Subject: ant-spore infection

From: [email-masked] (L. Detweiler)
Date: Fri, 17 Sep 1993 03:17:15 GMT

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: [email-masked] (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.

--

[email-masked]

Newsgroups: bionet.neuroscience
From: [email-masked] (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 <[email-masked]> L. Detweiler ([email-masked]) 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
[email-masked]

Newsgroups: bionet.neuroscience
From: [email-masked] (L. Detweiler)
Subject: Re: rain forest ant-spore neurobiology
Date: Fri, 10 Sep 1993 05:03:53 GMT

[email-masked] (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.

--

[email-masked]

From: [email-masked] (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:	    [email-masked]
University of California	CompuServe: 76646,1321
Irvine, CA  92717-4550		FAX:	    (714) 725-2447
U.S.A.				Voice:	    (714) 856-1776

--

[email-masked]

---

From: Kathie Hodge <[email-masked]>
Date: 18 Sep 1993 16:38:51 GMT

>grows, and releases new airborn spores from a high position.

Bizarre but true.  What you describe is typical of some insect pathogens
in the weird fungal order Entomophthorales (Zygomycota).  Insects doomed
by the fungus often climb up to high, exposed places and lock themselves
on by using their mouthparts in a deathgrip.  The fungus often further
secures them by sending out specialized hyphae that bind the unfortunate
bug to the substrate.  After they die, the fungus produces spores that
are forcibly discharged and thus escape into the air.

Although these fungi aren't too commonly found, you may be able to find
some RIGHT NOW if you go look on your windows for dead flies.  Look for a
dead fly hanging head downwards by its legs and proboscis, probably with
its wings held out to the sides, and surrounded by a delicate white halo
of discharged spores.  If you look closely, you'll see that the fly's
abdomen is swollen and between the segments you may be able to see white
masses of the fungus protruding.  This is most likely to be
_Entomophthora muscae_.

Although this climbing behavior is very typical of the Entomophthorales,
it can also be found in other fungi, such as species of _Cordyceps_ (a
very distantly related genus in the Ascomycota).  In fact, this may be
what your TV show was talking about, as the Entomophthorales are less
common in the tropics.  We know that these fungi do invade the brains of
their hosts, but we don't understand the mechanism by which they induce
this unusual behavior of climbing and locking on.  I wish we did. 
Perhaps someone out there in netland would find this an interesting
project!

My thanks to Ulf Andrick for his fascinating description of the biology
of Dicrocoelium dendriticum.

Kathie Hodge
[email-masked]