After being frozen for years many metres down in the permafrost, the
Siberian salamander can thaw out, get up and run off. Local legend has it
that some may have been frozen alongside mammoths in the Pleistocene age
– and still come to life when thawed out.
Much as scientists would love to have a specimen of DNA from an organism
that lived so long ago, the legends are unlikely to be true. Although frozen
salamanders have been found in layers of ice 14 metres down, which were
deposited in the Pleistocene age more than 12 000 years ago, they probably
fell to this depth much later, through deep cracks in the permafrost.
The Siberian salamander, Hynobias keyserlingii, also known as the Siberian
newt, is nevertheless remarkable. Daniil Berman and colleagues from the
Institute of Biological Problems of the North in Magadan, Siberia, who went
to the upper Kolyma River to study it, found that it can survive in temperatures
as low as -50 degreeC.
The salamander grows up to 13 centimetres long, with females usually
larger than males. It is a superb swimmer and a good traveller. As it moves
forward it makes distinct snake-like undulations of its body and tail.
Berman found that the salamander is perfectly adapted to living in areas
where the lower layers of the soil are permanently frozen into permafrost.
It has no amphibian competitors north of the Arctic Circle, where its range
extends from the eastern borders of Europe through western and eastern Siberia
all the way to the Chukotka peninsula. It overlaps only with the Siberian
frog, Rana sibirica, in the south of its range, where the permafrost becomes
The salamander reproduces in small ponds and puddles which form during
the summer. Spawning females produce two transparent spiral-shaped sacs,
each containing 50 to 60 eggs. These hatch after 17 to 22 days in the northern
part of the range and 23 to 28 days in the south.
After metamorphosis, the young salamanders disperse up to 1 kilometre
from the ponds, while the adults remain close to the water throughout the
summer. Summer lasts only three to four months in most parts of the range.
For the rest of the year, the salamanders remain frozen, hidden in the soil
The researchers found that the young salamanders hibernate in tussocks
and rotten tree roots in the forest, where the temperature does not fall
below about -15 °C. The adults hibernate closer to the ponds in cushions
of moss. Here the temperature can drop to as low as -30 degreeC. Being in
more exposed areas, these animals are also the first to thaw out – and can
therefore establish themselves in the best positions in the pond.
The salamander’s ability to survive when frozen is not unique. Most
frogs can hibernate on the forest floor or in the water underneath the ice,
with up to 65 per cent of their body water in the form of ice. But it seems
to take prolonged, severe cold in exposed conditions to kill the Siberian
salamander. Berman found that in the absence of the insulation provided
by snow and vegetation it required several weeks of temperatures below -50
degreeC before they froze to death. He suspects that the key factor is loss
of water rather than the cold.
Sudden frost is a serious problem for the Siberian salamander. It needs
time to adapt to the cold and produce the ‘antifreeze’ chemicals that replace
water in blood and cells and protect tissues from damage by sharp ice crystals.
Some animals use glucose, glycerol and related compounds to protect them
from freezing in this way. The exact mechanism in the Siberian salamander
is not known.
Berman reports that many young salamanders die in spring, when they
are caught by frost while moving towards the nearest water. By contrast,
adults, which winter near the water, can survive huge swings in spring temperatures
by escaping into a pond.
The Siberian salamander can definitely remain frozen for years. But
the belief that some deeply buried frozen specimens date from the Pleistocene
age awaits proof from radiocarbon dating. The day the lightning broke all records.