The first two blind troglobitic spiders of the genus Ochyrocera from caves in Floresta Nacional de Carajás, state of Pará, Brazil (Araneae, Ochyroceratidae)

Abstract The first two anophthalmic species of spiders of the genus Ochyrocera Simon, 1892, are described for caves located in the iron formation of Floresta Nacional (FLONA) de Carajás in southeastern Pará State, Brazil. The caves are located in the municipalities of Parauapebas and Canaã dos Carajás, in the eastern portion of the Amazon Forest domain. Ochyrocera ritxocosp. nov. and O. ritxoosp. nov. are described based on males and females. The species have similar body characteristics with the total absence of eyes and complete depigmentation, characteristics that indicate possible evolution in subterranean environments , and thus are classified as troglobites. Each species is associated with a single geomorphological unit (mountain range), with Ochyrocera ritxocosp. nov. being restricted to caves of Serra Norte (North Mountain) and O. ritxoosp. nov. to caves of Serra Sul (South Mountain). Both species were collected in aphotic zones of the caves. Small and tangled webs of O. ritxocosp. nov. were observed under blocks of stone in the soil or in cracks of the walls.


Introduction
Ochyroceratidae currently contains 10 genera and 166 species (World Spider Catalog 2020), with the recent elevation of Psilodercidae reducing its diversity by half (Wunderlich 2008). Despite this, the distribution the family can be considered wide, occurring in tropical areas of the Neotropical, African and Indo-Pacific regions. Its species are common on the ground and in cave environments, with sizes not greater than 2 mm, and having six eyes and long, thin legs (Jocqué and Dippenaar-Schoeman 2006).
Although many ochyroceratids live in hypogean environments, few have morphological specializations related to life in caves, which would characterize them as troglomorphic. We highlight here, at least five species of the family whose members possess some type of troglomorphism, namely: Speocera caeca described by Deeleman- Reinhold (1995) from Indonesia, Speocera eleonorae Baptista, 2003from Brazil, Theotima pura Gertsch, 1973 and Theotima martha Gertsch, 1977, which occur in caves on the Yucatan Peninsula, Mexico, and Ochyrocera peruana Ribera, 1978 from Peru. Only two species are blind spiders (S. caeca and T. pura), while the others are characterized by reduced or small size of the eyes, depigmented body and long thin legs (Gertsch 1977).
In this work, we describe two new troglobitic species of the ochyroceratid genus Ochyrocera. These species represent the first blind and depigmented members of the genus, which currently possesses 50 species worldwide (World Spider Catalog 2020).
The two species were collected from iron formation caves in FLONA de Carajás (Carajás National Forest), state of Pará, northern Brazil and expand the diversity of spiders known for this ferruginous region (Brescovit et al. 2018).
Morphological terms follow Brescovit et al. (2018), except for macrosetae of endites which follow Baert (2014). Descriptions and measurements were performed using a Leica 165C stereomicroscope, while photographs were taken with a Leica DFC 500 digital camera mounted on a Leica MZ16A stereomicroscope. Focal range images were made using Leica Application Suite software, version 2.5.0. Total and femur lengths were measured in lateral view without detaching any part from the specimen. All measurements are in millimeters. Female genitalia were excised with a sharp needle and photographed mounted on Hoyer´s microscope slides. For scanning electron microscopy (SEM), body parts were dehydrated in a series of graded ethanol washes (80% to 100%), critical point dried, mounted on metal stubs using adhesive copper tape and nail polish for fixation and covered with gold. SEM images were taken with FEI Quanta 250 and LEO 1450VP scanning electron microscopes, at Laboratório de Biologia Celular of Instituto Butantan, São Paulo and Museu Paraense Emílio Goeldi, Belém, respectively.

Study area
The caves where the spiders were sampled are inserted in iron formations located in the Carajás area in southeast state of Pará, in the eastern region of the Amazon Forest in Brazil (Fig. 10). The caves are within the FLONA de Carajás (Brazilian System of Conservation Units), which encompasses approximately 411 thousand hectares and includes parts of the municipalities of Parauapebas, Canaã dos Carajás and Água Azul do Norte. In the region of the park there is a mosaic of protected areas forming a continuous area of 1.31 million hectares of preserved forest (Rolim et al. 2006), which is surrounded by pastures that replaced original forest Martins et al. 2012;Carmo and Jacobi 2013). The park area mainly comprises forest formations (ombrophilous or seasonal) and only 5% of campo rupestre (rocky/rupestrian fields), which develops on the laterite plates (crusts) of high areas of the region .    the spermathecae and a shorter columnar uterus externus with 3-4 internal chambers in the female genitalia (Fig. 8C, D).
Etymology. The specific name Ritxòkò means "ceramic dolls" in the female language of the Karajá people, an indigenous population of the region. The dolls are produced by Karajá women, who model, burn, paint, and sell them (Silva 2015).
Natural history. Ochyrocera ritxoco sp. nov. is a small troglobitic spider that is exclusive to caves in the Carajás karst region. Specimens were found only in aphotic zones of caves. They build small, tangled webs under blocks of stone on the ground or in slits (Fig. 6). The observed sex ratio for the species was 2.4F:1M (N = 66). Ochyrocera ritxoco sp. nov. was generally found in large cavities with horizontal projections varying from 9.5 to 216 meters (N = 13, mean = 107 m). All caves where the species was found have only one entrance and are located only in the middle and high slopes of Serra Norte. Most caves have aphotic zones or twilight zones (except for cavities N1_0103 and N1_0084) and high humidity, thus explaining the observed presence of small bodies of water in almost all cavities, especially during the wet season. The number of troglobitic species in these caves varied from one to ten (average 5.3 per cave), with species of the following taxa: spiders -Oonopidae (many species), Caponiidae (Carajas paraua Brescovit & Sánchez-Ruiz, 2016)    Diagnosis. Ochyrocera ritxoo sp. nov. is distinguished from O. ritxoco sp. nov. by having the embolus as long as the bulb of the male palp (Figs 7C-F, 8A, B) while O. ritxoco sp. nov. have an elongated embolus, which is two times longer than the bulb in the male palp (Fig. 1F), and by a short and striped distal area of the spermathecae and a shorter columnar uterus externus with approximately 3-4 internal chambers in  the female genitalia (Fig. 8C, D) while the other species have a long and globose distal area in the spermathecae and an elongated columnar uterus externus with approximately eight internal chambers (Fig. 2C, D).
Etymology. The specific name Ritxòò also means "ceramic dolls" but in the male language of the Karajá people, an indigenous population of the region. The making of these dolls, however, is an exclusive activity of women (Silva 2015).
Natural history. Ochyrocera ritxoo sp. nov. is a small troglobitic spider that is exclusive to caves in the Carajás karst region. Specimens were collected only in aphotic zones of caves. The observed sex ratio for the species was 1.4F:1M (N = 17). Ochyrocera ritxoo sp. nov. was generally found in large cavities with horizontal projections varying from 26 to 245 meters (N = 7, mean = 102 m). These caves have one to three entrances and are located in all compartments of the Serra Sul landscape (top, high, medium and low slopes). All caves have aphotic zones and other troglobitic species were found in most caves, with the richness of troglobitic species per cave varying between one and six (average of four). The following taxa were found: spiders -Gnaphosidae  Distribution. Known exclusively from caves in a range of approximately 10 km of the Serra Sul (South Mountain), FLONA de Carajás, Canaã dos Carajás, state of Pará, northern Brazil (Fig. 10).

Discussion
The fauna of subterranean spiders of the family Ochyroceratidae located in caves in Brazil is represented mainly by specimens of the genera Ochyrocera Simon, 1892, Speocera Berland, 1914, and Theotima Simon, 1893. The first two genera have troglomorphic spiders among their representatives and are a significant part of the yet unknown diversity of subterranean spiders in these environments (Baptista 2003). The genus Ochyrocera stands out for its abundance and diversity of species in ferruginous ecosystems, such as the Carajás system of the present study, with species colonizing the edaphic zone to the deep cave environment (Brescovit et al. 2018).
Both Ochyrocera ritxoco sp. nov. and O. ritxoo sp. nov. are troglobitic spiders that are restricted to iron formation caves in FLONA de Carajás. The description of these spiders expands the number of the endemic subterranean species (troglobites) and, together with Carajas paraua Brescovit & Sánchez-Ruiz, 2016 (Caponiidae) and Paracymbiomma caecus and P. bocaina (Gnaphosidae; Rodrigues et al. 2018), is evidence of a diversified subterranean araneofauna in the Carajás ferruginous system which must be considered in projects aimed at conservation and sustainable use of its natural resources.