Chactas braziliensis, Lourenço, Wilson R., Aguiar, Nair O. & Franklin, Elizabeth, 2005

Lourenço, Wilson R., Aguiar, Nair O. & Franklin, Elizabeth, 2005, First record of the scorpion genus Chactas Gervais, 1844, for Brazil with description of a new species from western State of Amazonas (Scorpiones: Chactidae), Zootaxa 984, pp. 1-8 : 2-4

Chactas braziliensis sp. n. ( Figs. 1–13 )

Type material: 1 female holotype, 3 female paratypes, Brazil, State of Amazonas, Guajara, Rio Ipixuna, 7°06’39”S, 73°05’25”W, 13–19/VI/1995, P. Bührnheim & N. O. Aguiar leg. Holotype and two paratypes deposited in the Instituto Nacional de Pesquisas da Amazonia ( INPA), Manaus. One paratype deposited in the Muséum national d’Histoire naturelle, Paris.

Etymology: The specific name refers to the country, Brazil, in which the new species has been found.

Diagnosis. Scorpions moderate to small in size, 33 to 35 mm in total length. Coloration blackish­brown, except for the venter which is reddish­yellow. Body and appendages very weakly granulated or smooth, with minute punctation. Pectines with 8 teeth in females. Allowing for sexual dimorphism, the male pectines should have 9 to 11 teeth. Trichobothrial pattern type C neobothriotaxic ‘majorante’. Chela with 4 ventral trichobothria; patella with 5 ventral and 17 external trichobothria.

Chactas braziliensis sp. n. represents a moderate to small sized Chactas species. The new species can be distinguished from others in the genus Chactas , and in particular from Chactas koepckei Lourenço & Dastych, 2001 which is distributed in Peruvian Andes, by the following features: (i) a generally darker coloration, blackish­brown, whereas C. koepckei is overall reddish­brown, (ii) a higher number of pectinal teeth: males of C. koepckei have 7 teeth, females should therefore have 5–6 teeth, (iii) the vesicle is totally smooth in the new species. Finally, the two species inhabit different environments. Chactas koepckei is a mountain species, whereas the new species lives in the lowlands of Amazon rainforest.

Description based on female holotype and paratypes. Measurements in Table I.

Coloration. Basically blackish­brown. Prosoma: Carapace blackish­brown. Tergites blackish­brown, paler than the carapace and with a central longitudinal yellowish strip. Metasomal segments blackish­brown, with blackish zones over carinae; vesicle reddishbrown. Chelicerae reddish­yellow, with diffused variegated brownish spots; fingers uniformly dense blackish; some teeth reddish. Pedipalps blackish­brown; femur blackish; patella blackish­brown and darker than chela; chela hand reddish­brown; finger blackish. Legs reddish­brown. Venter and sternites reddish with some yellowish zones; pectines and genital operculum yellowish.

Morphology. Carapace: Anterior margin with a weak concavity; lustrous and acarinate, with minute punctation behind median eyes; lateral sides with very thin granulation; furrows shallow. Sternum pentagonal, wider than long. Tergites acarinate, smooth and shiny with punctations. Pectinal tooth count 8­8, fulcra absent. Sternites smooth and shiny, VII acarinate; spiracles small oval in shape. Metasomal segments with a lustrous tegument; dorsal carinae weak on all segments; latero­dorsal carinae vestigial on segments I and II, absent on III and IV; other carinae absent; segment V with small spinoid granulations on distal half of ventral aspect; vesicle smooth and lustrous. Pedipalps: Femur with dorsal internal, dorsal external and ventral internal carinae strongly marked; ventral external carina weakly marked; dorsal and ventral faces without granulations, smooth; internal face moderately granular. Patella smooth and lustrous; dorsal internal and ventral internal carinae moderate; ventral external carinae weak to vestigial; other carinae absent. Chela lustrous; ventral median and dorsal internal carinae weak; other carinae vestigial or absent; internal face with a few weak granules, other faces smooth. Dentate margins on movable and fixed fingers with a median denticle row composed of 8 groups of granules. Chelicerae with the dentition typical of the family Chactidae ( Vachon, 1963) , and with intense setation ventrally. Trichobothriotaxy type C; neobothriotaxic ‘majorante’ ( Vachon, 1974); chela with 4 ventral trichobothria; patella with 5 ventral and 17 external trichobothria. Ventral surface of tarsus in legs III and IV with a median series of small spines and 5 external and 4 internal setae.

Pectinal tooth count in female paratypes: 8­ 8 in all three specimens.

TABLE I. Morphometric values (in mm) of female holotype of Chactas braziliensis sp. n.

Total length 35.6 Carapace:

– length 5.4 – anterior width 3.8 – posterior width 6.2 Metasomal segment I:

– length 1.8 – width 2.5 Metasomal segment V:

– length 4.8 – width 1.9 – depth 1.7 Vesicle:

– width 2.0 – depth 1.7 Pedipalp:

– Femur length 4.6 – Femur width 1.9 – Patella length 5.1 – Patella width 2.1 – Chela length 10.1 – Chela width 3.5 – Chela depth 3.8 Movable finger

– length 4.3

Figures

FIGURES 1 – 5. Chactas braziliensis sp. n., female holotype. 1. Chelicera, dorsal aspect. 2. Disposition of granulation over the dentate margins of the pedipalp­chela movable finger. 3. Metasomal segments IV – V and telson, lateral aspect. 4. Pecten, external aspect. 5. Sternite IV showing spiracles, ventral aspect.

FIGURES 6 – 12. Chactas braziliensis sp. n., female holotype. Trichobothrial pattern. 6 – 8. Chela, dorso­external, ventral and internal aspects. 9 – 11. Patella, dorsal, external and ventral aspects. 12. Femur, dorsal aspect.

FIGURE 13. Map showing distribution of the genus Chactas in South America (open circles), and type locality of Chactas braziliensis sp. n. (black circle with white star).