Underwater spider uses air bubble as oxygen tank

The only spider to spend almost all of its life underwater creates a bubble of air in its web, which actually extracts oxygen from the surrounding water. This allows the spiders to stay in their aquatic webs for more than a day at a time.

By LiveScience

From: http://www.mnn.com/

SCUBA SPIDER: A diving bell spider has snagged a water flea and is consuming the prey inside the air-bubble chamber. (Photo: Stefan Hetz)

Like eight-legged scuba divers, some spiders can breathe underwater using an air bubble as an oxygen tank of sorts. Now, scientists have figured out some of the fascinating details of this arachnid diving bell, including that it can give the spiders more than a day's worth of air.

While scientists knew diving bell spiders (Argyroneta aquatica) — spanning just 10 to 15 millimeters in length — used an air bubble to breathe underwater in lakes and ponds, this is the first study that measures exactly how that happens and calculates how long the spider could stay underwater before resurfacing to replenish its bubble with fresh air.

"We were surprised how low the oxygen in the bubble could get before the spiders venture to the surface," study researcher Roger Seymour, of the University of Adelaide, told LiveScience. [See images of the underwater spiders]

Diving bells

Seymour and Stefan Hetz from Humboldt University in Germany, brought diving spiders into the lab, placing them into tanks mimicking conditions of a stagnant pond on a hot summer's day — revealing how the animals fare in extreme, low-oxygen conditions.

Immediately, most of the spiders constructed webs between the pondweeds and aquarium sides. Then each spider came to the surface to collect a large air bubble held between the hydrophobic (water-repelling) hairs on its abdomen and its rear legs. Webbing was placed around the lower sides of this gas chamber, which the spiders entered from the bottom.

Some spiders created chambers just large enough to enclose their abdomens, leaving their rears and rear legs hanging out; others had larger bubbles that enclosed their entire bodies. For instance, the spiders would enlarge the bubble by laying down more web and adding air before pulling just-snagged prey into the chamber.

Tiny sensors measured oxygen levels inside the bubbles and in the surrounding water, finding that the spiders extracted oxygen from the water as if it were a gill; the sensors also showed that the spiders could survive on very low oxygen levels.

Shrinking bubbles

Even so, the bubble shrinks over time and forces the spider to resurface for a fresh one. Like the atmosphere, the bubble contains primarily both oxygen and nitrogen, and as the spider takes oxygen from the bell, the nitrogen must increase. That increase pushes nitrogen out of the bubble by diffusion. Eventually, the lab spiders had to resurface.

The tiny spiders still were able to sit tight for more than a day, much longer than previous estimates suggesting a 20-minute underwater stint.

"It is advantageous for the spiders to stay still for so long without having to go to the surface to renew the bubble, not only to protect themselves from predation, but also so they don't alert potential prey that come near," Seymour said.

The research is detailed in the current issue of the Journal of Experimental Biology.

This article was reprinted with permission from LiveScience.

Trippy Bowls Inspired By Spiders On Drugs

Trippy Bowls Inspired By Spiders On Drugs

by Stephen Messenger

from http://www.treehugger.com/

Photos via Guillaume Lehoux

Spiders are one of nature's most capable engineers, crafting their delicate webs with uncanny precision, making it seem so effortless -- but when they get high on drugs, boy is it a different story. Once, in order to test the effects of psychoactive substances on the behavior of living things, NASA doped-up several spiders and watched them build. What resulted were some undeniably trippy web patterns. Now, one designer has replicated those drug-inspired creations into some unique-looking bowls, sure to leave you a bit dazed and confused.

During the testing, several spiders were given doses from one of four different substances: marijuana, benzedrine, caffeine or chloral hydrate. Interestingly, the web patterns the intoxicated spiders then produced seemed to reflect their altered state, deviating significantly from their standard web design.

Despite the rather cruel nature of those NASA experiments, French designer Guillaume Lehoux found the outcome to be fascinating and began working on the SOD_project, which of course stands for Spiders On Drugs.

The designer explains his motivation behind the project:

This experience seemed interesting to me for the visual and graphic aspects of its results. The webs produce by spiders offer something rare: a tangible and comparable visualization of the way some drugs affect the behavior of a living being.

My designer reflection focused on one side on how to reinvest the patterns of the webs of the experiment in one or more objects in volume and on the other side, the reflection was on the search for a typology of objects relevant to the environment of the experiment, namely the science/medicine, the drugs and the spiders.

The normal web (sober spider) is a dense and regular pattern. The design of the web, made of concentric circles and diagonals, seems to be governed by a general idea.

Marijuana affects concentration of the spider. Parts of the web, especially toward the outside, so late in the making of the web, are incomplete or missing.

Caffeine greatly disturbs the spider which is no longer capable of doing anything other than a fully heterogeneous and disorderly web.

Benzedrine, stimulating substance, causes great excitement among the spider. It works hard to weave his web but his haste causes significant omissions in the construction.

Chloral hydrate, sedative substance, slows down the actions of the spider. It fells asleep quickly without completing the making of the web. That explains the very brief appearance of this one.

Following the spirit of the spiders' original creations, Lehoux designed his webs to 'trap' or hold things as well, finding use as fruit bowls and loose change trays. Still, I suspect they'll serve better as a conversation piece -- or a place to store your old Pink Floyd cassettes.

NOTE: Just to clarify, this post was written to showcase one artist's provocative work, the focuses of which centers on the results from a controversial series of experiments performed by NASA some years ago. It should be said that I do not condone the animal-testing that inspired these designs, nor does, necessarily, the artist. I believe that the lives of all creatures, even common spiders, should be treated with respect and dignity.

Creepy Crawlies Up Close [PICS]

telegraph.co.uk — Amazing Scanning Electron Microscope pictures of insects and spiders.

click here to see these Alien looking bugs: Creepy Crawlies

Even-More-Gigantic Giant Orb Spider Discovered

• By Hadley Leggett

Scientists have found the world’s largest species of golden orb-weaver spider in the tropics of Africa and Madagascar. The discovery marks the first identification of a new Nephila spider since 1879.

Females of the new species, Nephila komaci, measure a whopping 4 to 5 inches in diameter, while the male spiders stay petite at less than a quarter of their mate’s size. So far, only a handful of these enormous arachnids have been found in the world.

“We fear the species might be endangered, as its only definite habitat is a sand forest in Tembe Elephant Park in KwaZulu-Natal,” ecologist Jonathan Coddington of the Smithsonian’s National Museum of Natural History said in a press release. “Our data suggest that the species is not abundant, its range is restricted, and all known localities lie within two endangered biodiversity hotspots: Maputaland and Madagascar.”

The first potential specimen of the new species was uncovered by Coddington and his colleague Matjaz Kuntner of the Slovenian Academy of Sciences and Arts in 2000. They found a huge female orb-weaver among a museum collection of spiders in Pretoria, South Africa, and she didn’t match the description of any known spider. Although they hoped the unusual-looking giant represented a new species, several dedicated expeditions to South Africa failed to find any live spiders of a similar description.

Then, in 2003, a second specimen from Madagascar was found at a museum in Austria, suggesting that the first spider hadn’t been a fluke. But despite a comprehensive search through more than 2,500 samples from 37 museums, no additional specimens turned up, and the researchers assumed the biggest of all orb-weavers was probably extinct.

Finally, three live spiders have been found to prove the scientists wrong: A South African researcher found two giant females and one male in Tembe Elephant Park, proving that the new species was not extinct, just incredibly rare.

“Only three have been found in the past decade,” Kuntner wrote in an e-mail to Wired.com. “None by our team, despite focused searches. Only an additional two exist in old museum collections. Compared to thousands of exemplars of other Nephila species in museums, that is disproportionately rare.”

The two biologists named the new species after Andrej Komac, a scientist friend of Kuntner’s who died in an accident near the time of the discoveries.

Like all Nephila spiders, females of the new species spin huge webs of golden silk, often more than 3 feet in diameter. In the report of the discovery of this rare spider, published Tuesday in PLoS One, the researchers also addressed the evolution of the dramatic size difference between male and female orb-weavers.

By mapping out the evolutionary tree of all known orb-weaver species, the scientists discovered that as the spiders evolved, females got bigger and bigger, while males stayed roughly the same size.

“It is good for females to be big, because they can lay so many more eggs,” Coddington wrote in an e-mail. In addition, large size probably helps females avoid being eaten by predators.

“Relatively few groups can safely pluck an orb-weaving spider from its web,” he wrote, “because you have to be able to hover to do so (hummingbirds, wasps, damselflies come to mind). None of these are large enough to tackle an adult Nephila, or even a large juvenile.”

Males, on the other hand, are better off staying small and reaching sexual maturity at a young age. Because males spend most of their time underground, hunting for a mate is one of the most dangerous activities they undertake.

“So males risk everything to find, probably, just one, huge female, inseminate her, and probably do not willingly leave her web to search for another,” Coddington wrote. “Nothing about sex says males must be big.”

Image 1: Tiny male Nephila spiders are dwarfed by their female counterparts. Matjaz Kuntner and Jonathan Coddington/PLoS ONE.
Image 2: A giant golden orb-web exceeding 1 meter in diameter, spun by a Nephila inaurata spider. M Kuntner.

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