I wouldn't be so sure about fish not recognising conductivity. It is well known that many fish produce electricity (eels eetc.) but not so well known that many more use it to navigate. All fish have electricity production cells along their lateral lines. Just because land animals don't use it doesn't mean that nobody does. Colin ------------------------------------------------------------------------- This is the apistogramma mailing list, apisto@listbox.com. For instructions on how to subscribe or unsubscribe or get help, email apisto-request@listbox.com. Search http://altavista.digital.com for "Apistogramma Mailing List Archives"!