Charinus taboa sp. n. comprises the twenty-second species of the genus described for Brazil. The new species belongs to the eastern Brazilian group, in which all species have sucker-like gonopods. Charinus taboa sp. n. has a marked sexual dimorphism in the pedipalps as do other members of the genus in the country. The description of Charinus taboa sp. n. offers an opportunity to discuss some aspects of ecology, troglomorphism and conservation within the genus. A key to the eastern Brazilian species of Charinus is provided.

Neotropics, subterranean species, taxonomy, whip spider

Knowledge of the Amblypygi fauna remained low and fairly constant for many years until last decade of the 20^th century, when studies and descriptions of whip spiders considerably increased in number (Harvey 2007). Yet, until 2015, the number of known species of Charinus in Brazil was just 11, but it has rapidly almost doubled over the last year, reaching 21 described species (Vasconcelos and Ferreira 2016, Giupponi and Miranda 2016). The most specious and widely distributed group of Amblypygi is the genus Charinus. It is found throughout the tropics, including diverse types of habitat and even oceanic islands (Weygoldt 2000, Miranda and Giupponi 2011, Jocque and Giupponi 2012, Harvey 2013, Vasconcelos et al. 2013, 2014, Réveillion and Maquart 2015). However, the considerable richness of the genus (more than 60 species) allied with its wide distribution and distinct morphologies of the female genitalia suggest that the genus is not monophyletic (Weygoldt 1996, 2000, Harvey 2013).

Species of the genus Charinus are dependent on moist environments, and as other whip spiders, they are of nocturnal habit (Weygoldt 2000, Vasconcelos et al. 2013). Together with their flattened bodies, one of the characteristics of Amblypygi, Charinus species also have small body sizes (up to 16mm), which allow them to shelter in a range of microhabitats, such as trunks, bromeliads, rocks, subterranean cavities and termite nests (Weygoldt 2000, Jocque and Giupponi 2012, Vasconcelos et al. 2014, Réveillion and Maquart 2015). Synanthropic habitats can also house some species of Charinus, such as C. vulgaris Miranda and Giupponi, 2011, and the parthenogenetic species, Charinus acosta (Quintero, 1983) and Charinus ioanniticus (Kristcher, 1959) (Armas 2005, Weygoldt 2005).

In Brazil, Charinus species typically use caves as habitat. Within the 21 known species of the genus in the country, 13 were described from individuals collected in caves: Charinus acaraje Pinto-da-Rocha, Machado and Weygoldt, 2002, Charinus mysticus Giupponi and Kury, 2002, Charinus troglobius Baptista and Giupponi, 2002, Charinus eleonorae Baptista and Giupponi, 2003, Charinus potiguar Vasconcelos, Giupponi and Ferreira, 2013, Charinus jibaossu Vasconcelos, Giupponi and Ferreira, 2014, Charinus caatingae Vasconcelos and Ferreira, 2016, Charinus iuiu Vasconcelos and Ferreira, 2016, Charinus ricardoi Giupponi and Miranda 2016, Charinus carajas Giupponi and Miranda 2016, Charinus orientalis Giupponi and Miranda 2016, Charinus ferreus Giupponi and Miranda 2016 and Charinus bichuetteae Giupponi and Miranda 2016. Among these species, C. troglobius, C. eleonorae, C. caatingae and C. ferreus represent hitherto the only strictly cavernicolous species in the country. Herein, a new species of Charinus is described from limestone caves located in Sete Lagoas, state of Minas Gerais, Brazil. Moreover, the possible troglobitic status of this species is discussed.

The specimens were collected through visual searches throughout floors and walls of the caves. All specimens were captured with a fine forceps and placed in vials containing 70% ethanol.

The description of the species was based on the entire type material. Measurements and general terminology were based on the proposals of Quintero (1981). The terminology of pedipalps and legs followed Harvey and West (1998). The tarsus as defined by Harvey and West (1998) is divided here into tarsus and claw (apotele), as there is no fusion of these two segments in Charinidae. Measurements of the pedipalps were taken between the condyles of each segment. Measurements were taken of the entire type-series (quantity indicated as “n”), presenting first their mean values followed by the range of variation in parentheses. The terminology of the structures of male gonopods followed Giupponi and Kury (2013).

The following abbreviations are used:

BT basitibia

DT distitibia

GO genital operculum

Fi fistula (gonopod tube)

Pi processus internus

LaM lamina medialis

LoD lobus dorsalis

LoL1 lobus lateralis primus

LoL2 lobus lateralis secundus

Photographs were taken using a Leica M205A stereomicroscope with the software Leica Application Suite Automontage. Illustrations of the male and female gonopods were made using a camera lucida coupled to a Leica MDLS phase contrast microscope.

The specimens were deposited in the following institution collections:

MNRJ Museu Nacional, Rio de Janeiro, Brazil

ISLA Seção de Invertebrados Subterrâneos, Coleção de Zoologia of the Universidade Federal de Lavras, Minas Gerais, Brazil

CAVAISC Fundação Oswaldo Cruz, Instituto Oswaldo Cruz, Rio de Janeiro, Brazil

DNS Geographical coordinates are given in Degrees, Minutes and Seconds

As proposed by Weygoldt (2005, 2006, 2008), species of Charinus can be divided into four groups based on the morphology of the female gonopods, including species with “sucker-like” gonopods (Charinus brasilianus group), “cushion-like” gonopods (Charinus australianus group), a group of species with “finger-like” gonopods (Charinus bengalensis group), and finally, the group represented by Charinus seychellarum, in which the gonopods were totally lost. In Brazil, the species distributed on the eastern side are included in the C. brasilianus group, while species distributed in the Amazon region are considered part of the C. australianus group. Charinus taboa is placed in the first group in conjunction with C. brasilianus Weygoldt, 1972, C. montanus Weygoldt, 1972, C. asturius Pinto-da-Rocha, Machado & Weygoldt, 2002, C. acaraje, C. mysticus, C. troglobius, C. eleonorae, C. potiguar, C. jibaossu, C. caantingae and C. iuiu. Charinus schirchii (Mello-Leitão, 1931) is also located in eastern Brazil, but it is considered a species inquirenda as the holotype specimen has been lost and so its morphological characteristics and grouping cannot be confirmed (Pinto-da-Rocha et al. 2002). Species of this group also differ from the other western species by being larger, presenting chelicera with a higher number of teeth and basitibia of leg IV with four pseudoarticles (Giupponi and Miranda 2016).

Among the species from southeast Brazil, another common character is found, a sexual dimorphism in the pedipalps (Table 1, Figs 18, 19). With exception of the troglobite species C. eleonorae (which is distributed further north), males of C. taboa and all other Charinus species that occur in this region of the country (C. montanus, C. brasilianus, C. asturius and C. jibaossu) have longer pedipalps than the females (Pinto-da-Rocha et al. 2002, Vasconcelos et al. 2014, Weygoldt 1972). The presence of this characteristic among these species may indicate that they share the same recent common ancestor. Or, alternatively, organisms of these species might have undergone similar selective pressures in the past, which could have led to homoplasy in this character. Therefore, there is pressing need for a phylogenetic analysis of Brazilian Charinus species to understand these questions of relatedness between species.

Charinus taboa differs from C. montanus, C. brasilianus, C. asturius and C. jibaossu by having less developed eyes, and with the exception of C. brasilianus, five thricobotria instead of six in each series of the basitibia of leg IV (Fig. 17). Charinus taboa also differs from C. montanus in the shape of the segments of the sternum. While the second and third segments of the sternum of C. taboa are rounded (Figs 8, 11), in C. montanus these segments are flattened. Charinus taboa differs from C. jibaossu by having four spines in the ventral side of the patella (Fig. 6) instead of three. The quantity of spines on the others segments of the pedipalps is similar among many of the cited species, which makes it difficult to separate them by this characteristic alone (Weygoldt 1972, Pinto-da-Rocha et al. 2002, Vasconcelos et al. 2014).

Charinus taboa differs from C. acaraje, C. troglobius, C. eleonorae, C. potiguar, C. caatingae and C. iuiu mainly by the fact that these species have shorter pedipalps, with fewer amount of spines on the femur and patella, and from C. mysticus and C. caatingae by the presence of three spines on the tarsus of the pedipalps. Charinus mysticus, C. acaraje, C. eleonorae, C. potiguar, C. caatingae and C. iuiu also have the frontal and caudal series of the leg IV with six thricobotria each, C. eleonorae has a pointed frontal process, and in C. troglobius, the tritosternum is lacking the typical cone shape (Baptista and Giupponi 2002, 2003, Giupponi and Kury 2002, Pinto-da-Rocha et al. 2002, Vasconcelos et al. 2013, Vasconcelos and Ferreira 2016).

The morphologies of the male gonopod are quite variable among Charinus species; however, in dorsal view the shapes of the genital organ and LoD of C. taboa (Fig. 15) are similar to those in C. eleonorae. The female gonopod of C. taboa (Fig. 14) has the width larger than its length, which makes it similar to those of C. asturius, C. eleonorae e C. mysticus. Besides that, C. taboa presents its gonopod with the edges similar to that of C. mysticus, yet its shape is more irregular (Pinto-da-Rocha et al. 2002, Giupponi and Kury 2002, Baptista and Giupponi 2003).

The newly described species presents poorly developed eyes, lighter coloration than other non-troglobite species of Charinus, and is, to our knowledge, restricted to only two caves, which make plausible its status of troglobitic. Different degrees of troglomorphisms may appear due to changes in environmental conditions and not necessarily depends on cave occupancy by the organism. According to Weygoldt and Van Damme (2004), if a given region goes through changes in climate and consequently in humidity, organisms adapted to the anterior conditions can retreat in caves, which may result in troglomorphisms after some time, such as reduction in eye size and coloration, and elongation of legs and other appendages. Changes engendered by the restricted life in the interior of subterranean habitats in Charinus are the reduction in eye size, being completely absent in some cases, lightening of the color of the cuticle, change in the position of the pedipalps, being vertical in relation to the body, and elongation of the spines on the pedipalps (Baptista and Giupponi 2002, Baptista and Giupponi 2003, Weygoldt and Van Damme 2004, Delle Cave et al. 2009).

There are few troglobitic species of Charinus around the world: four in Brazil (C. troglobius, C. eleonorae, C. caatingae, C. ferreus), two in Venezuela (Charinus tronchonii (Ravelo, 1975) and Charinus bordoni (Ravelo, 1977)), and three in the Arabian Peninsula (Charinus socotranus Weygoldt, Pohl and Polak, 2002, Charinus stygochthobius Weygoldt and Van Damme, 2004, Charinus omanensis Delle Cave, Gardner and Weygoldt, 2009). Charinus stygochthobius represents the most troglomorphic species of those already described, since it lacks all its eyes, its cuticle is almost transparent, it has the pedipalps forming an angle of 45° in relation to the body and long spines on the pedipalps (Weygoldt and Van Damme 2004). Charinus troglobius presents total absence of the median eyes and small eyespots replacing the lateral eyes, depigmentation of the body, rotation of the pedipalps, as occurs to C. stygochthobius, and elongated spines (Baptista and Giupponi 2002). Charinus eleonorae has reduced lateral eyes, eyespots in the place of median eyes, light coloration, rotation of the pedipalps and elongated spines (Baptista and Giupponi 2003). Charinus caatingae presents lateral eyes reduced to eyespots, light pigmentation, and rotation of pedipalps in some individuals, being the least troglomorphic species in the country. Charinus ferreus presents almost complete loss of eyes and little coloration of the cuticle.

In the case of C. taboa, the eyes are still present, but they are smaller than those of most Charinus species in Brazil. In addition, this species has lighter coloration of the body compared to other species. However, some specimens of C. taboa present pigmented lateral eyes with a lesser degree of reduction (Figs 2, 9). The varying degree of troglomorphism within a population is common, although not well studied, and may be a characteristic of various groups. One example is the isopod Asellus aquaticus, which has polymorphisms in the degree of pigmentation of the eyes and body, in the size of the sensory appendages and body proportions (Prevorcnik et al. 2004).

With a cladistic analysis unavailable, it is not possible to ascertain whether a species of Charinus is troglobitic based solely on troglomorphic characters, since the species may have not been in a cave for sufficient time to develop morphological adaptations (beyond other factors, as the original size of the isolated population, species variability, etc.). Therefore, the condition of a given species of maintaining a viable population strictly inside caves should also be taken into account when deciding on the classification of a cave-dwelling species (Bolfarini and Bichuette 2015). This might be the case of C. taboa, which presents few troglomorphic characteristics, but is found within two caves located in a heavily deforested and human-modified landscape; the species seems to be unable to establish populations outside of its existing range. Yet, despite C. taboa has morphological characteristics suggesting the exclusive subterranean habit, more inventories are needed to confirm the non-occurrence of the species outside of these habitats.

Many species of Charinus in Brazil are highly vulnerable to extinction as a result of vast destruction of their habitat by deforestation or mining. C. taboa, which was recorded in only two very close caves, is considered rare and endemic. Thus, according to the laws of Brazil, this species may increase the biological importance of both the Taboa and BR-24 caves, and therefore ensures the continued preservation of those unique habitats.

We would like to thank Pedro Ratton, Maysa F. V. R. Souza and Luiz F. M. Iniesta for assistance in the field, and Dr. Paulo Rebelles Reis (EPAMIG-CTSM/Eco Centro Lavras) for enabling the use of the microscope with camera lucida. We thank Adriano B. Kury (MNRJ) for providing a repository for the specimen and Fábio Bondezan (UFMG) for collecting additional type-material and providing information regarding the Cave BR-24. We also thank Gustavo Miranda, Abel Pérez and Mark Harvey for criticism of the manuscript. We are grateful to Vale Company and to CEBS for the financial support, and to CAPES – edital Pró-equipamento 2010 for the equipment for auto-montage and the National Council of Technological and Scientific Development (CNPq) (grant no 304682/2014-4).