Sloths, along with armadillos and anteaters, are part of the genus Xenarthra, the only clade of placental mammals originating from South America. Recent research has sequenced and analyzed the chromosomal-level genome of Linnaeus’s three-toed sloth (Choloepus didactylus) and the Southern anteater (Tamandua tetradactyla). This study identified unique genetic elements linked to energy production in sloths, shedding light on how these remarkable creatures evolved the slowest metabolism of any mammal.
Linnaeus’s three-toed sloth (Choloepus didactylus) at London Zoo. Image credit: Dick Culbert / CC BY 2.0.
Xenarthrans have existed for over 65 million years, with ancestors that included gigantic sloths. Today, modern sloths are tree-dwelling creatures classified into two groups: three-toed and two-toed sloths.
These fascinating mammals primarily inhabit trees, camouflaging themselves by remaining motionless. When they move among branches to forage for leaves and fruits, their actions are characteristically slow.
Sloths boast the lowest metabolism of all mammals, often producing less than half the energy expected for their body size.
To conserve energy, sloths can switch between self-regulating their body temperature and allowing it to fluctuate with their environment.
Despite their slow nature, sloths are proficient swimmers, capable of covering considerable distances underwater in search of mates.
In a groundbreaking study, Wellcome Sanger Institute researcher Marcela Uliano Silva and her team utilized genomics to delve deeper into the unique ecology of sloths.
Dr. Uliano Silva noted, “Billions of experiments in evolution exist. By examining exotic species like sloths, we often uncover biological solutions that humans have not evolved.”
She continued, “Our genomic research revealed a ‘jump gene’ that sloths have preserved for millions of years.”
Researchers found that these sloth-specific genes are associated with mitochondria and metabolic pathways, suggesting their involvement in the sloths’ remarkably slow metabolism.
The study sequenced and analyzed the genomes of Linnaeus’s three-toed sloth and Southern anteater, uncovering several active transposable elements known as “transposons” or “jumping genes.” These DNA sequences can relocate within the genome by copying and pasting themselves.
Mapping the evolution of sloths revealed that these “jump genes” originated from the last common ancestor of all existing sloth species about 30 million years ago, being conserved and integrated into sloth-specific gene sequences.
Researchers discovered that many of these genes are linked to mitochondria, the cell’s powerhouses responsible for energy production, and metabolic pathways.
Given sloths’ unique metabolic characteristics, these specific genes are believed to play a crucial role in their adaptation to the environment and the evolution of their slow metabolism.
“Despite having the slowest metabolism, sloths remain healthy,” states Dr. Camila Mazzoni from the Leibniz Zoo and Wildlife Institute. “Understanding their cellular adaptations could provide insights into efficient energy management.”
Dr. Pedro Galante from Sirio Libanes Hospital remarked, “This research may help us understand energy production issues related to several human diseases, including diabetes and neurodegenerative disorders.”
Ultimately, studying sloth cell lines could offer a natural model for understanding how organisms cope with low-energy conditions, benefiting research in medicine, aging, and even long-duration space travel.
This pioneering study is published in the journal BMC Biology.
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M. Uliano Silva et al. Increased retrocopy load and sloth-specific expansions reveal mammalian genome evolution. BMC Biol published online on May 19, 2026. doi: 10.1186/s12915-026-02632-5
Source: www.sci.news
