Ariadna tangara, Marsh, Jessica R., Baehr, Barbara C., Glatz, Richard V. & Framenau, Volker W., 2018

Marsh, Jessica R., Baehr, Barbara C., Glatz, Richard V. & Framenau, Volker W., 2018, New species of tube web spiders of the genus Ariadna from South Australia (Araneae, Segestriidae), Evolutionary Systematics 2 (2), pp. 137-149 : 137

Ariadna tangara sp. n. Figs 4 A–J, 5 A–H, 6 A–C, 7 A–C, 8

Type material.

AUSTRALIA: South Australia: Holotype: ♂, Tangara Drive, American River, Kangaroo Island, - 35.787321S, 137.767032E, 12 June 2017, in tube web under bark at 1 m height, Eucalyptus diversifolia , J. Marsh (SAM NN29863). Paratypes:1♀, same data as holotype (SAM NN29864); 1♂, American River Reserve, Tangara Drive, American River, Kangaroo Island, - 35.788054S, 137.769594E, collected 5 Dec 2017, matured in captivity May 2018, in tube web under bark of Melaleuca halmaturorum , J. Marsh (CeNak ZMH-A0003053); 1♀, Tangara Drive, American River, Kangaroo Island, - 35.805480S, 137.794437E, 26 Jan 2018, in tube web with spiderlings, in crevice in bark of old apple tree, J. Marsh (CeNak ZMH-A0003054).

Other material examined.

AUSTRALIA: South Australia: Kangaroo Island: 1♀, Cannery walking trail, American River, - 35.773707S, 137.781111E, 23 Jun 2017 (SAM NN29867); 1♀, Pelican Lagoon walking trail, American River, - 35.7925800S, 137.757909E, 12 May 2017 (SAM NN29871); 1♀, same data, except 10 Oct 2017 (SAM NN29882); 1♀, Pelican Lagoon walking Trail, American River, - 35.796496S, 137.750963E, 2 Nov 2017 (SAM NN29898); 1♀, Pelican Lagoon Conservation Park, - 35.8016850S, 137.7742141E, 22 Jul 2017 (SAM NN29877); 1♀, American River Reserve, American River, - 35.787622S, 137.767650E, 9 Jul 2017 (SAM NN29873); 2♀, Tangara Drive, American River, - 35.787181S, 137.766994E, 8 Jul 2017 (SAM NN29869, NN29896); 1♀, same data, except - 35.805480S, 137.794437E, 25 Jan 2018 (SAM NN29901); 1♀, same data, except 26 Jan 2018 (J. Marsh research collection, Se064); 1♀, same data, except 19 Jun 2017 (J. Marsh research collection, Se024); 2♀, Antechamber Bay, Chapman River, - 35.785218S, 138.066738E, 9 Sept 2017 (SAM NN29884, NN29885); 1♀, Beyeria Conservation Park, Haines, - 35.7804109S, 137.590886E, 27 Jul 2016, (SAM NN29875); 1♀, same data, except - 35.780488S, 137.590851E, 21 Aug 2017 (SAM NN29894); 1♀, same data, except 10 Dec 2017 (SAM NN29900); 1♂, same data, except coll. 24 Jan 2018, matured in captivity May 2018 (SAM NN29904); 1♀, Loverings Road, MacGillivray, - 35.894155S, 137.569538E, 10 Jan 2018 (SAM NN29902); 1♀, same data, except - 35.902882S, 137.572836E, 10 Jan 2017 (SAM NN29907); 1♀, Three Chain Road, MacGillivray, - 35.910587S, 137.549724E, 30 Jan 2018 (SAM NN29905); 2♀, same data, except 1 Aug 2018 (SAM NN29906, J. Marsh reference collection, Se091); 1♂, 1♀, same data, except 14 Jun 2018 (J. Marsh research collection, Se079, Se080); 1♀, Three Chain Road, MacGillivray, - 35.910674S, 137.550490E, 7 Aug 2017 (SAM NN29887); 1♀, same data, except 9 Aug 2017 (SAM NN29878); 2♀, same data, except 30 Jan 2018 (SAM NN29903). Fleurieu Peninsula: 1♂, 1♀, Douglas Scrub, McLaren Flat - 34.917740S, 138.494675E, May/ June 1987 (SAM, not accessioned).

Etymology.

The specific name “tangara” refers to the type locality, Tangara Drive, where both the male holotype and the female paratype were collected. It is a noun in apposition.

Diagnosis.

Ariadna tangara differs from A. clavata , A. burchelli , A. segmentata and A. muscosa by the lack of abdominal markings. Males of A. tangara differ from all other described Australian male Ariadna spp. by the presence and shape of apophyses and grouped spines on the metatarsus and tibia I (Fig. 4F). Comparison with A. octospinata holotype showed females of A. tangara differed by the size of the preening comb on the fourth metatarsi, which in A. octospinata is about half the length of the tarsus, but is shorter in A. tangara (Fig. 5H) and also by the shape and size of the tooth on the inferior tarsal claw, which is small in A. tangara (Fig. 5G) and long and curved in A. octospinata . Ariadna tangara differ from A. decatetracantha by the presence of a small tooth on the inferior claw, which is bare in A. decatetracantha and by the number of teeth on the main tarsal claws in females, being four in A. decatetracantha and five or six in A. tangara (Fig. 5G, Main 1954, plate II, fig. 3), additionally A. decatetracantha has seven pairs of spines ventrally on metatarsus I, whereas A. tangara has between eight and 12 pairs of spines ( Main 1954, plat II, fig. 6). Ariadna tangara differs from A. natalis , A. montana and A. thyrianthina by the number of spines on the apex of femur I, bearing five spines in A. tangara (Fig. 5F), whilst A. natalis has six, A. montana two and three spines in A. thyrianthina . Additionally, A. tangara differs from A. montana by the presence of retrolateral and prolateral spines on tibia I, which are absent in A. montana (Fig. 5E). Ariadna tangara differs from A. major by the number of spines on the prolateral edge of femur I (five spines apically in A. tangara versus two spines in A. major ), by the number of teeth on the tarsal claws (eight or nine in A. major versus five or six in A. tangara ), and by the absence of a tooth on the inferior tarsal claw of A. major (Fig. 5G).

Description.

Male holotype (SAM NN29863). Carapace length 3.5 mm, dark brown, darker anteriorly; faint, dark radial striae extending from the fovea towards the outer edge of the carapace (Fig. 4A). Sternum yellowish brown, with darker patches between coxae; endites and labium yellowish brown, endites white anteriorly; chelicerae brown; legs yellowish brown, leg I becoming darker distally (Fig. 4B). Abdomen length 3.0 mm, dark grey dorsally, lighter grey ventrally, covered with short, black setae. Carapace oval in shape, posteriorly concave, with edges rebordered; surface finely reticulated, with a fine covering of black setae on the pars cephalica; fovea is an indented pit (Fig. 4A). Carapace flattened when viewed laterally, only rising slightly anteriorly. Labium lateral margins rebordered, concave anteriorly, ¾ the length of the endites (Fig. 4B). Sternum oval, with precoxal triangles, anteriorly with neck and concave; coxae I and II swollen at base so that they slightly overhang the sternum (Fig. 4B). Chelicerae hypognathous, laterally with basal transverse ridges (Fig. 4C), retromargin with single tooth, promargin with three teeth. Endites elongate so that when viewed dorsally they extend beyond the chelicerae. Posterior eye row straight, eye group takes up over ¾ of the width of the carapace (Fig. 4C). Leg I: elongated and robust; tarsus is robust and laterally thickened, with a prolateral apophysis (AP1) and an opposing retrolateral apophysis (AP2); tibia with three stout grouped spines (RGS) on prominent base, situated distally on retrolateral surface, and with one prolateral spine opposing the three stout spines (Fig. 4 E–G). Leg measurements (I--IV): femora 3.41, 3.20, 2.27, 2.71; patellae 1.24, 1.01, 1.26, 1.01; tibiae 2.69, 2.68, 1.61, 2.25; metatarsi 2.40, 2.42, 1.58, 1.71; tarsi 0.95, 0.84, 0.89, 0.78; total 10.57 10.38, 7.36, 8.71. Spines: Leg I: femur d1, dp3ap, d2ap; tibia p1-1-1-1, vp2bas, vr2bas, r1-1-1, r3ap (three spines grouped together, on a raised common base; Fig. 4G); metatarsus vp1bas, vp1ap, vr1ap (Fig. 4 E–G). Leg II: femur d1-1, dp2ap, d2ap; tibia p1-1-1-1, vr1-1-1, vr2bas, vr2ap, r1-1-1-1; metatarsus p1-1, p1ap, vr1-1, r1/0-1-1-1, r1ap. Leg IV: femur d1/0-1/0-1-1-1-1, tibia vp1ap, v1, metatarsus v1/0, vr1/0, vr2ap, retrolateral distal preening comb with four spines (Fig. 4D). Tarsal claws of legs I and II with 10 teeth, inferior claw with 1 tooth; tarsal claws of legs III and IV with 6 wide teeth, inferior claw with one small tooth. Scopulae ventrally on metatarsi II, III and IV covering entire metatarsus. Scopulae distally on metatarsus of leg I, covering the first third of the ventral surface of the metatarsus. Pedipalp bulb large, rounded, 1.5 width of pedipalp tibia. Embolus long, thin, curved at its apex, back towards the bulb (Fig. 4H, J). Pedipalp tibia basally expanded, pale in colour. Cymbium short, approx. 1.5 times as long as wide, medially indented dorsally (Fig. 4I).

Description.

Female paratype (NN29864). Carapace length 4.1 mm, legs, endites and chelicerae golden-brown; carapace with faint darker radial striae extending from fovea; abdomen length 6.6 mm, dorsally pale, mottled grey, ventrally without markings, pale light grey in colour (Fig. 5A). Sternum yellowish brown with darker patches between coxae (Fig. 5B). Lateral margins of abdomen with a longitudinal pale line extending from anterior of the abdomen for ¾ of its length. Carapace with sparse black setae, becoming denser anteriorly; long black setae projecting anteriorly from the clypeus (Fig. 5C). Carapace oval, narrowed at front, apically square; from anterior view clypeus rounded, with its ventral edge indented medially in a ”U” shape; caput gently raised; fovea a shallow indented pit (Fig. 5A, C). Sternum oval, anteriorly concave, posteriorly forming a broad point between the fourth coxae; sternum with precoxal triangles; coxae I and II basally swollen so the ventral edges overhang the sternum (Fig. 5B). Labium ¾ length of maxillae, widest at midpoint. Posterior eye row slightly procurved, chelicerae hypognathous, laterally with basal transverse ridges, anterior surface of chelicerae with long, fine, pale-brown setae and thicker black setae (Fig. 5C). Retromargin with single tooth, promargin with 3 teeth. Legs I and II ventrally and prolaterally covered with long, fine, pale-brown setae (Fig. 5D). Femur I bowed (Fig. 5A, F). Leg measurements ( I–IV): femora: 2.93, 2.60, 1.91, 2.35; patellae 1.37, 1.37, 1.04, 1.42; tibiae 2.15, 2.19, 1.44, 2.17; metatarsi 1.81, 1.86, 1.39, 1.35; tarsi 0.62, 0.57, 0.63, 0.68; total 8.88, 8.59, 6.41, 7.97. Spines: Leg I: femur dp3ap, d2ap; tibia p1-1, v2/1-2-2-2-2/1-2 (5 paired spines ventrally, 2/1 additional unpaired prolateral spines), r1/0; metatarsus v2-2-2-2-2-2-2-2-1-1/0 (Fig. 5 D–F). Leg II: femur dp2ap; tibia p1-1, v2-2-2-2-1; metatarsus v 2-2-2-1-2-2-2-2. Leg IV: metatarsus vr1ap, distal retrolateral preening comb with four spines (Fig. 5H). Tarsal claws of legs I and II with six teeth, a minute tooth on the inferior claw (Fig. 5G). Tarsal claws of legs III and IV with three or four uneven teeth, inferior with a very minute tooth. Epigastrium a raised, lightly sclerotised mound (Fig. 5B). Internal genitalia: anterior receptaculum bilobed, ventral lobe about 1.25 times longer than dorsal lobe. Fig. 6 A–C.

Variation

(see Suppl. material 1: Table S1): Males (n=4), carapace length: range 3.47-3.93 mm, mean 3.72 mm, standard deviation 0.23 mm. Females (n=25), carapace length: range 4.06-6.96 mm, mean 4.82 mm, standard deviation 0.58 mm. Whilst leg spination did vary between males, some spines, or combination of spines remained constant. Spines that were constant in the specimens examined included the paired spines basally on the prolateral and retrolateral sides of the tibia of legs I and II (Fig. 4F, G), and two apical spines on metatarsus I (Fig. 4E). The grouped retrolateral spines (RGS) on the tibia, and the apophyses (AP1, AP2) on metatarsus I, showed no variation in the males examined (Fig. 4E, G).

Spination of females varied, both between specimens and between the left and right legs of individuals. Prolateral and retrolateral spines were present on tibia I of all specimens. The number of spines per specimen varied between two or three prolateral spines, and one or two retrolateral spines. The number of paired ventral spines on tibia I varied between seven and five pairs per specimen. The ventral paired spines on metatarsi I varied between eight and eleven pairs per specimen. The prolateral spines at the apex of femur I was constant (Figs 4E, 5F). The structure of the preening comb showed very little variation (Figs 4D, 5H).

Distribution.

South-eastern South Australia, including the Fleurieu Peninsula and Kangaroo Island (Fig. 8).

Life history and habitat preferences.

Ariadna tangara has a similar distribution to, and was often found sympatric with A. clavata . Both species were mainly collected from within tube webs located beneath rugose or cracked bark of older trees. As with A. clavata , tree species appeared to be less important than the structure of the bark. Distribution was highly patchy. Hundreds of specimens may be present on one tree, while the species was hard to find on other trees in the locality. Tube-webs of juveniles were often found grouped around those of mature females, with sometimes hundreds of webs belonging to specimens of different ages (as discerned by varying entrance size and specimen size) on a particular tree. Despite a concerted effort to collect males, only two mature males were collected manually, both in winter (June). One of the mature males was collected from under bark in a tube web adjacent to a female web. During captivity, two males matured in May (both collected in December the previous year) constructed tube-webs similar to those of the females, but with less dense weaving. Mature females were collected across the year. Females with eggs or with spiderlings were collected in December through to February. Eggs were not enclosed in an egg sac, but located on the bottom of a thick tube-web, with the female in situ. Once emerged, the spiderlings remain with the female prior to dispersing.

Function of the modified first legs in males.

In captivity, Ariadna tangara males employed two distinct coupling tactics, depending on whether the female was in a tubular retreat or not. Where the female was free roaming (n=5), the male approached the female whereupon she adopted a defensive posture with fore legs raised. He hooked the front coxae/trochanters with AP2, the RGS hooked on to the female’s front femora and with AP2 wedged against the lateral edges of the female’s carapace (n=7) (Fig. 7A, B). The male then turned the female on to her back and mated with her in that position (n=5) (Fig. 7A, C). Where the female was occupying a tubular retreat (n=2), the male placed his front legs on the entrance of the retreat and vibrated his body rapidly (n=2). The female emerged slowly, with front legs raised. Once the female’s front legs were out of the retreat the male gripped her front coxae/trochanters as described above, but mated with the female upright, whilst her abdomen was still in the retreat. Most often the male mated with both emboli inserted in the epigyne concurrently.