Typhlochactas sissomi, a new species of troglomorphic scorpion in the subfamily Typhlochactinae Mitchell, 1971, is described, based on a single subadult male collected under a stone in a mesophilous forest in the mountains of the state of Queretaro, Mexico. This is the seventh species in the genus Typhlochactas Mitchell, 1971. Although all seven species are troglomorphic, four are troglobitic and two are humicolous. The new species described here is probably also humicolous. A key to the identification of Typhlochactas species is presented.
INTRODUCTION
The genus Typhlochactas Mitchell, 1971 (Typhlochactinae Mitchell, 1971) contains six species of troglomorphic scorpions that are endemic to Mexico (table 1). Four species are troglobites, known only from caves in the Sierra Madre Oriental. The other two are leaf litter inhabitants of forests in the same Sierra and therefore considered to be humicolous.
Table 1
Typhlochactas Mitchell, 1971 species, locality, habitat and specimen data
Abbreviations as follows: T. cav. = T. cavicola Francke, 1986; T. gra. = T. granulosus Sissom & Cokendolpher, 1998; T. mit. = T. mitchelli Sissom, 1988; T. red. = T. reddelli Mitchell, 1968; T. rho. = T. rhodesi Mitchell, 1968; T. sis. = T. sissomi, n. sp.; T. syl. = T. sylvestris Mitchell & Peck, 1977; OAX = Oaxaca; QRO = Queretaro; TAM = Tamaulipas; VER = Veracruz.
Typhlochactas cavicola Francke, 1986 is known only from the holotype female, collected in Cueva del Vandalismo, Tamaulipas (fig. 1). Typhlochactas granulosus Sissom and Cokendolpher, 1998 is known only from the holotype male, collected in Sotano de Poncho, Veracruz. Typhlochactas reddelli Mitchell, 1968 is known from the holotype female and three juveniles collected subsequently in La Cueva del Ojo de Agua de Tlilapan, also in Veracruz. The fourth troglobite, Typhlochactas rhodesi Mitchell, 1968, is known from three female specimens collected in La Cueva de La Mina, Tamaulipas. The two humicolous species, Typhlochactas mitchelli Sissom, 1988, known from two males and one subadult female, and Typhlochactas sylvestris Mitchell and Peck, 1977, known only from the holotype female, inhabit leaf litter in montane forests in Oaxaca.
Figure 1
Map of Mexico showing type localities of known species of Typhlochactas Mitchell, 1968: T. sissomi, n. sp. (1); T. rhodesi Mitchell, 1968 (2); T. cavicola Francke, 1986 (3); T. reddelli Mitchell, 1968 (4); T. granulosus Sissom and Cokendolpher, 1998 (5); T. mitchelli Sissom, 1988 (6); T. sylvestris Mitchell and Peck, 1977 (7).
In total, the genus Typhlochactas is known from only fourteen specimens. As such, the recent discovery of a fifteenth, representing a new species, is significant. In the present contribution we describe the seventh species of Typhlochactas. The single specimen on which this description is based (fig. 2) was collected under a stone in a mesophilous forest in the mountains of the state of Queretaro, approximately halfway between the type localities of the two northern troglobites in the state of Tamaulipas, and the two southern ones in the state of Veracruz, and quite distant from the type localities of the two humicolous species in the state of Oaxaca. The collection of this new species under a stone on the surface, instead of inside a cave, suggests that it may also be humicolous.
MATERIAL AND METHODS
Measurements were taken and illustrations prepared using a Nikon SMZ-800 stereomicroscope fitted with an ocular micrometer and a camera lucida. Measurements follow Stahnke (1970) and were recorded in mm. Morphological terminology follows Vachon (1974) for trichobothrial nomenclature, but we adopt the interpretation of Typhlochactas trichobothrial patterns presented by Prendini and Wheeler (2005), Hjelle (1990), and Sissom (1990) for pedipalp segmentation; Stahnke (1970), Sissom (1990), and Prendini (2000) for remaining features. Photographs were taken under UV and visible light using a MicropticsTM ML-1000 digital imaging system. The holotype is deposited in the Colección Nacional de Arácnidos (CNAN), Instituto de Biología, Universidad Nacional Autónoma de México, Mexico City. Left leg I, removed from the specimen and preserved in 95% ethanol for DNA isolation, is deposited in the Ambrose Monell Cryocollection (AMCC) at the American Museum of Natural History, New York. Distribution maps were produced using ArcView GIS Version 8.3 (Environmental Systems Research Institute, Redlands, California) by superimposing georeferenced point locality records on spatial datasets of topography (contour intervals of 500 m) and the boundaries of Mexican states.
SUBFAMILY TYPHLOCHACTINAE Mitchell, 1971
Typhlochactas Mitchell, 1971
Key to species of Typhlochactas Mitchell, 1968
1. Prolateral pedal spurs absent2
– Prolateral pedal spurs present4
2. Cheliceral fixed finger, median and basal teeth fused into a bicuspT. granulosus
– Cheliceral fixed finger, median and basal teeth separate, not fused3
3. Cheliceral movable finger with four dorsal teethT. cavicola
– Cheliceral movable finger with five dorsal teethT. rhodesi
4. Cheliceral fixed finger, median and basal teeth fused into a bicuspT. reddelli
– Cheliceral fixed finger, median and basal teeth separate, not fused5
5. Cheliceral fixed finger with four teethT. sissomi, n. sp.
– Cheliceral fixed finger with three teeth6
6. Cheliceral movable finger with four dorsal teethT. sylvestris
– Cheliceral movable finger with three dorsal teethT. mitchelli
Typhlochactas sissomi, n. sp.
Figures 1–Figure 2Figure 3Figure 4Figure 5Figure 67, table 2
Figure 3
Typhlochactas sissomi, n. sp., subadult ♂ holotype (CNAN T-0308), dextral chelicera and sinistral pedipalp chela finger dentition. A. Chelicera, dorsal aspect. B. Chela, movable finger dentition, dorsal aspect. C. Chela, fixed finger dentition and distribution of trichobothria, dorsal aspect. Scales = 0.5 mm.
Figure 4
Typhlochactas sissomi, n. sp., subadult ♂ holotype (CNAN T-0308). A. Carapace, dorsal aspect. Scale = 0.5 mm. B. Sternum, genital operculum, pectines and sternite III, ventral aspect. Scale = 0.5 mm.
Figure 5
Typhlochactas sissomi, n. sp., subadult ♂ holotype (CNAN T-0308), dextral pedipalp femur and patella showing distribution of trichobothria. A. Femur, dorsal aspect. B. Patella, dorsoexternal aspect. C. Patella, external aspect. D. Patella, ventrointernal aspect. Scale = 1 mm.
Figure 6
Typhlochactas sissomi, n. sp., subadult ♂ holotype (CNAN T-0308), dextral pedipalp chela showing distribution of trichobothria. A. Dorsal aspect. B. External aspect. C. Ventrointernal aspect. D. Ventral aspect. Scale = 1 mm.
Figure 7
Typhlochactas sissomi, n. sp., subadult ♂ holotype (CNAN T-0308), metasoma and telson, dorsolateral aspect. Scale = 1 mm.
Table 2
Meristic data for Typhlochactas sissomi, n. sp., subadult ♂ holotype (CNAN T-0308)
Type material
Holotype: 1 subadult ♂ (CNAN T-0308), leg (AMCC), Mexico: Queretaro: Municipio de Jalpan: Cañada de La Joya, 21°27′23″N 99°08′26″W, 1944 m, H. Montaño and A. Valdez, 12.vi.2004, rock-rolling.
Etymology
The new species is named in honor of Dr. W. David Sissom, West Texas A&M University, Canyon, Texas, U.S.A., for his numerous contributions to scorpion taxonomy.
Diagnosis
Typhlochactas sissomi differs from all other species in the genus on the basis of the following combination of characters: cheliceral fixed finger with four teeth, median and basal teeth not forming a bicusp; cheliceral movable finger with five dorsal teeth; pedipalp chela fixed and movable fingers each with six imbricated subrows of denticles in median denticle row, terminal subrow very short, comprising single denticle; prolateral pedal spurs present on all legs.
Relationships
The trichobothrial pattern of T. sissomi is similar to that of its congeners, except that the patellar em group is displaced distally. Typhlochactas sissomi resembles the four troglobitic species of Typhlochactas in possessing four teeth on the cheliceral fixed finger; the two humicolous species each possess only three teeth. As in most species of the genus, the two basal teeth on the cheliceral fixed finger of T. sissomi are clearly separated; the basal teeth are fused, forming a bicusp, in T. granulosus and T. reddelli only. The new species is similar to T. reddelli and T. rhodesi in possessing five dorsal teeth on the cheliceral movable finger, whereas the other species possess either three or four dorsal teeth. As with T. reddelli and the two humicolous species, T. sissomi possesses prolateral pedal spurs, which are absent in the other three troglobites. Finally, T. sissomi displays six subrows of denticles in the median denticle row of both the fixed and movable fingers of the pedipalp chela, as in T. rhodesi, whereas the other species display different numbers and are usually asymmetrical, with one less subrow on the fixed finger than on the movable finger (Sissom and Cokendolpher, 1998: 287, table 1).
Description
This description is based on the holotype and only known specimen (fig. 2), complete measurements of which are provided in table 2.
Color: Cheliceral manus pale yellow, teeth light brown. Carapace, pedipalps, tergites, and metasoma, straw-colored. Coxosternal region, legs, sternites, and telson vesicle, pale yellow. Telson aculeus reddish-brown.
Chelicerae: Fixed finger with four distinct, separate teeth dorsally; median and basal teeth separate, not forming a bicusp (fig. 3A). Movable finger with five teeth dorsally and strong, prominent serrula ventrally.
Carapace: Carapace surfaces smooth, shiny; posteromedian and posterolateral sulci shallow, broad; anterior margin straight; ocelli absent (fig. 4A).
Pedipalps: Pedipalp femur rounded in cross-section, with poorly defined carinae (fig. 5A); dorsal and internal surfaces sparsely and coarsely granular; ventral and external surfaces smooth. Patella dorsointernal carina well developed and coarsely granular; internomedian carina comprising only a basal granule; dorsoexternal carina weakly developed, smooth; all other carinae obsolete, smooth (fig. 5B–D). Chela manus surfaces smooth proximally, becoming moderately granular medially (fig. 6A–D); dorsomedian, dorsal secondary and ventroexternal carinae weakly granular. Fixed and movable fingers each with six imbricated subrows of denticles in median denticle row; terminal subrow short, comprising one or two denticles (fig. 3B, C).
Trichobothria: Pedipalps orthobothriotaxic Type C. Femur, patella, and chela with three, 19 and 26 trichobothria, respectively. Femur with three dorsal trichobothria (fig. 5A): i, d, e. Patella with 19 trichobothria (fig. 5B–D): three dorsal: d1 (petite), d2 (petite), i; two ventral: v1, v2; and 14 external: et1, et2 (petite), et3, est, em1–em3, esb1, esb2 (petite), eb1, eb2 (petite), eb3–eb5. Chela manus with 16 trichobothria (fig. 6), two dorsal: Db (petite), Dt; four ventral: V1 (petite), V2–V4; and 10 external: Et1–Et3, Et4 (petite), Et5 (petite), Est, Esb (petite), Eb1–Eb3. Fixed finger with 10 trichobothria: four dorsal, distributed across proximal two-thirds of finger: dt, dst, dsb, db (petite); four external, equally distributed: et, est, esb (petite), eb; two internal, situated proximally on finger: it, ib (fig. 6A–C).
Legs: Prolateral pedal spurs present. Retrolateral pedal spurs absent. All surfaces covered with scattered transparent microsetae. Basitarsi with fewer setae than telotarsi. Basitarsus I, ventral surface with short rows of closely aligned, distally directed spinules. Basitarsi, retrolateral surfaces with very short row of tiny spinules distally. Telotarsi, prolateral, and retrolateral margins each with six to eight pairs of large macrosetae, without median row of spinules ventrally. Ungues moderately long; dactyl moderately developed, slightly curved.
Tergites: Surfaces I–VI smooth, shiny (fig. 2A); VII coarsely granular in posterior half, acarinate.
Sternum: Subpentagonal, wider than long posteriorly; longitudinal sulcus shallow, indistinct (fig. 4B). Coxosternal region smooth, asetose.
Genital operculum: Opercula separated, smooth, shiny, asetose. Genital papillae present (fig. 4B).
Pectines: Each pecten with two marginal lamellae, one median lamella, no fulcra, and five teeth (fig. 4B).
Sternites: Surfaces III–VI smooth, shiny, with book lung stigmata (spiracles) very small and round (fig. 4B); VII acarinate.
Metasoma: Metasoma, intercarinal surfaces smooth, shiny (fig. 7). Dorsosubmedian carinae, segments I–IV, moderately developed, coarsely and sparsely granular; V, absent. Dorsolateral carinae, segments I–IV, absent to obsolete, smooth; V, obsolete, sparsely granular. Median lateral carinae, segments I–V, absent. Ventrolateral carinae, segment I, absent; II–IV, obsolete, smooth; V, moderately developed, granular. Ventrosubmedian carinae, segments I–IV, absent. Ventromedian carina, segment V, absent.
Telson: Vesicle relatively large, globose, smooth, with sparse setae ventrally and distally. Aculeus short.
Hemispermatophore: Hemispermatophore unknown (holotype was dissected and no paraxial organs were found).
Remarks: The metasoma of the holotype is separated from the body at the articulation of segments I and II, the left pedipalp chela is crushed, and the posterior margin of the carapace is slightly damaged (fig. 4A). Left leg I was removed and retained at the AMCC for DNA isolation, amplification and sequencing.
Ecology
This troglomorphic species was taken from under a stone on the ground surface in a mesophilous forest. The fact that it was not collected inside a cave, taken together with its similar habitus to the two humicolous species, T. mitchelli and T. sylvestris, suggests that it is probably also humicolous.
Acknowledgments
We are grateful to Alejandro Valdez and Héctor Montaño, collectors of the holotype, for donating it the Colección Nacional de Arácnidos, Instítuto de Biología, UNAM, and to Edmundo González Santillán for sharing it with us. The second author was supported by two grants from the Theodore Roosevelt Memorial Fund (2004, 2005) at the AMNH. The third author was supported by National Science Foundation grant BIO-DEB 0413453.
