"Proboscis", even...
Posted on 11/08/2005 6:04:06 AM PST by Loud Mime
Oct. 28, 2005— Like the character Count Dracula and his real-life vampire bat counterparts, a small, East African jumping spider has a taste for blood, according to a recent study.
The spider, Evarcha culicivora, lacks the ability to pierce skin and to sip blood, so instead it feeds indirectly on blood by choosing, as its preferred meal, female mosquitoes that have just engorged themselves with a victim's blood.
The blood-hungry spider is the first predator ever identified that selects its prey based upon what the prey just ate. Similar to a protein shake, blood can be a highly nutritious drink that goes down smoothly.
"Perhaps blood is a ready-made nutrient-rich liquid meal for which minimal energy expenditure in terms of processing is needed," said Ximena Nelson, lead author of the study, published in a recent Proceedings of the National Academy of Sciences.
Nelson, a scientist at Macquarie University in Australia, and her team conducted a food preference test with Evarcha culicivora serving as the critic. They first put the spider in a glass vial so that it could not smell prey choices, which were a mixture of male mosquitoes that do not consume blood, female mosquitoes fed a sugar concoction and female mosquitoes that had just feasted on blood.
Using sight alone, the spider always chose the blood-engorged females, who looked fat and somewhat red.
The researchers next pumped odors of the mosquitoes into a test chamber that the spider entered. The spider, using only its weak sense of smell, went for the females that had just dined on blood.
Nelson told Discovery News that feeding on blood is a dangerous activity, so this spider appears to minimize its risk.
"Animals that are bitten have a reflective 'swatting' response — humans use their arms, tailed animals use their tails, etc.— and often the insect is killed," Nelson explained. "It may be safer for Evarcha to obtain blood by killing a mosquito, then risk being swatted, even if they did have the mouth parts required to pierce skin and locate a blood vessel."
The spider also uses a rather clever technique for catching its fat female mosquitoes. The spider stalks the mosquito like a cat, and then pounces either on top or underneath the mosquito before taking a bite.
With such a hunger for blood, evolution would seem to favor this spider gaining the ability to directly suck blood from victims, but Nelson thinks the way Evarcha holds its fangs might prevent this from happening.
"They hold them close to their face, not forward projecting as mosquitoes do," she said. "Perhaps they might stab themselves, and this would kill them as spiders rely on a high hydrostatic pressure inside their bodies to 'hold them up.'"
The spider, then, would sort of burst like a holiday parade balloon that has hit a pointy light post.
Steve Heydon, senior scientist and collection manager for the Bohart Museum of Entomology at the University of California at Davis, was surprised to hear of the discovery.
"I know of parasitic wasps that find their caterpillar prey based on the smell of the caterpillar's feces, but I'd never heard of a spider like this before," Heydon told Discovery News. "Spiders don't have much sense of smell, so that part of the study is especially surprising."
Heydon agrees with Nelson that spiders now probably lack the right body parts and structure to evolve into direct bloodsuckers, but he does not completely rule this out for the distant future.
"Maybe spiders will end up like bed bugs," he said. "They could have that bed-bug lifestyle of laying around and coming out at night when a big, huge, monstrous food item comes tantalizingly near them and simply goes to sleep."
"a small, East African jumping spider has a taste for blood"
I stopped reading right there! I think i passed out on my keyboard.....
"This bring up an interesting question that I have wondered about before, if male mosquitoes do not eat blood, what do they eat?"
They are vegetarians, who drink nectar for food.
Ok, I'm going to need a tiny little cross, a sharpened matchstick and an eyedropper full of holy water.
>>A spider which has evolved to drink blood. But, it can't get blood from animals that manufacture blood. So, it evolved to drink blood from animals that already drank blood. Because that's easier.
Evolution is surprising.
If the spider evolved to drink blood but at the same time couldn't get it due to it's inefficient fangs, then it would have died due to a lack of blood -- and the potential lineage would have gone with it.
Think about it, if it couldn't get blood from any other animal, how was it to survive? How did it know about fat juicy mosquitos?
Those who believe in the DOGMA of evolution treat the process as an intelligent entity, able to make conscious decisions. It's sad because there is much to be said about the theory of evolution, but it get's clouded by the adherents of the "religion" of evolution...
So it feeds off of the thing that sucks the blood from its victims?
Welfare recipients!
Or PBS!
*So it feeds off of the thing that sucks the blood from its victims?
Welfare recipients!*
I was thinking lawyers.............
"Proboscis", even...
That's why evolution doesn't work in the ridiculously simple-minded way you describe.
Think about it, if it couldn't get blood from any other animal, how was it to survive? How did it know about fat juicy mosquitos?
...because it evolved from a spider that lived on a more generalized insect diet (like most spiders), but eventually evolved to specialize on just the blood-laden mosquitoes it was catching along with all the other stuff, because they were a more nutritious food source.
Duh.
Those who believe in the DOGMA of evolution treat the process as an intelligent entity, able to make conscious decisions.
No, we don't, because we know how the process actuall works. But idiotic creationist pamphlets like to portray it that way, based on their own misunderstandings about how such a process could "only" work that way (via "foresight", etc.)...
It's sad because there is much to be said about the theory of evolution, but it get's clouded by the adherents of the "religion" of evolution...
There is no such "religion of evolution", but there's a lot of false propaganda said about evolutionary biology by followers of actual religions.
Poing.
Junior, archival ping.
Yet you can't prove your earlier statement:
...because it evolved from a spider that lived on a more generalized insect diet (like most spiders)...
Without that proof, it is a matter of faith. Don't misunderstand me--it may very well have dined on the general insect population at one point. But there is no proof of that.
>>There is no such "religion of evolution", but there's a lot of false propaganda said about evolutionary biology by followers of actual religions.
Really? While there may not be a central diety, there is nevertheless a dogmatic *philosophy/ideology* concerning the theory of evolution.
The theory is treated as if it were infallible fact that simply cannot be questioned by rational people...
Yet in reality, it is simply a theory with many holes. Does this mean "creationists" are right? No.
>>No, we don't, because we know how the process actuall works
STOP THE TAPE! You *think* you know how the process works. This is my point, you treat the possible as actual instead of a hypothetical.
Also, if you read what you write, you give character to evolution which it does not have.
...I can't even go there...
Hey, I tried..LOL..whatever it is, it ain't a Fang..
>>Sure there is. It's called the scientific method. You are entitled to incorrectly believe that science is a religion
The scientific method is open to being wrong when there is reasonable uncertainty, weights all evidence, and doesn't declare contrary thinking an anathema.
This does not describe Evoluntionists for the most part.
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