Tmesiphantes hypogeus sp . nov . ( Araneae , Theraphosidae ) , the first troglobitic tarantula from Brazil

A new species of Tmesiphantes Simon, 1892, is described from sandstone/quartizitic caves of Chapada Diamantina, Bahia State, Brazil. This is the fifth species of the genus and the first record of a troglobitic mygalomorph in Brazil. A key is presented for all Tmesiphantes species.


INTRODUCTION
Theraphosid is the largest mygalomorph family, containing 937 of the 2,683 described mygalomorph species (Platnick 2011).Despite its high diversity and wide distribution throughout most tropical and subtropical areas in the world, a few troglobitic species are known (cave restricted organisms with autapomorphic character-states related to this isolation, mainly regression of eyes and body pigmentation -sensu Holsinger and Culver 1988).All of these species are included in a single genus, Hemirrhagus Simon, 1903, found exclusively in Mexico.Hemirrhagus has 16 species, and all species with published collection records were found inside caves, among which six are proven troglobites (Gertsch 1973, 1982, Pérez-Miles and Locht 2003, Redell 2005).Indeed, Hemirrhagus troglobitic species show high endemism, with each species restricted to a single cave.
Herein we describe a new species of theraphosid found in two Brazilian caves in the State of Bahia, representing the first theraphosid troglobites found in Brazil.The species is putatively included in the genus Tmesiphantes.This genus has 4 species: T. nubilus Simon, 1892, T. amadoi Yamamoto et al., 2007, T. bethaniae Yamamoto et al., 2007, and T. caymii Yamamoto et al., 2007, all found in the State of Bahia, Brazil.

MATERIALS AND METHODS
All measurements are presented in milimeters and were obtained with a Mitutoyo digital calliper with an error of 0.01 mm.Leg and palp measurements were taken from the dorsal aspect of the left side (unless appendages were lost or obviously regenerated).
235-243 ROGéRIO BERTANI, MARIA ELINA BICHUETTE and DENIS R. PEDROSO A Nikon SMZ1500 dissecting microscope was used for illustrations (with a camera lucida attachment).Urticating hairs were examined and photographed with a Leica DM LB2 compound microscope.Urticating hair terminology follows Cooke et al. (1972), and leg spines terminology follows Petrunkevitch (1925) with modifications proposed by Bertani (2001).
Specimens are deposited in the Museu Nacional do Rio de Janeiro (MNRJ).

Diagnosis:
Females can be distinguished from all Tmesiphantes species by highly reduced AME that is shorter than PME, mostly transparent eye THE FIRST TROGLOBITIC TARANTULA FROM BRAZIL  2C), slender legs (Fig. 1) and reduction of the urticating hair area to two small patches on dorso-lateral abdomen (Figs 1, 2A).

Etymology:
The specific name is from the Latin adjective (masculine) hypogeus (underground), referring to the isolated site condition.

DISCUSSION
Tmesiphantes hypogeus sp.nov.has a reduced anterior median eye that is even smaller than its posterior median eye, a characteristic uncommon in theraphosids (Fig. 2C) that could be considered a troglomorphic character.The eye tubercle is low and mostly transparent, allowing one to see the internal structures of the anterior lateral eye, posterior median eye, and posterior lateral eye (Fig. 2C).Pigmentation circumscribes central eye tubercle area (Fig. 2C).Legs are long and slender (Fig. 1) and quite lacking in pigment (Fig. 4), another troglomorphic character possibly related to isolation in cave habitats.Urticating hairs (Fig. 3) are present only in two small postero-lateral dorsal patches (Figs 1, 2A).All of these characteristics are shared with species of Hemirrhagus, the only theraphosid genus containing troglobitic species, and are considered evidence for a troglobitic lifestyle (Gertsch 1973, 1982, Pérez-Miles and Locht 2003).On the other hand, Tmesiphantes hypogeus sp.nov.lacks two proposed synapomorphies of Hemirrhagus: ventral coxae with retrolateral THE FIRST TROGLOBITIC TARANTULA FROM BRAZIL projection and type VI urticating hair on the abdomen dorsum (Pérez-Miles 1998, Pérez-Miles andLocht 2003).Therefore, we consider the shared characteristics to be morphological convergences due to their similar habitat use, and we include the new species putatively in the genus Tmesiphantes because of the almost circular sternum (Fig. 2B), low number of labial cuspules (Fig. 2B), presence of type III urticating hair (Fig. 3) and widely separated spermathecae that taper to their apex (Figs 2D, 2E).Furthermore, all four described Tmesiphantes species are found also in State of Bahia.A more precise classification of the species would be possible only if a male were collected; however, due to the rarity of the species this is not expected to occur soon.Due to the absence of Tmesiphantes hypogeus sp.nov.from epigean environments in Chapada Diamantina as well as the presence of troglomorphic characteristics, we deduce that this species is categorically a troglobitic species, indicating a process of differentiation occurring in isolation in the hypogean environment.Distribution: Two sandstone/quartzitic caves in Povoado de Igatu, Andaraí county, Central Bahia, northeastern Brazil: Gruna das Cobras and Gruna da Parede Vermelha (Fig. 5).

Habitat description:
The localities where Tmesiphantes hypogeus sp.nov.were found are sandstone/quartzitic caves 0.8 km distant from each other.The area is in the Espinhaço mountains (Fig. 5), and the region is composed of metasedimentary rocks deposited over a billion years ago (Proterozoic era) formed mainly by sandstone, siltites and argilites.This spider shows a preference for rocky and humid substrates typical of parietal species.Both specimens were recorded exposed in the rocks, not showing cryptobiotic habits, as is typical of Mygalomorphae species, so there is strong evidence of regression in this behavior.