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The Gynaephora groenlandica
(the Arctic woolly bear moth)
caterpillar can tolerate
temperatures down
to -70°C.
ZOOLOGY Severe frost is a
challenge to living organisms,
as cold makes enzymes and cell
membranes function more
poorly, whereas ice crystals
might harm cell structure.
Insects are characterised by
low heat production and poor
insulation, so in cold regions
they have developed enzymes
and cell membranes which can
function at low temperatures.
A few insects produce anti-
freeze proteins that reduce the
freezing point of bodily fluids,
whereas some insects from the
Arctic deliberately produce ice
in body cavities outside cells to
protect the cell’s vital parts
from ice that takes up much
more space than water.
But the ice-free environment
inside the cell makes the water
leave the cell, causing it to
shrink. To avoid shrinking
damage, insects have
developed cryoprotectants
that support the cell structure.
A common cryoprotectant is
glycerol, which accumulates in
cells and prevents them from
becoming emptied of liquid.
BEETLES AND
CATERPILLARS
CAN TOLERATE
SEVERE FROST
A
Some moth
caterpillars can spend
the winter in a frozen
state, tolerating body
temperatures down to -70°C.
B
The Alaskan beetle
contains anti-freeze
molecules of sugar
and fatty acids, which help it
tolerate temperatures of -60°C.
C
Gall midge larvae grow
inside goldenrod aster
stems and survive
temperatures of -55°C by means
of special anti-freeze proteins.
How can insects
survive freezing?
Why can insects tolerate extreme cold without frost injury and death?
In 2012, American
scientists showed
that at least seven
genes contribute to
determining breast
size. But twin
studies indicate
that genes can
only explain 56%
of differences
in breast size.
Another important
factor is weight. If
a woman puts on
weight, some of
the extra kilos
will materialise in
the breast tissue,
giving her bigger
breasts. Moreover,
hormones such
as oestrogen play
an important role
in breast size.
At least seven genes contribute to
determining the size of a woman’s
breasts, alongside other factors.
WHAT MAKES
BREASTS LARGE
OR SMALL?
THI
NKS
TOC
K