A mouse that eats...scorpions?!

Grey Havoc

Grey Havoc

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http://www.youtube.com/watch?v=-E35OMfL4A4&feature=player_embedded

Before crunching into its prey, the grasshopper mouse howls. The sound is a high, sustained whistle which pierces the desert night. It is as if the rodent is imitating a wolf at miniature scale – the grasshopper mouse even stands on its hind legs and throws its head back during the shrill call. And while the rodent may cry spontaneously or emit the sound as a warning when it spots another of its kind, the grasshopper mouse regularly howls just before a kill.

The three species of grasshopper mice – all members of the genus Onychomys – are among the most carnivorous of all rodents. These are not adorable grain-eaters. Grasshopper mice are agile little predators which regularly take on prey as large, if not larger, than themselves. Insects, scorpions, lizards, and other mice make up about ninety percent of a grasshopper mouse’s diet. And, like other carnivores, they roam relatively large territories but have low population densities – a swath of habitat can only support so many hunters.

Wired.com
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now i have see and hear everything
Howling mouse, barking cats...
http://www.youtube.com/watch?v=aP3gzee1cps
 
Warning. Rant coming in.

What Dr Martin is saying suggesting is, that, because he can't think of a way the bombardier could have evolved, it has to be the product of something else. This leaves me guessing, and I'm guessing he's suggesting it's divine creation at work. Or intelligent design. Leaving me, of course, with the question how this process of divine creation/intelligent design came about, never mind how the intelligence behind it came to be.

I'll have stab at providing an evolutionary view. Here, in fact. For your convenience, I've extracted the step-by-step process proposed by Mark Isaak.
  • Quinones are produced by epidermal cells for tanning the cuticle. This exists commonly in arthropods. [Dettner, 1987]
  • Some of the quinones don't get used up, but sit on the epidermis, making the arthropod distasteful. (Quinones are used as defensive secretions in a variety of modern arthropods, from beetles to millipedes. [Eisner, 1970])
  • Small invaginations develop in the epidermis between sclerites (plates of cuticle). By wiggling, the insect can squeeze more quinones onto its surface when they're needed.
  • The invaginations deepen. Muscles are moved around slightly, allowing them to help expel the quinones from some of them. (Many ants have glands similar to this near the end of their abdomen. [Holldobler & Wilson, 1990, pp. 233-237])
  • A couple invaginations (now reservoirs) become so deep that the others are inconsequential by comparison. Those gradually revert to the original epidermis.
  • In various insects, different defensive chemicals besides quinones appear. (See Eisner, 1970, for a review.) This helps those insects defend against predators which have evolved resistance to quinones. One of the new defensive chemicals is hydroquinone.
  • Cells that secrete the hydroquinones develop in multiple layers over part of the reservoir, allowing more hydroquinones to be produced. Channels between cells allow hydroquinones from all layers to reach the reservior.
  • The channels become a duct, specialized for transporting the chemicals. The secretory cells withdraw from the reservoir surface, ultimately becoming a separate organ. This stage -- secretory glands connected by ducts to reservoirs -- exists in many beetles. The particular configuration of glands and reservoirs that bombardier beetles have is common to the other beetles in their suborder. [Forsyth, 1970]

  • Muscles adapt which close off the reservior, thus preventing the chemicals from leaking out when they're not needed.
  • Hydrogen peroxide, which is a common by-product of cellular metabolism, becomes mixed with the hydroquinones. The two react slowly, so a mixture of quinones and hydroquinones get used for defense.
  • Cells secreting a small amount of catalases and peroxidases appear along the output passage of the reservoir, outside the valve which closes it off from the outside. These ensure that more quinones appear in the defensive secretions. Catalases exist in almost all cells, and peroxidases are also common in plants, animals, and bacteria, so those chemicals needn't be developed from scratch but merely concentrated in one location.
  • More catalases and peroxidases are produced, so the discharge is warmer and is expelled faster by the oxygen generated by the reaction. The beetle Metrius contractus provides an example of a bombardier beetle which produces a foamy discharge, not jets, from its reaction chambers. The bubbling of the foam produces a fine mist. [Eisner et al., 2000]
  • The walls of that part of the output passage become firmer, allowing them to better withstand the heat and pressure generated by the reaction.
  • Still more catalases and peroxidases are produced, and the walls toughen and shape into a reaction chamber. Gradually they become the mechanism of today's bombardier beetles.
  • The tip of the beetle's abdomen becomes somewhat elongated and more flexible, allowing the beetle to aim its discharge in various directions.
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I am not saying this is the way it happened, neither is Mark Isaak. What I am saying is that Mark Isaak's explanation remains nicely within the bounds of current evolutionary thinking. It also offers 'a way the bombardier could have evolved', something that Dr Martin was unable to offer.
I don't mind people telling me life came about as a result of divine intervention. What I do mind is people telling me there's scientific proof for that statement and failing to provide a proper answer when asked for that proof.

End rant.

I did enjoy the footage of the bombardier beetle's antics. And the barking cat. Plus the howling mouse. Immensely. So, thank you, Justo, Michel Van, Grey Havoc.
 
I believe there are two types of evolution: The Classic one that requires million of years and the explosive one that may occur in just one generation.

First one is comparable to the geologic erosion (Lyell) and to the ongoing technical perfectioning engineers apply to their machines

The second is comparable to great impacts of comets and asteroids (Alvarez) and to the great scientific discoveries that changed the world

In my opinion, were the most cowards of our ancestors who, afraid of the lightning, created god.
 

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