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Thread: Sexual Cannibalism - Was It Good For You?!

  1. #1 Sexual Cannibalism - Was It Good For You?! 
    Forum Masters Degree Double Helix's Avatar
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    Most of us have heard about the black widow spider eating the male after mating. A nasty thing if you are being consumed. It better have been good. This is known as sexual cannibalism, and is not limited to the black widow (1).

    However, another spider has evolved an escape mechanism, one which allows it to mate prior to catapulting itself away from the jaws of the female (2).

    Most of the guys out there, myself included , can appreciate this means of mating and skipping out without having to deal with such terminal activities!


    "Sexual Cannibalism"

    1. https://en.wikipedia.org/wiki/Sexual_cannibalism


    "This Male Spider Catapults Itself Into the Air to Avoid Sexual Cannibalism"

    2. https://www.smithsonianmag.com/scien...ism-180979966/


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  3. #2  
    ox
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    Why do spiders have 8 legs?


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  4. #3  
    Forum Masters Degree Double Helix's Avatar
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    Quote Originally Posted by ox View Post
    Why do spiders have 8 legs?
    Spiders and other eight legged arachnids diverged from the arthropod line about 400 mya *.

    Arthropods make up a large phylum (Arthropoda) which includes all invertebrates with hard exoskeletons, segmented bodies and paired legs. There have been countless millions of varieties, with different numbers of legs. Insects are at the top in numbers with six legs, and some arthropods have hundreds of legs (centipedes, etc.).


    "First divergence time estimate of spiders, scorpions, mites and ticks (subphylum: Chelicerata) inferred from mitochondrial phylogeny "

    * https://pubmed.ncbi.nlm.nih.gov/18931924/
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  5. #4  
    ox
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    But why do spiders actually need 8 legs. Could they get by with 6?
    Why do they have 8 eyes (usually). Could they get by with fewer?

    I'm turning this into an evolution question as to why it never quite makes sense.
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  6. #5  
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    Quote Originally Posted by ox View Post
    But why do spiders actually need 8 legs. Could they get by with 6?
    Why do they have 8 eyes (usually). Could they get by with fewer?

    I'm turning this into an evolution question as to why it never quite makes sense.
    While it may never quite make sense to us, it certainly makes sense for natural selection. There are many instances of new species diverging from the main arthropod line with more than 6 legs and 8 eyes (some spiders have no eyes, others have 12 eyes).

    Why does a centipede need 100 legs? These are but a trace sampling of the unknown aspects of evolution which are not easy to explain, but are certainly facts - they exist. One might suggest that a lack of human imagination to understand, at this point in time, why all the variations of life forms evolved as they did. But that they did is beyond question.

    Perhaps AI will provide an answer for all these issues in the future, but would not hold my breath. It seems there is no more complex topic in all of science than the appearance and evolution of life on Earth.

    You might find some ideas in the wiki link below. It has specific references to spiders:


    https://en.wikipedia.org/wiki/Arthro...ionary_history
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  7. #6  
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    Quote Originally Posted by Double Helix View Post
    One might suggest that a lack of human imagination to understand, at this point in time, why all the variations of life forms evolved as they did. But that they did is beyond question.
    But evolution is based upon unimaginable cruelty in the past and natural selection never produces perfection.
    We are the pinnacle of evolution and yet we only live for a few decades and few of us actually die of old age.
    If evolution arms spiders with extra legs and eyes then perhaps the only reason is to help escape predators.
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    Quote Originally Posted by ox View Post
    Quote Originally Posted by Double Helix View Post
    One might suggest that a lack of human imagination to understand, at this point in time, why all the variations of life forms evolved as they did. But that they did is beyond question.
    But evolution is based upon unimaginable cruelty in the past and natural selection never produces perfection.
    We are the pinnacle of evolution and yet we only live for a few decades and few of us actually die of old age.
    If evolution arms spiders with extra legs and eyes then perhaps the only reason is to help escape predators.
    Many would suggest that cruelty is a human definition for certain natural processes. As such, Mother Nature does not deal in cruelties. The notion of perfection might also seem like a human invention as well. Relative to evolution, perfection might be defined as successful enough to survive and replicate.

    Based on our understanding of science and all its discoveries, we are the "pinnacle of evolution". But our proclivities at destroying what we need to survive appears to undermine that claim.

    Longevity is only essential for reproduction of the species - reaching maturity. After sufficient reproduction has occurred, longevity is irrelevant. In humans, it appears to be an evolutionary disadvantage based on ~ 7.9 billion people and their impact on the planet.

    Variations in morphology, such as extra legs and eyes, can help both predators and prey. It all boils down to a specific species moving forward under all the environmental pressures, and how natural selection plays out with regard to its future evolution. These aspects of evolution are surely some of the most profoundly difficult to determine and understand.
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  9. #8  
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    Quote Originally Posted by Double Helix View Post
    Many would suggest that cruelty is a human definition for certain natural processes. As such, Mother Nature does not deal in cruelties. The notion of perfection might also seem like a human invention as well. Relative to evolution, perfection might be defined as successful enough to survive and replicate.
    Humans have developed language which is all metaphor, so cruelty would be as good a word as any.
    Perfection does happen but it never lasts long (a favourite subject for great poets).

    Based on our understanding of science and all its discoveries, we are the "pinnacle of evolution". But our proclivities at destroying what we need to survive appears to undermine that claim.
    Longevity is only essential for reproduction of the species - reaching maturity. After sufficient reproduction has occurred, longevity is irrelevant. In humans, it appears to be an evolutionary disadvantage based on ~ 7.9 billion people and their impact on the planet.
    It seems that soon after puberty parts of our bodies start to decay. Longevity is largely based on luck.

    Variations in morphology, such as extra legs and eyes, can help both predators and prey. It all boils down to a specific species moving forward under all the environmental pressures, and how natural selection plays out with regard to its future evolution. These aspects of evolution are surely some of the most profoundly difficult to determine and understand.
    In evolution you have to run faster and faster just to stand still.
    What happens if you are overtaken is not pleasant for any species, and why humans are bound to become extinct one day.
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    Trying to figure out what cannibalizing a mate does for the species. I guess it ensures that Dad won’t be impregnating rival females. Why that would be good for the species I’m not sure, since the best available genetics may be chowed down before it gets another chance to breed.

    Do those female spiders who consume their mate instinctively know they’ve chosen poorly should they be able to capture their lover and devour him? You’d think if a male escapes capture then the choice is a good one over all. I wonder if the spiders who have papa for dinner can terminate their pregnancies should they instinctively judge their captive to be weak?
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
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  11. #10  
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    Quote Originally Posted by zinjanthropos View Post
    Trying to figure out what cannibalizing a mate does for the species.
    It is believed that eating the male provides instant nutrition to the female to start developing the eggs into baby spiders. Certainly bad for the male, but as long as it does not cause extinction, it works.

    Quote Originally Posted by zinjanthropos View Post
    I wonder if the spiders who have papa for dinner can terminate their pregnancies should they instinctively judge their captive to be weak?
    Any weakness in the captive would be in its genetic makeup, not directly in its nutritional value. And it is better to eat a weaker male than allow it to mate again.

    Genetics of offspring can however be mediated by the adults, unrelated to sex. In at least one case, male lions will kill the cubs of another male if they take over a pride. That seems like the winner is getting rid of a weaker genetic link in those offspring. The stronger lion then mates to create stronger lions.

    One suspects there are other examples like this in wildlife. Let's hear about them, as this seems like a pretty unique behavior.
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