Platyoides Walteri

''Platyoides'' is a genus of spiders belonging to the family Trochanteriidae. Its members are known as scorpion spiders and are found in sub-Saharan Africa and its islands, Madagascar, Réunion, Aldabra and the Canary Islands.

The genus is nocturnal in habit and has developed extreme flattening of the body adapted to living in narrow cracks, particularly under loose bark.

Origin of the word 'Platyoides'

The ancient Greek language is the basis a vast array of scientific terminology. The word '''Platyoides''' is a compound word broken up into two distinct parts. The first element of the word '''Platyoides''' is 'Platy'. The ancient Greek definition of 'Platy' means broad and flat. This first section of the word directly relates to the asethic genetic makeup of the genus. The second element of the word which also originates from the Ancient Greek language is 'oid'. 'Oid' means 'form of'. Together the two segments of this compound word confirms this distinct feature of the flat back and gives this genus its name.

Common names

The common name scorpion spider is derived from its distinctive flat back and carapace orange colouring.Lawrence, R.F. (1937). Transvaal Museum Expedition to South-West Africa and Little Namaqualand. ''Natal Museum, Pietermaritzburg, 1(''1), 215-226. This colouring is evident around the mouthpiece and on the anterior aspects of the legs. These similar features of the genus ''Platyoides'' in comparison to a scorpion is often why this genus is referred to as the scorpion spider.

Taxonomy

As a result of DNA testing, the genus ''Platyoides'' has been deemed a member of the Trochanteriidae family.Australia, A., 2021. ''Genus: Platyoides''. nlineBie.ala.org.au. Available at: https://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:afd.taxon:c659814c-6c57-4f90-a019-92fab38380fc ccessed 24 March 2021 Substantial interest in the genus ''Platyoides'' would have been sparked by their unique ability to flatten their abdomen in order to adapt to their environment. South African arachnologist and myriapodologist described ''Platyoides'' using specimens submitted to him for identification by the Director of the Transvaal Museum and Mr V. Fitzsimons, Keeper of the Invertebrate collections at the Natal Museum, Pietermaritzburg. The collection consisted of thirty-three species all in the genus ''Platyoides''. The spider genus ''Platyoides'' is part of the Trochanteriidae fauna species that was first recorded by in 1903 and was given the binomial name of '' Platyoides grandidieri''.Platnick, Norman. (1985). Studies on Malagasy spiders. 2, The family Trochanteriidae, with a revision of the genus Platyoides. American Museum novitates. ''American Museum of Natural History'', ''1''(1), 1-17. This genus is unique to sub-Saharan Africa and its surrounding islands. Further genomic differences have too contributed to being able to determine the ancestry of the genus ''Platyoides'' by creating a lineage diversification system.

Species

''Platyoides'' O. P.-Cambridge, 1890
* ''Platyoides alpha'' Lawrence, 1928 — Angola, Namibia, South Africa
* ''Platyoides costeri'' Tucker, 1923 — South Africa
* ''Platyoides fitzsimonsi'' Lawrence, 1938 — Namibia
* '' Platyoides grandidieri'' Simon, 1903 — Kenya, Madagascar, Aldabra, Réunion
* ''Platyoides leppanae'' Pocock, 1902 — Mozambique, South Africa
* ''Platyoides mailaka'' Platnick, 1985 — Madagascar
* ''Platyoides pictus'' Pocock, 1902 — South Africa
* '' Platyoides pirie'' Platnick, 1985 — South Africa
* ''Platyoides pusillus'' Pocock, 1898 — Tanzania, Zimbabwe, South Africa
* ''Platyoides quinquedentatus'' Purcell, 1907 — South Africa
* ''Platyoides ravina'' Andriamalala & Ubick, 2007 — Madagascar
* ''Platyoides rossi'' Platnick, 1985 — South Africa
* ''Platyoides vao'' Andriamalala & Ubick, 2007 — Madagascar
* ''Platyoides velonus'' Platnick, 1985 — Madagascar
* ''Platyoides venturus'' Platnick, 1985 — Canary Islands
* ''Platyoides walteri'' (Karsch, 1886) — East, Southern Africa, introduced in Australia

Description

The body size of the genus ''Platyoides'' is sexually dimorphic, females being much larger than males. The most notable feature of the genus is its flat back creating a large surface area.Azevedo, Griswold, Santos. (2017). Systematics and evolution of ground spiders revisited (Araneae, Dionycha, Gnaphosidae. ''Wiley Online Library, 34''(6), 579-626. The species of the genus have a unique ability to flatten their abdomen due to a genetic predisposition that results in loose trochantheriids and gnapsoides. This means they have loose joints allowing them to flatten their bodies; a direct product of their environment.  The introduction of new research techniques including a scanning electron microscopy helped aid to distinguish between different species and determine these unique genus qualities. Another notable feature that links to their common name the ‘scorpion spider’ is the colouring of the genus ''Platyoides''. A distinct carapace orange surrounds the mouth, radiating down onto their legs and on the dorsal aspect of their abdomen. The anterior side of the abdomen is a pale, ashy grey. The genus has a unique feature in their teeth with a triangular tooth existing on their upper margins, behind the regular fangs which aids in chewing prey. Another defining feature of the genus ''Platyoides'' description is the elongation of the fourth trochanter. The dimensions of the genus ''Platyoides'' species is 9mm with the carapace measuring 3.6mm.

Similar Species

Solifugae

There is a species of spider that is commonly mistaken for the genus ''Platyoides''. This species is called the Scorpion spider also known as the Solifugae. There are a number of similarities between the ''Solifugae'' and the genus ''Platyoides''. The main similarity is the anatomy and colouring of the two species. In particular, the ''Solifugae'' and the genus ''Platyoides'' share the distinctive feature of longer than average extremities that aid both of the spider species to flatten themselves under rocks and bark. Both species possess a distinct orange colour that aids them in camouflaging to their environment. The ''Solifugae'' is often found living in semidesert environments existing on all continents except for Australian and Antarctica.

Behaviour

A distinctive feature of the behaviour of the genus ''Platyoides'' is a unique adaptation.  The genus is a product of its sub-Saharan environment and has developed an extreme flattening of their back and abdomen. The flattening of the body is an adaptation that allows the genus ''Platyoides'' to living under bark and in small cracks.  Many specimens of the genus have been found in these areas and has become a distinctive feature of the species’ natural history. Despite being a nocturnal species, the carapace orange that follows a number of the main body features of the genus including the abdomen and legs.  This colour aids in camouflage for the species as the colour is similar to that of the robust, sandy environment.

Distribution and habitat

The genus ''Platyoides'' is found in sub-Saharan Africa and the surrounding islands it entails including Madagascar, Reunion, Aldabra and the Canary Islands. The genus ''Platyoides'' is nocturnal. If a species such as the genus ''Platyoides'' is nocturnal they become their most active in the evenings throughout the night and find relief during the day. All animals including the '''Platyoide genus need to have an element of withdrawal from activity to drop their metabolic rate. There is little evidence to suggest what the length of the inactivity period is. Spiders that hunt for prey during the daylight are species that tend to rely on their eyesight as opposed to their webs and traps. The taxonomic position of the genus and the interrelationships the genus ''Platyoides'' shares with other genus’ is often questioned. Other species exist in the Canary Islands, however no species similar to the genus ''Platyoides'' exist north of Africa. It has been deemed by arachnologist Norman I. Platnick that the genus is old and a substantial element of the species diversification occurred prior to Madagascar separating from continental Africa.

Other locations

There are nine species of the genus found in South Africa. One of these nine species has recently been found in South Australia, Australia. Sightings from this species found in South Australia were only inside a man made building.

Risk to humans

There is little evidence to suggest that the genus ''Platyoides'' genus poses any risk to humans.

References

{{Taxonbar, from=Q3392051

Spiders of Africa
Araneomorphae genera
Trochanteriidae