Heterobiantes geniculatus ( Pocock, 1903 )

Tan, Desmond Kai Teck, Fong, Jonathan J. & Zhang, Chao, 2023, Re-description of the genus Heterobiantes and its type species H. geniculatus (Opiliones: Laniatores: Epedanidae) with additional genital and external morphology data, Zootaxa 5353 (6), pp. 533-550 : 536-546

Heterobiantes geniculatus ( Pocock, 1903)

Figs 1–6 ; 7B, E, G, N ; 8L

Epedanus geniculatus Pocock, 1903: 446 , plate XII, f. 1.

Pseudobiantes geniculatus Hirst, 1911: 633 , 636.

Epedanestus geniculatus Roewer, 1938: 109 , f. 27; Wang 1953: 504.

Heterobiantes geniculatus Roewer, 1912: 219 ; Roewer 1923: 191–192, f. 217; Li & Song 1993: 238.

Type Material Examined: Holotype (male) and syntype (sex unknown), both specimens collected under record number 1643424, both in 75% industrial methylated spirit ( IMS). The former with the labels: ‘48.60, Epedanus geniculatus, Pocock. Hong Kong’ and ‘Roewer (Nr. 111.06) x. 1937 revid, sub: Epedanestus (n.g.) geniculatus (Pocock) , Hong Kong, one specimen. (Typ.) verstümmelt vorgefunden [= found mutilated].’ The latter also with two labels: ’56.113, Epedanus geniculatus, Pocock. Hong Kong.’ and ‘Roewer (Nr. 11107) x. 1937 revid, snb: Epedanestu s (n.g.) geniculatus, (Pocock) , Hong Kong, one specimen. (verstümmelt vorgefunden)’ ( Fig. 9 ).

New Material Examined: Males ( LINGU-INV 01, LINGU-INV 05, LINGU-INV 06) and female ( LINGU-INV 07), CHINA: Hong Kong, Lantau Island , Discovery Bay, 22.18916°N, 114.01322°E, 3 May 2022 ( LINGU-INV01 ) ; CHINA: Hong Kong, New Territories , Tai Mo Shan, 22.40906°N, 114.12033°E ( LINGU-INV05 ), 31 March 2022, CHINA: Hong Kong, Hong Kong Island, Lung Fu Shan , 22.27605°N, 114.132767°E, 6 May 2022 ( LINGU-INV06 ) ; CHINA: Hong Kong, Hong Kong Island, Aberdeen Country Park , Lady Clementi’s Ride, 22.25519°N, 114.18230°E, 24 May 2022 ( LINGU-INV07 ). Six male genitalia ( LINGU-INV02 , LINGU-INV03 , LINGU-INV04 , LINGU-INV08 , LINGU-INV09 , LINGU-INV10 ), CHINA: Hong Kong, Lantau Island , Discovery Bay, 22.18946°N, 114.01294°E ( LINGU-INV02 ) ; 22.316417°N, 114.021383°E ( LINGU-INV03 ) ; CHINA: Hong Kong, New Territories , Tai Mo Shan, 22.409562°N, 114.118812°E ( LINGU-INV09 ) ; 22.42820°N, 114.11852°E ( LINGU-INV08 ) ; 22.408352°N, 114.118619°E ( LINGU-INV10 ) CHINA: Hong Kong, Hong Kong Island, Pok Fu Lam ( LINGU-INV04 ), 19 August 2021.

Etymology: Species name geniculatus is derived from the way the tibia is connected at an almost-right angle from the patella. Thus, the name is taken from the word ‘geniculate’, meaning ‘bent at a sharp angle’ ( Pocock 1903).

Habitat: Roams on the forest ground or under leaf litter, also in small crevices within soil slopes besides walking trails. Mostly nocturnal but can be seen roaming during daytime.

Distribution: Throughout Hong Kong.

Dorsum ( Figs 1A–B , 6B ). Dorsal scutum trapezoidal in shape and divided into five scutal areas (areas I– II fused), largest in the fifth scutal area. Anterior margin of the scutum mostly unarmed, but with about three granules scattered on each side of the anterior margins. There are two yellow spots at both lateral sides of the lower prosoma. Lateral and posterior margins of the body lined with transverse granules. Ocularium well-defined with a long median spine between the two eyes. A total of 8–10 granules (varies among individuals) can be found transversely on areas I– II, often with two more granules found on both sides of the anterior margin of the area (oftentimes may not be obvious); 10 granules can be seen respectively on areas III and IV. Posterior border of area V and free tergites are lined with longitudinal rows of hair-tipped tubercles. The coxa IV extends out and backwards from the body.

Venter ( Fig. 1C ). Mostly unarmed; small granules scattered on coxae I– III, with a longitudinal row of granules situated in a small crevice between coxae II and III.

Chelicerae ( Figs 2 , 6A ). Proximal segment strong, with 9–13 granules scattered around its ventral surface. Second segment with 12–14 dorsal hair-tipped tubercles, strong tubercles on both dorsal and ventral surface are clustered on the anterior margin of the segment. Fingers strong and bifid, movable finger with two dorsal tubercles located nearing the fingertip ( Figs 2A–B ). Numerous hairs are scattered throughout the second segment ( Figs 2C– F ).

Pedipalps ( Figs 3A–C ). Elongated and slender, pedipalpal coxae extend well beyond the body. Trochanter with one dorsal tubercle and two ventral hair-tipped tubercles. Femur slightly arcuate, armed with five tubercles dorsally and 8–9 hair-tipped tubercles ventrally; one disto-lateral tubercle can be found near the patella. Patella without apophysis and unarmed ( Figs 3B–C ). Both tibia and tarsus clavate, tibia extends in a straight angle from the patella. Ventral surface armed with three pairs of strong, curved, setiferous tubercles, and one pro-medial short tubercle; proximal tubercles being the longest while the distal pair being the shortest. Tarsus armed with three mesal- and four ectal-setiferous tubercles ventrally. Both tibia and tarsus are also armed with hairs and granules scattered ventrally. The claw is strong, long, and curved. The tubercles, along with the curved claw, which could be contracted inwards, form a ‘basket claw’ ( Fig. 3A ) ( Wolff et al. 2016).

Legs ( Figs 3D–G , 4A–C ). Leg II is the longest, followed by IV, III, and finally I. All legs mostly unarmed, except for short hairs throughout the leg, especially on tarsus. Trochanter often, but not always, with one small dorsal tubercle. All femora elongated and arcuate. Tarsi I and II with single simple claw while III and IV with double simple claws. All distitarsi with three tarsomeres ( Figs 4A–B ). Tarsal formula: 11/24/9/9. All tarsi without scopulae ( Fig. 4C ).

Penis ( Figs 4D–F ; 5 ; 7B, E, G, N ; 8L ). Penis slender and elongated, with a complex, crown-like apical structure. There are 10 strong basal setae in a circular arrangement a little lower from the apical structure ( Fig. 4F ). The structure itself is divided into two visible components: the ventral plate and the glans. The ventral plate is narrowly-shaped like a knife, raising above and perpendicularly positioned to the glans ( Fig. 5B ). Though there is no reinforcement in the dorsal area of the structure, the lateral and ventral area is heavily armed with similarly strong setae. There are six ventral setae of the glans (three on each side), situated between the glans and the ventral plate. These are followed by 10–12 lateral setae (5–6 on each side) that surround both lateral sides of the lower ventral plate to the venter of the apical structure. The glans is comprised of the dorsal and ventral stylar lobe, which is kept hidden when unexpanded. When expanded, both lobes are unfolded outwards, like the petals of a blooming flower ( Figs 4E–F ). The glans also extends laterally and curved outwards. The straight and narrow stylus, located at the centre of the glans, protrudes out and upwards from the structure. The wall of the capsula interna is densely-lined with small soft spines, forming a ‘prickly funnel’ ( Fig. 7E ) (Stacheltrichter, Martens 1986). Basal sac is located within the shaft, around the area of the basal setae ( Fig. 5 ).

Female ( Figs 6C–D ). General appearance very similar to males, except with a slightly slenderer body shape, together with a shorter width at its widest portion ( Fig. 6D ). The most distinct difference is the size of the chelicerae, with the female chelicerae being significantly smaller ( Fig. 6C ). All distitarsi with three tarsalia. Tarsal formula: 12/25/9/9.

Measurements: Males LINGU-INV 06 ( LINGU-INV 01): Body 6.7 (5.94) long, 5 (4.68) at the widest portion. Ocularium 0.82 (0.64) long, 1.45 (1.27) wide, median spine 2.47 (2.79) long. Penis: 2.44 (2.79) long. Pedipalpal claw 2.38 (2.36) long. The other measurements are in Table 1 .

Female LINGU-INV 07: Body 7.38 long, 5.06 wide at the widest portion. Ocularium 0.66 long, 1.23 wide, median spine 1.26 long. Pedipalpal claw 2.4 long. The other measurements are in Table 2 .

Remarks: For this study, only one female specimen was captured and examined. Ovipositor was destroyed during the examination process. While researching the species, we have designated a vernacular name of ‘ Hong Kong Krabby Harvestman’, derived from how it looks like Mr. Krabs from the hit children’s TV show SpongeBob SquarePants when viewed dorsally and with its pedipalps extended. For the Chinese name, we designate ‘ ởffiḇNj üǥ ’, inspired by the Chinese name of Kilungius bimaculatus Roewer (1915) ‘ ḇfflfføüǥ ’, which incorporated its distinctive yellow lateral spots on the posterior prosoma ( Figs 1A–B & 6B–D ).

Figures

FIGURE 1. Heterobiantes geniculatus (Pocock, 1903), males, body. A lateral view (LINGU-INV02); B dorsal view (LINGU- INV06); C ventral view (LINGU-INV06). Scale bars: 1 mm.

FIGURE 2. Heterobiantes geniculatus (Pocock, 1903), male (A–D, LINGU-INV06), male (E–F, LINGU-INV05), chelicera.A Distal segment of left chelicera, frontal view; B Distal segment of right chelicera, frontal view; C Left chelicera, lateral view; D Right chelicera, lateral view; E Full right chelicera, lateral view; F Full left chelicera, lateral view. Scale bars: 1mm.

FIGURE 3. Heterobiantes geniculatus (Pocock, 1903), male (LINGU-INV06). A Close-up of pedipalpal tibia-tarsus-claw, lateral view; B Right pedipalp, lateral view; C Left pedipalp, lateral view; D Leg I, lateral view; E Leg II, lateral view; F Leg III, lateral view; G Leg IV, lateral view. Scale bars: 1 mm.

FIGURE 4. Heterobiantes geniculatus (Pocock, 1903). A photograph of the distitarsus I (LINGU-INV01); B Close-up of the distitarsus I (LINGU-INV06); C Scanning electron microscopic leg IV tarsus (LINGU-INV01), a part of the distitarsus is missing, but the lack of scopulae is still clearly shown; D Scanning electron microscopic full dorso-lateral view of male genitalia (LINGU-INV10); E Scanning electron microscopic lateral view of expanded male genitalia (LINGU-INV08), arrows indicate how the lobes unfold and expand; F Scanning electron microscopic dorsal view of unexpanded male genitalia (LINGU-INV10), arrows indicate how the lobes unfurl and the direction of penial expansion. Scale bar: 1 mm (A, B); 500 µm (C); 100 µm (D, E, F).

FIGURE 5. Heterobiantes geniculatus (Pocock, 1903), penis. A apical structure (LINGU-INV10), ventral view; B apical structure (LINGU-INV17), lateral view; C full penis (LINGU-INV04), lateral view. Scale bars: 200 µm.

FIGURE 6. Photograph comparing chelicerae and the dorsal body of Heterobiantes geniculatus (Pocock, 1903) on sexual dimorphism.A Chelicerae of male (LINGU-INV06); B Dorsal body of male (LINGU-INV06); C Chelicerae of female (LINGU- INV07); D Dorsal body of female (LINGU-INV07). Scale bar: 1 mm.

FIGURE 7. Comparisons of apical structures of male genitals. A – C Penis comparisons of ‘spoon’ and ‘cup’ form between H. geniculatus and other Epedanidae species; A Pseudobiantes japonicus Hirst, 1911, taken from Kury et al. 2019; B Heterobiantes geniculatus (Pocock, 1903); C Parabeloniscus corneus Zhang & Zhang, 2012; D – F Examples and comparisons of ‘prickly funnels’ in everted Epedanidae genitals, all genitals beside H. geniculatus are taken from Zhang & Martens 2020; D Toccolus globitarsis Suzuki, 1969; E Heterobiantes geniculatus (Pocock, 1903); F Euepedanus dashdamirovi Zhang & Martens, 2020; G – N Comparison of lateral genitals of male Epedanidae; G & N Heterobiantes geniculatus (Pocock, 1903); H Toccolus globitarsis Suzuki, 1969, taken from Zhang & Martens, 2020; I Epedanus pictus Thorell, 1876, taken from Kury et al. 2019; J Euepedanus dashdamirovi Zhang & Martens, 2020, taken from Zhang & Martens 2020; K Pseudobiantes japonicus Hirst, 1911, taken from Kury & Villarreal 2015; L Kilungius bimaculatus Roewer, 1915, taken from Suzuki 1973; M Kilungius insulanus (Hirst, 1911), taken from Suzuki 1973.

FIGURE 8. Comparison of dorsal and ventral genitals of male Epedanidae. A & H Kilungius bimaculatus Roewer, 1915, taken from Suzuki 1973; B, E & I Kilungius insulanus (Hirst, 1911), taken from Suzuki 1973; C & J Plistobunus columnaris Lian et al., 2011; D Pseudobiantes japonicus Hirst, 1911, taken from Kury & Villarreal 2015; F & M Epedanus pictus Thorell, 1876, taken from Kury et al. 2019; G & N Euepedanus dashdamirovi Zhang & Martens, 2020, taken from Zhang & Martens 2020; K Toccolus globitarsis Suzuki, 1969, taken from Zhang & Martens 2020; L Heterobiantes geniculatus (Pocock, 1903).

FIGURE 9. Type specimen tags found with the specimens studied by Roewer, photo taken by the British Museum of Natural History (BMNH).