Page 68 - BBC Wildlife Volume 36 #12
P. 68
OLMS
Research has shown The water create some Below right:
found inside
concretions
fascinating
that, in extreme cases, caves can be formations. keep on
teaming with
In this case,
growing only
life, albeit on a a deposit of thanks to
olms can survive for a minute scale. copper oxide precipitation –
Below left: appears as a here, forming
decade without feeding. on cave walls, collection of into the shape
concretions blue 'teeth'! of coral.
Skin pigmentation isn’t the only
thing the olm lacks. Its eyes are severely
undeveloped and, in fact, after a few months
of development during its larval stage, its
eyes begin to atrophy (wither away). It does
retain a small amount of photosensitivity, but
why bother growing eyes at all if they aren’t
going to be used for subterranean hunting?
Instead, priority is given to its other senses.
The olm has enhanced mechanosensory
and chemosensory abilities. “Hearing is
essentially mechanosensory – picking up
vibrations or sounds caused by the motion
of prey,” says Professor Geoff Boxshall, a Caves are low-energy systems, with no The olm develops relatively slowly and
zoologist at the Natural History Museum light and thus no plants nor photosynthesis. scientists don’t actually know how long it
in London. “Similarly, for chemosensory Cave food-webs are reliant on nutrients lives. One captive olm was recorded as being
abilities – it would be important for a flowing into the cave from outside. The at least 58 years old, but there are
scavenger locating decaying bodies, as unreliability of such systems means that some estimates that olms could live to be
there would be a good source of chemicals patience is the key for a cave’s residents. 100 – there's still much to be discovered
diffusing out of them, and the scavenger The olm is an ambush predator, lurking about this elusive species.
could home in on that.” silently and completely still, waiting for some
However, the olm also has an extra unknowing creature to enter its bioelectric Abundance of life
sense – the remarkable ability to sense the field. During times of plenty, the olm is Postojna Cave, and the surrounding cave
bioelectric field of other organisms. “All able to consume considerable amounts of system, is famous for the unusual number
animals produce a weak bioelectric field prey and lay down reserves in its liver, to of species adapted to live in this ecosystem.
from nerve impulses, muscle contractions, tide it over when food is scarce. Research Alongside the olm, there are over 100 other
and so on,” continues Boxshall. “The olm is has shown that, in extreme cases, olms can troglobites in Postojna, including spiders,
able to sense when its own bioelectric field is survive for a decade without feeding. If food pseudoscorpions and shrimp. In fact, the
disturbed by an interaction with the field of is scarce, an olm will reduce its activity and first ever troglobite described by science –
an approaching creature, such as a shrimp, lower its metabolic rate. In severe cases, it the slenderneck beetle or blind cave beetle,
and can then catch its prey.” can even reabsorb its own tissue for nutrients. Leptodirus hochenwartii – was from Postojna.
68 BBC Wildlife December 2018
