Amazing Shark Behavior!

Involuntary stomach eversion - frequently performed by Shark researchers.

Remember Juerg's paper about intra-gastric tags?
Here it is again, in full length. You may notice that the retention time of the transmitters varied considerably, from less than 24h to 34 days.

The shortest retention times are likely the result of voluntary gastric eversion.
That is the faculty of many (if not all - does anybody know?) Sharks to eliminate indigestible or unwanted items by voluntary turning their stomach inside out through their mouth. The process is very short and consists in relaxing their stomach muscles and using abdominal pressure to prolapse and speedy retraction of the stomach to empty indigestible particles, parasites, or mucus, researchers speculate. This may also aid them in keeping a healthy alimentary tract. This can be accompanied by head shaking and I must confess, always fatally reminds me of that old condom recycling joke - yes you can Google it!

Where was I?

Oh, yes.
It just so happens that Juerg is da man when it comes to gastric eversion in Sharks.
His 2005 paper is a classic and analyzes the voluntary eversion by a Caribbean Reef in, I believe, Walker's Cay, one of the first Shark destinations to seamlessly integrate adventure and Shark conservation. Juerg was extremely fortunate in being able to record the behavior, and this is what he filmed.

Is this totally amazing, or what!
And before the usual Shark slanderer and defamer starts snickering and pointing at Starfish and the like: dude, not that you would ever understand, but I'm talking cool animals, the pinnacle of evolution - not such lowly, utterly useless and creepy stuff!

Now, Juerg has published a new paper about the gastric eversion by a hooked Longfin Mako, likely in an attempt to rid itself of the hook, and proposes a mechanism by which Sharks can perform this amazing (!) feat. It, too, is based on a video that was recorded in 2004 by Frank Nielsen aka MalibuFrank of Sharkfootage.

Here it is - enjoy!