Researchers find animals that evolve to have no stomach have same missing genes

Dec 04, 2013 by Bob Yirka report
Platypus skeleton at Melbourne Museum. Credit: Peter Halasz/Wikipedia.

(Phys.org) —A small team of international researchers has found that every type of jawed vertebrate they tested that has over time lost its stomach to evolution, such as chimaeras, numerous teleosts, lungfish and the platypus, also has the same missing genes. In their paper published in the journal Proceedings of the Royal Society B: Biological Sciences, the team describes their investigation into the genes of stomach-less vertebrates and it appears that they all lost the genes necessary for bringing them back should the need arise.

The , as most are aware, is the place food winds up after being eaten. Inside of it, along with food and bacterial biota are pepsins which help break down proteins, along with acids that soften food to make it easier to digest. Both pepsins and acids exist because of characteristics within our genome. Without them, we'd die. But not all vertebrates have stomachs or some other similar organ to serve as a vessel for the dispersal of pepsins and digestive acids. This got the researchers to wondering if the responsible for causing the creation of them might have gone away as well. To find out, they studied 14 species of both with and without stomachs to see what differences they might have. More specifically, they checked to see if there were any differences in their genes.

As it turned, out, there were such differences. Every single one of the stomach-less creatures was missing the genes responsible for the production of pepsins and . This, the researchers note, means that such animals could not re-evolve a stomach should the need arise—they'd have to start from scratch, a much lengthier process.

Other animals, the team notes, have also lost other parts to evolution, but have retained the genes responsible for their creation. Thus, if conditions change, all that's needed is for a marker to be turned back on for those parts to return. In the case of the animals that have lost the genes, the researchers theorize that it might have come about as a way to recover the energy lost in conserving such genes.

Next up for the researchers will be a new study to try to determine if there is a missing link in some animal—one that has devolved a stomach but still has the genes to go back if necessary.

Explore further: Are crocodiles secret fruit-lovers?

More information: Recurrent gene loss correlates with the evolution of stomach phenotypes in gnathostome history, Published 4 December 2013 DOI: 10.1098/rspb.2013.2669

Abstract
The stomach, a hallmark of gnathostome evolution, represents a unique anatomical innovation characterized by the presence of acid- and pepsin-secreting glands. However, the occurrence of these glands in gnathostome species is not universal; in the nineteenth century the French zoologist Cuvier first noted that some teleosts lacked a stomach. Strikingly, Holocephali (chimaeras), dipnoids (lungfish) and monotremes (egg-laying mammals) also lack acid secretion and a gastric cellular phenotype. Here, we test the hypothesis that loss of the gastric phenotype is correlated with the loss of key gastric genes. We investigated species from all the main gnathostome lineages and show the specific contribution of gene loss to the widespread distribution of the agastric condition. We establish that the stomach loss correlates with the persistent and complete absence of the gastric function gene kit—H+/K+-ATPase (Atp4A and Atp4B) and pepsinogens (Pga, Pgc, Cym)—in the analysed species. We also find that in gastric species the pepsinogen gene complement varies significantly (e.g. two to four in teleosts and tens in some mammals) with multiple events of pseudogenization identified in various lineages. We propose that relaxation of purifying selection in pepsinogen genes and possibly proton pump genes in response to dietary changes led to the numerous independent events of stomach loss in gnathostome history. Significantly, the absence of the gastric genes predicts that reinvention of the stomach in agastric lineages would be highly improbable, in line with Dollo's principle.

Related Stories

Are crocodiles secret fruit-lovers?

Nov 12, 2013

Seed dispersal by animals is important for plants to help them occupy new areas of land. Usually bugs, birds, or intrepid kittens do that job. Now we can add crocodiles to that list. A new study reviewed ...

Obese stomachs tell us diets are doomed to fail

Sep 16, 2013

The way the stomach detects and tells our brains how full we are becomes damaged in obese people but does not return to normal once they lose weight, according to new research from the University of Adelaide.

Strange worm reveals the evolution of digestion

Oct 26, 2012

A Swedish–Norwegian research team shows in a new study that the intestines of the peculiar Penis worm develop in the same way as those in humans, fish and starfish. This surprising discovery shows that ...

Experts identify critical genes mutated in stomach cancer

Apr 08, 2012

An international team of scientists, led by researchers from the Duke-NUS Graduate Medical School (Duke-NUS) in Singapore and National Cancer Centre of Singapore, has identified hundreds of novel genes that are mutated in ...

Recommended for you

Male monkey filmed caring for dying mate (w/ Video)

21 hours ago

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Orchid named after UC Riverside researcher

Apr 17, 2014

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

Apr 17, 2014

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

Apr 17, 2014

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 0

More news stories

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Male monkey filmed caring for dying mate (w/ Video)

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Researchers develop new model of cellular movement

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

Impact glass stores biodata for millions of years

(Phys.org) —Bits of plant life encapsulated in molten glass by asteroid and comet impacts millions of years ago give geologists information about climate and life forms on the ancient Earth. Scientists ...