BANGALORE: Researchers from Indian Institute of Science have found that the egg-laying organs of wasps (ovipositors) have saw-like teeth coated with zinc. They lay eggs inside figs by drilling into the fruit. Insights gained from this study may help build tools that can aid in robot-assisted surgery, and novel mechanisms to bore through hard surfaces.
Boring into various surfaces to lay eggs is part of the female insect’s life. To successfully drill holes, and lay eggs in safe places, the insects have to overcome some key bio-mechanical challenges. Namrata Gundiah, Assistant Professor, Department of Mechanical Engineering, IISc and Lakshminath Kundanati, student, have shed light on how the egg laying organ of parasitoid wasps doubles up as a reliable drilling machine, says a press release from the IISc.
Each Fig, with a fleshy part in the inside called syconium, has its own wasp species, the pollinator wasp, which enters the syconium through a special opening and lays its eggs. The flowers get pollinated by the female wasp walking around inside. There are other wasps, called parasitoid wasps, which don’t pollinate or benefit the fig plant in any way. They sit outside the fig, drill a hole through the outer covering and lay eggs inside. The larvae of parasitoid wasps feed on the pollinator wasp larvae, making the inside of a fig a populated war zone.
A pollinator wasp has to enter the fig through a hole made for it, it has a smooth ovipositor. However, a parasitoid wasp that has to bore a hole through the fig needs to have a strong ovipositor. Through techniques like Scanning Electron Microscopy and Atomic Force Microscopy, researchers have deciphered what the two ovipositors are made of.
In a paper published in the Journal of Experimental Biology, the researchers say the parasitoid wasp is just 2 mm in length, with a 5 mm long ovipositor, which has teeth-like structures, similar to a double-edged saw; coated with zinc at the tips. Though the presence of such metals is suspected to make stronger tips, researchers are yet to find a conclusive evidence for that.
The pollinator wasp (Ceratosolen fusciceps), with much less demanding requirements, has a relatively smooth, spoon-like structure.
“There is a mutualism that exists between the pollinator fig and the wasps that has evolved over millions of years. The parasitoid tries to take advantage of this situation and this has evolved with her trying to access the pollinator larvae so that she may parasite them to ensure the evolutionary success of her offspring,” explained Namrata.
In both the wasps, the ovipositors are bigger in the tip region (‘big’ is comparable to the width of a strand of spider web silk). Similarly, the tip, one that should actually drill the hole, is much stronger than the inner regions of the ovipositor.
Though it is a study of an insect, it is completely relevant to engineering. “We are basically trying to understand material characterisation and mechanics of a biological system. The knowledge we gain here can be applied elsewhere like, for developing tools that aid in novel surgical methods,” says Laksmikanth Kundanati.