Lesser water boatman – Micronecta scholtzi

Lesser waterboatman. Image: Jérôme Sueur

Tiny freshwater bugs create a cacophony in inventive ways…!

This month’s entry into the Cabinet of Freshwater Curiosities is the lesser waterboatman – Micronecta scholtzi – a common freshwater bug that produces a peculiar courtship song by rubbing its penis along its abdomen, a sound which reaches an incredible 99.2 db!  That’s a sound level equivalent to sitting in the front row of an orchestral concert, or standing close to a passing train!


As Dr James Windmill at the University of Strathclyde – a lead researcher on the June 2011 study “So Small, So Loud: Extremely High Sound Pressure Level from a Pygmy Aquatic Insect” published in the open-access journal PLoS – describes:

“Remarkably, even though 99% of sound is lost when transferring from water to air, the song is so loud that a person walking along the bank can actually hear these tiny creatures singing from the bottom of the river.”

The sound, used by tiny (2mm) males to attract mates, is produced by rubbing the penis and the abdomen together, in a process called stridulation. In the lesser waterboatmen the area used for stridulation is only about 50 micrometres across, roughly the width of a human hair.  This stridulation process is similar to that used by grasshoppers and crickets to produce their idiosynchratic chirps and chirrups.

Dr Windmill continues: “If you scale the sound level they produce against their body size, Micronecta scholtzi are without doubt the loudest animals on Earth.”

Animal noise/size comparison. Image:Jérôme Sueur

The loudest human shout ever recorded is 129db by British teaching assistant Jill Drake in 2000.  Sperm whales have been recorded emitting sounds reaching an incredible 236db, a cacophony required to communicate across vast, turbulent oceanic distances.  Decibels are a measure of the intensity or ‘loudness’ of a sound, measured on a logarithmic scale.  This means that for every increase of 10 decibels, there is a 10 fold increase in sound energy.

Micronecta.

For comparison, a normal human conversation is generally measured at around 60db.  Incredibly, at 99.2db, the sound made by the lesser waterboatman is almost 10,000 times more powerful!  Whilst completely different in size, the incredible sounds emitted by both the lesser waterboatman and sperm whale, shows how aquatic animals have evolved to be able to communicate despite the muffling effects of the underwater environment.

This remarkable little bug is a fantastic wee addition to our Cabinet of Freshwater Curiosities, and like previous entries the bladderwort, the caddis larvae and the mayfly shows that incredible creatures live in the most everyday, developed freshwater environments: curiosity close to your home.

Let us know your thoughts on the waterboatman in the ratings and comments boxes below, and we’d welcome any budding “Curators of Curiosity” to get in touch using the box on the right with any amazing animals they’d like to see in the Cabinet in the future.

More links and information:

Strathclyde University Press Release on the story

Sueur et al 2011: The original journal article in PLoS One

Wired article on this incredible insect 

Wired article on the “bioacoustics” of animal sounds

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