Along came a sadistic spider

Arachnophobes beware: Researchers have discovered a male spider in the Judean foothills of Israel with a sadistic sexual perversion. Males of the aptly named __Harpactea sadistica__ spider jab their spiked copulatory organs into the body walls of female spiders to inject their sperm and outcompete rival males -- an arachnid first, according to a study published online tomorrow (Apr. 29) in the Proceedings of the Royal Society B. Image: Milan ŘezáčStabbing sex, also known as traum

By | April 29, 2009

Arachnophobes beware: Researchers have discovered a male spider in the Judean foothills of Israel with a sadistic sexual perversion. Males of the aptly named __Harpactea sadistica__ spider jab their spiked copulatory organs into the body walls of female spiders to inject their sperm and outcompete rival males -- an arachnid first, according to a study published online tomorrow (Apr. 29) in the Proceedings of the Royal Society B.
Image: Milan Řezáč
Stabbing sex, also known as traumatic insemination, is common among many hermaphrodite species as well as some insects with separate sexes, most famously the bed bug. But it has never before been observed in other arthropods. "Now we have a very odd biological phenomenon in an unrelated taxonomic group," Mike Siva-Jothy, a Sheffield University evolutionary physiologist who studies bed bugs and was not involved in the study, told __The Scientist__. "It's like finding a peacock's tail in a non-bird species." __H. sadistica__ -- a non-web-building, predatorial spider that the study author Milan Řezáč, an arachnologist at the Crop Research Institute in Prague, Czech Republic, first described last year -- engages in a 15-minute mating grapple, in which the male first spends five minutes aggressively wooing his mate through a series of taps, fang grasps, and hooking advances. For the next 10 minutes or so, he then repeatedly pierces alternating sides of the female's abdomen with his penile prong to deposit his sperm into both of the female's two reproductive organs, Řezáč found.

The parallel evolution of this malevolent mating tactic in insects, arachnids, and other taxonomic groups shows that traumatic insemination is more than just an oddball zoological curiosity. Rather, it could be an important driving force in the evolution of mating systems across diverse taxonomic groups. "It tells us that there's some level of generality behind the selective pressures and the mechanisms that have generated traumatic insemination," said Göran Arnqvist, an evolutionary biologist at the University of Uppsala in Sweden who was not involved in the research. "It's a dramatic male adaptation to sperm competition, basically." __H. sadistica__ females and closely related spiders all have round, cul-de-sac shaped sperm storage organs. These structures allow males to scoop out any sperm already present from past suitors before they mate, and so, ordinarily, the last male to mate is the first to fertilize the eggs. But by going the way of the abdomen rather than the sperm-storing genitalia, traumatically inseminating __H. sadistica__ males keep their sperm out of the reach of later-mating males. Thus, with this mating tactic, it's first come, first to sire. But Řezáč only studied the spider's behavior and didn't examine the sperm itself, so he never showed this experimentally, noted Ted Morrow, another Uppsala evolutionary biologist. "The crucial bit of data that he doesn't have is patterns of sperm precedence," he said. The parallels between __H. sadistica__ and other traumatic inseminators go beyond the painful pas de deux. Unlike other spider eggs, which are fertilized in the uterus shortly before being laid, __H. sadistica__ eggs are fertilized in the ovaries and laid as early-stage embryos up to one month later. Such internal fertilization is also found in bed bugs and related traumatically-inseminating insects, noted Siva-Jothy. Thus, "there's an awful lot of convergence that's going on between the two groups, but exactly what that means is still unclear," he said. It's impossible to say whether this form of reproduction evolved because of internal fertilization or the other way around, because the two are found in lock-step with each other, Siva-Jothy said. But __H. sadistica__ might offer a good system to tease this apart, because, unlike bed bugs, closely related species in the spider's genus do not engage in traumatic insemination. Comparative studies open up "interesting experimental possibilities," noted Arnqvist.
**__Related stories:__***linkurl:Wham, bam, now I'll die, ma'am;
[28th July 2003]*linkurl:Spider's web;
[27th March 2001]


Avatar of: Ellen Hunt

Ellen Hunt

Posts: 199

April 30, 2009

Just because there is penetration of a carapace does not mean that this causes pain to the female spider. It might, and it might not. Spiders don't have skin like ours, they have a hard carapace. They have little evolutionary need for receptors for anything but touch in their abdomen, if that. \n\nIt is a good question whether what we all pain is a meaningful concept for a spider. Considering the relative simplicity of spider nervous systems, and their general lack of sensory nerves in their abdomen, there is reason to think it isn't meaningful. \n\nThe only reason we think this is sadistic is because it would hurt us if we were stabbed in our delicate, soft, sensitive abdomens. But we can be probed in our brains and not feel a thing. We can put skewers through insensitive areas and feel little except tugging sensations. Why anthropomorphize a spider?
Avatar of: Donald Duck

Donald Duck

Posts: 39

May 2, 2009

I don't believe in evolution. Life is simply too bizarre for the idea to be even plausible. Genitalia to swords? Leaves to bug eating leaves? Gills to lungs? Feathers for warmth to feathers for flight? Come on, folks, how ridiculous do the connections have to get? There is logic in the 'before' and 'after' but no reason for evolution 'during' the major change.\n\nGuided evolution makes sense. Of course, no-one believes (or should believe) in anything religious because a group of scientists reach a consensus, that got us the Nicean Creed. Long story, but a guy who didn't understand Christianity went and made it the dominant religion. \n\nThis applies to us as well, you aren't considered religious just because you decide that all the smartest people are LDS and therefore you ought to be. One of the most common things for us to hear is the "find out for yourself" line. Many scientist just say "we found out for you" then scream at you for not believing them.\n\nBy 'scientists' I really mean 'scientists who hate me,' no offense to scientists that merely disagree with me. Disagreeing is fine. It was trying to get everyone to _agree_ which got us the Nicean Creed.\n\nPS Excellent article, 5/5 stars. Just commenting about evolutionists in general, this article didn't strike me as annoying. I only hate the ones who claim they know everything... then talk about the holes in their theory. You have no idea how much a little humility helps an article.
Avatar of: Carter Thomasson

Carter Thomasson

Posts: 2

May 19, 2009

This Donald duck takes some aggressive shots at one of the most intelligently considered theories of all time. Deep time is a concept that skeptics neglect when considering evolution. You are skeptical because you understand the small and usually subtle mutations that lead to changes with in a species, but you don't believe that they can accumulate to become a new species. You don't seem understand how ungodly long deep time is. These billions of years hold amazing evolutionary possibilities that remain difficult to prove and understand. I think that skeptics approach evolution with too closed of a mind. It really takes an imagination, after all it is a theory, and you must be willing to seriously consider, or sometimes creatively imagine all aspects of a theory to better understand such an abstract and complex idea.

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