RE: RE: NANFA-L-- chemical defenses -- madtoms and others

Christopher Gutmann (cgutmann-in-dupageforest.com)
Tue, 15 Feb 2005 15:26:09 -0600

Dave,
That's a very interesting point regarding aposematic coloration vs. cryptic coloration. Given that madtoms are primarily nocturnal, would there be a heavy selection pressure for the development of aposematic coloration? Species with aposematic coloration that first spring to my mind tend to be diurnal (i.e., wasps, monarchs, dart frogs). Are there any nocturnal organisms with aposematic coloration? I'm racking my brain trying to think of one. Anyway, food for thought.

Chris Gutmann
Des Plaines River drainage
Oak Brook, IL

-----Original Message-----
From: owner-nanfa-l-in-nanfa.org [owner-nanfa-l-in-nanfa.org]On Behalf
Of dlmcneely-in-lunet.edu
Sent: Tuesday, February 15, 2005 2:34 PM
To: nanfa-l-in-nanfa.org
Subject: Re: RE: NANFA-L-- chemical defenses -- madtoms and others

Bruce, seems like I read that the birds swallow the peppers whole, and so do not release the capsaicin from the peppers until digestion is initiated in the gizzard. Then the capsaicin has the same cathartic effect that it has in people -- that is, the undigested seeds are passed more quickly than they would be if there were no capsaicin involved. The capsaicin stimulates pain receptors in mammals, which masticate the chili berries, but not in birds, which have no teeth. Seems like Jantzen, of University of Pennsylvania (or one of his students) did some work on this with long-billed thrashers in S. Texas and in Arizona, and found that indeed, capsaicin is cathartic in them. These birds eat a lot of peppers where they grow wild as part of the shrub stands in S. Texas. I think that there was even speculation that the chili advertises itself to the birds by its bright colors.

Could pain on attempted predation have the same benefit for madtoms that nausea on ingestion of monarch butterflies has in their bird predators? In that case, after a bluejay eats a monarch, the butterfy's chemical defenses (cardiac glycosydes present in the milkweed foliage eaten by the caterpillar and sequestered in the internal organs of the butterfly) sicken the bird, and it vomits. A person would find this experience unpleasant. Bluejays that have had this experience then avoid monarchs in the future. Since monarchs in the same vicinity are likely to be genetically related, the prey is protecting its kin, and the trait of sequestering these poisons is naturally selected. Orioles that prey on monarchs with impunity, however, dissect the butterflies and strip out the offending organs, which they drop on the ground, eating the non-toxic parts!

Maybe a bass that eats a madtom has an unpleasant experience, (a sting in the gullet or stomach. The feeding method of a bass is unlikely to result in a sting in the mouth), and so avoids madtoms in the future. That would protect the madtoms kin, thought not the one eaten. Or, like you said, maybe the protection evolved historically for predators that no longer exist. Or maybe it works very well for predators that require more handling of the madtom than does a bass -- say a heron, which has to manipulate its prey, or a racooon, which has to handle the fish with its paws, then its mouth. More chances to be stung. One thing wrong with this scenario is that madtoms tend to be cryptically colored, and to seek protective shelters. In other animals, where a prey is protected in the way I've speculated for madtoms, the protected animal exhibits warning coloration -- the bright colors of a monarch, or a wasp, for example.

Interesting to consider, anyway.

Dave

David L. McNeely, Ph.D., Professor of Biology
Langston University; P.O. Box 1500
Langston, OK 73050; email: dlmcneely-in-lunet.edu
telephone: (405) 466-6025; fax: 405) 466-3307
home page http://www.lunet.edu/mcneely/index.htm

"Where are we going?" "I don't know, are we there yet?"

----- Original Message -----
From: Bruce Stallsmith <fundulus-in-hotmail.com>
Date: Tuesday, February 15, 2005 1:40 pm
Subject: RE: NANFA-L-- Michigan Chapter

> Plants are necessarily the best comparison. Birds have little or
> no sense of
> taste, for instance, so the various peppers are hot to deter other
> herbivores, while birds eating the fruits benefits the pepper
> because birds
> can spread the seeds by pooping. Madtoms may benefit even a little
> from
> being able to inject a noxious substance into a predator, which
> could work
> for a positive selection force on the venom. Or was the venom more
> effective
> against a predator in earlier times who no longer exists, and the
> venom is
> now vestigial? Just a thought, you never know.
>
> --Bruce Stallsmith
> the springlike Tennessee Valley
> Huntsville, AL, US of A
>
> >From: jlw-in-dune.net
> >Reply-To: nanfa-l-in-nanfa.org
> >To: nanfa-l-in-nanfa.org
> >Subject: RE: NANFA-L-- Michigan Chapter
> >Date: Tue, 15 Feb 2005 12:30:59 -0700
> >
> >Don't forget also, that predators develop defenses against their
> prey's>defenses. In other words, they can evolve to be list
> effected by venom, or
> >its
> >method of injection. Certainly individuals-in-any given time are
> going to
> >be
> >more effected than others -- we can see this even in human
> beings. I love
> >hot
> >peppers, and make a plate of chili that makes my S. O. want to
> leave the
> >house
> >(we'll pretend it's the CHILI that does that). Yet, I have a
> friend who
> >thinks
> >its "Not bad, a little weak."
> >
> >Fish are the same way -- one bass grabs a madtom and it's like a
> platefull
> >of
> >hot peppers. Another grabs one, thinks, "SPICY!" and heads off
> in search
> >of
> >another. :)
> >
> >JW.
>
>
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