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Amateur question

Marc R. Labeau labeamr3 at WFU.EDU
Mon Mar 13 11:02:02 EST 1995


On 11 Mar 1995 Paul Lewis wrote:

> John Janovy wondered why the same phenomenon  (pigmentation and=20
> motilityleading to either increased conspicuousness or mimicry of a
> food item)had not evolved independently in other trematode groups. =20
> In fact, it has.  One example I=D5m familiar withis enlarged (up to 15=20
> mm long) and conspicuously pigmented cercariae of the genus=20
> Proterometra (family Azygiidae).  These emerge from freshwater=20
> Goniobasis snails, and alternately swim to the surface, then settle to=20
> the bottom, mimicking a mosquito wriggler.  Young centrarchid fishes=20
> gobble =D4em up.

Just adding to Paul's information on the Azygiidae.  Cercariae of the other=
=20
genera in the family(Leuceruthrus, Azgyia, Otodistomum) and those=20
belonging to the Bivesiculidae are also actively preyed upon by their
respective definitive hosts.  The cercariae of Proterometra=20
sagittaria, the largest member of the genus, actually range up to 22 mm=20
in length.  It is also interesting that the different species and perhaps=
=20
strains of Proterometra cercariae display various swimming behaviors
that may selectively attract their hosts.  These behaviors
include crawling/wriggling on the bottom by P. edneyi cercariae, a
parasite of darters and sculpin, "coiling side to side" by P. sagittaria=20
cercariae, and variations on the strong swimming behavior described by
Paul in P. macrostoma and P. albacauda to attract different centrarchid=20
species.=20

Marc LaBeau
Wake Forest University



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