FLOUNDERS CHANGE COLOUR

Press, Volume LXXIV, Issue 22371, 7 April 1938, Page 10

FLOUNDERS CHANGE COLOUR

Experiment in Matching Surroundings

Remarkable changes of colour in flounders according to their surroundings were described by Mr David Graham, formerly of the Marine Fisheries Investigation Station at Portobello, Dunedin, in an address to the Canterbury branch of the Royal Society of New Zealand last evening.

In an experiment, said Mr Graham, he took 21 flounders, whose normal colour was greenish grey, ranging in size from four to seven inches, and distributed them among seven boxes with sea water running through. The floor of one box was clean grey sand, the floors of the others comprising brownish weed, claycoloured gravel, broken cockle shells showing blue and White, a black tarred surface, a white enamel dish, and patterned linoleum.

The fish placed in the clean sand changed to suit their surroundings in three seconds. Those in brownish weed took 10 minutes to change to a mottled brown, and in another 10-minutes were quite brown. Those in clay coloured gravel took eight minutes to change, those in the cockle shells five minutes, and those in the tarred box 20 minutes before they became black. Those in the enamel bowl changed to a sickly white in a few seconds.

“The fish on the linoleum took days to change, but eventually they did, and it was most interesting to see one half of a flounder with a triangular pattern near the head and the rest of it with a square of another colour,” said Mr Graham. “During the experiments I used a blind flounder, and in no instance did it ever change from a dull greyish green.”