NATURE COLUMN: Bill Cawley
IT WAS an interesting walk to Rudyard the other week. It gave me the opportunity to explore the canalised section that leads from the lake back to the road which I had never explored.
It was a fine sunny day and I noticed a number of possible subjects to write future Nature Notes. The dyke beside the canal furnished two critters the subject of this week’s essay - Daphnia and Water Boatmen.
Daphnia or water fleas were present moving randomly and at speed on the surface of the water. It was fascinating to watch them zooming off at different angles.
Like the woodlouse which I wrote about several weeks ago are crustacean and are not fleas at all.
Water fleas are translucent and are useful for the study of stimulants on organisms.
They are prone to alcohol intoxication, and make excellent subjects for studying the effects of the chemical on the nervous system due to the transparent bodies and the visible heart rate.
They are tolerant of being observed under a microscope and appear to suffer no harm when returned to the pond.
This experiment can also be performed using caffeine, nicotine or adrenaline, each producing an increase in the heart rate.
One aspect of the water flea may be of interest to players of brass instruments. The following article appeared in the Belfast Newsletter in April 1910: “Daphnia is particularly sensitive to certain notes on the treble trombone. When imprisoned in a microscope live box it preserves a stolid indifference to most musical sounds.
“It is only when the B Flat above the Middle C of the trombone in full blast that it expresses displeasure by flexing its first pair of antennae under its body.”
Why anyone would conduct such an experiment in the first place is open to speculation.
However the musicality of another creature I saw in profusion that day has been the subject of interesting scientific debate.
The water boatman was very prominent. There are almost forty different species on Britain’s ponds and waterways.
It has long hind legs, covered in hairs that it uses rather like paddles to swim.
Its middle is slightly shorter, but its front legs are shorter and used to scoop food from the bottom of ponds- they are vegetarian.
It is the loudest animal on Earth relative to its body size.
Scientists have recorded the aquatic animal “singing” at up to 99.2 decibels, the equivalent of listening to a loud orchestra play while sitting in the front row.
Researchers say the song is a courtship display performed to attract a mate.