Theridion promiscuum Domenech & Crespo, 2020

Domenech, Marc, Crespo, Luis C., Enguidanos, Alba & Arnedo, Miquel A., 2020, Mitochondrial discordance in closely related Theridion spiders (Araneae, Theridiidae), with description of a new species of the T. melanurum group, Zoosystematics and Evolution 96 (1), pp. 159-173 : 159

Theridion promiscuum Domenech & Crespo sp. nov. Figs 5 , 8

Type material.

Holotype ♂: Spain, Parc Nacional d’Aigüestortes i Estany de Sant Maurici, 42.5491, 0.8714, 1739 m. Hand collecting, June 30, 2013 (Marcos Roca-Cusachs leg.). Deposited at CMCNB under the code MZB 2017-3715.

Paratypes: 6♂ and 5♀ from Spain, Parc Nacional d’Aigüestortes i Estany de Sant Maurici, 0.8725, 42.5496, 1760 m. June 29, 2013. Four males and three females deposited at CMCNB under the codes MZB 2019-1687, MZB 2017-3710, MZB 2017-3713, MZB 2017-4570, MZB 2019-1688, MZB 2017-3712, and MZB 2017-3714. Two males and two females deposited at CRBA under the codes CRBA-89454, CRBA-89455, CRBA-89456, and CRBA-89457.

Etymology.

The specific name promiscuum is derived from the Latin word for “intermingling”, referring to the morphological similarity with other species of the T. melanurum group. It also makes reference to the possible introgression between this species and other closely related species here reported.

Diagnosis.

Males of T. promiscuum sp. nov. can be distinguished from other species in T. melanurum group by a bent and twisted embolus, forming a marked angle (Fig. 5e ); embolus shorter in T. promiscuum sp. nov. than in sympatric T. mystaceum (Fig. 6e ) and T. harmsi (Fig. 7e ); tip of the embolus pointing distally in T. promiscuum sp. nov. (Fig. 5c ) and pointing retrolaterally in remaining species (Figs 6c , 7c ); base, prolateral part of the embolus more sclerotized in T. promiscuum sp. nov. (Fig. 5e ) than in remaining species of the T. melanurum group (Figs 6e , 7e ); presence of small barbs in embolus base distal border is unique to T. promiscuum sp. nov. (only visible in SEM; Fig. 8a, b ). Females of T. promiscuum sp. nov. can be distinguished from T. mystaceum and T. harmsi by the lower position of copulatory duct openings in atrium in T. promiscuum sp. nov. (Fig. 5f ), which are central in T. harmsi (Fig. 7f ) and close to or under lateral walls of atrium in T. mystaceum (Fig. 6f ); copulatory ducts shorter, fewer coils in T. promiscuum sp. nov. (Fig. 5g ) than in T. mystaceum (Fig. 6g ) and T. harmsi (Fig. 7g ).

Description.

Holotype male: Total length 1.81; abdomen 1.04; cephalothorax length 0.84, width 0.78. Leg length (total, coxa, trochanter, femur, patella, tibia, metatarsus, tarsus): I: 4.46, 0.22, 0.16, 1.18, 0.42, 0.97, 1.02, 0.5; II: 3.38, 0.2, 0.11, 0.91, 0.37, 0.63, 0.75, 0.41; III: 2.49, 0.16, 0.08, 0.69, 0.3, 0.4, 0.53, 0.34; IV: 3.32, 0.21, 0.1, 0.98, 0.38, 0.56, 0.7, 0.39. Leg formula: 1>2>4>3. Eye diameter: AME 0.07; ALE 0.06; PME 0.06; PLE 0.07. Distance from AME to clypeus 0.18. Length of chelicera 0.26, fang 0.14. Dark circles around the eyes, with eye region darker than the rest of carapace. Carapace yellowish brown, with blackish triangular patch not reaching the eyes (see paratype MZB 2017-3713; Fig. 5b ). Margin of the carapace also blackish. Sternum yellowish, paler in the middle and darker in the margins, with thin black border. Legs pale with darker annulations. Dorsal abdomen with light central dented band running longitudinally and bordered with black (see paratype MZB 2017-3713; Fig. 5b ). Thinner reddish band running through the middle of the light central band. Rest of the abdomen brown with darker spots. Ventral side with white spots. Spinnerets bordered by thick black line. Colulus absent. Palpal tibia pale. Embolus base wide, well sclerotized basally and prolaterally. Embolus wide, angularly bent, basally well sclerotized (see paratype MZB 2017-3713; Fig. 5e ). Presence of small barbs in the distal border of the embolus base, visible in SEM (see paratype MZB 2017-3713; Fig. 8a ) but very hardly visible in stereomicroscope given the membranous and translucid nature of these barbs.

Paratype female (MZB 2019-1688): Total length 2.18; abdomen 1.33; cephalothorax length 0.93, width 0.84. Leg lengths (total, coxa, trochanter, femur, patella, tibia, metatarsus, tarsus): I: 4.74, 0.24, 0.14, 1.28, 0.45, 1.01, 1.13, 0.5; II: 3.42, 0.24, 0.1, 0.94, 0.37, 0.61, 0.76, 0.41; III: 2.65, 0.22, 0.08, 0.74, 0.3, 0.39, 0.57, 0.36; IV: 3.7, 0.29, 0.1, 1.08, 0.38, 0.63, 0.82, 0.41. Leg formula: 1>2>4>3. Eye diameters: AME 0.08; ALE 0.07; PME 0.06; PLE 0.07. Distance from AME to clypeus 0.17. Length of chelicera 0.34, fang 0.13. Spine-like bristles in leg I: 2 in patella, 2 in tibia. Relative positions in tibia I: 0.25, 0.68. Thickness of tibia I: 0.1. Serrated bristles on tarsus of fourth leg. Cephalothorax yellowish brown with a black central area reaching the eye region, and broad, dark edge (Fig. 5a ). Sternum yellow, paler in the middle and darker in the margins. Abdomen more spherical than in male. Spinnerets bordered by thick black line. Colulus absent. Epigynal cavity wider than long. Openings of the copulatory ducts close to the posterior margin of the epigynal cavity (Fig. 5f ). Copulatory ducts relatively short and with few coils (Fig. 5g ).

Intraspecific variation.

Spine-like bristles in tibia of leg I of paratypes: two in patella, two in tibia. Relative positions of first spine in tibia: 0.25-0.32 (average 0.275). Relative positions of second spine in tibia: 0.7-0.74 (average 0.717). Thickness of tibia I: 0.11-0.13 (average 0.123).

Genetic information.

We obtained a 568 bp sequence of the COI mitochondrial gene for the holotype (stored in Genbank under the code MT215600) and five paratypes (MZB 2017-3710, MZB 2017-3712, MZB 2017-3713, MZB 2017-3714, and MZB 2017-4570 with GenBank codes MT215603, MT215604, MT215602, MT215606 and MT215601, respectively). We also obtained sequences of the ITS2 of up to 469 bp, including up to 26 bp of the 28S gene and up to 69 bp of the 5.8S gene, for the holotype (GenBank code MT117179) and the five paratypes mentioned before (codes MT117182, MT117181, MT117180, MT117183 and MT117184).

Distribution and natural history.

The holotype and paratypes were collected in an oak forest of Quercus pubescens Willd. in Aigüestortes i Estany de Sant Maurici National Park, located in the southern slopes of the Catalan Pyrenees. The specimens were captured either by beating, sweeping or direct sampling, but not by pitfall traps, which suggests that this species is found in the vegetation at a certain height above the ground. Only the three specimens captured by beating method were captured during the day, whereas the sweeping and direct sampling ones were captured at night, which indicates that this species is mostly active at night.

Other taxa analysed.

The specimen tentatively referred to as T. sp. 15 is morphologically similar to the species T. cinereum Thorell, 1875, T. petraeum L. Koch, 1872, T. furfuraceum Simon, 1914, T. pyrenaeum Denis, 1944, and T. wiehlei Schenkel, 1938. However, the male palp of the single specimen available showed slight differences in the shape of the median apophysis, slightly tilted, and the more pronounced basal curvature of the shorter embolus, which refrained us from assigning it to any of the former species. The DNA barcodes, on the other hand, identified the specimen unambiguously as T. cinereum .

Figures

Figure 5. Theridion promiscuum sp. nov. a) Female paratype MZB 2019 - 1688, dorsal habitus. b) Male paratype MZB 2017 - 3713, dorsal habitus. c) Left male palp, ventral. d) Left male palp, retrolateral e) Male embolus f) Female epigynum, ventral g) Female vulva, dorsal. Scale bars: 1 mm (a, b); 0.1 mm (c, d, f, g); 0.05 mm (e).

Figure 6. Theridion mystaceum. a) Female, dorsal habitus b) Male, dorsal habitus. c) Left male palp, ventral. d) Left male palp, retrolateral e) Male embolus f) Female epigynum, ventral g) Female vulva, dorsal. Scale bars: 1 mm (a, b); 0.1 mm (c, d, f, g); 0.05 mm (e).

Figure 7. Theridion harmsi. a) Female, dorsal habitus. b) Male, dorsal habitus. c) Left male palp, ventral. d) Left male palp, retrolateral e) Male embolus f) Female epigynum, ventral g) Female vulva, dorsal. Scale bars: 1 mm (a, b); 0.1 mm (c, d, f, g); 0.05 mm (e).

Figure 8. Scanning electron microscope image of left male palp. Top: ventral view. Bottom: prolateral view. a, b) Theridion promiscuum sp. nov. c, d) Theridion mystaceum. e, f) Theridion harmsi. Scale bars: 0.1 mm.