Why the Platypus Will Never Have a Stomach

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Bizarrely, many species of animals, such as the carp and platypus, lost their stomachs in the evolutionary past, and new research suggests they may never evolve the organs back.

The stomach is the part of the gut where the main part of digestion takes place. Glands in this organ secrete enzymes known as pepsins, which break down proteins, and strong acids that soften food and help the enzymes work. The glands first appeared about 450 million years ago, and they represent an evolutionary innovation found exclusively in jawed creatures with backbones.

Surprisingly, the gastric glands that define the stomach are missing in a number of jawed vertebrates. In 1805, the French zoologist Georges Cuvier discovered that many teleosts, or the largest living group of fish, such as the carp family, lack stomachs. The past 200 years of research suggests that up to 27 percent, speaking conservatively, of all teleost species may lack stomachs. Primitive bony fish such as lungfish and some cartilaginous fish such as chimeras lost the organs as well.

Fish are not the only creatures that can lack stomachs. All of the monotremes, or egg-laying mammals such as the platypus and echidna, also lost their stomachs during the course of evolution.

Written By: Charles Q. Choi
continue to source article at livescience.com

6 COMMENTS

  1. I just love all the new bits of information I gain on this site. The problem is trying to work them seamlessly into a conversation over drinks. All I can come up with here is “Hey buddy, a platypus wouldn’t just have barfed on my shoes!”

  2. Rimshot, huh?

    Very interesting pattern of loss, here. I have seen loss of an organ due to mistakes in hox genes (and think of this mode as the paradigm). However, loss of an organ due to loss of an gene for an enzyme that functions within the organ…. very strange — cool, but strange…

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