[10] There have also been suggestions that the pouch in northern hemisphere species has been used by males during breeding times for gathering stones to make a nest.

Ammocoetes remain in fresh water for about four years until undergoing a six-month metamorphosis,[12] changing to silver with blue-green stripes.

[9] The central nervous system of the pouched lamprey develops notably during metamorphosis to the large-eyed macropthalmia stage, with particularly large increases in the volume of visual areas of the brain.

[14] The pouched lamprey is widespread in the Southern Hemisphere, occurring in New Zealand, Chile, Argentina, the Falkland Islands, South Georgia and the southwest and southeast corners of Australia.

[7] It has been hypothesised that the apparent decline in lamprey numbers could be caused by the degradation of water quality in lowland waterways.