Evolution’s Playground A small sea creature is shedding light on the genetic changes that drive evolution.
L
et’s take a trip two hundred kilometres up the coast from Barcelona, skipping the beaches and amusement parks of the Costa Brave and heading over the French border to the small seaside town of Banyuls-sur-Mer. It’s here, in the shallows of the Mediterranean, that we find our scientific
subjects.
Real amphioxus, or lancelets. Credit: Vincent Moncorgé
Dig into the sand and you’ll pull out a handful of small, pointed animals known as lancelets (also called amphioxus, from the Greek for ‘sharp at both ends’), which look similar to the slender, tasty anchovies that live around here too. But although it might share the same appearance as these bony little fish, amphioxus is a simpler type of organism. Vertebrates like fish, birds and mammals have a bony spine that protects the long nerve cord running along their back. While they share the same basic body plan and have a central nerve (protected by a thick tube known as a notochord), amphioxus lacks this protective backbone, making it a sophisticated chordate rather than simple vertebrate. In fact, it is one of the closest living relative of back-boned animals, and thought to be the closest thing we have today to an ancient vertebrate ancestor. Amphioxus’ unusual characteristics and close relationship to more complex vertebrates have fascinated evolutionary biologists for more than 150 years, placing these unusual sea creatures at a pivotal point in the tree of life. Amphioxus has now come firmly into the 21st century, thanks to a major study published in the journal Nature by CNRS researcher Héctor Escriva, José Luis Gómez-Skarmeta from the Centro Andaluz de Bio-logía del Desarrollo, and CRG group leader Manuel Irimia. They’ve been combining huge datasets from nearly 100 different samples of amphioxus tissues– including nine separate body parts and 16 developmental stages ranging from egg to adult – to create the most detailed molecular blueprint of the species to date, mapping out exactly how genes are switched on and off to create its needle-like body.
Executive Summary 2018 - 7