This video says about itself:
This video says about itself:
A long-tailed spider (Ariamnes cylindrogaster, family Theridiidae) moving along a long horizontal non-sticky line between the branches. This species is known to be a spider-hunting spider (araneophagy). I’m not sure if this one was spinning its unique simplistic web to catch other spiders. Eventually, the spider stretched itself as if mimicking a green pine needle hanging in the air. Filmed in the morning (9:23 am – 9:28 am) of early October 2015 in Japan.
Hawaiian stick spiders re-evolve the same three guises every time they island hop
March 8, 2018
We don’t usually expect evolution to be predictable. But Hawaiian stick spiders of the Ariamnes genus have repeatedly evolved the same distinctive forms, known as ecomorphs, on different islands, researchers report on March 8 in the journal Current Biology. Ecomorphs — which look the same and live in the same kinds of habitats, but aren’t as closely related as they appear — are surprisingly rare, and the researchers hope that these newly described ones might help us understand what’s behind this strange evolutionary pattern.
The stick spiders live in the forests of the Hawaiian archipelago, over 2,000 feet above sea level, on the islands of Kauai, Oahu, Molokai, Maui, and Hawaii. Although they’re nocturnal arthropods that can’t see well, they’re still brightly and distinctly colored. “You’ve got this dark one that lives in rocks or in bark, a shiny and reflective gold one that lives under leaves, and this one that’s a matte white, completely white, that lives on lichen“, explains Rosemary Gillespie, an evolutionary biologist at the University of California, Berkeley.
These different colorings allow the spiders to camouflage themselves against specific similarly colored surfaces in their respective habitats and avoid their major predator, birds called Hawaiian honeycreepers. But what’s remarkable is that as the spiders have moved from one island to the next during their evolutionary history, these same forms have evolved over and over again. This process produces new species that are more closely related to spiders of different forms on the same island than they are to lookalikes from other islands.
And it happens fast — at least in evolutionary time. A dark spider that hops from an old island to a new one can diversify into new species of dark, gold, and white spiders before gold and white spiders from the old island have time to reach the new one. “They arrive on an island, and boom! You get independent evolution to the same set of forms”, Gillespie says.
It’s also important that these forms are the same each time. “They don’t evolve to be orange or striped. There isn’t any additional diversification”, she says. This, she believes, suggests that the Ariamnes spiders have some sort of preprogrammed switch in their DNA that can be quickly turned on to allow them to evolve rapidly into these successful forms. But how that process might work is still unclear.
It hasn’t really been studied, because ecomorphs aren’t common. “Most radiations just don’t do this”, she says. Typical adaptive radiation, like with Darwin’s finches, usually produces a wide diversity of forms. And convergent evolution, where two different species independently evolve the same strategy for fulfilling a certain niche, doesn’t usually happen repeatedly. There are just a few good examples of this kind of fixed pattern of repeated evolution: the Ariamnes spiders, the Hawaiian branch of the Tetragnatha genus of long-jawed spiders, and the Anolis lizards of the Caribbean.
“Now we’re thinking about why it’s only in these kinds of organisms that you get this sort of rapid and repeated evolution,” Gillespie says. While it’s a question she’s still working on, the three lineages do all live in remote locations, have few predators, and rely on their coloring to camouflage them in a very particular habitat. They are also all free living in the vegetation: neither of the two spider groups builds a web, which means that they, like the lizards, are free to move about and find the kind of habitat they require for camouflage. She hopes that examining what these groups have in common will “provide insight into what elements of evolution are predictable, and under which circumstances we expect evolution to be predictable and under which we do not.”
She also hopes that this research will help the world to understand how much Hawaii’s vulnerable forests still have to offer. “Often, I hear people saying, ‘Oh, Hawaii’s so well studied. What else is there to look at?’ But there are all these unknown radiations that are just sitting there, all these weird and wonderful organisms. We need everyone to understand what’s there and how extraordinary it is. And then we need to see what we can do to protect and conserve what still waits to be described.”
This 2015 video says about itself:
Australian hospitals are in desperate need of live funnel web spiders to make anti-venom. Spider expert Stacey Denovan shows the safest way to catch them.
From San Diego State University in the USA:
World’s most venomous spiders are actually cousins
Study finds the deadly Australian funnel-web spiders and mouse spiders are more closely related than previously thought
February 15, 2018
Two groups of highly venomous spiders might be seeing more of each other at family reunions. A new study led by San Diego State University biologist Marshal Hedin has found that two lineages of dangerous arachnids found in Australia — long classified as distantly related in the official taxonomy — are, in fact, relatively close evolutionary cousins. The findings could help in the development of novel antivenoms, as well as point to new forms of insecticides.
The spiders in question are those from the families Atracinae and Actinopodidae and include Australian funnel-web spiders and eastern Australian mouse spiders, respectively. One member of Atracinae, Atrax robustus, is considered by many to be the most venomous spider in the world.
“A reasonable number of people get bitten every year, but basically nobody dies from it anymore because of the wide availability of antivenom”, Hedin said.
Historically, the spiders were thought to have diverged from a common ancestor more than 200 million years ago and therefore were only distantly related. Based on their anatomy and other traits, funnel-web spiders and mouse spiders closely resemble other species of spiders known to be distantly related. Yet based on their highly similar venom — the same antivenom can treat bites from both Atricinae and Actinopodidae — many biologists suspected these spider groups might be more closely related than previously thought.
“The funnel-webs always were an uncomfortable fit in their taxonomic place”, Hedin said. “I could see the writing on the wall.”
So he and colleagues, with help from biologists in New Zealand and Argentina, collected new spiders from both branches throughout Australia, sought out museum specimens and raided Hedin’s own collection to come up with dozens of specimens representing various branches of spiders both closely and distantly related. Then the scientists sequenced large chunks of the spiders’ genomes, looking for genetic patterns that would reveal how the species are related to one another.
After this analysis, the researchers discovered that the Australian funnel-web spiders and mouse spiders were, in fact, fairly closely related, although it’s unclear exactly when they diverged from a common ancestor. In addition to solving that mystery, Hedin and colleagues discovered the existence of three entirely new taxonomic families of spiders. The researchers published their findings last month in Nature Scientific Reports.
Online taxonomy databases have already begun updating to reflect these changes, Hedin said. “We’ve convincingly resolved this relationship.”
Knowing these spiders’ ancestry could help scientists devise a kind of general-purpose antivenom to treat bites from a wide variety of related spider species, Hedin explained. In addition, funnel-web and mouse spider venom is notable for containing many different types of peptide molecules, including some that specifically target insects. Knowing more about how their venom evolved could help bioengineers to design bio-insecticides that target insects but are harmless to vertebrate animals.
This video says about itself:
7 March 2014
Pelican spiders hunt other spiders, plucking at their webs to lure the prey closer and then using long necks and jaws to hold them at a distance. Read more at sciencenews.org.
From the Smithsonian in the USA:
Spider eat spider: Scientists discover 18 new spider-hunting pelican spiders in Madagascar
Discovery highlights the case for conserving a shrinking, unique biodiversity hotspot
January 11, 2018
Summary: Scientists examined and analyzed hundreds of pelican spiders both in the field in Madagascar and through study of pelican spiders preserved in museum collections. Their analysis sorted the spiders studied into 26 different species — 18 of which have never before been described. The new species add to scientists’ understanding of Madagascar’s renowned biodiversity, and will help scientists investigate how pelican spiders’ unusual traits have evolved and diversified over time.
In 1854, a curious-looking spider was found preserved in 50 million-year-old amber. With an elongated neck-like structure and long mouthparts that protruded from the “head” like an angled beak, the arachnid bore a striking resemblance to a tiny pelican. A few decades later when living pelican spiders were discovered in Madagascar, arachnologists learned that their behavior is as unusual as their appearance, but because these spiders live in remote parts of the world they remained largely unstudied — until recently.
At the Smithsonian’s National Museum of Natural History, curator of arachnids and myriapods Hannah Wood has examined and analyzed hundreds of pelican spiders both in the field in Madagascar and through study of pelican spiders preserved in museum collections. Her analysis, focused on spiders of the Eriauchenius and Madagascarchaea genera, sorted the spiders she studied into 26 different species — 18 of which have never before been described. Wood and colleague Nikolaj Scharff of the University of Copenhagen describe all 26 pelican spider species in the Jan. 11 issue of the journal Zookeys.
Wood says pelican spiders are well known among arachnologists not only for their unusual appearance, but also for the way they use their long “necks” and jaw-like mouthparts to prey on other spiders. “These spiders attest to the unique biology that diversified in Madagascar“, she said.
Pelican spiders are active hunters, prowling the forest at night and following long silk draglines that lead them to their spider prey. When a pelican spider finds a victim, it swiftly reaches out and impales it on its long, fang-tipped “jaws,” or chelicerae. Then it holds the capture away from its body, keeping itself safe from potential counterattacks, until the victim dies.
Today’s pelican spiders are “living fossils,” Wood says — remarkably similar to species found preserved in the fossil record from as long as 165 million years ago. Because the living spiders were found after their ancestors had been uncovered in the fossil record and presumed extinct, they can be considered a “Lazarus” taxon. In addition to Madagascar, modern-day pelican spiders have been found in South Africa and Australia — a distribution pattern that suggests their ancestors were dispersed to these landmasses when the Earth’s supercontinent Pangaea began to break up around 175 million years ago.
Madagascar is home to vast numbers of plant and animal species that exist only on the island, but until recently, only a few species of pelican spiders had been documented there. In 2000, the California Academy of Sciences launched a massive arthropod inventory in Madagascar, collecting spiders, insects and other invertebrates from all over the island.
Wood used those collections, along with specimens from other museums and spiders that she collected during her own field work in Madagascar, to conduct her study. Her detailed observations and measurements of hundreds of specimens led to the identification of 18 new species — but Wood says there are almost certainly more to be discovered. As field workers continue to collect specimens across Madagascar, “I think there’s going to be a lot more species that haven’t yet been described or documented,” she said.
The spiders Wood personally collected, including holotypes (the exemplar specimens) for several of the new species, will join the U.S. National Entomological Collection at the Smithsonian, the second-largest insect collection in the world, where they will be preserved and accessible for further research by scientists across the globe.
All of the pelican spiders that Wood described live only in Madagascar, an island whose tremendous biodiversity is currently threatened by widespread deforestation. The new species add to scientists’ understanding of that biodiversity, and will help Wood investigate how pelican spiders’ unusual traits have evolved and diversified over time. They also highlight the case for conserving what remains of Madagascar‘s forests and the biodiversity they contain, she says.
Funding for this study was provided by the Danish National Research Foundation and the National Science Foundation.