ant-spore infection

L. Detweiler ld231782 at LANCE.ColoState.Edu
Thu Sep 16 22:17:15 EST 1993


Hello, I posted this originally to bionet.neuroscience, and someone
requested that I post here. I'd appreciate any further information,
particularly in email.



Newsgroups: bionet.neuroscience
From: ld231782 at LANCE.ColoState.Edu (L. Detweiler)
Subject: rain forest ant-spore neurobiology
Date: Tue, 07 Sep 1993 03:51:55 GMT

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.
 
Yes, it sounds like SF but I'm not making this up (to quote Dave Barry).

Does anyone have more information on this? In particular I'm curious as to
the neurobiological underpinnings of the interaction.

tx.

--

ld231782 at longs.LANCE.ColoState.EDU



Newsgroups: bionet.neuroscience
From: ura at strix.cluster.sub.org (Ulf Andrick)
Subject: Re: rain forest ant-spore neurobiology
Organization: Nocturnal Unix System in Kaiserslautern, Germany
Date: Thu, 9 Sep 1993 12:57:57 GMT

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



Newsgroups: bionet.neuroscience
From: ld231782 at parry.lance.colostate.edu (L. Detweiler)
Subject: Re: rain forest ant-spore neurobiology
Date: Fri, 10 Sep 1993 05:03:53 GMT

ura at strix.cluster.sub.org (Ulf Andrick) writes:
: D. dendriticum is a trematode (phylum plathelminthes), a `worm' with a
: complex life cycle. [...]

wow, you're saying this `worm' goes through not one, not two, but *three*
animal species in its cycle of propagation? can it propagate in a subcycle
or are all three elements (sheep/cow to snail to ant) required?

I'm quite positive that what I saw in the series was some kind of fungus
or spore -- they showed a picture of the fungus growing and budding out of
the carcass of the ant on the elevated location on the plant. I recall the 
narrator stating that `ants killed this way are quite commonly encountered'.

what is the approximate count of neurons in the ant? I understand the typical
ant has on the order of a few 100K neurons. It might be possible to argue
that the less complex the nervous system the easier it for some kind of
evolutionary parasite like D. dendriticum to evolve. In `accidentally' 
targeting some subregion a mutation would have fewer areas to `consider'
or `experiment with' so to speak. 

One wonders on the specific interaction with the nervous system. Likely,
it is simple such that the bacteria may mimic a neurotransmitter local
to a particular region, or maybe is toxic to some subset of neurons.
Is it `excitatory' in stimulating existing neurons or `inhibitory' in
`turning them off' or killing them? I'm generally making the assumption
that this mechanism is localized to at least some subregion in the ant.
I would wager that most `global' pathological effects on the nervous
system render it generally completely nonfunctional -- not useful for
the transportation of the worm-parasite.

Looking at D. dendriticum from an evolutionary perspective is rather 
puzzling as well. How could this parasite-worm develop? did it develop
from some other parasite that only involved the *two* animals, from one
that only involved *one*? to imagine that it just burst on the scene 
capabable, by some fantastic accident, of picking pecular `hooks' into
3 species is rather mind-boggling.

I also saw a special on ABC recently called `the hidden world' or something 
like that of an amazing fungus-spore-organism that appears in ordinary 
backyards.  the spores collect at one stage in life and actually migrate
in an oozelike fashion. Then they `bud' or `sprout' upon each other, with
lower ones drying up and hardening for others to advance upon. Then this
eventually `buds' into armlike projections that passing insects (the whole
thing is totally microscopic) brush off on, as I recall.

I wonder if there are any books on `bizarre life forms' -- all of this
is so unusual as to seem alien. They show how many of our categories -- 
`worms, parasites, virus, bacteria, plant, animal' etc. are not so
clear-cut as we would like to imagine. In fact the boundary between
life and non-life is increasingly blurred itself.

--

ld231782 at longs.LANCE.ColoState.EDU



From: ddoherty at sanger.bio.uci.edu (Donald Doherty)
Subject: Re: rain forest ant-spore neurobiology
Newsgroups: bionet.neuroscience
Organization: University of California, Irvine
Date: 10 Sep 93 07:43:13 GMT


   If I recall my invertebrate zoology correctly, multible animal hosts
are common with parasites and other invertebrates.  You are right that
these little animals can be soo amazing that they seem almost alien.
In fact, the first Alien movie did a relatively good job of showing
the life cycle of an overgrown invertebrate that you might find on
earth (even its proboscis)!

   The other thing you describe sounds something like slime mold which
I remember being totally facinated with in botany.  It seems like something
between plant and animal.

   Check out a good zoology textbook.  Hickman et al., "Integrated
Principles of Zoology" was a good one but I'm not sure what is best now.

-------------------------------------------------------------------------------
Donald Doherty
Department of Psychobiology	Email:	    ddoherty at darwin.bio.uci.edu
University of California	CompuServe: 76646,1321
Irvine, CA  92717-4550		FAX:	    (714) 725-2447
U.S.A.				Voice:	    (714) 856-1776



--

ld231782 at longs.LANCE.ColoState.EDU



More information about the Mycology mailing list