A new troglomorphic species of Harmonicon (Araneae, Mygalomorphae, Dipluridae) from Pará, Brazil, with notes on the genus

Abstract A new species of Harmonicon F. O. Pickard-Cambridge, 1896 (Araneae, Dipluridae) is described, from a medium-sized lateritic cave in Parauapebas, Pará, Brazil. The male holotype and only specimen known of H. cerberus sp. n. was found near the entrance of Pequiá cave. This taxon is the fourth species described and the southernmost record for the genus. The new species displays some troglomorphic characteristics, such as reduction and merging of the posterior median and both pairs of lateral eyes and pale yellow to light brown coloration. Both characters are diagnostic when compared to the normal separated eyes and reddish to dark brown of other Harmonicon species. Other diagnostic characteristics are isolated, long, rigid setae distal to the lyra and the shape of the copulatory bulb. This is the second troglomorphic mygalomorph species from Brazil and the first from the Amazonian region.


introduction
Harmonicon F. O. Pickard-Cambridge, 1896 is a Neotropical genus of Mygalomorphae, belonging to the family Dipluridae. There are three described species from the Amazon region (Platnick 2014): H. audeae Maréchal & Marty, 1998 (males and females, from Sinnamary, French Guiana), H. oiapoqueae Drolshagen & Bäckstam, 2011 (males and females, from Saint Georges, French Guiana), and H. rufescens F. O. P.-Cambridge, 1896 (immature, from Santarém, Pará state, Brazil). This genus was removed from former synonymy with Diplura C. L. Koch, 1850 by Maréchal and Marty (1998), and it was recently placed in Diplurinae by Drolshagen and Bäckstam (2011), due to the presence of a lyra. In the family Dipluridae, this structure is known only in two other genera of that subfamily, Diplura and Trechona C. L. Koch, 1850.
The new species was found in the entrance of Pequiá cave, a medium-sized lateritic cave in the Floresta Nacional de Carajás, Parauapebas, Pará, Brazil. One of approximately 1,100 caves in iron ore deposits found in Carajás, Pequiá cave is situated at 06°05'15" S; 50°07'13"W (DMS), circa 427 m above sea level (IBAMA 2003, Piló and Auler 2009, IPHAN 2013. This cave has a projection of approximately 72 m, an L-shaped form, and contains a permanent water pool covered with guano (IBAMA 2003, Magalhães 2012, IPHAN 2013. Pequiá cave harbors important remains of earlier indigenous occupation in the Amazon region (IBAMA 2003, Magalhães 2012, IPHAN 2013. There are several studies on the cave fauna of the iron ore cave region of Carajás (ex. Cunha et al. 2007, Pellegrini and Ferreira 2011, Prous et al. 2011. Several troglobitic species have been found in these iron ore caves, including a beetle and a centipede (Trajano and Bichuette 2010;Pellegrini and Ferreira 2011). There is a high potential of iron caves as habitat of troglobitic invertebrates in Brazil (Trajano and Bichuette 2010). As determined by Prous et al. (2011), there are an average of 2.5 troglobitic species in each cave with permanent water bodies in the Carajás region. This is the second troglomorphic mygalomorph species from Brazil, but the first species from the Amazonian region. Recently, a troglobitic Theraphosidae was described from Bahia state (Bertani et al. 2013). Troglobitic or troglomorphic Dipluridae are common in subfamilies other than Diplurinae (ex. Euagriinae, see Coyle 1988), but the only other diplurine described solely from caves is Linothele cavicola Goloboff, 1994. This species lacks most of the modifications commonly associated with cave life, such as pigmentation and eye reduction, but displays elongated appendages, a reduced number of teeth on tarsal claw, and does not spin webs (Goloboff 1994).

Methods
The color pattern was based on a specimen preserved in 75% ethanol. Observations, photographs and measurements were made with an Olympus stereoscopic microscope. Measurements are given in millimeters, unless otherwise noted. Cephalothorax length was measured from the posterior border to the anterior margin of the clypeus. Total length was measured from the posterior border of the anal tubercle to the anterior margin of the clypeus, not including the spinnerets. Each article of the pedipalp and legs was measured in retrolateral view, from the basal condylus to the distal one. Photographs were taken with a Sony Cybershot DSC-V1 camera attached to the stereomicroscope. The software package COMBINEZ, version COMBINEZP (Hadley 2013), was used to create composite images with extended depth of field. Geographical coordinates for localities were obtained from GEONAMES (2013). The distribution map was elaborated using ESRI ARCGIS 10 software.
Distribution (Map 1). know only from type locality, in southern Pará state, Brazil.

Remarks
Troglomorphism. The pale body, fused and reduced eyes and the elongated chelicerae (Figs 1-3) observed in H. cerberus sp. n. seem to be troglomorphic. Harmonicon species display usually a highly contrasting color pattern, with a reddish carapace, a black, dark brown or reddish brown abdomen and dark brown legs. Eyes of Harmonicon tipically are without modification, with two large AME, surrounded by distinct ALE, PME and PLE. The retina and pigmentation of the AME are easily seen through the clear crystalline lens. In contrast, the AME of the new species bears a milky crystalline and no trace of a retina or pigmentation are visible behind it. The ALE and AME of the other Harmonicon bear distinct crystalline and spherical lenses. However, ALE, PME and PLE of H. cerberus sp. n. are fused, forming an irregular and asymmetrical white macula, covered by a shallow and irregular lens (Fig. 3). To the best of our knowledge, the crescent shaped lateral eye mass is a rare character in spiders. The elongated chelicera (more than 40 % of the length of carapace) is longer than in other species of the genus. The legs and spinnerets are also elongated, but males of H. audeae and H. oiapoqueae also have similar long legs. An additional possible troglomorphic character is the elongated trichobothria at the leg tarsus. In comparison to other Harmonicon species, the trichobothria of the new species are approximately twice as longer than the covering hairs and clearly visible in lateral view. Furthermore, H. cerberus sp. n. seems to bear more unequivocal troglomorphic characteristics compared to Linothele cavicola, the only other cave inhabiting Diplurinae (Goloboff 1994). This spider may be a troglobitic species, despite the small dimensions of Pequiá cave. Several other troglobitic species have been collected in some of the more than a thousand iron ore caves in Carajás (Piló and Auler 2009, Trajano and Bichuette 2010, Pellegrini and Ferreira 2011. Most of those caves are reduced in size (horizontal projection 20-30 m), but they may be connected by small conduits, due to the porosity and spongiform nature of the iron ore deposits of the area (Piló and Auler 2009).
Pequiá cave and its surroundings have been thoroughly investigated recently (Pedroso, pers. obs.). However, no additional specimens of Harmonicon have been found. On the other hand, only the entrance and the beginning of the lateral tube were investigated (around 1/3 of the cave), as there is a large water pool mixed with abundant guano. Unfortunately, the exploration of the terminal portion of the lateral tube of Pequiá cave needs special equipment, such as floaters. This portion appears to be the best candidate for new attempts to find additional specimens of H. cerberus sp. n., as it is farthest away from the mouth and the darkest area of the cave. Other possible areas for exploration are the numerous caves near Pequiá cave, specially Gavião cave, a larger cave situated circa 4 km from Pequiá cave (Magalhães 2012).
Notes on Harmonicon. In their paper on the revalidation of Harmonicon, Maréchal and Marty (1998) proposed a series of diagnostic characters for the genus: leg I longer than IV (leg formula 1423), contrasting with formula 4123 found in Diplura and other Diplurinae; legs longer and thinner than in Diplura; metatarsus I of males without the prolateral knob found in other Diplurinae; lyra formed by only 5 setae, with a flattened and curved tip, compared to Diplura, where it presents more setae, with a different tip.
The diagnosis of Harmonicon is not so clear-cut. Regarding the leg formula, the female of H. audeae itself, the species described by Maréchal and Marty (1998), has leg formula 4123, as does the female of H. oiapoqueae (Drolshagen and Bäckstam 2011). The males of H. audeae and H. oiapoqueae do have a leg formula of 1423. On the other hand, the legs of the male holotype of H. cerberus sp. n. follow the formula 4123. Furthermore, most Diplurinae males have longer anterior legs, following the formula 1423 (and even 1243), so this character is not reliable for diagnosing Harmonicon.
Another inconsistent character is the absence of the prolateral knob of male metatarsus I. Both H. oiapoqueae and H. cerberus sp. n. present the cited knob, so its absence may be an autapomorphy of H. audeae.
Considering the lyra, the number and shape of the setae are not consistent throughout Diplurinae. Some Diplura species we have examined have lyra with just a few setae (down to 2), sometimes with tip curved and somewhat flattened. The setae tip though is not as curved and flattened as in Harmonicon. Again the number of setae is not a reliable character for Harmonicon, as already suggested by Drolshagen and Bäckstam (2011).
Additional diagnostic characters for Harmonicon were proposed by Drolshagen and Bäckstam (2011): presence of dense scopula in more than the apical third of pedipalpal tarsus, presence of scopula in the apical third of most leg metatarsi, and leg tarsi "pseudosegmented" (instead of showing only a few cracks). The dense scopula in legs is similar to that found in Trechona, where it is very dense. In Diplura, the scopula is thin, sometimes not conspicuous at all.
The presence of additional, rigid, and somewhat thickened, setae situated distally to the lyra (Fig. 6) may be diagnostic for Harmonicon or at least most of its species. Besides H. cerberus sp. n., these setae are found in specimens of H. rufescens from Altamira (unpublished data), H. oiapoqueae (see a picture on the website of Drolshagen 2013) and several undescribed species from Brazil. However, an undescribed Harmonicon from Mato Grosso lacks these setae altogether. No such setae were found in all other species of Diplurinae genera we examined.
Some additional characters may prove to be diagnostic, at least in relation to Diplura. The longer tibia of the male pedipalp may distinguish Harmonicon from Diplura species, in which tibia are usually short and stout. Long and relatively thin tibia are found also in the diplurines Trechona (ex. Baptista 2004, Pedroso et al. 2008) and Linothele Karsch, 1879 (ex. Paz and Raven 1990). The copulatory bulb of males of most Harmonicon is also remarkably similar to Trechona species (ex. Baptista 2004, Pedroso et al. 2008), with an enlarged basal portion and an elongated embolus.
The legs and palp with denser and longer scopula, the longer tibia of the male palp and the flexible, highly cracked tarsi may indicate a closer relationship between Harmonicon, Trechona, and perhaps Linothele. Another common trait of these genera is the increased body size, compared to Diplura. Compared to Trechona, some easily seen diagnostic characters of Harmonicon are the lyra composed by less than ten setae (vs. complex lyra, with more than 50 setae in several layers) and the absence of the chevron pattern on the abdomen (vs. presence).
All the published records for described Harmonicon species are located in the northeastern Amazon region, from northern French Guiana to central Pará state, Brazil (Map 1). The type locality of H. cerberus sp. n. is the southernmost record for the genus, located in southern Pará state. However, we examined specimens of several Harmonicon species covering a much larger area, ranging from Peru in the west, to states in northeastern (Bahia, Ceará) and central (Mato Grosso, Goiás) regions in Brazil.