Imma Perfetto
Cosmos science journalist
Spiders don’t need a tight-laced corset to achieve their shapely hourglass figures, according to a new PLOS Biology study they’ve got it covered with a single gene.
US researchers discovered the gene, which they have named “waist-less”, in the Texas brown tarantula (Aphonopelma hentzi).
Waist-less (wsls) is responsible for forming the narrow boundary that separates a spider’s body into 2 segments – the cephalothorax in the front, where the eyes, legs, and mouthparts attach, and the abdomen in the back.
By studying the spiders through different stages of embryonic development, the researchers discovered 12 genes expressed at different levels in embryonic cells on either side of the waist.
They silenced each of these genes in embryos of the common house spider (Parasteatoda tepidariorum) to understand their functions during development. But only waist-less was required for the for the development of the spider waist.
The gene is a member of the Iroquois complex of homeobox genes, which has previously been studied in insects and vertebrates (animals with a spine).
Homeobox genes are known as “master control genes” because they can produce a protein (transcription factor) that goes on to regulate the expression of many other genes. Iroquois genes participate in many developmental processes.
“Our available data suggest that waist-less acts as a gap gene at the boundary of the 2 spider [segments],” the authors write in the paper.
Gap genes produce sharp boundaries, like the segments of a larva, during embryonic development.
The researchers say the discovery of waist-less fills a long-standing gap in spider developmental genetics.
The boundary between the front and rear body sections is a defining characteristic of chelicerates — the group that includes spiders, scorpions, mites, and horseshoe crabs – but further research is needed to understand it’s role in other chelicerates.
