Nine new species of Assassin spiders discovered

Feb 14, 2006 11:03 GMT  ·  By

Not all spiders build webs. Some of them are active hunters going after their prey with a frightening arsenal of jaws and venom. And not even their tiny size is capable to intimidate them. Some of the smallest such species, measuring only around 2 mm, have been discovered recently. They are among the so-called Assassin spiders that hunt other spiders.

They probably have a well deserved reputation of being among the most grotesque spiders in the world. They have elongated jaws that allow them to attack from a relative distance and they use their bizarre fangs to stab their prey and to inject the venom. These extremely elongated jaws are about ten times longer than the jaws of most spiders of their size.

Carrying around such jaws is no easy task and in order not to drag them on the ground they have also developed long necks. This way, they can attack their prey without getting to close to it.

Entomologist Charles Griswold from California Academy of Sciences and San Francisco State University graduate student Hannah Wood discovered the nine new species of Assassin spiders as they were documenting the spiders of Madagascar. For the past few years, since 2000, they have processed over 2 million arthropod specimens. Prior to their study, only about a dozen Assassin spider species were known.

Hannah Wood has also conducted molecular and morphological studies. To their surprise, the DNA data revealed that the elongated necks of these spiders had evolved independently at least two times. This is called "convergent evolution". Thus, her findings suggest that the need to strike out at prey from a distance was sufficiently important that it encouraged the evolution of extended body parts again and again.

The fossil record shows that Assassin spiders had once lived all over the planet, but today they exist only in Australia, South Africa, and Madagascar. The venom of spiders, although deadly to insects (by the way, spiders are not insects) is relatively harmless to mammals (unlike the venom of some insects).

Photo credit: Jeremy Miller