Navigation Links
Humidity increases odor perception in terrestrial hermit crabs
Date:7/5/2012

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. Humidity significantly enhanced electrical signals induced in their antennal neurons as well as the corresponding behavioral responses to the odorants. The olfactory sense of vinegar flies, on the other hand, was not influenced by the level of air moisture at all. Exploring the molecular biology of olfaction in land crabs and flies thus allows insights into the evolution of the olfactory sense during the transition from life in water to life on land. (Proc. R. Soc. B, June 2012)

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?

"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.

Voltage and behavior

In a series of experiments, Anna-Sara Krng, who worked on an EU-funded Marie Curie Project, tested 140 odor substances with different chemical properties, such as acids, aldehydes, amines, alcohols, esters, aromatic compounds, and ethers. She measured the excitation in the neurons of the crabs' antennae in response to single substances. The results were so-called "electroantennograms" (EAGs) which measured tiny voltage changes across the cell membranes in the microvolt range.

A striking feature of the subsequently performed bioassays was that the crabs' behavioral responses to odorants were more obvious and much faster at a significantly increased humidity, assumingly due to an enhanced electrical excitability of their antennal neurons. The EAG showed in fact a reaction at the neurons which was three to ten times stronger if active odors were applied at a higher humidity. In contrast, antennal neurons of vinegar flies did not show any differences and responded evenly and independently of the degree of humidity.

Evolution of olfaction

The analysis of the experiments revealed that hermit crabs responded primarily to water-soluble polar odorants, such as acids, aldehydes and amines, because their effect may be easily enhanced in humid air. These results suggest that crabs have so-called ionotropic receptors in their antennal neurons. Such receptors were found in other crustaceans, such as water fleas (Daphnia pulex) or lobsters (Homarus americanus). In the water flea genome, no genetic information was actually found for so-called olfactory receptors, which are responsible for the highly sensitive olfactory system in insects, such as vinegar flies. Although the receptor genes which are present in the hermit crab genome have not been elucidated yet, the scientists assume that olfaction in crabs is mediated by the original, evolutionarily older ionotropic receptors. It is generally believed that the ancestors of many insect species made the transition from the seas to the continents during much earlier geological eras and that insects have adapted their olfactory system to life on land very well. Terrestrial crustaceans, on the other hand, may be able to use their sense of smell on land thanks to a basic molecular "equipment", but their olfaction is still quite underdeveloped in comparison to insects. Therefore hermit crabs usually stay near the coast: not only because of the short way back to the sea where they reproduce, but also because of their limited sense of smell which does not allow them to orient themselves without any problems in the dry air of the heartlands. [JWK/AO]


'/>"/>

Contact: Bill S. Hansson
hansson@ice.mpg.de
49-364-157-1401
Max Planck Institute for Chemical Ecology
Source:Eurekalert  

Related biology news :

1. Got nectar? To hawkmoths, humidity is a cue
2. Ability to estimate quantity increases in first 30 years of life
3. Discovery increases understanding how bacteria spread: U of A study
4. Common genetic mutation increases sodium retention, blood pressure
5. Family history of liver cancer increases risk of developing the disease
6. Study finds soda consumption increases overall stroke risk
7. Misperception of weight is an important barrier to weight loss
8. Perception and preference may have genetic link to obesity
9. New understanding of terrestrial formation has significant and far reaching future implications
10. Study jointly led by UCSB researcher supports theory of extraterrestrial impact
11. Preventing home invasions means fighting side-by-side for coral-dwelling crabs and shrimp
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Humidity increases odor perception in terrestrial  hermit crabs
(Date:6/2/2016)... 2016 The Department of Transport Management ... 44 million US Dollar project, for the , ... Personalization, Enrolment, and IT Infrastructure , to ... and implementation of Identity Management Solutions. Numerous renowned international vendors ... Decatur was selected for the most compliant and ...
(Date:5/24/2016)... patient care by providing unparalleled technology to leaders of the medical imaging industry.  As ... added to the range of products distributed by Ampronix. Photo - ... ... ... ...
(Date:5/9/2016)... 9, 2016 Elevay is currently ... expanding freedom for high net worth professionals seeking travel ... globally connected world, there is still no substitute for ... duplicate sealing your deal with a firm handshake. This ... taking advantage of citizenship via investment programs like those ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... MA (PRWEB) , ... June 23, 2016 , ... ... Peel Plate® YM (Yeast and Mold) microbial test has received AOAC Research Institute ... platform of microbial tests introduced last year,” stated Bob Salter, Vice President of ...
(Date:6/23/2016)... FRANCISCO , June 23, 2016   EpiBiome ... has secured $1 million in debt financing from Silicon ... ramp up automation and to advance its drug development ... its new facility. "SVB has been an ... beyond the services a traditional bank would provide," said ...
(Date:6/23/2016)... , ... June 23, 2016 , ... In a new ... in Denmark detail how a patient who developed lymphedema after being treated for breast ... results could change the paradigm for dealing with this debilitating, frequent side effect of ...
(Date:6/23/2016)... -- Andrew D Zelenetz , ... Published recently in Oncology & ... Andrew D Zelenetz , discusses the fact ... placing an increasing burden on healthcare systems worldwide, ... the patents on many biologics expiring, interest in ...
Breaking Biology Technology: