Three new species of the spider genus Plato and the new genus Cuacuba from caves of the states of Pará and Minas Gerais, Brazil (Araneae, Theridiosomatidae)

Abstract Three new species of the genus Plato from caves in the states of Pará and Minas Gerais, Brazil, are described. P. novalima sp. n., from Minas Gerais, is the first record of the genus in the southeastern region of Brazil. P. ferriferus sp. n. and P. striatus sp. n., from Carajás, Pará, north of Brazil, are also described. The former is an extremely abundant species, whereas the latter has only one known male specimen. Cuacuba gen. n. is proposed and represented by two new species, C. mariana sp. n. (type species) and C. morrodopilar sp. n., both from the state of Minas Gerais. Morphology of genitalia in Cuacuba gen. n. is similar to other Theridiosomatidae genera and is herein discussed. None of the proposed species presents troglomorphic adaptations. They are widespread, abundant inside caves in different and large karst areas, and each genus prefers different lithologies.


Introduction
The family Theridiosomatidae Simon 1881 is currently represented by 18 genera and 111 species worldwide (World Spider Catalog 2017). Specimens of this family differ from others by the presence of pits on the anterior margin of the sternum (except in Chthonos Coddington, 1986), connate spermathecae in female genitalia (except in Coddingtonia Miller, Griswold &Yin, 2009 andTagalogonia Labarque & and tibial dorsal trichobothria, usually 2 to 4 times longer than tibial diameter (shorter only in Wendilgarda Keyserling, 1886) (Coddington 1986).
The diagnostic characteristics that differentiate Plato from other genera in Theridiosomatidae are the presence of a median projection in the female epigynum base, grooves in the distal or mesal area of the cymbium, and a strong, curved ventral apophysis in the conductor of male palp (Coddington 1986). Plato includes six species: the type species Plato troglodita Coddington 1986, from Ecuador; Plato bicolor (Keyserling 1986), from the Amazonian region in Brazil; Plato bruneti (Gertsch 1960), from Trinidad and Tobago; Plato guacharo and Plato miranda, both described by Brignoli (1972), from Venezuela; and Plato juberthiei Lopez 1996, from French Guiana (World Spider Catalog 2017. Their distribution is currently limited to South America and, so far, only P. bicolor has been described from Brazil. Specimens of Plato are found in caves, near stream passages, or on the wall, next to water bodies, preying on small flying insects ( Fig. 3B; Trajano and Bichuette 2010).
Two species were collected from the Carajás region, Plato ferriferus sp. n. and Plato striatus sp. n. Plato novalima sp. n. was collected in the Iron Quadrangle region and surrounding cave areas in the state of Minas Gerais. Besides Plato, other Theridiosomatidae genera are also commonly found inside caves, such as Baalzebub, also from the state of Minas Gerais (Prete et al. 2016), and Wendilgarda (Trajano 1987;Gnaspini and Trajano 1994) and Epilineutes (Gnaspini and Trajano 1994), both from the state of São Paulo.
Furthermore, two new species are described and included in the newly proposed genus, Cuacuba gen. n. Specimens of this genus were recorded in the literature as unidentified Plato sp. from the caves Lapa Encantada (Pinto-da-Rocha 1995) and Morena (Gnaspini and Trajano 1994), both in the state of Minas Gerais. While reexamining the material currently deposited in the IBSP collection, we detected diagnostic characters, mainly in the genital structures, that allow us to propose a new genus to include the type species Cuacuba mariana sp. n. and Cuacuba morrodopilar sp. n., both from caves of Iron Quadrangle formation. The species of this genus have a set of characteristics that do not place them into any Theridiosomatidae genus. Males are diagnosed by having a bifid conductor with two long apophyses: the posterior one involving a long embolus and the anterior one distally ornamented. Females present an epigynal plate with a projected posterior margin. Relationships among the new genus and other Theridiosomatidae still need to be evaluated phylogenetically as the morphological characters of genitalia in this genus do not allow it to be placed within any of the current subfamilies.

Materials and methods
A total of 3868 adult specimens of five species from 1007 different caves was analyzed. Spiders were collected in different karst areas throughout the states of Minas Gerais and Pará in Brazil. Iron and carbonate formations are the most representative among the explored areas. All samples were manually collected.
The material was studied using a stereomicroscope Nikon SMZ 745T. Multifocal photos were taken using a stereomicroscope Leica DFC500 and the Leica Application Suite v3.3.0 software. Scanning Electron Microscopy (SEM) images of the left palp of males (as is standard in arachnological studies) were made using a FEI Quanta 250 microscope from Laboratório de Biologia Celular of Instituto Butantan.
Genitalia were dissected and illustrations were made using a Leica MZ12 stereomicroscope with an attached camera lucida. Descriptions of species follow Coddington (1986). All measurements are presented in millimeters (mm). Maps were produced using GPS Track Maker-PRO and edited in GIMP v2.8.14 and Inkscape v0.48.4. Graphics and tables were made in Microsoft Office Excel 2013. Abbreviations:

ALE
anterior lateral eyes, AME anterior median eyes, MF multifocal photo PLE posterior lateral eyes, PME posterior median eyes, SEM scanning electron microscopy.

Collecting sites
Five new species of Theridiosomatidae were found inside caves in the states of Pará and Minas Gerais, Brazil. The species' distributions are mainly restricted to two karst areas of great economic and mineral interest. One of them is the region of Carajás, state of Pará, an important speleological area in Brazil. Its iron formation has a great potential for forming cavities, as it concentrates one of the largest iron reserves in the world. These caves have a singular biological evolution (Ab'Sáber 1986; Piló and Auler 2009), in which a series of discontinuous mountains and hills are separated by wide valleys of iron ore that emerge above the forested plateau with elevations of 600 to 800 m. The main elevations are the northern and southern mountains (Serra Norte e Serra Sul) (Cunha Jr. et al. 2007). The second area is in the Iron Quadrangle, located in the central part of the state of Minas Gerais, and covers approximately 7,200 km 2 . During the evolution of the area`s relief, small erosion surfaces were formed, distributed at different altitudes and with a clear lithostructural control. This region is a unique landscape when compared to the other southeastern geological patterns in Brazil (Varajão 1991).

Family Theridiosomatidae Subfamily Platoninae
Genus Plato Coddington, 1986 Type species. Plato troglodita Coddington, 1986, by   Etymology. The specific name is a masculine noun in apposition and refers to the word ferro, which means iron in Portuguese. This name describes the type of lithology where the species is found in abundance.
Diagnosis. Male resembles P. novalima sp. n. in the rounded tegulum, posterior portion of conductor hyaline and partially overlapping the embolus, and longer than larger bulb; it can be distinguished by the bifid conductor with a long and digitiform distal projection and rounded basal projection, and median apophysis with a single small tip ( Fig. 1C-F). Female resembles P. novalima sp. n. in the large epigynal plate (Fig. 2B-C) and canoe-shaped sclerotized internal plate surrounding the spermathecae (Fig. 2C) but differs in the ample and rounded curvature of the copulatory ducts (Fig. 2C).
Distribution. Canaã dos Carajás, Parauapebas, Curionópolis, Altamira and São Geraldo do Araguaia, Pará, Brazil (Fig. 16).   Natural history. All specimens were collected in caves in iron formations. Most specimens were collected in the middle of orbicular webs, usually in the twilight zone ( Fig. 3A-D). Egg sacs had a cubic shape and were fixed on cave walls (Fig. 3D). In some cases, more than four egg sacs were found in a single guide wire (Fig. 3C). The number of eggs per egg sac varied from eight to seventeen. They were recorded on different types of prey, and the most common prey items were winged species of orders Diptera (Fig. 3B) and Lepidoptera.
Diagnosis. Plato striatus sp. n. resembles P. guacharo in the twisted projection of the conductor (see Brignoli 1972: fig. 22), and P. novalima sp. n. and P. ferriferus sp. n. in the rounded tegulum, posterior portion of conductor hyaline and partially overlapping the embolus, and longer than large bulb. It differs from these three species in the proximal portion of the conductor simple, arrow-shaped, twisted and pointing upwards, embolus with proximal apophysis elongated, distal apophysis fused to the membrane (Fig. 4C-E) and fourth pair of legs with dark stripes on the articulations (Fig. 4A).

Plato novalima sp. n.
http://zoobank.org/1A1653F3-0C7D-4C07-A000-FFE0F2DEDA7F Figures 3E, 5, 6, 16 Plato sp.: Pinto-da-Rocha, 1995: 74 (examined, now in IBSP 56068, IBSP 56075, and IBSP 56081  Etymology. The specific name is a noun in apposition from the type locality. Diagnosis. Male resembles P. ferriferus sp. n. and P. striatus sp. n. in the rounded tegulum, posterior portion of conductor hyaline and partially overlapping the embolus, and longer than larger bulb. It can be distinguished by the proximal portion of the conductor with an elongated tip and a prickly projection (Fig. 5C-F) and median apophysis with a single long rounded tip (Figs 5D). The female resembles P. ferriferus sp. n. in the larger than long epigynal plate, with a sclerotized canoe-shaped internal plate surrounding the spermathecae, but is distinguished by the smoothly projected posterior edge (Fig. 6A-B) and straight curvature of copulatory ducts (Fig. 6C).
Distribution. Common in the Iron Quadrangle, state of Minas Gerais, Brazil (Fig. 16).  Natural history. Most specimens were collected in caves in iron formations, in the middle of their orbicular webs and usually in the twilight zone (Fig. 3E). Egg sacs had a cubic shape and were fixed on the walls of caves. In some cases, more than one egg sac was observed on a single guide wire.
Etymology. The generic name "Cuacuba" means hidden in the native language of the South American indigenous tribe Tupi. It refers to the embolus of the male palp.
Diagnosis. Males of Cuacuba gen. n. can be distinguished from the other males in the family by the C-shaped conductor, split into anterior and posterior apophysis ( Fig.  9B-C). The anterior apophysis has distal filamentous ornaments (Figs 9D, 14E) and the posterior one covers the embolus (Figs 9B, 11C-E). Resembles the genus Sinoalaria Zhao & Li, 2012 in the morphology of the conductor covering the embolus and in not having an embolic division (see Lin et al. 2014: fig. 6A). Females of Cuacuba gen. n. are similar to females of Sinoalaria in the curves of the copulatory ducts, and in position and shape of spermathecae (see Lin et al. 2014: figs 10A-B), but can be distinguished by the lack of scapus, and by having epigynum with salient posterior margin, distally notched in the transversal groove (Figs 10B, 15C-D).

Relationships
Among the results obtained with the genus Plato, the three new species have the five putative synapomorphies indicated for Platoninae (see Coddington 1986: 18−19). A phylogenetic analysis is necessary to establish the relationships among all species of the genus. On the other hand, the peculiar characteristics of Cuacuba gen. n. genitalia make it difficult to insert the genus into any of the current four Theridiosomatidae subfamilies (Coddington 1986;Labarque and Griswold 2014). The same occurs even if we consider the two subfamilies proposed by Wunderlich (2011), Luangnaminae Wunderlich (with two tribes, and the genus type synonymized with Coddingtonia La-ation among the species of the former genus. Sinoalaria bicornis Lin, Li & Jäger, 2014 has the same route of the copulatory ducts as in Cuacuba gen. n. (see Lin et al. 2014: fig. 13E). The main difference between the female genitalia in the two genera is in the scape, as Cuacuba gen. n. has no scape, only a marked prolongation of the posterior region of the epigynal plate. Both genera have a transverse groove in the posterior area of the epigynum.
The female genitalia of Ogulnius and Tagalogonia also resemble those of Cuacuba gen. n. in the curves of the copulatory ducts. Ogulnius females have connate spermatheca, wide and sinuous copulatory ducts and a transverse groove. Cuacuba gen. n. (Figs 10A−B, 13D) has more complex curves in the copulatory ducts, more similar to those of Tagalogonia, besides presenting the posterior margin of the elongated and accentuated epigyinal plate. In addition, Sinoalaria females share the twisted routes of the coupling ducts with Coddingtonia, Tagalogonia, Ogulnius, Theridiosomatinae, and Cuacuba gen. n.
In general, the internal morphology of genitalia of Theridiosomatidae is conservative within each genus. The median spermathecae is present in most genera, usually paired, globular, connate or with little distance between them, in addition to coiled or enveloped ducts, peripheric to the spermathecae, generally varying more in width than length (Figs 2C, 6C, 13D, Coddington 1986: figs 26, 51, Labarque andGriswold 2014: figs 3F, 6F). Although Sinoalaria was well characterized by the authors, it has not been formally included in any subfamily. It was, however, considered a probable member of the Epeirotypinae or Platoninae subfamilies, due to the distal embolic opening and absences of apophysis and embolic division (Labarque and Griswold 2014).
Cuacuba gen. n. is very similar in external morphology and in general habits to Plato, so they can be easily confused (Pinto-da-Rocha 1995). In addition, some similarities in the genitalia are similar to Sinoalaria, Tagalogonia and Ogulnius. Cuacuba gen. n. resembles Ogulnius in the long and tapered embolus covered by the conductor, in addition to the female characteristics mentioned above; however, it does not present the diagnostic characteristics of Ogulninae Coddington, 1986, such as the abdomen greatly overlapping cephalothorax, leg IV longer than leg I and reduced body size. Important synapomorphies of Platoninae (probable subfamily to which Sinoalaria belongs) such as pointed cymbium, T-shaped paracymbium and median apophysis recurved with long-tip, are absent in Cuacuba gen. n. Thus, Cuacuba gen. n. shares general characteristics with different subfamilies and does not currently fit into any known subfamily. Without an extensive analysis of the intrageneric family relationships, the new genus cannot be allocated to any of the current subfamilies, nor can we confirm it is a sister group of Sinoalaria.

Distribution and associated lithologies
Even with the development of biospeleology in Brazil, undersampled or even nonsampled areas (Trajano and Bichuette 2010) and large mappings of this fauna are ex-  tremely scarce. In this work, we identified 3868 adult spiders distributed in 1007 caves, and observed that the spider species in Plato and Cuacuba gen. n. are highly related to cave environments. They are troglophile aerial spiders that build orbicular webs but do not present troglomorphic characteristics. They mostly occur in dark environments and may occupy dysphotic environments, twilight regions and cave entrances. According to Coddington (1986), all described Plato species were located in cryptic habitats and/or in caves, corroborating the observed for species included in this work. This characteristic behavior was also observed for species of Cuacuba gen. n., which were sometimes confused with Plato (Pinto-da-Rocha 1995). The species of Plato, Baalzebub Coddington, 1986 and Cuacuba gen. n. are the most frequent theridiosomatides in Brazilian caves. Plato ferriferus sp. n. is one of the spiders most commonly found in the ferruginous caves located in FLONA Carajás and surrounding regions, in the state of Pará. Plato novalima sp. n., and Cuacuba mariana sp. n., together with Baalzebub acutum Prete, Cizauskas & Brescovit, 2016 are the most frequently observed species in caves in the state of Minas Gerais. Plato novalima sp. n. is mainly found in the karst region of the Iron Quadrangle.
Due to the high abundance of individuals collected, we evaluated the frequency of capture of the species recorded in this study. We observed that the species of Plato are mostly located in caves in iron formations, whereas those of Cuacuba gen. n. are usually found in other lithologies, such as carbonates. Plato ferriferus sp. n., the most abundant species in this study (3098 adult spiders collected), was observed in 816 caves, 809 of which (99% of the records) were inserted in ferruginous rock outcrops. The sole representative of Plato striatus sp. n. was also collected in a ferruginous cave in FLONA de Carajás.
A more detailed analysis was performed on Plato novalima sp. n. and Cuacuba mariana sp. n., as they are the only species herein studied living in sympatry inside caves (n = 2) of the region of Iron Quadrangle in the state of Minas Gerais. Cuacuba morrodopilar sp. n. was collected only in two quartzite caves. Table 1 shows the number of individuals collected and from how many caves. For both species, the mean number of individuals collected per well was approximately two (Fig. 18A). However, when we evaluated the cave environment where the specimens were captured we observed that there is a preference for caves inserted in different lithologies (Fig. 18B).