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DISPLAYING POSTS TAGGED: sea cucumbers (2)

Ice Ice Baby

Author
by Mel
Publish date
3 May 2012
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Mel helps manage MV's Marine Invertebrates collections. In her spare time she works with honorary associate Mark O’Loughlin and others to develop her specialist knowledge of holothuroids, or sea cucumbers.

Ice was what I saw from my porthole each morning as I’d wake yet again to the realisation... Woohoo! I’m in Antarctica!

What a wonderful realisation it was. For nearly two months this summer my home was the British ice-strengthened research vessel the RSS James Clark Ross, and I loved every minute of my freezing, rolling, ice-crunching scientific voyage. On board at the invitation of the British Antarctic Survey and with the support of Museum Victoria, I was part of the biological research team tasked with collecting marine benthinc invertebrates from the shelf and slopes of the Weddell Sea in Western Antarctica.

View from the top View from the top of the RSS James Clark Ross
Image: Mel Mackenzie
Source: Museum Victoria

My regular work in the museum's Marine Invertebrate Collections held me in good stead to assist the biological team with our daily work of collecting, sorting, identifying, preserving, and DNA-sampling specimens as we brought these bottom-dwelling 'beasties' up in nets and sleds from the ocean floor. Our aim was to assess the biodiversity and evolutionary history of the area, and my particular focus was on sea cucumbers (holothuroids) which I have studied for a number of years now under the mentorship of Museum Victoria honorary associate Mark O'Loughlin.

James Rudd (ship’s doctor) The biology team
Image: Mel Mackenzie
Source: British Antarctic Survey

Relatives of animals such as the sea star, many sea cucumbers actually look more like sausages with tentacles (which explains their name), and have developed a variety of different feeding and reproductive methods to adapt to environments worldwide. They are diverse in Antarctic waters with over 180 species (including many undescribed) recorded south of the Antarctic Convergence, and as such, they make a good group for evolutionary study. Often coming up squashed in trawls they can be tricky to identify, but the key lies in a variety of identifiers from tentacle shape and number, to tube-foot arrangement and the tiny little skeletal remnants known as 'ossicles' which can be viewed in dissolved tissue under a microscope.

Sea cucumbers and bivalves clinging to urchin spines. Sea cucumbers and bivalves clinging to urchin spines.
Image: Mel Mackenzie
Source: Museum Victoria

With my previous experience of Antarctic sea cucumbers limited to pickled museum specimens, I was very excited to finally see these animals in living colour! They were amazingly diverse, from the tiny Psolids which clung to sea-urchin spines, to my favourite football-shaped 'sea-pigs' which the ship crew were delighted to see. We even got some footage (from cameras lashed to one of our collecting sleds) of different species feeding and moving about on the sea floor.

Along with sea cucumbers we saw many other amazing critters, from nets crawling with sea spiders to beautiful glass sponges filled with brittle stars and deep-sea fish with 'lights' attached to their heads... and that was just from below the water! On top we saw breaching Minke whales, majestic Emperors and curious (and chatty) chin-strap penguins against the always gorgeous background of floating icebergs. Stopping in the sub-Antarctic British Base at Signey to help close up for winter, we even had the chance to see (while firmly holding our noses) the huge elephant seals which roll their way around the camp.

Emperor penguin (left), Elephant seals Emperor penguin (left), Elephant seals at the UK’s Signy base
Image: Mel Mackenzie
Source: Museum Victoria

Links:

Skeletons of sea cucumbers, MV Blog post, April 2011

Skeletons of sea cucumbers

Author
by Blair
Publish date
28 April 2011
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I learned this week that sea cucumbers slink along the sea floor with a hidden skeleton. Known to most of us as those sloppy, sausage-like things that sometimes wash-up on our beaches, sea cucumbers are pretty much a tube of muscle with a mouth at one end and an anus at the other. Underwater, they bury in sand or camouflage themselves against rocky reefs.

sea cucumber A colourful sea cucumber (or holothuroid).
Image: Julian Finn
Source: Museum Victoria
 

Rather than running through the middle of the body, the skeleton effectively surrounds the body to reinforce the muscular body tube. It is made up of tiny structures called ossicles, which can be fifty times smaller than a millimetre. They are like miniature fish scales, but more intricate in design and not usually visible. Some of the structures make some animals sticky to touch.

Here’s an example of the ossicles of an Antarctic species:

Sea cucumber ossicles Ossicles from Sigmodota contorta, a species misidentified under about ten different names. Wheel and hook forms on the left from the body wall, and branched rods on the right from the tentacles.
Source: O’Loughlin and VandenSpiegel (2010) Memoirs of Museum Victoria 67: 61–95.
 

These weird and spectacular structures vary in form. Not only do they prevent the body from turning into a mush of intestine and muscle, but they are also a microscopic key to identify many species – so don’t be too disappointed if you can’t identify a sea cucumber when diving or looking in a rock pool!

Oh and if you're interested...

Sea cucumbers belong to a group of animals called holothuroids, part of the wider group of echinoderms – more commonly known for its sea stars and sea urchins. MV Honorary Associate Mark O’Loughlin is a world expert in identifying sea cucumbers. He has shown me a few tricks of the trade on his way to describing over 20 new species in recent years from Victoria and its neighbouring oceans. He is currently sorting out whether the common local species, Paracaudina australis, is actually multiple undescribed species. His work was recently published in the Memoirs of Museum Victoria.

Links:

O’Loughlin, P. Mark and Didier VandenSpiegel. A revision of Antarctic and some Indo-Pacific apodid sea cucumbers (Echinodermata: Holothuroidea: Apodida) Memoirs of Museum Victoria 67: 61-95 (2010)

Question of the Week: Aboriginal-Indonesian trade in sea cucumber

Reef Education Network: Sea cucumbers

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