Date: Mon, 22 May 2000 09:40:59 -0300 From: Vitor Fernandes Oliveira de Miranda <vmiranda@rc.unesp.br> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg1610$foo@default> Subject: re: bladder mimics?
Richard wrote:
> Hi Howard and Vitor,
> A visual mimicry between the traps of aquatic Utricularia and a
> particular crustacean. Why not!?
> Meyer and Strickler found that the antennae and bristles of an
> aquatic species (U. vulgaris) enhanced the attraction and capture
> of prey (Chydorid Cladocera). In experiments I found that benthic
> crustaceans (harpacticoid copepods) were attracted to traps of a
> terrestrial Utric (U. uliginosa) due to a particular chemical rather
> than sight (they are blind).
> However, many of the pelagic microcrustacea (eg. Daphnia,
> Chydorids and Calanoid copepods) certainly do visualise their
> environment, so a form of visual mimicry is not out of the question.
> But anyway Meyer and Strickler's work did support Darwins
> "funnel" hypothesis were the longish antennae and mouth bristles
> of U. vulgaris form a funnel to the trap door for chydorids. For other
> prey organisms there may be a visual or even oldfactory mimicry.
> Any other thoughts out there?
> Best,
> Richard
Dear Richard,
Very interesting your comments. Well commented by you, I guess both
ideas are not exclusives. I mean, funnel hypothesis or even visual
mimicy idea could be feasible. Therefore I think there is no much
evidences to believe in visual mimicy. Before regarding this idea, I
think we should have another evidences that could corroborate it. A good
way could be the relation of some utrics species with always the same
crustaceans species. If some crustaceans were captured by the same
utrics species so we could regard the feasibility of these animals had
be attracted for the traps. So another evidences would be important to
verify if wich kind of aftraction is happening: a visual or olfatory
one.
There is no much agreements about these questions. Meyers and
Strickler could noticed that organisms capture was decreased when
antennas were removed from the traps. But, on the other hand, Hegner
(20's) could notice antennas seem to disturb the traps; instead of they
lead preys into the mouth, these ones run away after touch them.
Particularly I still believe in the idea that these structures enhace
the capture.
Wallace and Koste (70's, 80's), researching on utrics as well, could
mention prevalence of some rotifers on some utrics species, even some
species around the mouth. Wallace regarded smell attraction. I think
could be a good explanation, mainly if we consider that some utrics
species have the moth of traps covered around by glands.
Therefore, even after all ideas, I prefer to believe in smell
attraction. I have noticed another organisms related with some species
of utrics. For instance, larvas of a aquatic Coleoptera (_Hydrocanthus_
sp.) always were related with _U. cucullata_. We have to agree that
there is no possibility of a visual attraction... As these larvas
crawled into the traps (they can not swim), I guess they reached the
mouth when looking for food. Who knows a smell attraction...
Well, while another evidences do not reach us, let's speculate...
(preferably with good arguments...)
Regards,
Vitor
Unesp, Rio Claro-SP
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