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about 8 years ago
Manta Ray hot lunch Marianas Variety (Press Release) — The Manta Ray Band will be having a hot lunch this Saturday, Feb. 6, 2016, to raise funds for their trip to the Tumon Bay Music Festival on Guam next month. The lunches are $5 each and include fried chicken, lumpia (fried spring roll ...
about 8 years ago
gulfnews.com Whale shark sightings along UAE coast not alarming: experts gulfnews.com Dr. Elsayed Ahmad Mohammed, Regional Director, Middle East and North Africa, of International Fund for Animal Welfare (IFAW), told Gulf News that the recent appearances of the fish make sense given the whale shark feeds close to the surface and often ... and more »
about 8 years ago
KHON2 Whale shark surprises tour group off Haleiwa KHON2 A group led by North Shore Shark Adventures was visited by a whale shark Friday morning, the intimate experience captured on video. They were about three miles off Haleiwa when the shark slowly emerged. “It swam right up to the boat, really slow ... and more »
about 8 years ago
Thanh Nien Daily Carcass of beached whale shark to be preserved by Vietnamese scientists Thanh Nien Daily The Nha Trang Oceanography Institute in central Vietnam has decided to preserve the carcass of a whale shark that died after it got caught in a fishing net last week. Fishermen and local authorities on Thursday handed over the dead fish to the institute. Giant whale shark to be embalmed for scientific researchVietNamNet Bridge all 2 news articles ...
about 8 years ago
National Geographic Manta Rays Get Crittercams for First Time Ever National Geographic We didn't think suction cups would work because manta ray skin is really rough like sand paper. We knew suction cups worked well on the smooth skin of whales. The cups were originally designed to move pieces of glass. But we gave it a try, and with a ... Scripps Grad Student Receives Prestigious Environmental FellowshipScripps Oceanography News all 4 news articles » ...
about 8 years ago
Video From a Whale Shark's Point of View National Geographic Their goal was to deploy Crittercams on whale sharks to get a glimpse of the sharks' underwater world and to better understand their behavior along the reef. Like most people, Wilhelm had never seen a whale shark. He worked on the Crittercams for about ... and more »
about 8 years ago
Zap2It Dominic Monaghan on meeting the Whale Shark: 'I had this sort of out of body experience' Zap2It “Wild Things With Dominic Monaghan” returned to Travel Channel with its third season on Wednesday (Jan. 27). The premiere, aptly titled, “Majestic Mozambique,” finds our host on the hunt for the elusive — and quite massive — Whale Shark. Early on in ... Monaghan knows where the 'Wild Things' areVirgin Islands Daily News all 9 news articles ...
about 8 years ago
CBC.ca Brian Keating swims alongside La Paz's mysterious whale sharks CBC.ca They're such huge animals," said Keating, who saw his first whale shark less than 15 minutes out of the bay. By the day's end, Keating had met at least a dozen whale sharks. He even managed to snap a few underwater photos from their tail end as proof.
about 8 years ago
FIS Fishing ban for giant manta ray FIS The Ministry of Production (Produce) has banned the capture of the giant manta ray (Manta birostris) in the Peruvian marine waters, in order to preserve this species on the coast of the country. The measure, established by a ministerial decree, is in ... and more »
about 8 years ago
The National Whale shark seen swimming in Abu Dhabi marina The National ABU DHABI // A whale shark between three and four metres long has been seen swimming in the marina at the InterContinental Abu Dhabi. Employees at the hotel first noticed the fish at 1.45pm on Friday and quickly took a video and photos to capture the ...
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Tuesday
Jun082010

Simple questions with complex answers: why is a cooked lobster red?

ResearchBlogging.orgSome really simple questions have surprisingly complex answers.  “Why is the sky blue?” ends up being all about differential absorbance of varying wavelengths of electromagnetic radiat… see, there, I’ve already wandered off into jargon land.

And so it is with the question “Why is a cooked lobster red, when a live lobster is not?”.  An odd question, but its exactly that kind of “I wonder why…” moment that has led to some of the greatest discoveries.  Anyway, you can argue that it is not a trivial question; indeed, the name of an entire restaurant franchise depends on the correct color change occurring when you drop a Homarus americanus into a pot of boiling Old Bay.  So what’s going on?

Well, its all about the astaxanthin, (lets call it AXT from now on).  AXT is a carotenoid, which means it’s a fat-soluble pigment that – generally speaking - is red or orange in colour.  Carotenoids give tomatoes their red (lycopene), egg yolks their yellow (lutein), carrots their orange (beta carotene), salmon their pink (canthaxanthin) and televangelists their freakish alien fake tans (but they do offset the glowing white dental veneers ever so nicely, don’t they?).  Lobsters don’t make AXT, they get it from eating their veggies like a good little lobster, because ultimately it’s a plant pigment (plants use it as a sunscreen – but that’s another post for another day!).  In its basic form, AXT is really vivid orange, almost vermilion.  But in lobster shells it doesn’t occur in its basic form; instead it’s mostly bound to a protein, called crustacyanin, which we’ll call CR for short.  AXT binds to CR in much the same way as oxygen binds to the haemoglobin in our blood, except for one big difference.  Unlike oxygen, which fits neatly in a haemoglobin molecule, AXT has to bend to fit into the CR molecule, like one of those freakshow contortionists who fold themselves up in a box.  In bending the AXT molecule to make it fit, the natural colour of astaxanthin changes – it shifts – from red to blue or blue-green.  Historically, this shift has been an interesting mystery to chemists and physicists interested in properties of pigments, because its unusual for the same pigment molecule to have both red and blue forms, as most avid flower gardeners can tell you.  On the right is a picture of the rare all-blue form of the American lobster (read more at the University of Maine website)

Enter Michele Cianci and colleagues from the University of Manchester in England.  These clever folks showed in 2002 that the colour change – technically called the bathochromic shift – is a result of the structure of the CR molecule and the way it flexes the AXT molecule like a loaded spring.  This is where the simple question yields the really complex answer.  Get a load of this phrase from their abstract:  “Recently, the innovative use of softer x-rays and xenon derivatization yielded the three dimensional structure of the A1 apoprotein subunit of CR, confirming it as a member of the lipocalin superfamily. That work provided the molecular replacement search model for a crystal form of the beta-CR holo complex, that is an A1 with A3 subunit assembly including two bound AXT molecules. We have thereby determined the structure of the A3 molecule de novo”.  Ex-squeeze me baking powder?

Yes, well, that's all well and good, but it doesn’t answer the simple question of why they go red when you cook them, does it?  Bear with me…  When next you are at the grocery store, take a look in the live lobster tank and you’ll see that they don't look like the handsome all-blue fellow above; they tend to be a mosaic of colours like orange, yellow, cream, green, blue and brown.  This patchwork arises from varying amounts of free and bound AXT in different layers of the shell, and some other factors like how thick the shell is, and whether the AXT is at the surface or in a deeper layer.  If you go ahead and buy one of these lobsters and drop it into a pot of boiling water, little happens to the AXT because it’s heat stable.  But the protein CR, on the other hand, is not.  Like most proteins, it loses its structure when you apply intense heat, unfolding like a jack-in-the-box, and flinging off the AXT in the process.  Liberated from its oppressive bathochromic bonds, the AXT reverts to its normal colour – intense orange-red.  Et puis, vous voila! – blue/green lobsters turn red when you cook them.

Much the same process happens in shrimp and crabs when you cook them too, but it was worked out for lobsters first because they only have one carotenoid – AXT – whereas other crustaceans had other carotenoids that complicated the picture even further.

PS - some genetic rarities give us all sorts of lobster colour patterns like the all-blue one shown above, but my favourite is the half-and-half.  The first time I saw one of these, I thought it was someone having a joke at my expense, but they're the real deal!  How it happens is still a mystery, but there's probably something wrong with the way they express CR on one side of the body.  Picture from National Geographic.

Tip of the Mackintosh hat to @AboutMarineLife on Twitter, for inspiration.

Cianci M, Rizkallah PJ, Olczak A, Raftery J, Chayen NE, Zagalsky PF, &; Helliwell JR (2002). The molecular basis of the coloration mechanism in lobster shell: beta-crustacyanin at 3.2-A resolution. Proceedings of the National Academy of Sciences of the United States of America, 99 (15), 9795-800 PMID: 12119396