Meet the spiders with 'exceptionally large' genitalia: Male tarantulas have evolved record-long sexual organs - to avoid being killed by feisty females during mating

Daily Mail​

7 days ago

They're some of the most awe-inspiring creatures in the animal kingdom.
But if these spiders weren't already extraordinary enough, scientists have just discovered they boast another impressive feature.
Four new species of tarantula have been identified in the Arabian Peninsula and the Horn of Africa - and they've evolved the longest genitalia of their kind.
Rather than a display of dominance, experts believe their record-breaking appendages have developed to help them avoid being killed by females during mating.
'Based on both morphological and molecular data, they are so distinct from their closest relatives that we had to establish an entirely new genus to classify them, and we named it Satyrex,' said Dr Alireza Zamani of the University of Turku, who led the study.
This name is a combination of two words - 'Satyr', which is a part-man, part-beast figure from Greek mythology with exceptionally large genitalia, and the Latin word 'rex' which means king.
'The males of these spiders have the longest palps among all known tarantulas,' Dr. Zamani said.
Palps - which look like two legs at the front of the body, near the face - are the specialized appendages used by male spiders to transfer sperm during mating.
Satyrex ferox, the largest of the four new species, has a legspan of about 14 cm (5.5 inches) and a male's palp can reach a length of 5 cm (2 inches).
This makes it almost as long as its longest legs, the researchers said.
'This species is highly defensive', Dr Zamani added.
'At the slightest disturbance, it raises its front legs in a threat posture and produces a loud hissing sound by rubbing specialized hairs on the basal segments of the front legs against each other.
'We have tentatively suggested that the long palps might allow the male to keep a safer distance during mating and help him avoid being attacked and devoured by the highly aggressive female.'
The name ferox, therefore, was chosen because it means 'fierce'.
As for the others in the group, the researchers named S. arabicus and S. somalicus after their respective regions of origin.
Meanwhile S. speciosus gets its name from its bright and beautiful coloration.
The new genus also includes an older species, S. longimanus, originally discovered in Yemen in 1903 and previously placed in a different genus.
All members of the new genus are fossorial, which means they live underground.
They can mostly be found in burrows at the base of shrubs or between rocks.
The study, published in the journal ZooKeys, is called 'Size matters: a new genus of tarantula with the longest male palps'.
WHAT ARE TARANTULAS AND WHAT DO WE KNOW ABOUT THEM?
Tarantulas are hairy and generally large spiders most commonly found in the US, Mexico and tropical America.
The largest species of tarantula are found in South America and belong to the genus Theraphosa.
They are almost three inches long (7.5cm) and has been known to even capture small avian prey.
Female tarantulas have a more stocky body than a male and is covered in a light brown or tan hair
The male is thinner and lankier, with black hair covering most of the body and reddish hairs on its abdomen.
Tarantulas have two body parts, the cephalothorax and the abdomen, eight walking legs and two pedipalps that are used for touching and moving prey.
Tarantulas are very sensitive to vibrations in the ground that may indicate the presence of prey or danger.
They are equipped with urticating hairs on their abdomen which can be released by kicking with the back legs; these hairs irritate the nose and eyes of would-be attackers.
Tarantulas live in dry, well-drained soils in open areas throughout the desert and grassland areas.
All North American tarantulas are ground-dwellers although some other species live in trees, cliffs, caves, or in crops like bananas and pineapples.
Some tarantula species are endangered because of habitat destruction and over-collection for the pet trade.
Tarantulas are nocturnal hunters. They feed primarily on insects like grasshoppers, beetles, other small spiders and arthropods, and will sometimes eat small lizards.
They will attempt to overcome anything of the right size that moves in their range. Most tarantulas have weak venom.