Drinking From The Giant Tortoise Pericardium

In preparation  for our Voyage of the Samba in the Galapagos Islands I’ve been reading the chapter of Darwin’s Voyage of the Beagle that describes his 31 days in the archipelago.
Darwin felt the reptiles of the Galapagos  gave the “most striking character to the zoology ” of the islands. He spends considerable time in his diary describing the creatures for whom the Spaniards named the islands. the giant tortoises.

Giant Tortoises

A Galapagos giant tortoise  can weight up to 600 pounds and live up to 150 years. A distinct species of tortoise developed on each separate island, adapting to differing environments.
On Charles Island (now Floreana) Darwin encountered the slowly

lumbering (4 miles per day) tortoises when they traveled to the central highlands to fill themselves with water.  Prior to encountering humans the tortoises had  had no natural predators and both the natives and the crews of whaling ships feasted on their easily obtained meat.

“the staple article of animal food is supplied by the tortoises. Their numbers have of course been greatly reduced in this island, but the people yet count on two days’ hunting giving them food for the rest of the week. It is said that formerly single vessels have taken away as many as seven hundred, and that the ship’s company of a frigate some years since brought down in one day two hundred tortoises to the beach.”

Natives savored both tortoise flesh and tortoise oil:

The flesh of this animal is largely employed, both fresh and salted; and a beautifully clear oil is prepared from the fat. When a tortoise is caught, the man makes a slit in the skin near its tail, so as to see inside its body, whether the fat under the dorsal plate is thick. If it is not, the animal is liberated and it is said to recover soon from this strange operation. In order to secure the tortoise, it is not sufficient to turn them”

Darwin also partook of tortoise:

“While staying in this upper region, we lived entirely upon tortoise-meat: the breast-plate roasted (as the Gauchos do carne con cuero), with the flesh on it, is very good; and the young tortoises make excellent soup; but otherwise the meat to my taste is indifferent.”

I’m pretty certain the passengers on the Samba will not be consuming any Giant tortoise meat this August but we will definitely encounter some of the surviving species on special farms and I will be listening for bellowing males:

During the breeding season, when the male and female are together, the male utters a hoarse roar or bellowing, which, it is said, can be heard at the distance of more than a hundred yards. The female never uses her voice, and the male only at these times; so that when the people hear this noise, they know that the two are together”

Perhaps I will be allowed to startle or ride a tortoise in the manner of Darwin:

“The inhabitants believe that these animals are absolutely deaf; certainly they do not overhear a person walking close behind them. I was always amused when overtaking one of these great monsters, as it was quietly pacing along, to see how suddenly, the instant I passed, it would draw in its head and legs, and uttering a deep hiss fall to the ground with a heavy sound, as if struck dead. I frequently got on their backs, and then giving a few raps on the hinder part of their shells, they would rise up and walk away; — but I found it very difficult to keep my balance.

Drinking FromThe Pericardium Of The Giant Tortoise

Finally, as this is a cardiology-oriented site I must take note of the following peculiar Darwinian observation:

“I believe it is well ascertained, that the bladder of the frog acts as a reservoir for the moisture necessary to its existence: such seems to be the case with the tortoise. For some time after a visit to the springs, their urinary bladders are distended with fluid, which is said gradually to decrease in volume, and to become less pure. The inhabitants, when walking in the lower district, and overcome with thirst, often take advantage of this circumstance, and drink the contents of the bladder if full: in one I saw killed, the fluid was quite limpid, and had only a very slightly bitter taste. The inhabitants, however, always first drink the water in the pericardium, which is described as being best.”

When I came across this description I was flabbergasted. Not at the inhabitants drinking tortoise urine (for indeed the tortoise does use his giant bladder as a water reservoir during times of drought) but at the Galapagoans drinking pericardial effusions.

The Pericardium

The pericardium is the sac around the heart. I am very familiar with the pericardium in humans as I look at it on every one of the  many echocardiograms I read.  Normally, it has only a very tiny bit of fluid in it, enough to lubricate the heart as it contracts and relaxes.
Thus, in a normal giant tortoise one would not expect more than an ounce of liquid in the pericardium-hardly worth butchering an ancient kind beast.
In the video below one can see a small to moderate sized pericardial effusion (the black crescent on the left of the heart) which corresponds to about 90 ml or 3 ounces.

I asked Jim Scharff, a cardiothoracic surgeon,who slices open the pericardium of humans on a daily basis what he typically encounters when the sac is opened. The question I texted him was:
“When you open the pericardium of someone without pericardial disease or effusion how much fluid do you typically encounter and what does it taste and look like?”
He responded  “Usually 15-20 mL of serous looking fluid. I have no idea what it tastes like but it does not have any odor.”
Serous means ” typically pale yellow and transparent” and limpid, Darwin’s term, means transparent and clear.
Some diseases cause inflammation of the pericardium (pericarditis) and with this fluid (pericardial effusion) can build up in the pericardial sac. Large pericardial effusions compress the heart, impeding blood from entering it, and can cause shock and death (tamponade).
Pericardial effusions due to inflammation typically are not limpid as they contain blood cells and protein from the inflammation of the pericardium.

Ultrasonic Explorations

If the inhabitants were sometimes encountering significant amounts of tasty, yet limpid fluid in the pericardial sac of the giant tortoises was this normal or did it indicate the turtles had pericardial disease?
I was unable to find any indication that giant tortoises suffer unduly from pericardial disease but I did encounter one study which utilized ultrasound to document a pericardial effusion in an 80 year old spur-thighed tortoise which was suffering from pneumonia.
Consequently, I’m looking into taking a portable ultrasound device to take with me to the Galapagos to examine the hearts of the giant tortoises and answer once and for all the mystery of the giant tortoise pericardial fluid.
Testudinally Yours,
-ACP