Pseudochthonius diamachi, Prado & Ferreira, 2023

Prado, Guilherme C. & Ferreira, Rodrigo L., 2023, Three new troglobitic species of Pseudochthonius Balzan, 1892 (Pseudoscorpiones, Chthoniidae) from northeastern Brazil, Zootaxa 5249 (1), pp. 92-110 : 93-98

Pseudochthonius diamachi sp. nov.

Material examined. Holotype female (ISLA 100994), preserved in ethanol: Brazil, Serra do Ramalho, Bahia, Gruna das Três Cobras Cave (13º37’6.63”S, 43º45’9.87”W), 15 September 2021, leg. R. L Ferreira . Paratype female ( ISLA 100995), same data as holotype .

Etymology. Diamáchi (“διαμαχη”) is a Greek word meaning “dispute”. The epithet diamachi is an allusion to the unfortunate disputes over the region’s caves and it intends to register our repudiation of any people or groups that consider themselves owners of Brazilian caves. This noun should be treated as noun in apposition.

Diagnosis. Differing from the other members of the genus by the following combination of characters: Absence of eyes or eyespots; carapace with a strong posterior constriction (confirmed by the difference between ocular width and posterior width); ist–est/ist–esb trichobothria ratio of 1.02 (1.11); chelal fixed finger with 41 acute teeth with alternate heterodonty, chelal movable finger with 42 acute and well-defined teeth; movable and fixed finger of chelicera with poorly defined and constricted teeth, and with a small distal isolated tooth in both fingers; presence of two and four setae on the first and second tergite, respectively; trichobothrium et proximad to dx and distad to it; body length of 2.02 (2.33) mm; chela 7.7 to 7.8 times as long as broad.

Description ( Figs 4C–D , 11A ). Body pale yellowish, very translucent; chelicerae slightly orange, abdomen beige. Some parts of the body scaly. Vestitural setae thin and anteriorly projected on prosoma and posteriorly projected on opisthosoma.

Carapace ( Fig. 3E ). 1.04 (1.07) times longer than broad, strongly constricted posteriorly showing a difference between ocular width and posterior width of 0.14 mm ( Fig. 3E ); anterior margin smooth (except for the epistome); no eyes or eyespots; epistome strongly dentate and serrated (ranging to seta ame); posterior margin of carapace smooth; chaetotaxy 4+2: 4: 4: 2: 2 (18).

Chelicera ( Figs 1C, E , 3H ). Hand with 5 setae; movable finger with 1 subdistal seta; galea present as a tubercle; fixed finger with 9 constricted teeth, of which the distal one just isolated; movable finger with 10 constricted teeth, of which the distal one is isolated; rallum with 7 blades; serrula exterior and interior with 15 and 12 blades, respectively.

Tergites. Not divided; surface smooth; chaetotaxy uniseriate, I–XI 2: 4: 4: 4: 6: 6: 6: 4: 6: 2: 2 + 2 sensory setae. Pleural membranes striate.

Coxae ( Figs 2C, F , 3A, F ). Manducatory process with two apical setae; rest of palpal coxae with 3 setae arranged in a triangle; delicate lamellae outlined by 8(9) small spines. Pedal ( Figs 2C , 3A ): coxal spines plumose, arranged in a single transverse row in coxae I (3–5) and II (4) ( Figs 2F , 3F ), chaetotaxy: I 4+1, II 5, III 8, IV 7–8(9); intercoxal tubercle absent.

Genital operculum of female: 8–9 setae distributed in three transversal rows: 2: 4: 2–3, genital opening not bifurcated.

Sternites: chaetotaxy IV‒XI: 10: 8: 8: 8: 8: 6: 4: 2. Anal operculum with 2 ventral setae.

Palp ( Figs 1A–B, D , 3C, G ). Trochanter 1.78 (1.62) times longer than wide, patella two times longer than wide, femur 6.84 times longer than wide. Femoral chaetotaxy 5: 6: 3(5): 5(6): 1(2). Trichobothrial pattern: ib and isb located at the half portion of the hand, adjacent to each other and slightly dislocated to the paraxial face of the chela, eb proximad to esb, ist distad to esb, it distad to est, et proximad to dx; ist halfway between esb and est (ratio distance ist-est/ist-esb = 1.02 [1.11]). Fixed finger slightly bent; movable finger slightly curved ( Figs 1A , 3G ). Chelal fixed finger with 41 acute, triangular, and widely spaced teeth, with heterodonty starting proximally from the 8 th teeth. Movable finger with 42 acute, triangular, and widely spaced teeth.

Leg IV ( Fig. 3B ). Arolia almost same length as claws; a tiny protuberance near end of telotarsus.

Measurements (length/width or depth in mm and ratios in parenthesis calculated by using three significant digits): Female holotype (female paratype in brackets). Body length 2.02 [2.334]. Carapace 0.59/0.56 (1.0) [0.60/0.56 (1.1)]. Palps: trochanter 0.33/0.18 (1.8) [0.28–0.17 (1.6)], femur 0.98/0.16 (6.8) [1.08/0.15 (6.8)], patella 0.37/0.18 (2.0) [0.37/0.18 (2.0)], chela 1.59/0.21 (7.7) [1.43/0.18 (7.8)], movable finger length1.02 [1.00]. Leg I: trochanter 0.22/0.16 (1.4) [0.18/0.14 (1.3)], femur 0.60/0.10 (5.9) [0.54/0.09 (6.2)], patella 0.31/0.08 (4.0) [0.30/0.07 (4.0)], femur/patella 1.93 [1.82], tibia 0.32/0.06 (5.6) [0.29/0.06 (5.0)], tarsus 0.64/0.05 (13.0) [0.57/0.05 (11.3)]. Leg IV: Trochanter: 0.28/0.16 (1.7) [0.27/0.15 (1.3)], femur + patella 0.95/0.28 (3.4) [0.89/0.26 (3.4)], tibia 0.58/0.10 (5.8) [0.53/0.10 (5.5)], basitarsus 0.33/0.09 (3.7) [0.29/0.08 (3.8), telotarsus 0.69/0.05 (13.9) [0.65/0.05 (13.4)].

Ecological Remarks. Specimens of Pseudochthonius diamachi sp. nov. were found in the Três Cobras cave, located in Serra do Ramalho municipality, in the southwest of Bahia state, Brazil. This cave has 5.620 meters of horizontal projection, presenting a labyrinth of internal conduits and chambers ( Figs 4A–B ). The cave has many entrances ( Fig. 4A ) that are situated mostly at the base of the limestone outcrop. Accordingly, the cave atmosphere is influenced by airflow from the entrances, which dries out several conduits during the dry season ( Fig. 4B ). However, inner chambers and conduits remain moist even during the dry season. In such moist and environmentally stable areas, most of the cave-restricted fauna is encountered, which includes specimens of P. diamachi sp. nov., usually observed walking on the cave floor ( Figs 4C–D ) a phenomenon that is not observed in non-troglobitic cave-dwelling species of Pseudochthonius , generally spotted underneath rocks on the cave floor, even in moist areas. The reduction of cryptobiotic behavior is commonly observed in multiple troglobitic invertebrates, including arachnids, such as palpigrades ( Souza & Ferreira 2010), amblypygids ( Vasconcelos & Ferreira 2017) and even pseudoscorpions from other families ( Viana et al. 2018).

The main organic resources occurring in the cave are plant debris from the epigean vegetation (which is mainly concentrated near entrances) and bat guano. The latter is most common in deeper regions of the cave where the pseudoscorpions were observed. Such piles attract many springtails and other small invertebrates, such as barklice and immature crickets, which may represent the main prey for the pseudoscorpions.

The cave receives no human visitors, except for a few speleologists that sporadically enter the cave for research. However, the external area is highly damaged ( Fig. 10A ). During our visit to the area, drone images revealed the extensive tree logging in the cave surroundings. Most areas surrounding the cave were converted to pastures or have had the vegetation cleared and burned, probably for pasture expansion. We suggest reforestation as a means to preserve the cave and its fauna.

Figures

FIGURE 1. Pseudochthonius diamachi sp. nov. SEM images of the paratype A Right chela general aspect, antiaxial view B Basal region of chelal fixed finger C Left chelicera, showing rallum, exterior serrula and lyrifissure, ventral view. D Detail of the hand, showing lyrifussures and trichobothria arrangement E Rallum, showing detailed blades. Scale bars: 0.5 mm (A); 0.3 mm (B–D); 0.05 mm (E).

FIGURE 2. SEM images of the new species A P. pali sp. nov. right chelicera of the paratype, dorsal view B P. pali sp. nov. left chelicera of the paratype, ventral view C P. diamachi sp. nov. coxae region of the paratype D P. koinopoliteia sp. nov. right chelicera of the paratype, dorsal view E P. koinopoliteia sp. nov. left chelicera of the paratype, ventral view F P. diamachi sp. nov. detail of coxal spines of the paratype. Scale bars: 0.2 mm (A–B); 0.4 mm (C); 0.1 mm (D–E); 0.05 mm (F).

FIGURE 3. Pseudochthonius diamachi sp. nov. A Female holotype palp and pedal coxae B Leg IV of female holotype C Pedipalp femur of female holotype, dorsal view D Leg I of female holotype E Carapace of female holotype F Detail of female holotype coxae I and II, showing arrangement of coxal spines G Left Chela of female paratype, antiaxial view H Left Chelicera of female holotype, showing trichobothrial pattern, antiaxial view. Scale bars: 0.2 mm (A, H); 1.0 mm (B, D); 0.5 mm (C, G); 0.25 mm (E); 0.1 mm (F).

FIGURE 4. Pseudochthonius diamachi sp. nov. A Três Cobras cave and karst landscape with an overlapped map B Três cobras cave entrance C Três Cobras cave general aspect D Live female holotype E Live female paraype.

FIGURE 10. Ecological impacts to the subterranean habitat A Deforestation near cave entrance B Vegetal coal furnace.

FIGURE 11. New species habitus. A Pseudochthonius diamachi sp. nov. paratype habitus. B Pseudochthonius pali sp. nov. paratype habitus C Pseudochthonius koinopoliteia sp. nov. holotype habitus. Scale bars: 2.0 mm (A); 1.0 mm (B–C).