Unicorn (spider)
Unicorn | |
---|---|
Male Unicorn sikus, viewed from above (legs omitted). | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Subphylum: | Chelicerata |
Class: | Arachnida |
Order: | Araneae |
Infraorder: | Araneomorphae |
Family: | Oonopidae |
Genus: | Unicorn Platnick & Brescovit, 1995 |
Type species | |
Unicorn catleyi Platnick & Brescovit, 1995
| |
Species | |
7, see text |
Unicorn ("one horn", in Latin) is a
Description
Species of Unicorn range from 2.2 to 3.0 mm in body length (from tip of the
Males and females show some differences in morphology: male jaws (chelicerae) are longer and more slender than those of females; the male palpal tibiae—the penultimate segment of the pedipalps—are enlarged compared to females; and males alone possess a "clypeal horn", a forward-pointing projection of the clypeus surrounded by long stiff hairs, from which the genus name Unicorn ("one horn" in Latin) derives.[1][a]
The copulatory bulb of males (the sperm-transferring organ at the tip of the pedipalps), terminates in a narrow, curving tip called an embolus, which in Unicorn bears a hook at its base and is accompanied by a similar curved extension called a translucent sclerite.[1]
Reproduction
Like most spiders, the pedipalps of mature males end in a bulb terminating in a thin, curved projection called an embolus, through which sperm is released during mating. Female U. catleyi have been observed with broken-off embolus tips lodged in their genitalia. This has been hypothesized as a type of "sperm-plug" or copulatory plug, where, by breaking off a piece of his anatomy (a process known as genital mutilation or genital breakage), a male physically precludes other males from successfully mating with the female, one of many types of sperm competition in animals.[3] An alternative to the sperm competition function is that genital mutilation might allow males to more rapidly escape and avoid being cannibalized after mating, although this function is thought to be unlikely in Unicorn since there are no significant size differences between sexes, and cannibalism is more common when females are much larger than males.[3] Sperm plugs of various types, including gelatinous or waxy substances, have been observed in at least 41 spider families, and are generally thought to ensure paternity.[4] U. catlyei is one of only few goblin spiders known or suspected to utilize sperm plugs.[3]
Habitat
Species of Unicorn have mostly been found at elevations between 1,000 to 4,000 m (3,300 to 13,100 ft) above sea level, many from
Species and distribution
The genus Unicorn was established in 1995 by
- Unicorn argentina (Mello-Leitão, 1940) — Western Argentina
- Unicorn catleyi Platnick & Brescovit, 1995 — Northern Chile and northwestern Argentina
- Unicorn chacabuco Platnick & Brescovit, 1995 — Chacabuco Province, central Chile
- Unicorn huanaco Platnick & Brescovit, 1995 — La Paz Department, Bolivia
- Unicorn sikus González, Corronca & Cava, 2010 — Salta Province, northwestern Argentina
- Unicorn socos Platnick & Brescovit, 1995 — Limarí Province, central Chile
- Unicorn toconao Platnick & Brescovit, 1995 — Antofagasta Province, northern Chile
Classification
Unicorn is a member of the family
Notes
References
- ^ a b c d e f g Platnick, N. I.; Brescovit, A. D. (1995). "On Unicorn, a new genus of the spider family Oonopidae (Araneae, Dysderoidea)" (PDF). American Museum Novitates (3152): 1–12.
- ^ a b c d Gonzales Reyes, A. X.; Corronca, J. A.; Cava, M. B. (2010). "New species of Unicorn Platnick & Brescovit (Araneae, Oonopidae) from north-west Argentina" (PDF). Munis Entomology & Zoology. 5 (2): 374–379.
- ^ PMID 22225476.
- S2CID 23020291.
- ^ Platnick, Norman I.; et al. (2012). "Tarsal organ morphology and the phylogeny of goblin spiders (Araneae, Oonopidae), with notes on basal genera" (PDF). American Museum Novitates (3736): 1–52.
- ^ Busschere, C.; Fannes, W.; Henrard, A.; Gaublomme, E.; Jocqué, R.; Baert, L. (2014). "Unravelling the goblin spiders puzzle: rDNA phylogeny of the family Oonopidae (Araneae)" (PDF). Arthropod Systematics & Phylogeny. 72 (2): 177–192. Archived from the original (PDF) on 2016-06-03. Retrieved 2015-04-11.
External links
Data related to Unicorn at Wikispecies