Echinotheridion gibberosum ( Kulczynski, 1899 )

Knoflach, Barbara & Harten, Antonius Van, 2006, The one-palped spider genera Tidarren and Echinotheridion in the Old World (Araneae, Theridiidae), with comparative remarks on Tidarren from America, Journal of Natural History 40 (25 - 26), pp. 1483-1616 : 1605-1613

Echinotheridion gibberosum ( Kulczynski, 1899)

( Figures 3, 4 , 10 , 21 , 23, 24 , 28–30, 36 , 39, 40 , 290–310 ; Tables XXXIV, XXXV) Theridion gibberosum Kulczynski 1899, p 364 , Plate 6 Figure 27 , Plate 7 Figures 37–40 ; n.

sp., ♀, type locality Madeira. Achaearanea gibberosa: Denis 1962, p 62 . Echinotheridion gibberosum: Schmidt 1973, p 369 . Tidarren pseudogibberosum: Schmidt 1981, p 96 , Figure 5 , „ from Gomera (misidentified). Tidarren gibberosum: Wunderlich 1987, p 207 , Figures 544, 545, ♀. Echinotheridion gibberosum: Knoflach 2002a, p 140 , Figures 1–10 , „ ♀.

Material examined

Spain: „„ ♀♀, Canary Islands, Tenerife, above Orotava / Aguamansa , 28 ° 469N, 17 ° 459W, pine and laurel forest, 1000–1100 m, 17 February 2000 (males adult in March 2000) ; „ ♀, mts. Anaga, near Las Mercedes, Cruz de Carmen , 28 ° 329N, 16 ° 129W, 20 February 2000, leg. Knoflach and Thaler (males adult in March 2000). Gomera , Montes del Cedro , 700– 1000 m, laurisilva, „ ♀, 4 March 2004, leg. Steinberger. Ibidem, 1 „ without palp, SMF 29627, sub Tidarren pseudogibberosum (see Schmidt 1981). Ibidem , 1♀, SMF 29411, leg. Schmidt 1976, det. 1977 . 2♀, SMF 29401, Gomera, Arure , June 1976, leg. Schmidt ( Schmidt, 1981). 1 „, SMF 34010, La Palma, leg. Wunderlich, det. 1985 .

Voucher specimens deposited in AMNH, CAS, CTh, MHNG, MNHN, MRAC, NHMB, NHRS, NMBS, NMW, SMF.

Description

Kulczynski (1899, ♀), Knoflach (2002, „ ♀).

Measurements (mm)

Dimensions of male/female [minimum–maximum (mean), n 510.] Body length 1.45–1.88 (1.67)/3.29–3.72 (3.53), prosoma length 0.59–0.72 (0.66)/1.35–1.56 (1.42), prosoma width 0.55–0.64 (0.59)/1.01–1.25 (1.11), length femur I 1.15–1.44 (1.25)/2.70–3.36 (2.95), tibia I 0.78–1.00 (0.84)/1.76–2.19 (1.92). Abdomen 0.92–1.56 (1.14)/2.54–4.15 (3.09) high, 0.86–1.13 (0.97)/1.88–2.93 (2.25) long, and 0.66–1.05 (0.80)/1.56–2.54 (1.89) wide. Ventral side (distance petiolus to spinnerets) 0.59–0.92 (0.73)/1.56–2.15 (1.73) long. Clypeus in male 0.21–0.29 (0.25) high, in female 0.27–0.37 (0.28). Chelicerae 0.22–0.29 (0.27)/0.49–0.59 (0.53) long. Sternum 0.39–0.47 (0.42)/0.78–0.88 (0.81) long and 0.39–0.43 (0.40)/0.66–0.72 (0.69) wide. Labium on average 0.07/0.16 long, 0.18/0.30 wide. Gnathocoxae 0.21–0.25 (0.23)/0.45–0.49 (0.47) long, 0.09–0.12 (0.10)/0.18–0.23 (0.20) wide. Femur of male palp 0.31–0.39 (0.34) long. Leg formula 1423, see Tables XXXIV, XXXV. Number of dorsal setae on tibiae I–IV 2/2/1/2. Trichobothria in retrodorsal/prodorsal row on tibia of female palp 1/1, of legs I–IV 3/2, 3/2, 3/3, 3/ 4 in female and 2/1, 2/1, 1/2, 2/ 2 in male (1 „, 1♀ examined). Metatarsi I–III with one trichobothrium, position on I in female (male) 0.36 (0.27), on II 0.38 (0.30), on III 0.39 (0.29). Tarsal claws of legs with four (three) side teeth in female (male), claw of female palp consisting of seven to eight teeth ( Figures 28–30 ). Tarsal organ on female palp at 0.76 ( Figure 36 ), on female (male) legs I–IV 0.41 (0.38), 0.38 (0.30), 0.35 (0.27), 0.36 (0.28).

Somatic features, colouration ( Figures 291–294 , 305–307 )

Females with a spur on posterior base of coxae IV ( Figures 23, 24 ). Sternum in female with small posterior tubercle, in male absent. Abdomen higher than long, cone-shaped, ending in tubercle.

Female ( Figures 291, 292, 294 , 305–307 ). Overall colouration highly variable (see also Knoflach and Pfaller 2004). Most common variant shows extended dark pigmentation ( Figures 291, 294 ), some females yellowish with only a few dark pigmented areas ( Figure 292 ), some predominantly reddish and with red instead of dark brown pigments. In common variant carapace either uniformly dark brown or light brown with broad dark margins and dark median band from eye region to centre. In lighter variants carapace uniformly yellow to reddish brown. Chelicerae dark or light brown. Gnathocoxae and labium light brown. Sternum usually reddish with light anterior median area and six light peripheral patches, opposite coxae I–III, sometimes light brown with a few reddish patches. Palps and legs yellowish (sometimes reddish) with dark patches and annulations of various extent. Coxae yellow. Abdomen with whitish dorsal median band and posterior white lines, which branch laterally. Aboral area with distinct white stripe from apex to spinnerets. Epigastric region and venter of variable colouration according to degree of overall pigmentation, book lung covers light brown. Epigynal protuberance heavily sclerotized in contrast to surrounding integument.

Male ( Figure 293 , 305 ). Carapace, chelicerae, gnathocoxae, labium, and sternum uniformly dark or reddish brown. Legs light to reddish brown, with some dark patches and annulations, sometimes largely suffused with grey. Distal parts of male palp dark to reddish brown. Abdomen usually dark or reddish brown, with a few white patches on dorsum, aboral area whitish with white stripe from apex to spinnerets. Epigaster dark to reddish brown, book lung covers yellow. Venter dark to reddish brown with two small white paramedian patches. Spinnerets dark to reddish brown.

Male palp ( Figures 10 , 295–298 , 304 , 308 , 309 )

Tibia ca 0.5 width of palpal organ at widest part (dorsal view); its base ca 0.3 width of distal rim ( Figure 296 ). Male palp pincer-shaped, owing to strongly protruding cymbium and conductor ( Figures 10 , 295 , 308 , 309 ). Cymbium ends in a hook-like, apical process and a hairy, narrow lobe, bearing tarsal organ and adjoining broad furrow of conductor ( Figure 297 , 309 arrow). Its apical margin is strongly incised ( Figure 297 ). On retrolateral side another, less distinct, hairy projection ( Figures 297, 298 ). Bulbus ca 0.4 mm long (including conductor) and 0.33 mm wide. Subtegulum and tegulum appear to be partially fused, though hard to recognize, connecting median haematodocha presumably reduced or at least inconspicuous. Distal rim of tegulum sclerotized and incised, with two small rounded, but indistinct projections ( Figures 295, 296 ). Conductor strongly developed, curved, forming a lamella with broad, shallow furrow, its inside curved surface covered with tiny scales ( Figures 295–298 ). Base of embolus slender and apparently lacking the two basal lobes present in all Tidarren species ( Figure 296 ), gradually passing into distal part. Distal part of embolus about 0.15–0.16 mm long. Haematodochae not modified, basal one largely expanded, distal and presumably also median one vestigial ( Figures 308–310 ).

Epigynum, vulva ( Figures 24 , 299–303 , 308 , 309 )

Epigynum a broadly rounded, heavily sclerotized protuberance ( Figures 24 , 299 , 303 ), ca 0.1 mm long in side view, 0.25 mm wide in ventral view, longer than receptacula. Anterior declivity sclerotized, forming a transverse suboval plate, clearly delimited from surrounding integument ( Figures 299, 300 ) and from posterior membranous, whitish declivity. Copulatory orifices well separated ( Figures 300 , 303 ), situated at midline of anterior declivity, in ventral view at level of anterior end of receptacula. Copulatory ducts strongly sclerotized throughout, rather long (ca 0.4 mm), coiled and folded, with narrow lumen, but with gibbous walls, so diameter not evenly wide ( Figures 300–302 ); coils visible through transparent integument of posterior declivity. Copulatory ducts turn posteriorly and enter receptacula at posterior side. Receptacula seminis 0.15 mm long and 0.13 mm wide.

Copulatory behaviour ( Figures 305–310 )

Echinotheridion gibberosum shows a similar bizarre mode of copulation as Tidarren argo . Copulation involves single usage of the male palp and regularly ends in exhaustion of the male, in emasculation and subsequent sexual cannibalism ( Knoflach 2002a). Copulation proceeds via a mating thread. Unlike T. argo , emasculation does not take place immediately after application of the male palp. At first, there is a normal insertion for about 4 min on average, during which both partners are completely motionless ( Figures 305, 306 ). The male seems to be dead, the female is cataleptic. When she awakes from her cataleptic state, she entangles the male and starts to turn around in circles. Emasculation takes more than 3 min, and the female has to try several times until she succeeds in breaking off the palp. The breaking point of the palp is usually between the tibia and tarsus, as in T. argo . Holdfast structures of the palp are sclerites, there is no haematodochal modification. These palpal sclerites clasp the epigynum like forceps, the hook-like apex of the cymbium locks on the membranous folds of the posterior declivity of the epigynum, and the conductor locks in front of the epigynal protruberance ( Figures 307–309 ). The male palp remains fastened to the epigynum for 5 h on average (up to 11 h) while the female is occupied with mate consumption ( Figure 307 ). The function of the coxal spurs on legs IV ( Figures 23, 24 ) of the female remains uncertain, as they seem to not be necessary for genital coupling ( Figure 310 ). Remarkably, the first observation on the copulatory behaviour of E. gibberosum was mistaken as a heterospecific copulation between two genera ( Schmidt 1980).

Natural history ( Figures 3, 4 , 290, 291 )

In Tenerife, the webs of Echinotheridion gibberosum were found at a height of about 1–2 m on tree trunks and between large branches. The spiders are concealed in their large retreats, which consist mainly of debris. The egg-sac has a parchment-like light brown envelope ( Figures 290, 291 ). In some of the retreats cocoons of the pirate spider Ero (Mimetidae) were also found, which may indicate possible predation by this araneophagic spider. For palp amputation ( Figures 3, 4 ) see generic diagnosis and Knoflach (2002a).

Distribution

Echinotheridion gibberosum is known only from laurel forests or mixed pine and laurel forests in Madeira and Canary Islands and appears to be the only representative of the genus in the Old World.

Figures

Figure 1. Tidarren sisyphoides (Walckenaer) from Mexico. (a) Female left, male right; (b) dead male after copulation with right palp still inflated. Note size dimorphism of male compared with female tibia IV.

Figure 2. Male of Tidarren cuneolatum (Tullgren), just moulted into subadult stage. (a) Moulting and amputation site below hub, the usual resting place of the spider; (b) male (left) removing his exuvia from the moulting site; (c) two-palped male before amputation.

Figures 3–6. Subadult males. (3, 4) Echinotheridion gibberosum (Kulczynski) from Tenerife. (3) Ecdysis just completed, male suspended on moulting thread, both palps present. (4) Palp amputation accomplished; arrow points to detached palp. (5, 6) Tidarren sisyphoides (Walckenaer) from Mexico. (5) Early phase of amputation, circling. (6) Amputated palp already sucked out.

Figures 7–10. Male prosoma, in lateral (7, 9) and frontal view (8, 10). (7, 8) Tidarren argo Knoflach and van Harten from Yemen. (9) T. cuneolatum (Tullgren) from Yemen. (10) Echinotheridion gibberosum (Kulczynski) from Tenerife. Note high and steep clypeus and site of palp amputation with trochanter still present. Scale bars: 0.2 mm.

Figure 309. Echinotheridion gibberosum (Kulczynski) from Tenerife. Functional contact of left male palp after emasculation. Sclerites keep palp fastened to epigynum. Cymbium locks behind, conductor in front of epigynal protruberance. Haematodochae not modified. Female parts dark, sclerites of male palp greyish. Scale bar: 0.2 mm.

Figure 310. Echinotheridion gibberosum (Kulczynski) from Tenerife. Functional contact of male palp after emasculation. Palp comes to rest close to female coxal spurs, but without direct contact.

Figures 18–22. Tidarren argo Knoflach and van Harten from Yemen (18–20, 22) and Echinotheridion gibberosum (Kulczynski) from Tenerife (21). (18) Female prosoma in frontal view. (19) Ditto, detail of left chelicera. (20) Male chelicerae separated from carapace, aboral view. Note frontal basal apodemes. (21) Male prosoma in frontal view showing amputation site of male palp. (22) Detail of remaining segments (coxa and trochanter) of amputated male palp. Scale bars: 0.2 mm (18, 20, 21); 0.05 mm (19); 0.02 mm (22).

Figures 23–27. (23, 24) Echinotheridion gibberosum (Kulczynski) from Tenerife. (25, 26) Tidarren argo Knoflach and van Harten from Yemen. (27) T. cuneolatum (Tullgren) from Yemen. (23) Female, ventral view. (24) Ditto, details of coxal spurs on legs IV and epigynum. (25–27) Epigynum, oblique aboral (25) and ventral view (26, 27). Scale bars: 0.5 mm (23); 0.2 mm (24, 25); 0.1 mm (26); 0.05 mm (27).

Figures 28–36. (28–30, 36) Echinotheridion gibberosum (Kulczynski) from Tenerife. (31–33) Tidarren argo Knoflach and van Harten from Yemen. (34, 35) T. cuneolatum (Tullgren) from Yemen. (28–31) Female palpal claw with characteristic large dentition. (32) Serrated setae of tarsal comb of female leg IV. (33) Female tarsal claw. (34, 35) Trichobothria on male tibiae IV and III. Pore on base of hair shaft represents the moulting pore (F. G. Barth, in litt.). (36) Tarsal organ on female palp. Scale bars: 0.05 mm (28); 0.02 mm (29–33); 0.005 mm (34); 0.01 mm (35, 36).

Figures 37–40. (37) Tidarren sisyphoides (Walckenaer) from Mexico. (38) T. argo Knoflach and van Harten from Yemen. (39, 40) Echinotheridion gibberosum (Kulczynski) from Tenerife. (37) Male epigaster with five epiandrous gland spigots. (38) Male spinnerets, colulus absent. (39, 40). Female spinnerets. Note absence of colulus and colular setae, a synapomorphy of Theridiinae according to Agnarsson (2004), and presence of large, compressed spigots of glandulae aggregatae on posterior lateral spinnerets, typical of Theridiidae. Scale bars: 0.02 mm (37); 0.05 mm (38); 0.2 mm (39); 0.1 mm (40).

Figures 290–294. Echinotheridion gibberosum (Kulczynski) from Tenerife. (290, 291) Female guarding egg-sac. Habitus of male (293) and female (291, 292, 294) showing colour variation.

Figures 295–298. Echinotheridion gibberosum (Kulczynski) from Tenerife. Right male palp, prolateral (295), dorsal (296), retrolateral-apical (297), and retrolateral view (298). Scale bar: 0.2 mm.

Figures 299–302. Echinotheridion gibberosum (Kulczynski) from Tenerife. Female epigynum/vulva in lateral (299), ventral (300), aboral (301), and dorsal view (302). Arrow points to fertilization duct. Scale bars: 0.2 mm.

Figures 303, 304. Echinotheridion gibberosum (Kulczynski) from Tenerife. (303) Female epigynum in lateralventral view. (304) Male palp, apical view. Scale bars: 0.1 mm.

Figures 305–308. Echinotheridion gibberosum (Kulczynski) from Tenerife, copulatory behaviour in different pairs. (305, 306) Insertion, advanced phase, male’s legs already contracted. (307) Emasculation accomplished by female. Male palp fastened to epigynum while female feeds on his body. (308) Functional contact of male palp after emasculation. Haematodochae unmodified. Palpal sclerites serve as holdfast structures. Scale bar: 0.2 mm.