Caerostris darwini
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Net of Caerostris darwini |
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| Kuntner & Agnarsson , 2010 |
Caerostris darwini , known in English as Darwin's bark spider (" Darwin's bark spider "), is a spider from the family of real orb web spiders (Araneidae). It produces one of the largest known wheel nets, the anchor lines of which can reach lengths of up to 25 meters. The spider was discovered in Madagascar in the Andasibe Mantadia National Park and receivedthe specific epithet darwini in honor of the naturalist Charles Darwin ; the species description appeared exactly 150 years after the publication of Darwin's work The Origin of Species on November 24, 2009.
features
The species in the genus are known as bark spiders because of their coloration, pattern and morphology. They imitate pieces of bark, twigs, thorns and similar plant material ( mimetic ). Like other species of the genus Caerostris , Caerostris darwini shows extreme sexual dimorphism ; Females reach a body length of 17.9 to 22 mm, males remain significantly smaller with 5.7 to 6.1 mm.
The genus has only been poorly treated taxonomically so far. Only females are known of many species, as the males live very hidden. In the course of the expeditions to research C. darwini a few more species were apparently discovered. Therefore, in the first description to define the species, both taxonomic methods and genetic methods were used for verification. The males are difficult to find because of their hidden way of life, but they are indispensable for securing the species status and for phylogeny.
The genus differs from all other genera in the family in that both prosoma and opisthosoma are broader than long. In the female paratype of C. darwini it is 6.2 mm in length and 8.6 mm in width for the prosoma, 12.8 mm in length and 14.8 mm in width for the opisthosoma, and 3.0 in the male paratype for the prosoma mm long by 3.1 mm wide and for the opisthosoma 3.3 mm long and 4.3 mm wide. The head area of the prosoma is significantly higher than the thoracic region. In C. darwini, the carapace has two lateral, pointed widenings (other species only have a pair of tips), the eyes are typically divided into two "eye mounds" and there is another "outgrowth", also typical of the species, a rostrum . The abdomen is flattened and also has pointed growths, which in C. darwini are only weakly developed in contrast to some other species of the genus. The tibiae , except for the third pair of legs, are also flattened. The leg hair is very pronounced, the femora of the fourth pair of legs have spatulate, flattened hair.
The epigyne is heavily sclerotized and has a pair of hook-shaped structures, the position of which allows a genital morphological differentiation from the other species of the genus. The copulation chambers are clearly separated and thus also distinguish C. darwini from all other species of the genus. The bulbs are large, the subtegulum huge, a paracymbium is missing and the embolus is completely enclosed by a sclerite . The conductor (a structure at the tip of the globe) is more pronounced than in the other species of the genus, has a straight tip, the pars pendula are shorter than in other species, the embolus is longer and spatulate.
The basic color of the females is black with white hair, that of the males red and light brown with white hair on the prosoma, opisthosoma and the distal parts of the legs, palps and chelicerae .
Way of life
The spider species was found together with two as yet undetermined flies, which are obviously in a kleptoparasitic relationship with it. These flies often feed on the spider's fangs and also on the prey before the spiders wrap it up. Several times the spiders have been observed chasing the flies away when they landed on the spider's prey.
Network construction
As far as we know today, spider silk of this type is the toughest biomaterial ever examined . It is more than ten times stronger than a comparable strand made of Kevlar . The average tenacity of the fibers is 350 MJ / m 3 , some reach up to 520 MJ / m 3 . This means that Caerostris darwini's spinning silk is twice as strong as any other known spinning silk.
The webs of this spider are not only remarkable because of their large spans (up to 25 m), they are also the largest known wheel webs at all; they reach sizes of up to 2.8 m 2 . Nephila komaci , which was discovered in 2009, and several other species in the genus Nephila build nets that grow to be about a square meter.
According to Ingi Agnarsson , director of the Zoological Museum at the University of Puerto Rico , the webs of these spiders occupy a unique ecological niche : “They build their webs so that the wheel hangs directly over the water of a river or lake, a habitat that none other spider can use. ”This position of the web allows the spiders to catch prey flying over the water; in some nets up to 32 mayflies were found at the same time. The strong threads and the large net probably developed with the introduction of the species into the unusual habitat. Scientists have investigated how the spiders can stretch such large webs over bodies of water, namely they have to stretch anchor lines from one bank to the other. This riddle seems solved. The animals act like bungee jumpers. They attach the starting thread to branches or leaves and drop into the depths. When hanging, the spiders secrete the threads up to 25 meters long, which are blown by the wind and often stick to the other side of the river. The threads successfully crossing the river are tensioned and then the net is built up.
Web links
Caerostris darwini in the World Spider Catalog
Individual evidence
- ↑ a b c d Matt Walker: Gigantic spider's web discovered in Madagascar , BBC News . September 16, 2010. Retrieved September 17, 2010.
- ↑ a b c d e f g h Matjaž Kuntner & Ingi Agnarsson: Web gigantism in Darwin's bark spider, a new species from Madagascar (Araneidae: Caerostris ) . ( PDF ) In: American Arachnological Society (Ed.): The Journal of Arachnology . 38, 2010, pp. 346-356.
- ↑ Kuntner, M. 2007. A monograph of Nephilengys, the pantropical 'hermit spiders' (Araneae, Nephilidae, Nephilinae). Systematic Entomology 32: 95-135.
- ↑ a b c Archive link ( Memento of the original from May 18, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ [1] ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ↑ a b Ingi Agnarsson, Matjaž Kuntner & Todd A. Blackledge: Bioprospecting finds the toughest biological material: extraordinary silk from a giant riverine orb spider . In: PLoS ONE . 5, No. 9, 2010, p. E11234. doi : 10.1371 / journal.pone.0011234 . PMID 20856804 . PMC 2939878 (free full text).
- ^ Matjaž Gregorič, Ingi Agnarsson, Todd A. Blackledge, Matjaž Kuntner: How Did the Spider Cross the River? Behavioral Adaptations for River-Bridging Webs in Caerostris darwini (Araneae: Araneidae) . In: PLoS ONE . 6, No. 10, 2011, p. E26847. doi : 10.1371 / journal.pone.0026847 . PMID 20856804 .
