You ever been pinched by a crab? I have. A Dungeness crab. It f***ing hurts. So if you heard that someone died from a crab you might have visions of being pinchered to death, with their claws stripping away your flesh, leaving behind sinew and bone. This might be a bit extreme, and I’ve most likely just given myself a new phobia, but you should know by now that if I mention death by crab, that only means one thing: Poison.

Coconut crab (Birgus latro) by L-Bit (CC 0)

Yes, there are poisonous crabs out there. In this case, the Coconut crab, Birgus latro, the largest land-based arthropod known. So-named because of its ability to pry open a coconut with its massive claws, the Coconut crab makes its home in the South Pacific islands and feeds off of damned near anything: coconuts, fruits, seeds, even carcasses of dead animals. Dirty scavenger. Iron Rats with claws.

On the plus side they appear to be edible, with some considering them a delicacy and even an aphrodisiac. I did say appear to be edible, right?

On the Loyalty Islands of New Caledonia – which is half-way between Fiji and Australia for you geographically impaired folks – the locals consume the Coconut crab, despite the knowledge that it could, at times, be toxic. Throwing caution to the wind, the crabs are sold in markets and consumed, which is understandable if you’re on an island in the middle of the Pacific Ocean. You use whatever is available to you.

On one fateful shopping trip however, two gentlemen, ages 41 and 75, bought Coconut crabs together from the same marketplace, but ate them separately. That same evening the 41 year old was admitted to the Emergency Department complaining of diarrhea, vomiting, and exhaustion. His blood labs showed a marked hyperkalemia (elevated plasma potassium) of 9.4 mmol/L. The patient declined quickly, became asystolic (no cardiac output), and resuscitative efforts commenced. But despite their efforts he expired several hours later. (1)

The next morning, 6 hours later, the 75 year old gentleman arrived at the ED, unaware of his friends death. He, too, was experiencing diarrhea, vomiting, and exhaustion. His potassium levels were rising, and soon went into cardiopulmonary arrest. He was given atropine and resuscitation, but died an hour and a half after admittance.

So what killed these two men? The crabs of course. These scavengers happened to eat “sea mangoes”, the fruit of Cerbera manghas. If Cerbera rings a bell, it’s because I wrote about it last week in the Suicide Tree post. All species of the Cerbera genus contain cardiac glycosides, namely cerberin, that inhibits sodium/potassium-ATPase, leading to hyperkalemia, cardiac arrhythmia, and eventual death. A review of its mechanism of action can be found on the pages of Foxglove, which cures a broken heart, and Oleander, which is still a dick.

Cerberin

Analysis of the crabs revealed the presence of these cardiac glycosides, as did the kernels from the sea mangoes. We know that poisoning can be treated successfully with Digoxin-specific antibody fragments (Digibind), but this expensive treatment was apparently not available on this small island hospital, or not used. This is unfortunate, as the islands are covered with Cerbera manghas, and poisoning is not out of the realm of possibility.

*Update (3/27/15): It appears that the clinicians in the cases above (and authors of reference 1, below), saw the need and were able to obtain Digoxin-specific antibody fragments (Digibind) and use it to successfully treat a patient poisoned by Coconut crab ingestion (2).

Cerbera manghas (sea mangoes) by Sarangib (CC 0)

But the other factor to consider is that you need to do more than just watch what you eat and expose yourself to. Locals know that the leaves, flesh, and kernels of the sea mango are poisonous, but now they have to be aware of what their arthropod meals are eating as well. It’s Nature’s poisonous world, and we’re just living in it.

*** Homepage featured image of Coconut crab by DIBP images (CC BY 2.0) ***

References:
1. Maillaud, C., S. Lefebvre, C. Sebat, Y. Barguil, P. Cabalion, M. Cheze, E. Hnawia, M. Nour, and F. Durand. “Double Lethal Coconut Crab (Birgus Latro L.) Poisoning.” Toxicon 55.1 (2010): 81-86.
2. Maillaud, C., Y. Barguil, M. Mikulski, M. Cheze, C. Pivert, M. Deveaux, and F. Lapostolle. “First Successful Curative Use of Digoxin-specific Fab Antibody Fragments in a Life-threatening Coconut Crab (Birgus Latro L.) Poisoning.” Toxicon 60.6 (2012): 1013-017.