Why do large dogs tend to live shorter lives than their smaller counterparts? The answer may be written into their epigenome, according to a new study in Science. The findings reveal that larger and male dogs undergo accelerated molecular aging, with pronounced DNA methylation on the X chromosome and at transposable elements. Learn more: scim.ag/3VZtl3f

A species of lungfish found in South America has claimed the title of the animal with the biggest genome sequenced so far. The DNA of Lepidosiren paradoxa comprises a staggering 91 billion chemical letters or “bases,” 30 times as many as the human genome, researchers reported in 2024. However, those 91 billion bases of DNA only contain about the same number of genes that humans have—roughly 20,000—with the rest consisting of noncoding, perhaps even “junk” DNA. By comparing this genome with those of other lungfishes, the researchers determined that L. paradoxa adds the equivalent of a human genome to its DNA every 10 million years. Learn more on #WorldAnimalDay: scim.ag/4o4YCe5