Tag Archives: spiders

Paleontologists discover new Cambrian age monster

Paleontologists recently unearthed another prehistoric crustacean – a predator with four eyes that lived in the Cambrian age and had a variety of claws with limbs, suggesting that the earliest arthropods may have experimented with the possibilities their limbs had.

The creatures has been identified as Yawunik kootenayi, and it lived about 508 million years ago, towards the end of the Cambrian Period in what geologists have termed the Paleozoic Era. While people generally think of dinosaurs when they think of prehistoric times, Yawunik was around well before them – less time elapsed between the date of your birth and when T-Rex died out, than there is between Yawunik and T-Rex.

Arguably, the animals Yawunik shared the Earth with were more intriguing than the dinosaurs too. It lived in an era when the major classes of animals – fish, insects, amphibians, first began to roam the Earth and the first sophisticated ecosystems began to take hold – an epic period of evolution known as the Cambrian Explosion, largely made possible by the oceans becoming fully oxygenated for the first time as levels of oxygen-absorbing marine bacteria began dying off.

Yawunik was part of a diverse group of shrimp, who shared the ocean with trilobites, spiny sea caterpillars appropriately named hallucigenia, and giant, predatory squid. The fossils bear a slight resemblance to modern crabs, one of its distant relatives, and have been compared to the size and shape of an empanada meat pie (6 inches, or 15 centimeters, long).

The discovery is just a matter of scratching the surface – it’s only the first of several discoveries made within a newly uncovered fossil bed in British Columbia’s Marble Canyon at Kootenay National Park. The Marble Canyon fossil beds were first discovered in 2012, and already may rival British Columbia’s world famous Burgess Shale for its wealth of soft-bodied fossils, preserved in a pristine state, according to scientists.

So far, they’ve found a myriad of Yawunik specimens among the shale, a flaky rock layer that results from layers of compressed mud. Since it was a predator, based on its size, it likely played an important part at the top of the food chain, according to the study’s lead study author C├ędric Aria, who is a graduate student of paleontology at the University of Toronto in Canada. Its role may have been akin to the function served by sharks, who are the apex predators of ocean reefs throughout the world.

“We actually found it on the second day [in 2012],” Aria said of the discovery. “It was one of the first really amazing discoveries.”

They named the arthropod Yawunik kootenayi both after the site and for the indigenous Ktunaxa people who long resided in the Kootenay area in which the Marble Canyon excavation site had been found. Yawu’nik in their language meant literally “where the rock stands,” referring to a covenant made between the people and the land in their creation myth.

The new species was first described on Friday in the journal Palaeontology.

Like modern shrimp, the Yawunik is of the group of animals known as leanchoiliid arthropods – a diverse phylum of animals that thrives to this day, making them among the most successful organisms on Earth with the wide variety of climates they have successfully adapted to. Today, they comprise roughly 80 percent of the known species on Earth. Closely related to insects, the phylum consists of shrimp, spiders, scorpions, and the closest modern relative of the trilobite – the horseshoe crab.

In light of these new discoveries, scientists now have yet to completely agree on how and when the basic segmented body and exoskeleton of the arthropod began to evolve – the components most often found in fossils. The reason is that like today’s arthropods, their Cambrian ancestors also had many legs, each set specialized for doing just one particular of any number of activities: whether it’s for eating, swimming, breathing, sensing or even attaching to a mate for reproducing.

A big difference between Yawunik and its modern cousins, however, is its front limbs. They might appear frail, but they were in fact a double threat – long claws which it used to both hunt and to grab onto its prey.

Both frontal limbs consisted of three long claws, two of them had long rows of teeth for trapping and holding onto food, similar to a lobster’s claws. Perhaps the strangest feature were sets of whiplike flagella jutting out of the tips of the claws. Aria suspects that the flagella acted like the front legs of a tarantula, allowing the Yawunik to seek out any passing fish or other organisms nearby, determining first how well they might taste. While Yawunik swam, it swept back and forth against the current with its limbs, which it could retract under its body and spread out when attacking prey.

“This dual function is very, very special, because it does not appear in modern forms.” Aria said. “If you take insects as an example, they have a very constrained body plan. But the constraints were not the same in Yawunik.”

the Yawunik is perhaps most closely related to the modern group chelicerates, which is comprised by spiders, horseshoe crabs and scorpions. This is because the claws are actually rather similar to those of living spiders. However, Aria suspects that this prehistoric beast is more likely part of a stem group, one that broke off of the direct ancestors of modern arthropods.

Since it was discovered back in 1909, over 200,000 fossils so far have been extracted from the Burgess Shale. The Marble Canyon quarry, just 25 miles down the road, could potentially be hiding even more prehistoric creatures and evolutionary links. The sites also date back to the same periods, separated only by 100,000 years – which to geologists is practically the blink of an eye when it comes to rock layers. However, the species found in both spots are vastly different, with the animals found at Marble Canyon more closely representative of creatures excavated at older sites discovered in China and Australia, than they resemble the finds in the Burgess Shale.

“This material is not only so well-preserved but it is so old that we are really tackling immense questions about the origins of modern ecosystems and modern animal groups,” Aria said.

The Royal Ontario Museum has plans to feature the Marble Canyon discoveries in a display currently under construction. Further analysis shows that the fossils actually contain a combination of preserved organic compounds, such as pieces of crustacean shell as well as calcified mineral deposits, which replaced its filaments after it died.

James Sullivan
James Sullivan is the assistant editor of Brain World Magazine and a contributor to Truth Is Cool and OMNI Reboot. He can usually be found on TVTropes or RationalWiki when not exploiting life and science stories for another blog article.

How Oral Sex Can Save Male Spiders

If you think dating is tough, it’s nothing compared to what male spiders have to go through – where getting laid can often mean getting eaten shortly after – a known practice that has given the Black Widow spider a rather fearsome reputation. Male Black Widows will sometimes catch and wrap a large insect in the web as a parting gift, a food item to distract their mate while they make their escape and avoid becoming the main course themselves. The Darwin’s Bark Spider (Caerostris darwini) has another idea for staying alive as long as it can. According to a recent report by a team of arachnologists (those who study spiders), male bark spiders may actually be providing oral sex to their female partners in order to avoid being eaten.

Simona Kralj-Fiser, a researcher at the Slovenian Academy of Sciences and Arts, led her team on a two-week field survey at the native home of this species in Madagascar, where they were able to observe the courtship of this intriguing species. The Darwin’s bark spider is already a popular interest by many in the field, considered to be one of the master artisans when it comes to web building – where they are said to build some of the most durable webs of any arachnid – spinning orb webs with anchor lines up to 82 feet in length. After limpet teeth, their silk is the second toughest known biological material, 10 times stronger than Kevlar.

Named for their resemblance to lichen, the bark spider is a rather recent discovery, found only in 2009, and so very little as actually known about this species’ ability to reproduce. This is what Kralj-Fiser and her colleagues initially came to investigate. They reported their findings last week at the annual Ethological Society’s “Causes and Consequences of Social Behavior” conference in Hamburg, Germany.

Like so many other male invertebrates, male bark spiders are significantly smaller than their female counterparts, and therefore are opportunistic maters. They were even observed mating with some of the younger females who had not yet grown fang cuticles and whose exoskeletons had not yet hardened over their bodies. For anyone who despises spiders already, this is probably the last thing you may want to read – but it is the result of an evolutionary advantage that males of this particular species are given over the females. Male bark spiders develop at faster rates, allowing them to defend their female partners as they compete against each other for rights to breed. However, this period of dominance is rather short lived.

“When a female’s cuticles harden and she can move and attack, she is able to prevent long copulations,” Kralj-Fiser explained on the New Scientist’s blog Zoo Logger.

At the conference, Krajl-Fiser explained a rather startling (although, perhaps unsurprising) statistic: When the females they observed reached their full maturity, 76 percent of them behaved aggressively towards the males. In about 35 percent of the observed cases, the females ended up cannibalizing their mates shortly after having sex. Despite the black widow spider’s reputation, females have only been shown to cannibalizes their mates only two percent of the time – quite a surprising contrast.

Recent research efforts have demonstrated that black widow males have developed the ability to sniff out their mate’s appetite for blood, allowing them to escape in time, the bark spider doesn’t appear to have adapted this useful ‘spidey-sense.’ The answer might cause you to never watch nature shows quite the same way again:

“Males nibble on female external genitals using their fangs, and then we observed that there was a liquid coming out of the fangs. We do not know what this liquid is, but it looks like digestive juices, which they usually secrete when eating,” Kralj-Fiser explained during the conference.

The researchers proposed a theory that by simply ‘going down’ on the female, the male bark spider keeps its mate calm before and after mating, a practice that helps ensure that the male won’t become dessert. Further supporting their theory is the observation that the males did not perform the same act on any of the younger, harmless females.

However, the researchers have noted that this proposal is hardly the only explanations for this ritual. For one example, female Darwin’s bark spiders will often mate with several males throughout their lives. Past research on other species of spider reveal that the males will often take measures to keep their mate content, as male black widows are known to do. However, this has been seen in non-cannibalistic species as well, as a way to be sure that they are not abandoned for another mate.

If you think the oral sex hypothesis sounds strange, females of the Leucauge mariana orb weavers seem to enjoy what arachnologists call a “hairy kiss.” A male spider who is a good ‘kisser’ has noticeably thick hairs on his mandibles which it uses to stimulate its mate. The mates of the successful ones are much more likely to stay around. For when it’s really serious, she will join him in forming a “genital plug,” in which a type of lubricant similar to that used for webs will signal that she has been claimed and prevent other males from having sex with her. As strange as it sounds, this has long been proposed as the arachnid equivalent to marriage.

Perhaps the bark spiders in performing this ritual are actually doing something similar to a genital plug rather than an oral sex act, but the research has yet to fully verify either claim.

James Sullivan
James Sullivan is the assistant editor of Brain World Magazine and a contributor to Truth Is Cool and OMNI Reboot. He can usually be found on TVTropes or RationalWiki when not exploiting life and science stories for another blog article.