Spider-tailed Horned Viper: A Viper that will Trigger your Arachnophobia

The spider-tailed horned viper (Pseudocerastes urarachnoides) is a species of viper belonging to the genus Pseudocerastes, commonly known as "false-horned vipers." Most of their appearance is quite similar to that of other members of their genus, featuring horn-like scales above the eyes—a trait common among all members of the genus. However, what truly sets them apart and makes them the most well-known members of their genus are their unique tails.Their tails possesses a bulb-like end bordered by long, drooping scales, which give it the resemblance of a spider, hence thier name.They use this feature as bait to lure their prey.

Spider-tailed Horned Viper  

(Pseudocerastes urarachnoides )

Pseudocerastes urarachnoides by Laura Bok  via Flickr

    

Scientific classification
Kingdom	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Viperidae
Genus:	Pseudocerastes
Species:	P. urarachnoides

The spider-tailed horned viper (Pseudocerastes urarachnoides) is a species of viper belonging to the genus Pseudocerastes, commonly known as "false-horned vipers." Most of their appearance is quite similar to that of other members of their genus, featuring horn-like scales above the eyes—a trait common among all members of the genus. However, what truly sets them apart and makes them the most well-known members of their genus are their unique tails.Their tails possesses a bulb-like end bordered by long, drooping scales, which give it the resemblance of a spider, hence thier name.They use this feature as bait to lure their prey.

The specific name, urarachnoides, is derived from Ancient Greek (οὐρά tail + ἀράχνη spider + οειδής like), and refers to this snake's spider-like tail tip, as does the common name, spider-tailed horned viper. 

 

The viper species is native to the western regions of Iran and the border area with Iraq. Its first sighting dates back to 1968 during the Second Street Expedition. Initially, it was described as Pseudocerastes persicus, with the abnormal appearance of its tail attributed to either parasites, deformities, or tumors. Another specimen was found in 2003, leading to the official description of P. urarachnoides in 2006.

Hunting Strategy

Spider-tailed Viper's tail's closeup by Matthieu Berroneau via Flickr

The spider-tailed horned viper utilizes its spider-like tail as a lure to attract insectivorous birds, such as larks, to within striking range. The snake waves its tail tip, mimicking the movements of a spider, which entices curious birds to investigate the potential prey. Once a bird approaches, the viper strikes with lightning speed, delivering a venomous bite to incapacitate its prey. This hunting behavior has been observed and documented in field studies, confirming the effectiveness of the viper's unique tail as a lure.

The venom of Pseudocerastes urarachnoides contains Cytotoxins

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Cytotoxins

The Cytotoxins are substances produced by living organisms, such as bacteria or certain cells in the body, which can cause damage or destruction to cells. These toxins have the ability to disrupt vital cellular processes, leading to cell death. They can target specific types of cells or have a more generalized effect. Cytotoxins are also present in snake venom. Snake venoms contain a variety of cytotoxins that can cause damage to cells and tissues.
Some examples of cytotoxins found in snake venom include hemotoxins, which destroy red blood cells and disrupt blood clotting, and myotoxins, which can damage muscle tissue.

. Unlike its sister species, the venom of the spider-tailed horned viper has minor neurotoxic effects. It exhibits a remarkable Procoagulant

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Procoagulant

Procoagulant refers to a substance or agent that promotes blood clotting. When there is an injury or damage to blood vessels, the body initiates a process called coagulation, or clotting, to prevent excessive bleeding. Procoagulants enhance this process by activating certain components in the blood that lead to the formation of blood clots.

For instance, tissue factor is a prominent procoagulant that is released in response to tissue damage, initiating the clotting cascade. Another example is thrombin, a key enzyme that converts fibrinogen into fibrin, the insoluble protein responsible for forming the meshwork of a blood clot.

activity, leading to rapid coagulation within approximately 13 seconds. Interestingly, this venom is highly specialized for birds, indicating the viper's preference for avian prey. However, it also affects mammals and amphibians to a significant extent, with toads potentially being an important food source for juvenile vipers. While the venom of P. urarachnoides has been found to have coagulant effects on humans in laboratory studies, no wild envenomation cases have been recorded, and the severity of its effects on humans remains uncertain. 

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Iranian spider-tailed viper's tail
via Seven Worlds One Planet, BBC

Habitat and Distribution

Geographic distribution of Pseudocerastes urarachnoides by rbrausse

The spider-tailed horned viper, which inhabits the western parts of Iran and the eastern part of Iraq, primarily in the Zagros Mountains, shares its distribution with other species in specific regions. In Gilan-e Gharb, next to Qasr-e Shirin, Kermanshah, it overlaps with P. fieldi, while in Bina and Bijar, Ilam Province, it coexists with P. persicus.

They favour higher elevations characterized by Gypsum

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Gypsum

Gypsum is a mineral that is found in the Earth's crust. It looks like a white rock and feels soft like chalk. When heated, gypsum loses water and becomes a powder called plaster of Paris. This powder can be mixed with water to make a paste, which hardens into a solid when it dries. People use gypsum to make things like plaster, wallboards, and sculptures. It is also used to improve soil quality in farms and gardens. Gypsum is a versatile and useful mineral.

formations and seeks refuge in deep cracks and holes within the rock. These microhabitats play a crucial role in providing the snake with the essential humidity and moisture retention required to endure the scorching summer months. 

During the course of the day, the viper can often be found seeking shade under bushes, making the most of its surroundings.

Conservation Status

The spider-tailed horned viper's current range is relatively small and shrinking, making it a species of conservation concern. Its preference for specific gypsum-rich habitats further restricts its distribution. Protecting these unique ecosystems and raising awareness about the viper's conservation needs are crucial for ensuring the survival of this remarkable species.

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References

• Fathinia, B., Rastegar-Pouyani, N., Rastegar-Pouyani, E., Todehdehghan, F., & Amiri, F. (2015). Avian deception using an elaborate caudal lure in pseudocerastes urarachnoides (serpentes: Viperidae). Amphibia-Reptilia, 36(3), 223–231.Retrieved July 9, 2023, from
  https://doi.org/10.1163/15685381-00002997.
 
• Mobaraki, A., Anderson, S., Papenfuss, T., Martins, M., Isailović, J., Spear, S., & Sigala, J. (2022). Pseudocerastes urarachnoides. The IUCN Red List of Threatened Species 2022: e.T164664A88004847. Retrieved July 9, 2023, from
https://dx.doi.org/10.2305/IUCN.UK.2022-1.RLTS.T164664A88004847.en.

• Fathinia, B., Rastegar-Pouyani, N., Pouyani, E. R., Toodeh-Dehghan, F., & Rajabizadeh, M. (2014). Molecular systematics of the genus Pseudocerastes (Ophidia: Viperidae) based on the mitochondrial cytochrome β gene. Turkish Journal of Zoology, 38(5), Article 7. Retrieved July 9, 2023, from
https://doi.org/10.3906/zoo-1308-25.

• Op den Brouw B;Coimbra FCP;Bourke LA;Huynh TM;Vlecken DHW;Ghezellou P;Visser JC;Dobson JS;Fernandez-Rojo MA;Ikonomopoulou MP;Casewell NR;Ali SA;Fathinia B;Hodgson WC;Fry BG;, B. op den B., Francisco C. P. Coimbra, Lachlan A. Bourke, Tam Minh Huynh, Danielle H. W. Vlecken, Parviz Ghezellou, Jeroen C. Visser, James S. Dobson, Manuel A. Fernandez-Rojo, Maria P. Ikonomopoulou, Nicholas R. Casewell, Syed A. Ali, Behzad Fathinia, Wayne C. Hodgson, & Bryan G. Fry. (2021, February 2). Extensive variation in the activities of pseudocerastes and Eristicophis Viper Venoms suggests divergent envenoming strategies are used for prey capture. Toxins..Retrieved July 9, 2023, from
https://pubmed.ncbi.nlm.nih.gov/33540884/.