Saturday, 30 April 2016

Evolution or Sadistic, Idiot Designer?

(A) Two males on a parasitized A. vaga (Osnabrück, 10.ii.2008).
(B) Five males on a parasitized host (Osnabrück, 23.ii.2008).
Photographs © W. Rutkies.
Traumatic insemination and female counter-adaptation in Strepsiptera (Insecta)

Parasitism itself, with it's inevitable arms race as the host evolves to combat the parasite and the parasite evolves to overcome its host's defenses is a major embarrassment to anyone trying to believe in any intelligence behind living things, or even intelligent evolution because, frankly, arms races are not intelligent.

But, even more of an embarrassment to intelligent (sic) design advocates, especially those who unashamedly link it to biblical literalism complete with the Christian god as the magic creator, are the exquisitely nasty mechanism some parasites have evolved. Their sheer malevolent nastiness precludes design by a benevolent designer and cannot possibly be presented as the work of a loving god or anything approaching one.

I've written about several of these before but this one, the details of which were published in Scientific Reports yesterday take some beating. It involves a parasitic fly known as the twisted-winged parasite which parsitises wild bees.

In a few insect groups, males pierce the female’s integument with their penis during copulation to transfer sperm. This so-called traumatic insemination was previously confirmed for Strepsiptera but only in species with free-living females. The more derived endoparasitic groups (Stylopidia) were suggested to exhibit brood canal mating. Further, it was assumed that females mate once and that pheromone production ceases immediately thereafter. Here we examined Stylops ovinae to provide details of the mating behaviour within Stylopidia. By using μCT imaging of Stylops in copula, we observed traumatic insemination and not, as previously suggested, brood canal mating. The penis is inserted in an invagination of the female cephalothorax and perforates its cuticle. Further we show that female Stylops are polyandrous and that males detect the mating status of the females. Compared to other strepsipterans the copulation is distinctly prolonged. This may reduce the competition between sperm of the first mating male with sperm from others. We describe a novel paragenital organ of Stylops females, the cephalothoracic invagination, which we suggest to reduce the cost of injuries. In contrast to previous interpretations we postulate that the original mode of traumatic insemination was maintained after the transition from free-living to endoparasitic strepsipteran females.

© 2016 The Authors / Macmillan Publishers Limited. Reprinted under Creative Commons Attribution 4.0 International License. (CC BY 4.0)

It starts off with the male twisted-winged fly stabbing the female with a hooked penis so he can inject sperm into her body cavity. This injures the female and lasts a relatively long time, thirty minutes, probably to reduce the chances of another male mating with her. Finding a female and mating with her is the sole function of the male who only lives as an adult for about five hours and has no mouthparts - they having been adapted as sensors.

To inseminate the female, the twisted-winged parasite attaches to the bee's abdomen and pushes its hook-shaped penis into the females neck region. After this the sperm fertilize many thousand egg cells in the body cavity of the female which then develop into extremely small larvae.

Miriam Peinert, co-author. Quoted in ScienceDaily
The female plays no part in this process because only the male is free-living. She has spent most of her life in the body of her host as a parasite, only showing a small area of her body to the world by pushing it through the body of her host. This is the area which will get stabbed by the male. The sperms find and fertilise her several thousand eggs which soon hatch.

This presents something of a problem for the grubs because by now the bee host has been mostly consumed by their mother. This is no real problem though, since they remain within their mother's body and set about consuming her. When ready and the mother is just about all consumed, the grubs emerge from the stab wound their father inflicted on her and set of looking for another wild bee to parasitise, so starting the cycle all over again.

Apart from harming wild bees, this hideous, uncaring and indifferent process appears to have no other purpose than making more twisted-winged flies. It presents no problem at all for biology to explain since this sort of uncaring, compassion-free system is exactly what neo-Darwinian evolution predicts. The only test applied is what produces the most offspring. There is no purpose or objective other than to make as many of the next generation as possible by whatever means produces the most.

For creationists who have to accommodate all manner of irrelevant details of their favourite imaginary designer, this looks like an insurmountable problem because no omni-benevolent designer could conceivably design something so grotesque as this. Apart from an understandable discomfort with the entire subject of parasites, creationist frauds tend to keep well clear of the biology of parasitism because it can't possibly be the result of intelligent design, let alone benevolence.

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  1. Any idea how the newborn females find another bee to parasitise?

  2. Biology has an indifferent and abhorent beauty. No so-called loving benovelent deity could countenance parasites and remain loved by its adherents. However, religous folk have an amazing ability for self delusion and will remain faithful, regardless. Now ain't that the sad truth.


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