Once referred to as a “living fossil” by Darwin due to it apparently unchanging nature, a new analysis of the lingulid brachiopod genome has revealed that the organisms have been rapidly evolving and possess considerable diversity in their chemical structures.
Writing in the latest edition of the journal Nature Communications, scientists from the Okinawa Institute of Science and Technology Graduate University (OIST), Nagoya University, and the University of Tokyo report that they have successfully decoded the first brachiopod genome, from Lingula anatina collected from the Amami Islands in the Pacific Ocean.
They found more than 34,000 genes comprising the L. anatina genome, and discovered that unlike their fellow “living fossils” the coelacanths, these creatures have apparently undergone morphological changes, despite the fact that their appearance has not changed much over the years. The authors also found “significant” changes in its genomic structure.
Similarities to mollusks, vertebrates investigated
Lingulid brachiopods, marine invertebrates with external shells and a stalk, bear an external resemblance to mollusks, but have shells on the top and bottom of their bodies instead of on the sides, the researchers explained. They earned the nickname “living fossils” because they have changed little in terms of physical appearance over the past 400 million years.
The evolutionary history of brachiopods and how they relate to other species remains unclear, but the phylogenetic analysis of the Lingula genome indicates that they are closely related to mollusks and are distant cousins of segmented worms. Additional research will be required to determine their relationship to other lophotrochozoans, however, the authors noted.
“At the molecular level, brachiopods are very similar to mollusks,” said first author Yi-Jyun Luo. “Both are protostomes – their embryos form mouths first and anuses thereafter. However, brachiopod embryonic development is very different from that of mollusks: it resembles that of deuterostomes, in which embryos form anuses first and mouths second.”
“The results of the Lingula genome project will help future research of these differences and the roles that specific genes play in development of various brachiopod body structures,” added Luo. The study also revealed that vertebrates and Lingula, both of which use calcium phosphate and collagen fibers for biomineralization, evolved different mechanisms for doing so independently.
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Image credit: Wikimedia Commons
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