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carnivorous females

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carnivorous females

Postby SPAZ » Sat Mar 31, 2007 12:20 am

some spider females eat their males after mating, I know the black widow does this, but which other arachnides do this, does anyone know?
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Postby Darby » Sat Mar 31, 2007 5:00 pm

I think there are several.

There is one - I think it's the Australian redback, but I haven't bothered to look it up - where the male, as he's finishing, flips onto the female's fangs. It's thought that while she's consuming him, she isn't available to other males, so it benefits the suicide-committer.
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Postby nugget » Sun Apr 01, 2007 2:24 am

Most spiders do, Argiope and Nephila species are involved in sexual cannibalism too. Most of them do, because male spiders can only mate twice. they have 2 pedipalps that they load with sperm, and they plug that into the female genitalia opening (she has two) basically he has no purpose to life anyway :P
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Postby Darby » Sun Apr 01, 2007 1:13 pm

As I'm doing a quick review of papers (and there aren't a lot), it doesn't seem that you can generalize - it seems like most free-range spiders (like tarantulas and jumping spiders) copulate and flee. Since the larger spiders can live quite long lifespans, it would make sense that males can reproduce repeatedly.

And just because there are only 2 pedipalps doesn't mean only 2 sperm packets can be produced.
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Postby nugget » Sun Apr 01, 2007 1:54 pm

yes it does, in most species, they can only insert twice... well in the cannibalistic ones anyway. it is a part of their sexual behaviour, it also makes sure that the female might not mate with anyone else. its like a mating plug, and also if she is better fed, there is better chance of the survival of his genes. the sexual behaviours of invertebrates are very complex
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Postby Locus » Sun Apr 01, 2007 6:16 pm

Once I sow fotos of coupling mantis, and on the fotos femele have eating the male - during the copulation! But I don't remember where I sow this :(
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Postby Darby » Sun Apr 01, 2007 11:18 pm

The exchange for each mating may be limited to two, but in circumstances when the male escapes, they can generate more packets and mate with other females. Especially useful in species where the next male may, as a first step, remove the previous male's packet (there's a lot of adaptation toward both preventing packet removal - like the redback do - and improving packet removal).

Keep in mind that, except where there are specific advantages to it, which is rare, it's unusual for males in any species to have only one reproductive opportunity in their lifetimes.
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Postby nugget » Sun Apr 01, 2007 11:29 pm

Darby, what im saying is that in the case that they loose their pedipalps - its not just a spermatophore that they insert, there is no point in life !! seriously and they dont have one reproductive opportunity, they have 2. thats why they try to escape after the first mating, they do things like suck their tummy in so that she cant nibble on the important organs and things like that so that they can mate twce. A male does not even eat after his moult into adulthood, his aim in life is to reproduce and the mating plug is to make sure that she wont mata with anyone else, as you said, but yes the next male can remove this, however if he sacrifices himself, this reduces the PROBABILITY that she will mate again. yeah i know about those adaptations too,

and Locus, yes that is true, Mantids to display sexual cannibalism, sometimes she will eat his head while copolating, and that actually can improve the copulation, plus there is a whole different nerve ganglion in the posterior end, which is why the mantid can do this weird thing.
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Postby Darby » Mon Apr 02, 2007 12:40 pm

What you're stating as certainties aren't, though it's apparently pretty common:

http://www.springerlink.com/content/q966617t331652k1/
(Note: the "mating only once" idea was based on observations of pedipalp damage, which apparently affects but doesn't preclude future matings)

http://www.blackwell-synergy.com/doi/ab ... 05.01114.x
(Here, loss of pedipalps does affect future meetings, but these males use only one at a time in this group)

It appears the basic idea of "mate once" is fairly old (this is 1957):

http://links.jstor.org/sici?sici=0003-0 ... size=LARGE
(and, like a lot of ideas that show up in old sources but weren't really confirmed, continue in the "general" sources with a life of their own)

But confirmation of the hypothesis has been rare:

http://beheco.oxfordjournals.org/cgi/co ... t/17/3/353

And doesn't appear to apply to tarantulas at all:
http://jrscience.wcp.muohio.edu/downloa ... ntulas.pdf

Here's one that addresses the original question, but notice all of the qualifiers around the current question:

http://www.google.com/search?num=50&hl= ... tnG=Search

One thing to remember about zoology is that there are very few things that apply universally to any particular group - it's almost always a very short list. However, in groups that are not broadly studied, a lot of old ideas based upon very little data persist.
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Postby nugget » Mon Apr 02, 2007 1:13 pm

Ok, well thanks for that, i dont recall saying ALL spiders were like that, did i? but i did mention argiope, as my lecturer who was the first researcher in one of those articles that you showed me also studies these and many other spiders. Thats why i am sure it occurs, because of the first hand evidence I have seen on the selected species that i have learnt about and read about. I dont remember saying tarantulas? but thats cool
i know the tendencies of zoology thanks lol
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