Genes Explain Why Some Animals Have No Stomachs

Ghost sharks, as well as lungfish and platypuses, have lost their stomach through evolution. Scientists have finally revealed the genetic changes that brought about this difference. According to Filipe Castro of the University of Porto in Portugal, The gastric glands arose some 450 million years ago but have dwindled away at least 15 separate times across the animal tree of life. Thus, more than a quarter of known bony fish species digest food without a true acid stomach.

The researchers analyzed the genes of 14 vertebrates with and without stomachs and found out that all those without stomachs lack high-functioning genes for maintaining a highly acidic zone in their digestive tracts. Furthermore, the animals also lack or have low-functioning genes for secreting the peptic enzymes that slice and dice proteins under acidic conditions.

For more details, read their report at Proceedings of the Royal Society B: http://rspb.royalsocietypublishing.org/content/281/1775/20132669.