a thick gelatinous gooey solution which was quite warm. She then asked me to give the sea cucumber back to her and to hold my hands out of the water with my fingers closed tight to one another. In what seemed a very short period maybe 20 seconds) the gelatinous secretion covering my hands became very warm and within a couple of minutes had solidified into a hard white (somewhat elastic) glue which she had to use a pair of scissors to cut between my digits to allow me to move my fingers again. For days I was peeling off this white hardened substance from the hairs on my hands. What is the nature of this secretion? Does anyone know?

Bruce Livett PhD
University of Melbourne, 3052,
Victoria, Australia

Livett, B. PhD, 1998 (Jun 18) Sea Cucumber secretions. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Bruce, unfortunately "sea slug" is a very ambiguous common name. Although to a malacologist a "slug" must be a mollusc, to many people "slug" is a generic term for anything soft and squishy and which exudes sticky or mucous secretions. Your "sea slug" is in fact a Holothurian or Sea Cucumber which are a class of Echinoderms related to Starfish and Sea Urchins. Many large tropical holothurians are collected and dried for food and known as Beche-de-mer or Trepang. Sea Cucumbers are an interesting parallel to opisthobranchs, both groups having lost the protection of the hard shell or exoskeleton found in their closest relatives. In both cases they have had to evolve other means to protect them from predation, and in both holothurians and opisthobranchs distasteful and sticky secretions are one of these means of protection. Unfortunately I don't know anything about the chemical nature of holothurian secretions. Probably the most comprehensive chemical review of opisthobranch secretions is Avila, 1995 which is listed under Sea Hares - attack & defence ... Bill Rudman.

Rudman, W.B., 1998 (Jun 18). Comment on Sea Cucumber secretions by Bruce Livett PhD. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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