FUNNEL-WEB SPIDER AND MOUSE SPIDER MORE CLOSELY RELATED THAN PREVIOUSLY THOUGHT
A report from Marshal Hedin at San Diego State found that two venomous spider species are more closely related than previously thought. The report identified them as the funnel-web spider and mouse spider.
The study analyzed the Atrax robustus and Missulena species of spiders. While funnel-webs spiders are considered one of the deadliest species, the mouse spider is also dangerous but not lethal. The researchers studied the venom protein from the two spider species and found it to be similar.
When scientists developed antivenoms to treat bite victims of the funnel-web spider, they discovered that the antivenom could also be used on victims of mouse spider bites. The researchers, led by Hedin, collected subgenomic DNA from several species of the two spiders, and they determined that the two species are closely related.
Their bases in reaching the conclusion that the funnel-web spider and mouse spider are closely related were all the biological similarities between the two species such as the venom and antivenom. Hedin attributed it to a common ancestor between the two species in the report titled “Phylogenomic reclassification of the world’s most venomous spiders (Mygolomorphae, Atracinae), with implications for venom evolution.”
The two species are native to Australia and were misplaced in the genetic tree that led to the reclassification, The Daily Aztec reported. The lab said that the study refutedly shook up the phylogenic tree.
The spiders were believed to have diverged from a common ancestor more than 200 million years ago.
Reconstructing the ancestral venom protein
Hedin said that given the knowledge on what the venom proteins look like in each of these two taxa, researchers can actually reconstruct the ancestral venom protein that would be found in the common ancestor. Scientists can actually make antivenom that would target it so that the result would be more of a general purpose antivenom that works for all of the potentially dangerous spiders.
Hedin disclosed that a reasonable number of people get bitten every year by the two species, but nobody dies from the bite anymore because of the wide availability of the antivenom, Newscenter reported.
Shahan Derkarabetian, the co-author of the report, said that when the relationship between the two species of spiders was confirmed, they were both surprised simultaneously and expected it. There were, after all, previous studies that indicated the two species might be closely related, although their results were never 100 percent conclusive.
However, with the data they collected, the scientists were able to provide enough support for the close relationship that would allow the researchers to say with certainty that the funnel-web spider and the mouse spider are each other’s closest relatives.
It helped that the researchers were able to use museum specimens for the species, Derbarabetian, a graduate of San Diego State University who joined Harvard University recently in a postdoctoral research position, said. He considers it exciting to have the ability to include specimens that have been sitting in museums for up to 30 years.
He pointed out that for genetic analysis like this, typically, researchers need fresh samples preserved specifically for genetic work. Derbarabetian said that most standard museum pieces are not preserved this way. But the laboratory method they used allowed the researchers to sequence the museum specimens and provided the scientists a lot of very usable data.
With assistance from biologists in New Zealand and Argentina, Hedin and his team collected new spiders from both branches throughout Australia, while they also sought out museum specimens and used his own collection to come up with dozens of specimens that represented various branches of spiders which were both closely and distantly related.
While the analysis confirmed the two species are closely related, it is still unclear exactly when the funnel-web spider and the mouse spider diverged from a common ancestor.
Hedin, besides studying spider species, also looks into the diversity and evolution of other arachnid species. For instance, Casey Richart, a doctoral student, focuses on millipedes and harvestmen. It is an order of arachnids which do not produce silk or venom.
The two species are some of the earliest species to live on the land, however, their movement and disbursement are limited. The scientists could test the older and more recent evolutionary and biogeographic hypothesis because of the early, evolutionary history.
The lack of movement by the two species allowed researchers to ask a very recent hypothesis on the effects of the last glacial maximum during the Pleistocene on the organisms. Richart said he tried to correlate what the evolutionary scenarios are that were affected by its evolution.
Hedin also discovered the existence of three entirely new taxonomic families of spiders which adds to the more than 35,000 distinct species of spiders in the world, IBT reported.
The team published the result of their study in February in Nature Scientific Reports. To reflect these changes, online taxonomy databases have already started to update, Hedin said.
[researchpaper 리서치페이퍼= Vittorio Hernandez 기자]