A New Genus of Prodidominae Cave Spider from a Paleoburrow and Ferruginous Caves in Brazil (Araneae: Prodidomidae) ^†

Abstract

A new monotypic genus of Prodidominae, Paleotoca gen. n., is proposed to include one cave species collected in a paleoburrow and ferruginous caves from Quadrilátero Ferrífero, Minas Gerais, Brazil: Paleotoca diminas sp. n. (♂♀). The new genus is closely related to other Neotropical Prodidominae by sharing the classic claw tuft clasper. Paleotoca gen. n. is diagnosed by the absence of a dorsal abdominal scutum, a ventral parallel rows of strong spines on the tibia and metatarsus I–II, a lack of a conductor, a discrete median apophysis on the bulb and a bifid retrolateral tibial apophysis in the male palp, a posterior extension that is beak-shaped, and folds of a copulatory duct ventrally visible in the female epigyne. Like other Prodidominae species from caves, P. diminas sp. n. is a troglobitic spider with morphological characteristics that indicate specialization to live in subterranean environments, including reduction in cuticular pigments, eye loss, heavy spination and trichobothria.

1. Introduction

Prodidomidae Simon, 1884 includes small to medium-sized spiders distributed Worldwide [1,2] and is currently represented by 190 species in 23 genera [3]. Only ten genera occur exclusively in the Neotropical region: Tricongius Simon, 1893, Lygromma Simon, 1893, Moreno Mello-Leitão, 1940, Caudalia Alayón, 1980, Chileomma Platnick, Shadab & Sorkin, 2005, Chileuma Platnick, Shadab & Sorkin, 2005, Chilongius Platnick, Shadab & Sorkin, 2005, Brasilomma Brescovit, Ferreira & Rheims, 2012, Paracymbiomma Rodrigues, Cizauskas & Rheims, 2018 and Indiani Rodrigues, Cizauskas & Lemos, 2020.

Among Neotropical spiders, seven species are considered subterranean: Lygromma gertschi Platnick & Shadab, 1976, known from limestone caves in Jamaica, L. anops Peck & Shear, 1987, from volcanic caves in the Galapagos Islands and from Brazilian caves Paracymbiomma caecus and P. bocaina Rodrigues, Cizauskas & Rheims, 2018 from ferruginous caves of the Pará State, and Tricongius ybyguara Rheims & Brescovit, 2004, from a limestone cave, Brasilomma enigmatica Brescovit, Ferreira & Rheims, 2012, from ferruginous, limestone and quatizitic caves, and Indiani gaspar Rodrigues, Cizauskas & Lemos, 2020 from limestone caves of the Minas Gerais.

In this paper we describe a new monotypic genus of Prodidominae, Paleotoca gen. n. to include one new species found exclusively in a paleoburrow and ferruginous caves from Brazil. The new genus belongs to a clade of Neotropical genera that has a classic claw tuft clasper as a non-homoplasious synapomorphy [4].

2. Material and Methods

The examined material is deposited in the collection of the Instituto Butantan, São Paulo, Brazil (IBSP, curator: A.D. Brescovit). Morphological observations and illustrations were made under a Leica MZ165C stereomicroscope with a camera lucida. Format of descriptions and terminology follow [4]. All measurements are in millimeters. The number and arrangement of spines follow [5]. Leg measurements are listed as total length (femur, patella, tibia, metatarsus, tarsus). Positions of embolar insertion are given according to clock positions, based on the left palp in ventral view. Pictures were taken using a MC170HD camera mounted on a Leica S8APO stereomicroscope. Extended focal range images were composed with the Leica Application Suite, version 4.0. Scanning electron micrographs (SEM) were taken with a FEI Quanta 250 scanning electron microscope from the Laboratório de Biologia Estrutural at the Instituto Butantan. Material used for SEM was dehydrated through a series of graded ethanol (80% to 100%), dried by critical-point drying method, mounted on metal stubs, and sputter coated with gold. Distribution maps were prepared using the Geographic Information System (GIS) software program Quantum Gis version 3.28.3. Geographical coordinates of caves were obtained from the National Speleological Information Registry (CANIE) on the CECAV/ICMBio (National Center for Research and Conservation of Caves, Brazil) website.

Abbreviations used throughout the text: A—atrium; ALS—anterior lateral spinnerets; CD—copulatory duct; CO—copulatory opening; Cy—cylindrical gland spigot; d—dorsal; E—embolus; EF−epigynal field; FD—fertilization duct; MA—median apophysis; MaAm—major ampullate gland spigot; MiAm—minor ampullate gland spigot; p—prolateral; Pcb—paracymbium; PEs—promarginal escort seta; PEx—posterior extension of epigynum; Pi—piriform gland spigot; PIn—postepigastric invaginations; PLS—posterior lateral spinnerets; PMS—posterior median spinnerets; PS—primary spermathecae; PRk—promarginal rake seta; PWh—promarginal whisker seta; r—retrolateral; RTA—retrolateral tibial apophysis; SS—secondary spermathecae; v—ventral; Wh—cheliceral whisker seta.

3. Taxonomy

3.1. Paleotoca gen. n.

Etymology. The generic name is the union of the “Paleo” prefix from the Greek adjective “palaios”, which means “old”, with “toca”, a word probably originating from the Tupi language “oka”, which means house. “Paleotoca” is a subterranean shelter excavated by extinct megafauna mammals. The generic name is feminine.

Diagnosis. Paleotoca gen. n. differs from the other genera of Prodidomidae due to the male palp lacking a conductor, a discrete median process in the bulb, originating in the central subapical region of the tegulum (Figure 1E,F and Figure 4A,B), a bifid tibial process with two projections, a long posterior one and an anterior one smaller, ventrally directed, and inserted on the retrolateral surface of the tegulum (Figure 1F and Figure 4B); females are distinguished by the inconspicuous atrium in a posterior position, a posterior extension of the beak-shaped epigyne (Figures 5A, 6C and 7F), and folds of the copulatory duct visible ventrally (Figures 5A and 6C). It resembles the genera Moreno, Chileomma, Brasilomma, Nopyllus, and Indiani due to the presence of a ventral parallel rows of strong spines on tibia and metatarsus I–II and also the absence of scopules (Figure 1B; see Rodrigues et al., 2020 [4], fig. 1C), but with a unique number of spines. As in Nopyllus, Paleotoca gen. n. has a rounded sternum, which is wider around coxae II, a very narrow posterior end, and a projection between coxae IV (see Ott, 2014 [6], fig. 27, Rodrigues & Rheims, 2020 [4], fig. 11I), but with the projection between coxae IV being longer and more pointed (Figure 1C). And as in Moreno, the male palp has an oval cymbium with an embolus in the apical position (Figure 1E, Figures 3C and 4A; see Platnick et al., 2005 [7], figs. 15, 19, 23 and 27). However, Paleotoca gen. n. has prolateral filiform embolus and a retrolateral tibial bifid apophysis, which is divided by a slit (Figure 1E,F, Figures 3D and 4B; see Platnick et al., 2005 [7], figs. 16, 20, 24 and 28).

3.2. Paleotoca gen. n.

Description. Carapace and legs pale yellow, abdomen weakly pigmented (Figure 1A). Carapace longer than wide, narrower at cephalic region. Fovea present as a narrow dark longitudinal line on posterior half of carapace (Figure 1A). Eyes absent (Figure 1A, Figure 2A, Figures 6A and 7A). Chilum present (Figure 7A). Chelicerae with a convex boss, promargin with one teeth and retromargin with five teeth, region proximal to the teeth differentiated in the form of scales (Figure 2B and Figure 7B,C). Endites slightly convergent anteriorly (Figure 1C); serrula present in single row, male three teeth (Figure 2C) and female five teeth (Figure 7E); labium with distal margin similar to basal margin (Figure 1C). Sternum rounded, widest around coxae II, posterior end very narrow and projecting between coxae IV (Figure 1C); precoxal triangles absent. Pedicel with ventral sclerite triangular. Leg formula 4123. Two ventral parallel rows of strong spines on tibia and metatarsus I–II (Figure 1B). Trichobothria present on dorsum of tibia, metatarsi and tarsi III, bothrium with three deep ridges (Figure 8C). Tarsal organ capsulate with elongated drop shape opening, located dorsally on tarsi (Figure 8D). Two pectinate tarsal claws; claw tufts inserted together composed of slightly widened tenent setae (Figure 3A and Figure 8E,F); claws with claw tuft clasper (Figure 3A and Figure 8E). Abdomen oval, longer than wide (Figure 1A and Figure 6A); dorsal scutum absent, dorsum of abdomen anteriorly with long, dark, posteriorly curved setae (Figure 1A and Figure 6A); postepigastric invaginations present (Figure 6C). Six spinnerets; ALS separated from each other by one diameter or more (Figure 6B), one major ampullate gland spigot and four piriform gland spigots elongated with few associated setae (Figure 2D); PLS and PMS conical and short, PLS larger than PMS (Figure 6B), PMS with one cylindrical gland spigot (Figure 2E) and PLS with one minor ampullate gland spigot (Figure 2F). Female pedipalp with one pectinate claw (Figure 8A,B). Male palp: femur with dorsal posterior spine, two prolateral anterior and one posterior; tibia short with bifid tibial apophysis with two branchs, anterior smaller, directed ventrally, posterior long, directed apically, both inserted in a large base on the retrolateral side of the tibiae (Figure 1F and Figure 3D), trichobothria present (Figure 3B), bothrium with four deep ridges (Figure 3B,E,F); cymbium oval without scopula and with one posterior dorsal strong setae and seven or eight ventral apical setae (Figure 1D–F); bulb oval; embolus prolateral, filiform, inserted at 9-o’clock position (Figure 1D and Figure 3C), tapering and curved at the margin of a subapical flattening of the tegulum toward the apical region (Figure 3C and Figure 4A); small median apophysis originating in the subapical central region of the tegulum (Figure 1E,F and Figure 4A,B). Epigyne: atrium small and narrow (Figures 6C and 7F), projected posterior extension border shaped medially (Figure 5A, Figure 6C and Figure 7F), folds of copulatory duct ventrally visible (Figure 5A and Figure 6D). Vulva: FD with hyaline part three times longer than sclerotized part closer to CO; PS elongate, roughly five times longer than wide (Figure 5A and Figure 6C); secondary spermathecae absent. (Figure 5B and Figure 6D).

Composition. Monotypic.

3.3. Paleotoca diminas sp. n.

Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8 and Figure 9 and Figure 11.

Type material: Holotype male and female paratype from Cave AP-0038 (Paleoburrow) [20°01′52″ W, 43°40′45″ S], Caeté, Minas Gerais, Brazil, 12 February 2012, R. Andrade et al. leg., deposited in IBSP 264705. 1♀, same data as holotype (IBSP 264708), 1♂, same data as holotype, 19−25 July 2008, R. Bessi et al. leg. (IBSP 264704), 2♀, same data as holotype, 31 May to 5 June 2012, R. Bessi et al. leg. (IBSP 264707).

Etymology. The specific name “diminas” is the popular Brazilian way to inform that the object in question originates from the State of Minas Gerais “De Minas Gerais”. The specific name is feminine noun.

Diagnosis. See generic diagnosis.

Description. Male (holotype). Cephalothorax pale yellow and depigmented abdomen. Total length: 1.75. Carapace 0.8 long, 0.61 wide; abdomen 0.81 long, 0.51 wide; sternum 0.56 long, 0.43 wide; ALS 0.18 long, 0.07 wide. Eyes absent. Chelicerae 0.17 long. Leg formula 4123; measurements: I: 2.52 (0.72, 0.27, 0.66, 0.46, 0.42); II: 2.26 (0.61, 0.23, 0.53, 0.47, 0.41); III: 2.13 (0.58, 0.21, 0.43, 0.50, 0.40); IV: 2.88 (0.79, 0.25, 0.63, 0.71, 0.50). Leg spination: I—femur d1-1-0-r1, p0-0-1, v0-1-0; tibia v2-1-2-2-1-2-2-2, d-0-1-0; metatarsus v2-2-2-2-2. II—femur d1-1-0-r1; tibia v2-2-1-2-2-2, p-0-0-1-0-0, r0-0-1-0-0; metatarsus v2-2-2-2. III—femur d0-1-0-r1-p1; tibia d0-1-0, p1-0-1, r1-0-1, v0-1-0; metatarsus v2-1p1r-2-1p1r. IV—femur d1-1-0-1r-1p; tibia r1-p1-d1-p1-r1; metatarsus r1-d1-p1-v1-r1-p1. Palp as in generic description (Figure 1D–F and Figure 4A,B).

Female: Female (paratype). Cephalothorax pale yellow and depigmented abdomen. Total length: 2.03 Carapace 0.765 long, 0.57 wide; abdomen 1.30 long, 0.62 wide; sternum 0.478 long, 0.414 wide; ALS 0.22 long, 0.065 wide. Eye absent. Chelicerae 0.186 long. Leg formula 4123; measurements: I: 2.12 (0.61, 0.21, 0.58, 0.35, 0.36); II: 2.02 (0.59, 0.24, 0.46, 0.36, 0.37); III: 1.93 (0.54, 0.22, 0.40, 0.42, 0.35); IV: 2.74 (0.67, 0.29, 0.59, 0.62, 0.48). Leg spination: I—femur d1-1-0, p0-0-1; tibia v2-2-2-2-2-2; metatarsus v2-2-2-2-2. II—femur d0-1-0; tibia v2-2-2-2-2-2; metatarsus v2-2-2-2-2. III—femur d0-1-0; tibia d01-0-1-0, p0-1-0-1, r0-1-0-1, v1-0-1-0; metatarsus d0-1-0-1, p0-1-0-1, r0-1-0-1, v0-1-0-1. IV—femur d1-0-1-0; tibia d0-1-0-1, v0-1-0-1; metatarsus v0-0-0-1, r1-0-1-1, p1-1-0-1. Epigynum as in generic description (Figure 5A,B, Figure 6C,D and Figure 7F).

Other material examined. BRAZIL, Minas Gerais: 1♀, Caeté, Cave AP-0069 [20°00′ 37″ W, 43°40′11″ S], 12−21 November 2009, R. Bessi et al. leg. (IBSP 264697); 1♀, Cave AP-0065 [20°01′24″ W, 43°41′04″ S], 31 May–5 June 2012, R. Bessi et al. leg. (IBSP 264706); 1♀, Mariana, Cave FN-0019 [20°12′28″ W, 43°26′19″ S] 30 June–1 July 2010, R. Andrade et. al. leg. (IBSP 264709); 1♂, Santa Bárbara, Cave APOL-0001 [20°00′35″ W, 43°39′56″ S], 30 June–8–31 July 2011, R. Bessi et al. leg. (IBSP 264710).

Remarks. Most of the individuals of Paleotoca diminas sp. n. (Figure 9A–D) were collected in a paleoburrow (Cave AP-0038), natural underground cavities of biogenic origin, excavated by extinct megafauna animals, such as giant ground sloths, that lived thousands of years ago [8,9]. It is located at an altitude of 1536 m and the horizontal projection is 345 m, with a difference in level of 6.8 m and an area of 676 m² and a volume of 798 m³. It is one of the ten largest caves in the world in iron formation [10]. This cave is inserted in the climatic context of the high-altitude tropical type (Cwb), with hot and humid summers and a well-defined dry season [11]. From a phytophysiognomic point of view, the area is located on the boundary between the Atlantic Forest and Cerrado biomes where the shrubby rupestrian field, herbaceous rupestrian field on cangas, and semi-deciduous seasonal forest in medium and advanced stages of regeneration can be observed (Figure 10A,B). The cave has sections of conduits in a semicircular shape and walls with uniform surfaces, a morphology that is unusual for caves located in the country’s iron formation (Figure 10C,E,F). Additionally, conduits grooves with dimensions ranging from 10 cm to approximately 90 cm in length and approximately 2 cm in thickness are observed (Figure 10D), which are compatible with claw marks from ground sloths [12]. In actuality, different taxonomic groups were observed in Cave AP-0038 like bats, amphibians, and a high diversity and abundance of invertebrates, including two troglobitic spiders: Tisentnops mineiro Brescovit & Sánchez-Ruiz, 2016 (Caponiidae) and Paleotoca diminas sp. n. (Prodidomidae) and others troglobiontes.

The specimens of Paleotoca diminas sp. n. were always located on the floor or under rocks in aphotic areas with high humidity. It is a troglobitic spider with reduction in cuticular pigments, eye absent, heavy spination and trichobothria.

Distribution. It is known only from ferruginous caves in Quadrilátero Ferrífero, state of Minas Gerais, Brazil (Figure 11).

4. Discussion

Paleotoca gen. n. has characteristics also observed in different Neotropical genera of Prodidomidae. The spinulation of legs I and II is also observed in Nopyllus [6], Chileomma and Moreno [7], Brasilomma [13] and, Indiani [14]. In the male palp, the absence of the conductor is also observed in Tricongius [4] and the presence of a bifid retrolateral apophysis in the palpal tibia is characteristic of the species of Moreno. The female has an extension of the epigynum plate also observed in Brasilomma. However, Paleotoca gen. n. does not present diagnostic autopomorphies of the aforementioned genera. For example, the presence of a large, clavate, translucent setae on the abdominal dorsum is observed in Moreno (Mello-Leitão, 1940 [15], fig. 49, Platnick, Shadab & Sorkin, 2005 [7], fig. 31). Moreover, a sternum with an anterior margin less than half maximum width (Rodrigues & Rheims, 2020 [6], fig. 11K) and a cymbium with a bunch of thick setae on the ventral terminal part (Rodrigues & Rheims, 2020 [6], fig. 27J) is present in Tricongius.

Among the spiders of the Prodidomidae family, Paleotoca diminas sp. n. is another troglobitic Neotropical species. Body depigmentation, anophthalmia and sensory organs (e.g., trichobrotria) are autapomorphies related to the way of life of this spider, specialized in the subterranean environment [16]. These characteristics are also observed in others species of Neotropical genera such as Brasilomma enigmatica, Indiani gaspar and Tricongius ybyguara. The spinulation of legs I–II is also present in Brasilomma, Chileomma, Indiani, Moreno and Nopyllus.

Still, little is known about the biodiversity of Neotropical Prodidomidae spiders [17]. Among the seventy-six Neotropical species, sixteen are known to Brazil, with six being from cave environments. Rodrigues & Rheims (2020) suggest that phylogenetic studies must be carried out to elucidate the evolutionary relation with the known Neotropical species. However, more studies that expand knowledge of the diversity of epigean spiders are essential for understanding the subterranean fauna.