This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Many spiders reach their maximum size about this time of year, having spent the summer eating, which helps explain their starring role in Halloween decorations. Researchers at the University of California, Davis, have found that one particular trapdoor spider, Aptostichus stephencolberti, which is about the size of a quarter, is big in another way: It has an outsized genome.
Given comedian Stephen Colbert's pompous pundit persona in the former Comedy Central show "The Colbert Report," it seems fitting that a spider named for him would have a genome roughly 50% larger than the human genome. "At 4.6 gigabases, or 4.6 billion DNA base pairs, it's not the largest genome among the spiders, but it's significant," said corresponding author Jason Bond, a professor in the UC Davis Department of Entomology and Nematology. Bond said the spider is the first member of its family to have its genome sequenced.
The study was published in the Journal of Heredity. Along Northern California's coastal dunes, beachgoers often, and unknowingly, come into contact with Colbert's spider namesake, which hides in burrows. While it lacks Colbert's developed sense of irony, the trapdoor spider has a flawless sense of timing.
Females spend their entire lives underground in silk-lined burrows sealed by a hinged, camouflaged door. They wait for vibrations, emerging quickly to catch prey that wander too close. Its venom is not dangerous to humans.
Of the more than 50,000 known spider species, only 30 to 50 have venom known to be toxic to people, Bond said. The spider's genome is also complex, with 52 chromosomes compared to 23 in humans. Much of that size, 77%, comes from repetitive sequences, copied many times throughout the genome, rather than additional genes.
All spiders, including this one, lack telomere repeats—the protection for the ends of chromosomes. This loss may explain the faster rate of chromosome evolution in spiders than we see in vertebrates. "It lends itself to broadening our understanding of spider genome composition and consequently how genomes have evolved across the animal tree of life," Bond said.
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