Posted by: genghisprawn | November 9, 2008

More Freshwater Barnacles

This is a photo submitted by one Peter to Avril Bourquin’s Man and Mollusc web page.  The freshwater snail was purchased complete with living hitchhikers from a pet store in New York (collection site unknown).  Vigorous discussion on the CONCH-L mailing list identified the snail as Vitta usnea (Röding, 1798), a member of the family Neritidae familiar to aquarists and shell-collectors as the olive nerite.

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Posted by: genghisprawn | November 7, 2008

Wonders of Regeneration

(I originally wrote this May 01, 2007):

Several months ago (before I fully appreciated this species’ uncanny ability to master aquarium dividers), I discovered one of my largest Macrobrachium carcinus in the process of consuming a conspecific.  Within the space of what was probably just a few minutes, the victim had lost all of its pereiopods, an antennal spine, much of its rostrum, and the forward fringe of its cephalothorax.

Hoping for the best, I immediately isolated it in a 10-gallon tank.  Even in its grublike state, the shrimp was able to flutter clumsily forward; thankfully, neither gill tissue nor eyes had been scathed.  Though the pearly gray of its wounds acquired black edges of necrotic tissue, the recovering patient remained as voracious as ever, first clutching food placed directly beneath its mandibles and later scooting about with its pleopods to secure sinking pellets.

Within three weeks, limb buds made their appearance.  Shortly afterward, the shrimp underwent its first regenerative molt.

Premolt (note incipient limb regrowth):

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Postmolt:

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Posted by: genghisprawn | October 24, 2008

Siemens High School Science Competition Results!

Earlier today, the results for the Siemens Competition in Math, Science & Technology — “the nation’s most prestigious teen science prize” — were announced.

A record-setting 1893 students entered with a total of 1205 individual and team projects.  Out of this pool, the largest yet by 10%, outstanding entries were selected as semifinalists and regional finalists.  The regional finalists, around 100 in total, will be called to compete at one of six Regional Competitions in November.  From each region, one team and one individual will advance to the national competition in New York, putting them in the running for six scholarship prizes ranging from $10,000 to $100,000.  A live webcast of the National Finalist Award Presentation will be viewable at the Siemens Competition website on December 8, 2008, at 9:30 AM U.S. Eastern Time.

Projects may be in any of the following categories (click to read sample abstracts):

Descriptions of past winners’ projects are viewable at the competition website.  Here’s a video on the 2007-2008 national finalists:

That said, now seems like the right time … to announce … that I’m a regional finalist!

I learned four hours ago that my project in Biology, “Morphological Phylogeography of a Giant American River Prawn, Macrobrachium carcinus (Decapoda: Caridea: Palaemonidae)”, had been selected, and I’m still absolutely elated.  Joining me in the Region 6 competition at Georgia Tech will be my friend and classmate Varun Bansal.

Seven other students attending Thomas Jefferson High School for Science and Technology were semifinalists.  A big congratulations to them and everyone else who entered!

All Semifinalists

All Regional Finalists

Expect to read more about my project and the competition process here on Amphidrome.

Posted by: genghisprawn | October 23, 2008

Self-Cloning Crayfish Invade Madagascar

Bad news for the Great Red Island?

The devil herself.

Marbled crayfish, or Marmorkrebs, are parthenogenic members of Procambarus (Decapoda: Cambaridae), an important genus of North crayfish; I covered the Nilotic shenanigans of P. clarkii, infamous Lousiana expat, here and here.

I say “members” because they have no specific name — asexual, all-female mudbugs first discovered in German fish tanks in the ’90s tend to be iffy as far as taxonomists are concerned.  This reproductive quirk, otherwise unheard of in decapod crustacea, has caught the attention of geneticists and developmental and evolutionary biologists on the lookout for model organisms (see here).

Their recent discovery in Madagascar (Jones et al., 2008) will do little for the blood pressure of the Eighth Continent’s already-beleagured wildlife advocates.  The perfect invader: a parthenogenic crayfish poses a new threat to Madagascar’s freshwater biodiversity, published August 2008 in Biological Invasions, has the score.  In 2005, University of Antananarivo biologists noticed a strange new decapod being sold at markets near the capitol city.  After a tip-off from Japanese researchers who’d pronounced them marmorkrebs in early 2007, a crack team of local and foreign investigators was soon on the ground.  What they found was not pretty.

Read More…

Posted by: genghisprawn | October 7, 2008

Mark Your Calendars: Tokyo 2009

What follows is from an e-mail sent by Dr. Ray Bauer of the University of Louisiana to CRUST-L, the mailing list of the The Crustacean Society, on 28 Sept. 2008.

The symposium “Life History Migrations of Freshwater Shrimps: Ecological and Adaptive Significance” organized by Ray Bauer (University of Louisiana at Lafayette, USA) and Hiroshi Suzuki (Kagoshima University, Japan) will be presented at the Summer Meetings of The Crustacean Society in Tokyo, Japan, Sept. 20-24, 2009 (see meeting and symposium webpages: http://wwwsoc.nii.ac.jp/csj4/TCSFirstPage1.html).

A symposium-related contributed paper session will be held in conjunction with the symposium.  Contributed papers on topics dealing with migrations of freshwater shrimps (amphidromy) or related life history topics will be considered.  If you would like your presentation to be included and listed on the symposium webpage as part of this contributed paper session, please contact either Ray Bauer (rtbauer@louisiana.edu) or Hiroshi Suzuki (suzuki@fish.kagoshima-u.ac.jp).

Here’s what’s in store:

Posted by: genghisprawn | October 5, 2008

Mating Behavior of Macrobrachium crenulatum

To my knowledge, this is the first visual documentation of mating behavior in this species.  Footage taken late June 2008.

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Posted by: genghisprawn | October 1, 2008

Coyaba “Crayfish”

Image from here.

As the display caption says, a “crayfish” (actually a prawn, Macrobrachium carcinus) from the Coyaba River in Ocho Rios (Saint Ann Parish, northern Jamaica).  The photographer refers to the creature as extinct, which certainly is not true in Jamaica as a whole, and — I would hope — not in the Coyaba either.

Posted by: genghisprawn | September 20, 2008

Death by Poison in Jamaica’s Rio Grande

From the New York Times (“In Remote Valley, a Grim Redefinition of ‘Fishing’,” by Marc Lacey, February 15, 2008):

Map of the Rio Grande region (The New York Times)

Map of the Rio Grande region (The New York Times)

RIO GRANDE VALLEY, Jamaica — Catching freshwater shrimp in the legendary Rio Grande here in the forested hills of eastern Jamaica used to be done at night with a homemade bamboo torch in one hand and a sharp spear in the other.

Wave the flame low over the water and the shrimp eyes glow. Aim the spear with a steady hand and throw. It is painstaking work. The results, though, are worth the effort — succulent shrimp, known locally as janga, that can be the size of lobsters.

Elders recall going down to the river just before dinnertime and plucking out as many shrimp as were needed that evening. The creatures were thrown in a pot with coconut milk, tomatoes and plenty of spice. The smell alone would bring the children to the table.

But those days are fading. Shrimp are getting harder to find on the Rio Grande, and those who live by its banks now eat more chicken and goat. When they do eat the shrimp, they must inspect them carefully inside and out for signs of poison.

. . .

Any toxin will do. Some favor the pesticide used to keep insects off the coffee plants. Others use the potent solution used to rid cows of ticks. When subjected to the poison, the shrimp — large and small — float right to the top. So do the fish. Catching them is as easy as scooping them up before the river washes them and the poison away.

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Posted by: genghisprawn | September 18, 2008

A Continent Without Crayfish

FIG 77.--MAP OF THE WORLD, showing the geographical distribution of the Crayfishes. 1. Eur-asiatic Crayfishes; II. Amurland Crayfishes; III. Japanese Crayfishes; IV. Western North American Crayfishes; V. Eastern North American Crayfishes; VI. Brazilian Crayfishes; VII. Chilian Crayfishes; VIII. Novozelanian Crayfishes; IX. Fijian Crayfishes; X. Tasmanian Crayfishes; XI. Australian Crayfishes; XII. Mascarene Crayfishes.
FIG 77.–MAP OF THE WORLD, showing the geographical distribution of the Crayfishes. 1. Eur-asiatic Crayfishes; II. Amurland Crayfishes; III. Japanese Crayfishes; IV. Western North American Crayfishes; V. Eastern North American Crayfishes; VI. Brazilian Crayfishes; VII. Chilian Crayfishes; VIII. Novozelanian Crayfishes; IX. Fijian Crayfishes; X. Tasmanian Crayfishes; XI. Australian Crayfishes; XII. Mascarene Crayfishes. (Huxley, 1879)

It’s the gaps that fascinate me the most.

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Posted by: genghisprawn | August 28, 2008

Feeding Macrobrachium crenulatum

This video depicts one of my male Macrobrachium crenulatum, a Palaemonid prawn from a high-elevation stream in northeastern Puerto Rico, as it feeds on blackworms (Lumbriculus variegatus).

Note the asymmetry and strong bristles of the second pair of chelipeds — traits which are less pronounced in females and immature specimens. Coloration is fairly similar to that exhibited by this specimen from Panama, but other males may exhibit red in place of yellow.

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