A distant cousin of jellyfish may survive without working mitochondria
In the pinkish muscle of some Pacific salmon lives a distant cousin of jellyfish that thrives without working mitochondria, the energy-producing part of cells thought to be a cornerstone of animal life, a study suggests. About 2 billion years ago, the ancestor of all eukaryotes — the large group of organisms with complex cells that includes everything from maple trees to manatees — engulfed a bacterium, striking up a mutually beneficial relationship (SN: 2/14/20). Eventually, this bacterium evolved into mitochondria, the cellular machine that converts food and oxygen into energy, a process called aerobic respiration. Mitochondria retain many of the instructions for aerobic respiration in their own genome, separate from an organism’s DNA housed in a cell’s nucleus. While a few single-celled eukaryotes have adapted to low-oxygen environments by ditching their mitochondrial genomes, rendering their mitochondria useless, scientists had assumed that more complex animals couldn’t get by without them. But a parasitic cnidarian can, researchers report February 24 in PNAS. This cnidarian — a group...