Desis formidabilis is a species of spider in the family Desidae. It is endemic to southern Africa, where it inhabits rocky intertidal zones along the coast.[1] The species is commonly known as the long-jawed intertidal spider.[2]
Several synonyms have been established through taxonomic revision, including Paradesis tubicolaPocock, 1898, Desis pentheriSimon, 1910, and Desis beckeriHewitt, 1913.[1]
This species is specialized for life in the intertidal zone, inhabiting rocky shores between the low water neap and high water neap tide levels. As a result, it is submerged twice daily for several hours during high tide cycles. The spider constructs retreats in rock crevices and is adapted to the semi-aquatic lifestyle typical of the genus Desis.[3]
Desis formidabilis exhibits sexual size dimorphism, with females being notably larger than males.[3] Adult males measure 9.5 to nearly 15 mm in length (excluding chelicerae), while females including the chelicerae reach 20 mm.[3]
The cephalothorax, chelicerae, labium, maxillae, and sternum are rich liver-colored. The legs and pedipalps are yellow-brown with reddish tinges. The opisthosoma is dull brown.[3] The cephalothorax is slightly longer than the chelicerae, with a broad-oval form that is truncated at the front. The surface is clothed with short, light brownish hairs, but not densely.[3]
The chelicerae are notably long and powerful, projecting forward and curved, with strong teeth on their inner sides. They are furnished with numerous hairs, and the fangs are long, strong, and slightly curved. The eye arrangement follows the typical pattern for the genus, with the posterior median eyes positioned much closer to each other than to the lateral eyes in the same row.[3]
The legs are moderate in length and strength, following the formula I, IV, II, III. They lack spines but are densely clothed with hairs, particularly on the metatarsi and tarsi, which almost form scopulae. The terminal claws are strong, with the superior pair furnished with 6-7 small teeth toward their base.[3]
Conservation
The species is listed as Least Concern on the South African Red List due to its relatively wide distribution range. However, potential threats include oil spills and coastal pollution, which could affect population numbers.[2]
1 2 3 4 Dippenaar-Schoeman, A.S.; Haddad, C.R.; Foord, S.H.; Lotz, L.N. (2021). The Desidae of South Africa. South African National Survey of Arachnida. doi:10.5281/zenodo.6619783.
1 2 3 4 5 6 7 8 Pickard-Cambridge, O. (1891). "On some new species and two new genera of Araneida". Proceedings of the Zoological Society of London. 58 (4): 620–629.
Further reading
Crews, S.C.; Garcia, E.L.; Spagna, J.C.; Van Dam, M.H.; Esposito, L.A. (2020). "The life aquatic with spiders (Araneae): repeated evolution of aquatic habitat association in Dictynidae and allied taxa". Zoological Journal of the Linnean Society. 189 (3): 862–920. doi:10.1093/zoolinnean/zlz139.
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