Saturday, September 21, 2019

Turtle Genome Analysis Gives Insight on Turtle Ancestry and Evolution

Data provided by the Joint International Turtle Genome Consortium (led by researchers from RIKEN in Japan, BGI in China and the Wellcome Trust Sanger Institute in the UK) shows that turtles are not primitive reptiles as previously thought. Instead, the turtles belong to a sister-group consisting of birds and crocodiles. By using next-generation DNA sequencers, the institutions have successfully decoded the genome of the green sea turtle (Chelonia mydas) and the Chinese soft-shell turtle (Pelodiscus sinensis). Based on the genomic information provided from the decoded genomes of the two turtles, researchers predict that turtles diverged from archosaurians almost 250 millions years ago.

Data from the turtle genome has also revealed that turtles follow the basic vertebrate embryonic pattern during development, despite having such a unique shell anatomy. Instead of developing directly into the turtle-specific body shape and shell, the turtle embryo first goes through the basic vertebrates' body plan and then enter a turtle-specific development phase. Researchers have found genes in this late-stage developmental phase related to limb-development, suggesting that the shell of a turtle evolved using the genetic program from limbs to develop a shell during embryonic development. Dr. Naoki Irie, who led the study from the RIKEN Center for Developmental Biology, states that "the work not only provides insight into how turtles evolved, but also gives hints as to how the vertebrate developmental programs can be changed to produce major evolutionary novelties."

This study has additionally revealed that turtles have a high number of olfactory receptor genes. More than 1,000 olfactory receptors were found in the Chinese soft-shell turtle, being one of the largest numbers found in a non-mammalian species. This finding also suggests that turtles have the ability to smell and detect a wide number of hydrophilic substances. Genes involved with taste perception, hunger stimulation, and hormone ghrelin (involved with energy homeostasis regulation) were lost in the turtle genome. Loss of these genes suggest this is why turtles have such low metabolism.

Genome sequencing, once again, has provided a plethora of information on the biology of a species. In this case, decoding the turtle genome has helped reveal the turtle's true ancestry, explain how the embryonic shell develops, and how the loss of genes have affected the way the turtle species tastes and processes food through a low metabolic rate. I believe it is important to look at genes from an evolutionary standpoint and to use that knowledge to explain how genes impact the survival and unique biological changes in a species.


1 comment:

  1. It is amazing how with technology in this day and age we are able to decode the entire genome of a species. Not only is it very interesting to learn about the turtle's true ancestry, but it also helps us to understand the evolution of the turtle's genes and with the help of more scientists and more research, possibly give us an idea of what life could be like in the future.