Biology:Poecilotheria subfusca
| Poecilotheria subfusca | |
|---|---|
| |
| Young female | |
Scientific classification 
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| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Class: | Arachnida |
| Order: | Araneae |
| Infraorder: | Mygalomorphae |
| Family: | Theraphosidae |
| Genus: | Poecilotheria |
| Species: | P. subfusca
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| Binomial name | |
| Poecilotheria subfusca Pocock, 1895
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| Synonyms[4] | |
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Poecilotheria subfusca, or the ivory ornamental, is a spider in the tarantula family, Theraphosidae. It is endemic to Sri Lanka. As of February 2019[update], the World Spider Catalog regarded Poecilotheria bara as a synonym.[4] Other sources, particularly in the pet trade, have historically treated highland and lowland forms as distinct species, with the lowland forms often referred to as P. bara.
Description
The female is larger than the male, with a body length of 8–9 cm, while males measure approximately 6–7 cm. The species can be distinguished from other members of the genus by its large, dark opisthosoma and a folium pattern consisting of three linked dark spots that extend halfway down the opisthosoma.[5]
Coloration and defensive display
Size and leg span
Habitat and ecology
Poecilotheria subfusca is a strictly arboreal species inhabiting forested regions of Sri Lanka. It occupies mature trees, favoring natural cavities, hollows, fissures beneath loose bark, and occasionally abandoned rot holes or woodpecker cavities. The species shows a strong association with old-growth or well-established secondary forest, where stable humidity and vertical structure are present.
Both lowland and montane forest habitats are utilized. Highland populations occur in cooler, humid montane regions at higher elevations, whereas lowland populations inhabit warmer forest zones at lower elevations. In all habitats, individuals rely on consistent canopy cover, high ambient humidity, and minimal disturbance.
The spider constructs a silken retreat within tree cavities and uses nearby bark surfaces as ambush sites for prey. Activity is primarily nocturnal, with individuals remaining concealed during daylight hours.
Environmental tolerance
Temperature tolerance varies slightly between populations: * Highland populations are associated with cooler conditions, typically ranging from approximately 18–22 °C, with high humidity.
- Lowland populations occur in warmer environments, commonly between 24–29 °C.
Prolonged exposure to excessive heat or low humidity is considered detrimental, particularly for highland-associated individuals.
Behaviour
Compared to other Poecilotheria species, P. subfusca is highly agile and reactive, capable of rapid vertical and lateral movement. When disturbed, it typically retreats quickly into tree cavities, but may bite if provoked.
The species has been documented in a possible mutualistic association with frogs such as Ramanella nagaoi, sharing tree holes that may contain eggs or juveniles of either species. The spider may deter predators, while the frog may reduce ant predation on spider eggs.
Venom
Like all members of the genus Poecilotheria, Poecilotheria subfusca is an Old World tarantula lacking urticating hairs and relying primarily on venom for defense. The venom is considered medically significant.
Juveniles are generally shy and easily startled, which can lead to the misconception that adults behave similarly. Adult specimens are reported to be more defensive and reactive, with a higher likelihood of biting when threatened.
The species is known for extremely rapid strike speed, with bites occurring with little visible warning. It is also capable of rapid jumping and multidirectional movement, increasing the risk of accidental contact.
Although no confirmed fatalities have been attributed to P. subfusca envenomation, bite reports involving closely related Poecilotheria species describe severe systemic symptoms, including intense localized pain, radiating discomfort, and prolonged muscle cramps or spasms lasting days to weeks. As a result, handling is strongly discouraged.
Conservation
Poecilotheria subfusca is listed as Endangered under the U.S. Endangered Species Act and is included in Appendix II of CITES. The primary threat to the species is habitat loss caused by deforestation, logging, agricultural expansion, and forest fragmentation in Sri Lanka.
Because the species depends on mature trees with suitable cavities, the removal of old-growth forest has a disproportionate impact on population viability. Collection for the international pet trade has also contributed to population pressure, leading to increased regulation and export controls.
References
- ↑ "Ivory Ornamental Tarantula (Poecilotheria subfusca)". U.S. Fish & Wildlife Service. https://ecos.fws.gov/ecp/species/9115.
- ↑ 83 FR 36755
- ↑ "Appendices | CITES". https://cites.org/eng/app/appendices.php.
- ↑ 4.0 4.1 "Taxon details Poecilotheria subfusca Pocock, 1895", World Spider Catalog (Natural History Museum Bern), https://www.wsc.nmbe.ch/species/37832, retrieved 2020-02-07
- ↑ Nanayakkara, Ranil P. (2014). Tiger Spiders Poecilotheria of Sri Lanka. Colombo: Biodiversity Secretariat, Ministry of Environmental & Renewable Energy. pp. 167. ISBN 978-955-0033-58-4.
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