As we’ve started talking about sexual selection in class, I find it fitting that this week’s blog be about that very subject. In class, we mentioned how the male scorpion fly presents ‘gifts’ to the female, usually a dead bug, in order to distract her so the male can copulate for an extended period of time. Well, as it turns out, these flies aren’t the only one paying for sex. Pisaura mirabilis, also known as the nursery web spider, is European species who also present ‘gifts’ to females in order to distract them so they can copulate. While most males present fresh prey wrapped in silk, some just wrap shell husks in silk and present. Scientists believe the stress of finding a mate forces these males to present anything in order to have a longer copulation time. Researchers from Aarhus University in Denmark and the Instituto de Investigaciones Bioloìgicas Clemente Estable in Uruguay took 20 spiders and set them in groups and gave them gifts to wrap: either no gift, a shell husk, a fresh fly, or a protein-enriched fly. They found the males would wrap the present with silk until it was unidentifiable, giving them more time for copulation as the females would inspect the gift. As expected, males who presented gifts had greater success mating, and those with edible gifts got to mate for a longer period of time. What separates these spiders from other gift-giving species is the other trick they use to mate. If they haven’t copulated for a long enough time, some males will pretend to die, with their gift in hand. The females would then drag the male ‘carcass’ along in order to try to take the gift. Once they stop dragging, the males will revive and mate with the females for a second time (talk about desperate). This feigning death is called thanatosis. And we think human men can pull some weird crap when trying to get a girl.
Picture of male spider giving gift:
Information came from the article “8-Legged Sex Trick? Spiders Give Worthless Gifts, Play Dead” written by Jennifer Welsh on Nov. 13, 2011 from livescience.com. Link:
http://www.livescience.com/17010-spider-gifts-play-dead-mating.html
Posted by Austin Gray (8)
Picture of male spider giving gift:
Information came from the article “8-Legged Sex Trick? Spiders Give Worthless Gifts, Play Dead” written by Jennifer Welsh on Nov. 13, 2011 from livescience.com. Link:
http://www.livescience.com/17010-spider-gifts-play-dead-mating.html
Posted by Austin Gray (8)
The part of this that seems the most interesting to me is that the spiders will give false gifts with an empty husk inside. I guess a real meal will keep the female occupied for longer, but the trick one is good enough for a quickie for a lazy spider. It's also cool that they take the effort to wrap the fly so thoroughly to disguise it and buy themselves a few more seconds. I wonder if the female spiders appreciate the protein-enriched flies more and allowed longer copulation, or didn't notice a difference between that and a regular fly.
ReplyDeletePosted by Rhys Ursuliak
I wonder if the female would ever attempt to eat the male spider if he was feigning death? There are some species of spider where that does occur- the male will only have a small chance of mating with the female because it is much more likely that she will eat him instead. So weird! But anyway, it is weird that the males will give fake gifts because they are so desperate for sex! I wonder how many other species also give gifts?
ReplyDeletePosted by Johanna Brophy
Human men are merely trying to impress women so we can pass on our genes, just like males of any other species! Though, in our species, that notion has been somewhat lost. I think this is a very good way to gauge the genes of the male fly. The more resourceful and better-gene'ed flies would have a more well-wrapped "gift" and therefore most chance of copulating. Genius, if you think about it!
ReplyDeletePosted by Michael Shi
This is another great example of female choice. I'm sure that besides the fly example and the one you just gave, that there are several species that present gifts before copulation. Though it is more often heard in insects, I wonder what the reason for that is? Also I'm curious how common it is for a spider to wrap up no food in web and try tricking the female since it requires less work.
ReplyDeletePosted by Nick Gast
It seems that some species put in more effort in attracting a mate than some human males do! I wonder if the male spiders that bring false gifts such as the shell husks take more time in wrapping the gift? Since the female will be undoubtedly disappointed when she finds that her "gift" is inedible, wrapping these fakes more intricately would allow them more copulation time. I also wonder if the females become aggressive towards the males that bare false advertisements?
ReplyDeletePosted by Sara Corey
Well hello fellow bloggers, it’s time for a response! Ok, to answer some of the questions. First off, the study did compare fresh fly gifts vs. protein-enriched fly gifts. They found that there was no difference in copulation time or preference amongst females. The study did not examine how well wrapped the ‘gifts’ were nor if spiders with husks wrapped them more thoroughly, though I can see how this would help them with copulation time. The study did note that husks are mainly used in ‘desperate’ male spiders, as time restraints and competition from other males often forces the spiders to wrap whatever’s available. I also tried to do some additional research to see if any studies were done on nuptial gifts in animals other than insects, but I could not find any. I saw gift giving in crickets, and a large variety of fly species. Look forward to reading your blogs (for those posting) this upcoming week.
ReplyDeleteResponse posted by Austin Gray (8)
This is very neat that in Evolution it seems that females select males based on their fitness and overall healthy traits. Where in the spiders it is quite different when it comes to mating and that giving a gift depending on it's quality gives you the right to mate and not physical traits. This goes against most animals mating behaviors we commonly discuss.
ReplyDeleteby: Andrew Ryan
Haha! It seems that deception in this "gift giving" trade for sex has proved to be far more beneficial then actually providing the female with what she desires. I agree with Michael in saying this is genius! If one's sole purpose is to ensure that his genes are passed to the next generation, an deception is the most successful way to attain that goal, then so be it. But what I don't quite understand is, why, if the male is "dead", does the female carry his carcass in order to retrieve the gift as opposed of simply stripping it from it's dead grasp? In a world where energy conservation is key, it is just a thought derived from observation.
ReplyDeleteComment by Jose Mijangos