Cucumber Wranglin’

As the beginning of March rolled around the crew was stocking up and preparing to head back into the open ocean and make the trip to the Falklands.  As they collected their supplies they came across several local people – probably wondering what the “savage” northerners where up to:

“All hands employed in getting in a stock of wood & water. There were three canoes full of Fuegians in this bay, who were very quiet & civil & more amusing than any Monkeys.  Their constant employment was begging for everything they saw; by the eternal word—yammer-scooner.— They understood that guns could kill Guanaco & pointed out in which direction to go. — They had a fair idea of barter & honesty. — I gave one man a large nail (a very valuable present) & without making signs for any return, he picked out two fish & handed them up on the point of his spear. — If any present was designed for one canoe & it fell near another, invariably it was restored to the right owner. — When they yammer-scooner for any article very eagerly; they by a simple artifice point to their young women or little children; as much as to say, “if you will not give it me, surely you will to them”. ” (Mar 1)

Most interesting to the locals was most likely the crazy Englishman who seemed to be completed preoccupied by the marine invertebrates living in the shallow waters along the coast. Throughout the end of February and early March, Darwin’s Zoological Notebook is full of descriptions of marine life – in particular bryozoans, sponges, crustaceans, mollusks and echinoderms.  Today I thought I’d take a brief look at the unusual of world of the sea cucumber (class Holothuroidea).

To get us started here is a brief except from one are Darwin’s descriptions of a sea cucumber from Tierra del Fuego – one that the footnotes in his diary suggest might be Psolus antarcticus or Psolus patagonicus:

“Body oval depressed, strikingly resembling a Nudibranch. Upper surface convex covered with scales, form truncated angular pointing from edges of body to central parts.— outer ones small (but not gradually) increasing towards the centre. Scales covered with punctures.— Lower surface soft concave.— The mouth is situated at ¼ length of body from anterior extremity; circular is completely closed by 5 pointed scales: Tentacula 10. long. ½ length of body: tapering, little branched, tree like (in contradistinction to bush-like).— Resemble that of Holuthuria — They surround the mouth.— The bony collar consists of 10 truncated gothic arches or rather 5 pair.— slightly stony.— When the Tentacula are retracted this collar is nearly in centre of body & lies in an inclined position with respect to the plain [sic] of body.” (Zoological Notebook)

It is the “scales” that Darwin describes in such detail that places this sea sponge in the echinoderm phylum.  Echinoderm means “hedgehog skin” and they have plates (or scales) made of calcium carbonate in their skin. Much like the bony plates found in the Xenthera (see Meet the Xenarthra), these little plates are called ossicles. It is these plates that make the “skin” of a starfish so hard, or that fuse together to form the outer “shell” (more technically “test”) and spines of a sea urchin (other echinoderms).

This Three-Rowed Sea Cucumber (Isostichopus badionotus) (from Wikipedia Commons)

Sea cucumbers are pretty odd critters.  Here are a few interesting tidbits, that always remind me to be amazed about the diversity of live of Earth:

• They can liquefy their body and literally “ooze” through very small openings. This is a way to get into safe crevices to avoid predators. (one in the hole they “firm up” again, which makes it virtually impossible to extract them if they don’t want to leave.
• When startled some species expel some of their internal organs (their respiratory trees, along with toxic fluids) into the surrounding waters. In a crude (and greatly oversimplified) analogy, imagine barfing up your lungs when a predator is about to try to eat you.
• Sea cucumbers can grow these respiratory trees back after expelling them.
• They communicate with one another by releasing hormones into the water.
• In the deeper ocean sea cucumbers can make up a large percentage of the biomass – moving across the ocean floor in great herds while eating up all the detritus they can find.  This raises the question – are there sea cucumber cowboys riding along with them.  Maybe their cousins the starfish :).
• They have no real “brain” as we know it – in fact, when the nerve ring in the head is removed, sea cucumbers keep on doing their thing.  So they are sort of like lobotomized herds of cattle.
• There are over 700 species worldwide.
• And lastly my personal favorite – of all the phylum of animals in the world, the echinoderms appear the be the most closely related to our phylum (the Chordata). My cousin the sea cucumber…

“Endless forms most beautify”, indeed!

Sea cucumber from Patagonia (by Anders Poulsen)

Sea cucumber (on it’s way to be coming a salad) from the Yucatan Times

Like the restless herds of sea cucumbers, the sailors from the other side of the world had to move on, and by the second day of March the Beagle was underway and heading southwest.  Along the way, they encountered more indigenous people, with whom Darwin seemed to be fascinated:

“The Captain determined to make the bold attempt of beating against the Westerly winds & proceeding up the Beagle channel to Ponsonby Sound or Jemmy Buttons country. — The day was beautiful, but a calm.” (Mar 2)

“Came to an anchor in the Northern part of Ponsonby sound. We here enjoyed three very interesting days: the weather has been fine & the views magnificent. The mountains, which we passed today, on the Northern shore of the Channel are about 3000 feet high. — they terminate in very broken & sharp peaks; & many of them rise in one abrupt rise from the waters edge to the above elevation. The lower 14 or 1500 feet is covered with a dense forest. — A mountain, which the Captain has done me the honour to call by my name, has been determined by angular measurement to be the highest in Tierra del Fuego, above 7000 feet & therefore higher than M. Sarmiento.—1 It presented a very grand, appearance; there is such splendour in one of these snow-clad mountains, when illuminated by the rosy light of the sun; & then the outline is so distinct, yet from the distance so light & aerial, that one such view merely varied by the passing clouds affords a feast to the mind. — Till near Ponsonby Sound we saw very few Fuegians; yesterday we met with very many; they were the men Jemmy Button was so much afraid of last year, & said they were enemies to his tribe; the intervening & thinly inhabited space of ground, I suppose, is neutral between the belligerents. — We had at one time 10 or 12 canoes alongside; a rapid barter was established Fish & Crabs being exchanged for bits of cloth & rags. — It was very amusing to see with what unfeigned satisfaction one young & handsome woman with her face painted black, tied with rushes, several bits of gay rags round her head. — Her husband, who enjoyed the very unusual priviledge in this country of possessing two wives, evidently became jealous of all the attention paid to his young wife, & after a consultation with his two naked beauties, was paddled away by them. — As soon as a breeze sprung up, the Fuegians were much puzzled by our tacking; they had no idea that it was to go to windward & in consequence all their attempts to meet the ship were quite fruitless. — It was quite worth being becalmed, to have so good an opportunity of looking & laughing at these curious creatures; I find it makes a great difference being in a ship instead of a boat. — Last year I got to detest the very sound of their voices; so much trouble did it generally bring to us. — But now we are the stronger party, the more Fuegians the merrier & very merry work it is. — Both parties laughing, wondering & gaping at each other: we pitying them for giving us good fish for rags &c; they grasping at the chance of finding people who would exchange such valuable articles for a good supper. ” (Mar 4)

I wonder what the local residents thought of sea cucumber?  The Yaghan people did fish in the cold southern waters – maybe they augmented their meals with a little cucumber… (RJV)