rain forest ant-spore neurobiology

Ulf Andrick ura at strix.cluster.sub.org
Thu Sep 9 07:57:57 EST 1993


In <Sep07.035155.71380 at yuma.ACNS.ColoState.EDU> L. Detweiler (ld231782 at LANCE.ColoState.Edu) writes:

: Some time ago I saw a public television documentary on the rain forest. It
: included information about a spore-ant relationship in which a fungal spore
: infects the nervous system of ground-dwelling ants, causing them to go
: `insane' and begin climbing plants, where they die. The fungus then buds,
: grows, and releases new airborn spores from a high position.

What you describe is well known from Dicrocoelium dendriticum. But this
is neither a fungus, nor is it special to rain forests.

D. dendriticum is a trematode (phylum plathelminthes), a `worm' with a
complex life cycle. The adult form is an endoparasite of mammals, mainly
sheep, but also cattle. Their eggs are spread with the faeces of the
hosts. Snails of the species Zebrina and Helicella take them up with
undigested plant parts. In the gut of the snail, miracidia hatch out of
the eggs and infect the hepatopancreas of the snail. They give rise to
sporocysts of first and second order, which produce cercaria. The
cercaria migrate to the lung of the snail from where they are ejected in
a mucous mass. Ants of the gender Formica like to eat that mass. All
cercaria but one wander through the ant, encycsting and giving rise to
metacercaria. The one individual encysts in the subpharyngeal ganglion
in a certain place and causes the ant to climb plants and to anchor at
a tip of the plant with its mandibles where it can easily be eaten 
by a sheep or cow. 

An interesting question is how the cercaria co-ordinate, so that one of
them implants in the subpharyngeal ganglion and how this individual
finds the place where to cause that unusual behaviour of the ant.

So, are you really certain that you speak of a fungus using that very
`technique' for its propagation?

-- 
Ulf Andrick
ura at strix.cluster.sub.org



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