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DISPLAYING POSTS TAGGED: crustaceans (4)

Orange army on the sea floor

Author
by Kate C
Publish date
23 May 2012
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Every year, thousands of Giant Spider Crabs (Leptomithrax gaimardii) congregate in Port Phillip Bay ahead of their annual winter moult.

When solitary, these crabs are often hard to spot; algae, sponges and sea squirts set up shop on their shells and provide excellent camouflage. However when the crabs aggregate and march, this hungry army is easy to spot. They scavenge whatever food they can find, including the wildlife on the shells of one another. The spectacle of hundreds of large orange crabs against the bare, sandy sea floor is an amazing sight.


It’s still a bit of a mystery what the aggregations are all about but senior curator Dr Julian Finn has some ideas from several years of observation.

Like many crustaceans, Giant Spider Crabs are protected by their hard body shell, rather like a suit of armour. The trouble is that a hard shell doesn’t allow room for growth. Crabs must shed their old skin to get bigger; they can expand their size in the brief window before the new skin hardens. The process of moulting takes up to an hour and all the crabs in an aggregation moult almost simultaneously.

Spider crab emerging Spider crab emerging from its old shell. The new shell is a vivid orange colour.
Image: Julian Finn
Source: Museum Victoria
 

Newly-moulted Giant Spider Crab Newly-moulted Giant Spider Crab in its fresh orange shell.
Image: Julian Finn
Source: Museum Victoria
 

A soft, freshly-moulted crab is irresistible to predators such as rays, seals and birds. By aggregating in the thousands an individual crab reduces its chance of being eaten, much the same way as mammals in herds find protection in numbers. Movement into shallow waters may help the crabs, usually dispersed throughout Port Phillip Bay, aggregate in a single mass and gain refuge from the strong tidal currents that scour the deep channels.

An earlier explanation that the annual aggregations were related to mating has thus far proved unlikely, as following the moulting of tens of thousands of crabs, only the odd couple has been observed to mate. We still don’t know however what happens when they disperse back into deep water. Julian believes this sudden influx of tender crab meat is an important part of the Port Phillip Bay food chain.

Spider crab moults Hundreds of cast-off spider crab moults on the sandy seabed.
Image: Julian Finn
Source: Museum Victoria
 

If you'd like to see some Giant Spider Crabs without the need for SCUBA gear, have a look at the entrance of the Marine Life exhibition at Melbourne Museum.

2012 EOL Rubenstein Fellow

Author
by Kate C
Publish date
19 January 2012
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Comments (1)

Dr Joanne Taylor has had a busy few months; just before Christmas the book that she co-edited was published, and now she has been selected as a 2012 Encyclopedia of Life (EOL) Rubenstein Fellow!

This prestigious fellowship is awarded by the Smithsonian Institution to support scientists to upload information about the species they study into the EOL. As a Rubenstein Fellow, Jo will be adding over 400 species of squat lobsters to this amazing resource about the world's biodiversity.

In 2009, Jo started a postdoctorate project to produce the first comprehensive book about this group of colourful crustaceans. The resulting book, The Biology of Squat Lobsters, was published by CSIRO last year.

Dr Jo Taylor Dr Jo Taylor in late 2011 with her hot-off-the-press preview copy of her book, The Biology of Squat Lobsters.
Source: Museum Victoria
 

Congratulations Jo!

Links:

MV News: New squat lobster species

MV News: Butterflies of the sea

Encyclopedia of Life

The Biology of Squat Lobsters, edited by Gary C B Poore, Shane T Ahyong and Joanne Taylor. CSIRO Publishing, 2011.

New shrimp in Port Phillip Bay

Author
by Kate C
Publish date
8 April 2011
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Comments (1)

MV marine biologist Dr Jo Taylor has reported a tropical stowaway in the warm waters around the Newport Power Station - the Sand Shrimp, Crangon uritai.

Sand Shrimp Sand Shrimp Crangon uritai blends in perfectly with the sandy habitats in which it lives.
Image: John Eichler
Source: Museum Victoria
 

This little crustacean with its cunning camouflage is common in East Asian coastal regions and is not native to Australia. Although other species belonging to the same family (Crangonidae) are common in Australian waters, including Port Phillip Bay, this is the first occurrence of this species anywhere in the Southern Hemisphere.

Reported this week in the online scientific journal, Marine Biodiversity Records, Jo and her co-author Dr Tomoyuki Komai suspect the shrimp was accidentally introduced to Port Phillip Bay. This new sand shrimp probably hitch-hiked in ship ballast while in its tiny larval form. It's only the second confirmed introduction of a shrimp to Australia.

Dorsal and lateral view of the Sand Shrimp. Dorsal and lateral view of the Sand Shrimp.
Image: David Staples
Source: Museum Victoria
 

Three specimens were found in 2008 by members of the Marine Research Group and were identified after comparisons with specimens at the Natural History Museum and Institute in Chiba, Japan. Jo has alerted local biologists and ecologists to keep an eye out for the newcomer so we can track its movement, if any, in local waters.

Links:

Article in Marine Biodiversity Records (abstract only)

Infosheet: Introduced marine organisms in Port Phillip Bay

Sand Shrimp on PaDIL

A crab called Tutankhamen

Author
by Blair
Publish date
31 March 2011
Comments
Comments (6)

I just heard of a crab species with the scientific name Tutankhamen. Crab Tut! Kind of cool considering we are about to open the world-famous Tutankhamun exhibition.

Tutankhamen cristatipes has a spiny triangular body, pointed nose (the rostrum) and elongated claws that look like a plumber’s wrench. It is quite small, with a body 15 mm wide and legs about 30 mm long.

Tutankhamen cristatipes Tutankhamen cristatipes
Source: Rathbun, M.J. (1925) The spider crabs of America. United States National Museum Bulletin, 129, 1-613
 

Tutankhamen cristatipes was named in 1925 by Mary J. Rathbun (1860-1943). In total, she described 1147 new species and subspecies, 63 new genera, one subfamily, three families and a superfamily.

“A few years earlier, King Tut’s tomb was uncovered and I think she could have named it in the Pharaoh-fever that swept the world at that time,” crustacean expert and PhD colleague Anna McCallum tells me.

Mary Jane Rathbun Mary Jane Rathbun at work. She began as an unpaid assistant to her brother, Richard Rathbun, and was later employed as a curator at the Smithsonian Institution.
Source: Smithsonian Institution Archives via Wikimedia Commons.
 

Crab Tut is almost as rare as King Tut too - it is known from only two specimens. Both Tuts had exclusive habitats: the king in the Egyptian deserts and the crab in deep waters on the outer continental slope off Florida. And they both reside in hard outer skeletons: King Tut in his sarcophagus, Crab Tut in its carapace.

I couldn’t find what colour Crab Tut is, but I’d like to dream it’s as colourful as the gold and blue sarcophagus of King Tut. This is definitely one cool character of the crustacean world.

Links:

Mary J. Rathbun on Wikipedia

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