Dr. Paul Nealen
  • Home
  • Research interests
  • Student research colleagues
  • Recent teaching
  • Office hours
  • Science news blog

I often share, and interpret, science news with my students -
some of these reports are collected here.

These Butterflies Evolved to Eat Poison. How Could That Have Happened? - The New York Times

10/12/2019

0 Comments

 

Good morning,

We've considered recently the concept of aposematism, the display of warning coloration to indicate to potential predators that one is unpalatable or otherwise unsuitable as a prey item.  As we have seen, there are many implications to this type of signaling, including the costs involved, the degree to which it is effective, and its potential to be mimicked (and thus rendered potentially less effective) by palatable species.

The issue of aposematic costs is one that has been considered for some time, particularly the metabolic costs of producing warning coloration as well as the predation cost of being conspicuous.  In addition to these are the metabolic costs of actually being unpalatable, and in no system has this been better explored than in monarch butterflies, conspicuous in both larval and adult forms, as well as highly unpalatable in each for the glycosidic compounds they acquire and sequester from milkweed plants (their near-exclusive forage).  These compounds are highly toxic disruptors of Na+ channels, and being able to ingest and store them has required some evolutionary tinkering. 

In the recent science news is consideration of this phenomenon, with some genetic work that explains the evolution of caterpillar resistance to these glycosides. The plant defenses have evolved to deter caterpillar feeding, but the caterpillars were able to evolve resistance with as few as three genetic mutations.  These researchers were able to induce these same mutations in fruit flies, rendering them resistant to the glycosides as well - a very powerful experimental demonstration.  The researchers also demonstrate some of the costs associated with the evolution of resistance to glycosides, including reduced ability to withstand physical shock.  No evolutionary benefit is free, and beneficial changes to genes often are paired with deleterious side-effects.  Here, the benefit (unpalatability) appears to outweigh the costs (reduced ability to withstand physical rotation).

Many of the plants and animals around us are conspicuous, while many others are cryptic.  Those that are colorful and eye-catching may be silently playing potentially-deadly games of chemical warfare.  Nature has been described as 'red in tooth and claw' (William Congreve); we might expand that to '... tooth, and claw, and toxin', for many toxins (including these glycosides) are quite deadly.  What is remarkable to me is the role of simple sugars in glycosides, forming one side of the glycosidic bond.  This is why some dangerous chemicals (such as automotive antifreeze, ethylene glycol) taste sweet and thus are dangerously attractive to the uninitiated.  It makes me wonder whether glycosides have ever been used in nature as deadly bait, to lure, and then poison, potential prey.  I'm willing to bet that it has...

https://www.nytimes.com/2019/10/02/science/monarch-butterflies-milkweed.html

Have a great weekend-
Dr. Nealen
0 Comments



Leave a Reply.

    Archives

    February 2020
    January 2020
    December 2019
    November 2019
    October 2019
    September 2019
    August 2019
    May 2019
    April 2019
    March 2019
    February 2019
    January 2019
    August 2018
    April 2018
    March 2018
    February 2018

    Categories

    All
    Addiction
    Art
    Behavior
    Cancer
    Circulation
    Cognition
    Consciousness
    Conservation
    Coronavirus
    Defenses
    Diet
    Evolution
    Exercise
    Genetics
    Health
    Heredity
    Hormones
    Humans And Their Environment
    Immunity
    Mental Disorders
    Migration
    Neuroscience
    Nobel Prize
    Pain
    Physiology
    Pollution
    Regeneration
    Renal Function
    Reproduction
    Respiration
    Sleep
    Sociality
    Space
    Sport
    Stem Cells
    Temperature
    Vaping
    Vision

    RSS Feed

Proudly powered by Weebly
  • Home
  • Research interests
  • Student research colleagues
  • Recent teaching
  • Office hours
  • Science news blog