Loxosceles niedeguidonae (Araneae, Sicariidae) a new species of brown spider from Brazilian semi-arid region

Abstract A new species of recluse spider, Loxosceles niedeguidonae sp. n., is described from the Parque Nacional Serra da Capivara, State of Piauí, Brazil. This is the first endemic species described from Brazilian semi-arid environment. The species is included in gaucho group of Gertsch (1967) due to its spermathecal shape and is considered close to Loxosceles chapadensis Bertani, Fukushima & Nagahama, 2010 by the unusual long male palpal tibia, a character not common for species of this group. An updated key for Loxosceles species of gaucho group is presented.


introduction
The Loxosceles Heineken & Lowe, 1832 species, brown recluse spiders, are spread throughout the world. Currently, there are 102 species described for the whole Neotropical region, Europe, Asia and Africa, eleven of them present and/or endemic to Brazil (Gertsch 1967;Gertsch and Ennik 1983;Bertani et al. 2010;Platnick 2011).
After Gertsch (1967), and despite the medical importance of the genus, little more has been added to the taxonomy of the South-American Loxosceles. Brignoli (1978) transferred Calheirosa anomala Mello-Leitão, 1917 andCalheirosa immodesta Mello--Leitão, 1917 to the genus Loxosceles. Álvares et al. (2004) redescribed L. anomala (Mello-Leitão, 1917) and considered this species to belong to the spadicea group. Other authors have expanded the knowledge about the geographic distribution of some species (Gonçalves-de-Andrade et al. 2001, 2007Gonçalves-de-Andrade and Tambourgi 2003;Silveira 2009). In the last decade two new species were described: L. puortoi considered to belong to laeta group, the first species of this group endemic to Brazil and, more recently (2010), L. chapadensis, which was included in the gaucho group.
The Parque Nacional Serra da Capivara is a federal protected area in Southeastern State of Piauí, Brazil. The 129,953 ha cover areas in the municipalities of São Raimundo Nonato, Coronel José Dias, João Costa and Brejo do Piauí (08°26', 08°54'S and 42°19', 42°45'W). Together with Parque Nacional Serra das Confusões it is one of the largest protected areas in the world with "Caatinga" vegetation formation, situated between the "Médio São Francisco" depression (Precambriam) and the Piauí-Maranhão sedimentary basin (Silurian-Devonian), the two largest geological formations in Brazilian Northeastern. Rainfall period is from November to March, with a yearly median precipitation of 689 mm. The annual median temperature is 28°C. General landscape of Parque Nacional da Serra da Capivara consists of uplands, plateaus, hills, mountain chains and plains. This distinct relief is a result of transformations occurring during millions of years in the sedimentar basin of Piauí-Maranhão and in the central São Francisco Depression composed of different types of minerals and rocks.
In this work we describe a new species of Loxosceles endemic to the Brazilian semiarid environment, from Parque Nacional Serra da Capivara, the second species of the gaucho group described for Northeastern Brazil and present an updated key for Loxosceles species of gaucho group.

Material and methods
Spiders were collected (the permissions for collect -number 11971-2 -and for work in Parque Nacional Serra da Capivara -number 18413-1 -was conceded to Rute Maria Gonçalves-de-Andrade by ICMBio a instance of the Brazilian Ministry of the Environment) in two localities: Toca do Buraco da Pedra Furada and Boqueirão do Gato. The specimens examined are deposited in Museu Nacional, Rio de Janeiro, RJ, Brazil (Dr. Adriano B. Kury). The copulatory organs of females were dissected and cleared with clove oil. A LEICA® MZ7.5 Stereomicroscope with 10x eyepiece was used for illustrations (with a camera lucida attachment) and measurements (using an ocular micrometer). Measurements are in millimeters. Abbreviations: ALE = anterior lateral eye, PLE = posterior lateral eye and PME = posterior median eye. Palpal tarsus almost 2 times longer than wide (Figs 2-4); lateral dentate dark bands on the dorsal side of the carapace faded (Fig. 9) ...L. niedeguidonae sp. n. -Palpal tarsus less than 1.5 times longer than wide; lateral dentate dark bands on dorsal side of the carapace conspicuous (Fig. 10)  Embolus straight in ventral view (Brignoli 1972 fig. 1 Dorsal part of the bursa copulatrix weakly sclerotized (Gertsch 1967  Diagnosis. Males can be readily distinguished from other species, except L. chapadensis by the following characters in combination: Palpal tibia more than 1.5 times longer than tarsus, embolus 1.5-1.8 times longer than diameter of tegulum, arising at distal half of tegulum, distally thin but not filiform and hardly curved, particularly not in distal direction (Fig. 2). Males differ from L. chapadensis by palpal tarsus almost two times longer than wide (Figs 2-4), embolus less curved (Fig. 4) and faded lateral dentate dark bands on the dorsal side of the carapace (Fig. 9). Females can be recognized by the following characters in combination: A narrow transversal plate in the spermathecae, straight, apically enlarged seminal receptacles and incrassate palpal tarsus, which is broader than palpal tibia (Figs 6-8).
Etymology. The specific name is a patronym in honor of Dr Niéde Guidon, one of the most important Brazilian archeologists, internationally acknowledged for her archeological work and her battle for the preservation of archeological sites in Brazil and the conservation of remnant patches of Caatinga vegetation, as well as important social work, especially in the Parque Nacional da Serra da Capivara.
Female (paratype MNRJ 04360) Total length (without chelicerae) 7.35. Carapace 3.79 long, 3.71 wide. Eye sizes: ALE: 0.22, PME: 0.16, PLE: 0.18. Clypeus: 0.32. Interocular distances -PME and PLE: 0.05, PME and ALE: 0.24. Leg formula: II, I, VI, III. Legs and palp length and width in Table 2. Labium 0.7 long, 0.54 wide. Sternum 1.85 long, 1.78 wide. Femur I 1.58 times longer than carapace. Palpal femur 5.0 times longer than wide, tibia 3.5 longer than wide, tarsus incrassate (Fig.  6). Spermathecae with long, straight, apically enlarged seminal receptacles; transversal plate narrow, weakly sclerotized; atriobursal orifices well visible, ovals, positioned on the internal edge of the central windows; dorsal part of bursa copulatrix weakly sclerotized (Figs 7-8). Coloration as in male, but darker (Fig. 12). Tarsi and tibiae of palps reddish-brown. Discussion. The female Loxosceles niedeguidonae sp. n. can undoubtedly be included in the gaucho group of Gertsch (1967) due to spermathecae bearing a transverse plate (Figs 7-8), which is characteristic of the group. However, the male resembles species of the laeta group due to its long palpal tibia (Fig. 2). These characteristics are also found in the recently described species Loxosceles chapadensis with which Loxosceles niedeguidonae sp. n. seems to be closely related. As already discussed by Bertani et al. 2010, the long palpal tibia of males of L. chapadensis (and now, L. niedeguidonae sp. n.) could be an homoplasy with species of the laeta and spadicea groups or a plesiomorphy, indicating a more basal position of the species in the gaucho group relative to these other species (Bertani et al. 2010). Despite these shared characteristics they can be separated by genitalic and somatic characteristics. The male has a straighter embolus (Figs 3-4), palpal tarsus almost two times longer than wide and color pattern are not very similar to the typical gaucho pattern, i. e. lateral dentate dark bands on the dorsal side of carapace. The male resembles an individual of the laeta group due to its light-brown coloration and faded dentate dark bands on the carapace (Figs 1-9, 11). The female can be easily separated by the narrow transversal plate in spermathecae (Figs 7-8) and incrassate palpal tarsus (Fig. 6), which is like the female Loxosceles adelaida, gaucho group (Gertsch, 1967), but more dilated than the latter. The distinct, but close geographical distribution of L. chapadensis and L. niedeguidonae sp. n. in Northeastern Brazil provides an additional indication that these two species are closely related.
Natural History. Specimens of Loxosceles niedeguidonae sp. n. were found in the locality of "Buraco da Pedra Furada". The male was collected over the ground and the female in a rock crevice close to a cave mouth. The arenitic walls in the Parque Nacional Serra da Capivara have innumerous crevices that make typical retreats for brown recluse spiders (Figs 13-14). However, despite the presence of so many crevices, a low population density was found in the analyzed ecotope.