Lagynochthonius fragilis, Judson, Mark L. I., 2007

Judson, Mark L. I., 2007, A new and endangered species of the pseudoscorpion genus Lagynochthonius from a cave in Vietnam, with notes on chelal morphology and the composition of the Tyrannochthoniini (Arachnida, Chelonethi, Chthoniidae), Zootaxa 1627, pp. 53-68 : 59-63

Lagynochthonius fragilis n. sp.

( Figs 1 –21)

Type material. Holotype Ψ, VIETNAM, Kien Giang Prov., Hon Chong karst, Nui Bai Voi, “grotte-hôpital de Mo So” (10°13'53''N, 104°36'59''E), 29 January 2003, hand-collected by A. Bedos & L. Deharveng ( MNHN Ps-704-41, in alcohol). The holotype is gravid: the distended opisthosoma contains about 15 small eggs. It is in fairly good condition, except that many hairs are lost and there is a transverse dorsal tear in the opisthosoma. Paratype Ψ, right palp only, same details as holotype, except collected by Le Cong Man & L. Deharveng ( MNHN Ps-704-42, in alcohol). The rest of this specimen was not present in the sample from which it was sorted. Both types are deposited in the Muséum national d’Histoire naturelle, Paris ( MNHN). The “grotte-hôpital de Mo So” is a horizontal calcareous cave that extends for over 500 m ( Deharveng et al. 1995).

Diagnosis. Troglomorphic species with reduced eyes and elongate appendages; tergites I–VII with 4 setae; chela of female 6.2–6.3 times longer than broad.

Description. Moderately large species with troglomorphic facies: pallid, eyes reduced and appendages elongate ( Fig. 1). Carapace distinctly constricted posteriorly ( Fig. 2 ); anterior eyes with very weak lenses, posterior eyes not visible externally; both pairs of eyes with reduced tapeta, though these still reflect incident light; anteromedian process absent, space between median setae slightly rounded, weakly depressed and wellsclerotized; hispid anterolaterally and reticulate posterolaterally; anterior margin (apart from median region) extremely thin and difficult to see without dissection of chelicerae, denticulate ( Fig. 5 ); chaetotaxy s4s-4-4-2- 2 (18).

Tergal chaetotaxy 4:4:4:4:4:4:4:5:5:4:TT:0; tergites VIII and IX each with an unpaired median seta. Sternal setae 10:(3m)s8s(3m):(3m)s6s(3m):10?:9:9:9:9:9:0:2; sternites VI–X with unpaired median seta. Coxae typical, anterior process of coxa I long ( Figs 3–4 ); setae P 5, I 3, II 3–4, III 4, IV 5; intercoxal tubercle absent. Coxae II each with 10–11 spines, arranged in an arc, distal (middle) spines longest, spines incised for about half their length.

Cheliceral palm ( Fig. 8 ) with 5 setae, ventrobasal seta shorter than others. Palm with moderate hispid granulation dorsally. Movable finger with a few hispid granules in middle of ventral face, but otherwise smooth. Fixed cheliceral finger with 10–11 teeth, distal tooth larger than others; movable finger with 9–10 teeth; spinneret weakly raised, keel-like, with 2 silk-duct openings ( Fig. 7 ). Serrula exterior with 20 and serrula interior with 14 blades. Rallum (‘flagellum’) ( Fig. 12 ) with 8 blades, distal blade recumbent basally, with fine barbules and set apart from the other blades, latter tightly grouped and with long pinnae, some of which are subdivided.

Palp (Figs 13–21) smooth, apart from a patch of minute denticles on ventral surface of patella (Fig. 21). Femur 1.7 times longer than carapace; setal formula 4-5-1-3-5-0. Chelal palm (Figs 13, 18) gradually constricted towards fingers; dorsal surface with a single row of 5 chemosensory setae between trichobothria esb and ib/isb; distal paraxial seta of palm only moderately enlarged (length 0.087 mm); antiaxial lyrifissure at base of fixed finger unusually small. Fingers weakly curved in dorsal view (Fig. 18). Fixed finger with 16 macrodenticles and 7 (6 in paratype) intercalary microdenticles, latter without canals; first 5 and last 4 macrodenticles smaller than others. Fixed finger also with a modified accessory tooth on dorso-antiaxial face (Figs 14 and 19: td), between the sensilla af and trichobothria dx. Movable finger with 7 (6 in paratype) macrodenticles and 5 (3 in paratype) intercalary microdenticles, latter without dental canals; base of finger with about 6 (12 in paratype) very low, vestigial teeth (without canals and therefore difficult to count accurately). Fixed finger with sensilla af 1–2 close together, near tip (Fig. 14). Movable finger with 4 sensilla: am 1–2 near tip (Fig. 17); p 1 just distad of last (7th) macrodenticle (Fig. 16); p 2 near dental margin, just behind 7th macrodenticle, with a long internal tubule (Fig. 16). Apodeme complex of movable finger strongly sclerotized. Tip of fixed finger (Fig. 14) with 1 enlarged, slightly lanceolate paraxial seta near tip, movable finger with 2 enlarged setae (not lanceolate) (Fig. 17).

Legs ( Figs 6, 9–11 ) typical, elongate. Fine granulation present on anterodorsal faces of femora I, II, IV and patella IV, and on anterior face of trochanters III and IV. Patella of leg IV 1.8 times longer than femur ( Fig. 6 ). Tarsi with small, simple, gland pores on dorsal surface (1 on tarsi I–III, 2 on tarsus IV). Arolia normal (figs 9–10). Setae of leg I (trochanter to tibia) 4:12:10:13, setae of leg IV (trochanter to basitarsus) 2:3:7:10:9; patellae of legs III and IV each with 3 setae in dorsal row; femora III and IV without dorsal setae; trochanter II with 4 setae, trochanter III with 2 setae; tactile setae present on basitarsus (TS = 0.31) and telotarsus (TS = 0.32).

FIGURES 13–21. Lagynochthonius fragilis n. sp., female holotype, right palp. 13, chela, lateral view [hairs of chemosensory setae, which are lost in holotype, added from paratype female]; 14, tip of fixed finger, antiaxial view; 15, detail of paraxial face at level of third tooth, showing pores; 16, detail of movable finger, antiaxial view, showing bothridium sb and sensilla p 1–2; 17, tip of movable finger, antiaxial view; 18, chela, dorsal view [chemosensory hairs of palm added from paratype]; 19, tip of fixed finger, dorsal view; 20, palp (minus chela), dorsal view; 21, patella, ventral view, showing weak granulation.

Abbreviations: af apical sensilla of fixed chelal finger; am apical sensilla of movable chelal finger; dx trichobothria dx; et, bothridium of trichobothrium et; p 1–2, proximal sensilla of movable chelal finger; sb, bothridium of trichobothrium sb; sc chemosensory seta; td, modified tooth; v, vestibulum of bothridium.

Measurements (in mm, ratios in parentheses; for the palp, the larger measurements and lower ratios are those of the paratype). Body length 1.6. Carapace 0.48 × 0.48 (1.0). Chelicera 0.43 × 0.20 (2.1), movable finger 0.24. Palp femur 0.81–0.90 × 0.13–0.14 (6.3–6.6), patella 0.32–0.35 × 0.15–0.16 (2.1), chela 1.19–1.32 × 0.19–0.21 (6.2–6.3), palm length 0.55–0.61 (2.9), movable finger length 0.71–0.73 (1.2–1.3 × palm). Leg I femur 0.433 × 0.073 (5.9), patella 0.248 × 0.062 (4.0), tibia 0.225 × 0.050 (4.5), tarsus 0.438 × 0.044 (10.0). Leg IV femur 0.255 × 0.235 (1.1), patella 0.470 × 0.218 (2.2), femoropatella length 0.676 (2.9), tibia 0.487 × 0.084 (5.8), basitarsus 0.216 × 0.071 (3.0), telotarsus 0.527 × 0.040 (13.1).

Remarks. Lagynochthonius fragilis is the third species of the genus to be recorded from Vietnam, the others being L. annamensis (Beier) and L. tonkinensis ( Beier) (Beier 1951; Jędryczkowski, 1998). The new species can easily be separated from these epigean species by its much larger size, more attenuated appendages and reduced eyes. Samples taken by A. Bedos and L. Deharveng from outside the cave at Nui Bai Voi included specimens of an epigean Lagynochthonius (1 ɗ, 2 Ψ, 2 tritonymphs, 1 deutonymph: Berlese extraction of secondary forest litter; MNHN) that agree with Beier’s (1951) description of L. tonkinensis , except that the measurements of the females are slightly smaller than those reported for the holotype.

The new species is similar to Lagynochthonius modor Harvey, 1989 , described from a cave in Queensland ( Australia), but differs from the latter in having slightly more robust palps, fewer chelal teeth, and the coxal spines arranged in an arc, rather than a straight line. The only other cavernicolous species known from Southeast Asia is Lagynochthonius guasirih (Mahnert, 1988) from Sarawak, which differs from L. fragilis in having the anterior eyes well developed, in retaining a vestige of the anteromedian process of the carapace and in having only 2 setae on tergites I and II. Although small eyes with tapeta are still present in L. fragilis , the general form of this species leaves little doubt that it is adapted to a hypogean existence. It is the first troglomorphic species of Tyrannochthoniini to be named from continental Asia; cavernicolous species of Tyrannochthonius Chamberlin have been recorded from Thailand ( Deharveng & Leclerc 1989), but these have yet to be described. Given that Lagynochthonius is abundant in SE Asia, it is likely that other troglomorphic species of this genus remain to be discovered in the region.

The very thin cuticle of the anterior part of the carapace seen in L. fragilis appears to be typical for Tyrannochthoniini, although it has not been emphasized previously. When the chelicerae are left undissected, the anterior margin can be very difficult to observe in transmitted light and it is likely that the line at which the cheliceral membrane joins the carapace (labelled λ in Fig. 5 ) has sometimes been mistaken for the anterior margin of the carapace (especially when the margin has been drawn as being concave on either side of the epistome). The presence of denticulations is therefore probably more widespread in Tyrannochthoniini than previous descriptions would suggest (it is certainly not unique to L. fragilis ).

Figures

FIGURES 2 – 12. Lagynochthonius fragilis n. sp., female holotype. 2, carapace; 3, process of coxa I, lateral view; 4, process of coxa I, ventral view; 5, anterior margin of carapace; 6, right leg IV, lateral view; 7, tip of movable finger of chelicera, showing spinneret, distoventral view. 8, right chelicera. 9, apotele of right leg IV, lateral view; 10, arolium and basal piece of apotele of right leg IV, ventral view; 11, right leg I, lateral view; 12, flagellum of right chelicera. Abbreviations: Δ condyle of palpcoxa; λ base of cheliceral tectum; Μ muscles; po preocular seta; tap tapetum of anterior eye; tec tectum of chelicera. Divisions of scales lines 0.1 mm (figs 2 - 5, 8, 11), 0.05 mm (fig. 6) or 0.01 mm (figs 7, 9 - 10, 12).