April 2, 2013

In the first of our series, “Dear Dr. Blue,” Dr. Sylvia Earle answers a simple query from a reader, “What is this?” ~ Ed.

You squished a poor defenseless sea cucumber — a holothurian, member of a class of echinoderms that also includes starfish, sand dollars, brittle stars and sea urchins.  Like other echinoderms, these animals have 5 part radial symmetry and a water vascular system that powers tiny tube feet that cover the skin and make it possible for them to creep along whatever they are sitting on (yes a creepy critter!)

In cross section the five part arrangement is evident, and in their five frilly feeding arms that extend from the front end.  Like an earthworm, most sea cucumbers lumber along, artfully picking up yummy bacteria and algae rich sand, digesting the good bits and extruding the scrubbed material out the other end. Unfortunately for some species, dried sea cucumbers are considered a culinary delicacy in Asian markets, valued owing to the chewy, rubbery quality of the five muscle-bands that run the length of their elongated bodies and their resemblance to you know what that allegedly imparts mighty sexual powers to those who consume them (just as eating lion hearts is thought to make a man lion-hearted).

Sea Cucumber

Eyed sea cucumber in eel grass at Manado in Sulawesi, Indonesia. (Matthew Oldfield)

Fishermen in the Galapagos have stripped a particularly desirable species from readily-accessible areas and in recent years have been so keen on obtaining those that live deeper that they have relentlessly — and recklessly — used scuba.  Bad news for the animals, and for the divers who have suffered so many fatalities and injuries from diving too deep and staying too long that a decompression chamber and full time medical staff has been established on the main island, Santa Cruz.

The orange mass along the side of the sand-covered black body in the first photo  is probably the brachial tree — a many-branched gill-like internal organ that can be expelled when a sea cucumber is disturbed (as in stepped on.)  Some sea cucumbers can distract a predator by spitting out some of  their branchial tree, and over time, if left alone, grow a new one.

So, there is hope for the survival of the mystery beast if the tide came in fast enough to re-immerse it in salt water, and if being stomped on did not permanently discombobulate the other internal organs.  Cukes are tough, resilient little guys so I am optimistic that being smooshed was inconvenient but not fatal.*

Google them!  Some sea cucumbers are transparent, bioluminescent, and swim midwater, never touching bottom; others carpet vast areas of the ocean floor thousands of feet down, serving as a kind of oceanic clean-up crew on the sea floor.

They are among the most numerous multi-cellular animals on earth, and also among the most under-appreciated.

* Later confirmed!

Photo: (c) Mark Crosby Photography.

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