MadSci Network: Zoology

Re: Can Snails Learn From Their Mistakes?

Date: Wed May 3 12:10:03 2006
Posted By: dave armstrong, Faculty, Biology, Cricklade college
Area of science: Zoology
ID: 1144686180.Zo

Dear Melanie,
     The African Land Snail (Achatina fulica, or one of its many cousins 
found throughout tropical forest areas) is probably your snail as it is one of 
the most invasive, and introduced, snails. As well as being a splendid pet, 
it is also excellent to eat or as a spreader of several diseases and zoonoses  
(animal-to-human pathogen). Like many land snails it is prone to fall because 
of the shell's weight.
    All Pulmonate (lunged) Gastropods have habituation responses in which they
fail to react to regular stimuli. The shelled species retract into their 
shells and either drop or use suction to hold on. Instead of losing suction, 
your friends could be reacting to a change in light or noise background or a 
vibration. Perhaps you should study to see if new recruits to your cage drop
more often than the longest serving members. Most related snails seem to have a
homing system that returns them to their exact shell location that they 
left before feeding. This too would affect whether they climb regularly to the 
warmth and dampness of a lid nd adjust to sleeping there.
    My advice would be to experiment on disorientation with a strange tank or 
area to see if they can settle down in a new environment within a day. If they 
are like garden slugs or limpets, they will find it difficult to travel in
straight lines to a suitable environment area. Disorientation like this can be
the death of many garden pests if they are slung onto a path area. Learning
however, would be hinted at if you return them to their tank and they resume the 
positions in which you would normally expect them to appear. Some snails can
travel 1.5 metres at least before returning to their homes every night. If you
marked their shells with different coloured pens, the results would be obvious
to their owners but the cause of discourteous comment from less conchophile
members of the human community. The only problem with the experiment is that it
doesn't prove learning has raken place. The snails, rather like the pheromonic
ants, could simply be following a chemokinetic route in their slime or even more
simply looking for the most favourable conditions. People have struggled for a
century now to research these common habits, but learning can only be proved
with associative or conditioned learning. This has been done with one or two
species of water snail which remembered the information for four days before
forgetting all about it!

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