Olfaction
in land crabs is still in an early transitional stage between life in water and
on land.
(July 9, 2012) Max Planck
scientists have found out that the olfactory system in hermit crabs is still
underdeveloped in comparison to that of vinegar flies. While flies have a very
sensitive sense of smell and are able to identify various odor molecules in the
air, crabs recognize only a few odors, such as the smell of organic acids,
amines, aldehydes, or seawater.
"The land hermit
crab Coenobita clypeatus is an ideal study object to answer this
question," says Bill Hansson, director of the Department of Evolutionary
Neuroethology at the Max Planck Institute for Chemical Ecology in Jena,
Germany. The animals live in humid regions close to the sea and regularly visit
water sources. Females release the larvae into the sea, where they grow into
young crabs. These young crabs look for empty snail shells and live on land.
They eat fruits and plants. This way of life suggests that the olfactory sense
in crabs is still at an early stage of development.
Crabs and flies
Crabs and flies are arthropods.
Like many other life forms, they made a transition from water to land life in
ancient times. The ancestors of the family of terrestrial hermit crabs
(Coenobitidae) probably took this step about 20 million years ago. Today,
hermit crabs live their entire lives on land, except for the larval stage. Odor
signals are important cues for the crabs’ search for food. In order to detect
odor molecules outside the water on land, the sensory organs of arthropods had
to adapt to the new, terrestrial environment. How did sensory perception evolve
during the transition from sea to land?