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Re: NFC: Planaria (behavior v. predation)
We should be careful here! The sudden appearance of planaria after removing fish indicates that planarian behavior, rather than predation per se, is responsible for the apparent absence of these flatworms when fish are present.
Predation is probably minimal and not enough to seriously check planaria populations. However, the presence of fish probably elicits cryptic behaviors in the planaria. That is, they are probably still there but when fish scent is present conduct their activity in interstitial spaces (i.e. between/under gravel) and perhaps resort to mostly nocturnal behaviors. Thus they would not be visible in tanks with fish. Remove the fish--Voila--suddenly they appear in a timeframe too brief to represent population growth.
Just a thought,
>>> Ipchay61 at aol_com 02/14/02 07:39AM >>>
I had set up a tank for some Elassoma okatie. The tank had previously had Fundulus lineolatus in it. The day after I took the topminnows out, I noticed a large number of planaria. I went ahead and put the pygmies in and in two days I didn't see anymore and still haven't to this day (about 2 months).