everything you ever wanted to know about sea cucumbers

Species & History

Sea cucumbers (Class: Holothuroidea, Phylum: Echinodermata) are a soft-bodied, invertebrate relative of the starfish and sea urchins.  Numbering some 1100 species worldwide, they are found in both tropical and temperate oceans, where they inhabit the intertidal zone as well as deeper waters.  The first fossil records of sea cucumbers date from about 400 million years ago.

These are tube-shaped animals which come in a variety of colors and range anywhere from less than an inch to over six feet in length.  Some resemble worms and burrow in ocean floor sediments.  Others filter feed using an array of retractable tentacles known as a 'flower' (Figure 1), used to trap organic debris and tiny marine organisms.  One writer aptly described the sea cucumber as, “A dill pickle that is sprouting it’s own dill."

Sea cucumbers propel themselves by means of tubular extensions or tube feet arranged in rows along the length of their bodies.  The feet can be extended or contracted by varying the internal fluid pressure.  Like other echinoderms (spiny-skinned animals), sea cucumbers have a unique type of connective tissue called “catch connective tissue” which can flow like a fluid, then stiffen reversibly under neural control.

Human Food Use

Humans have eaten and traded these animals for centuries.  For example, the Chinese have been harvesting them from the waters of Malaysia and Australia for at least 1000 years.  They are eaten in soups, raw as sushi and as appetizers and delicacies.  The Malaysians refer to sea cucumber as 'trepang'.  The raw or pickled body and internal organs are called 'konowata' by the Japanese and the salted, fire or sun dried body wall is known worldwide as 'beche de mer' literally translated as 'beast of the sea'.  Hong Kong trade in beche de mer reached US $20 million in 1990.

Sophisticated Immune System

Invertebrates such as starfish and sea cucumbers are ancient animals, but nevertheless they possess a sophisticated immune system whose elements closely resemble those of modern vertebrates.  These elements include cellular immunity (defender cells eating invading organisms), a complement-like system (a chain of biochemical events leading to the encapsulation or destruction of foreign objects), cytokines (chemical messengers such as interferon and interleukin which quarterback the immune response) and lectins (protein molecules involved in the recognition of foreign invaders).

In the sea cucumber, cells of the immune system are housed in the Polian vesicles, hollow organelles contained in lymph node-like tissue lining the throat of the animal.  This tissue has been postulated to be the forerunner of the tonsils, adenoids and thymus. 

Why might a creature such as the sea cucumber be useful as a therapeutic food?  At the risk of stating the obvious, since sea cucumbers have survived for over 500 million years... and our immune systems have evolved from theirs, many of the molecules and strategies they have evolved should also work for us.

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Above is provided courtesy of Dr. George Gillson, M.D., PhD.