Nature
PUBLISHED
Sap drinking is thirsty work for froghoppers, also known as spittlebugs (Philaenus spumarius). While most insects opt for phloem, a sugary and easy-to-access sap, the ambitious froghopper goes for xylem. This sap poses quite the challenge, being so nutrient-poor as to need to be drunk almost constantly to glean any benefit. The side effect of this sap-chugging lifestyle is urine, a lot of urine. So much urine, in fact, that if it weren’t for a rather impressive bit of engineering the tiny bugs would likely drown in their own wee.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Thankfully, evolution armed the froghopper with a bit of kit that sits like a butt-mounted catapult. The miniature ballistic is able to fling the critters’ urine roughly 10 centimeters (4 inches), said associate professor of comparative physiology Philip G. D. Matthews, of the University of British Columbia, to the New York Times. That might not sound like much, but, when you take into account the froghopper itself is about 5–7 millimeters (0.20–0.28 inches) long, that’s really quite the projectile p!ss.
As if we weren’t already in awe of these tiny insects and their prize-winning polyuria, it seems they have another trick up their (no doubt urine-soaked) sleeves’. New research, published in the journal Proceedings of the Royal Society B and co-authored by Matthews, decided to take a closer at the froghopper’s liquid intake rather than its outtake. Its lack of nutrients isn’t xylem’s only downfall, as it’s much harder to suck out of a stem than phloem. While phloem will gush forth once a stem is pierced, xylem is actually really quite difficult to suck out.
The difference exists because of the pressures that drive the two separate parts of the plant. Xylem sap exists in the vessels of the plant that draw water up from the soil, creating negative pressure. The knock-on effect for our little froghopper is that when they chomp on a stem to suck up that malnourishing goo, the vessels pull inwards. So, how do the tiny addicts get to the good stuff?
To find out, the researchers on the new study looked at scans of the froghoppers’ head morphology and paid particular attention to a structure called the cibarial pump. It’s a muscular structure that can create negative pressure in the mouth of the froghopper by expanding. The same effect is what enables our lungs to drag in air as our lungs expand with the aid of our diaphragm.
Measurements of the cibarial pump revealed that the tiny froghoppers can create a negative pressure within their heads to challenge even the most unyielding of xylem pressures at around 1.6 megapascals. If the significance of that is hard to comprehend, Matthews was, fortunately, able to squash the stats into a metaphor that’s fresh out of There Will Be Blood.
According to his estimations, if froghoppers “were on the top of the Statue of Liberty’s torch, they could have a straw going all the way down to the ground going into a glass of water, and they could be quite happily sucking it up.”
Residents of New York, hold onto your milkshakes.
[H/T: New York Times]
