Pachygnatha, SUNDEVALL, 1823

Álvarez-Padilla, Fernando & Hormiga, Gustavo, 2011, Morphological and phylogenetic atlas of the orb-weaving spider family Tetragnathidae (Araneae: Araneoidea), Zoological Journal of the Linnean Society 162 (4), pp. 713-879 : 794-800

publication ID	https://doi.org/ 10.1111/j.1096-3642.2011.00692.x
persistent identifier	https://treatment.plazi.org/id/7D5E87AD-C038-5550-FF16-4C11D285F986
treatment provided by	Valdenar
scientific name	Pachygnatha
status

Treatment

PACHYGNATHA SUNDEVALL, 1823 View in CoL View at ENA ( FIGS 105–108 View Figure 105 View Figure 106 View Figure 107 View Figure 108 )

Type species: Pachygnatha clercki Sundevall, 1823 . The type specimens of P. clercki are deposited at the Natural History Museum of Geneva ( Levi, 1980).

Diagnosis: Pachygnatha species can be distinguished from other tetragnathids by the following combination of characters: lack of aggregate and flagelliform silk gland spigots and the PMS spigot nubbin ( Fig. 105C, E View Figure 105 ); sternum projecting between the coxae ( Fig. 106B View Figure 106 ); carapace covered with thin and short macrosetae immersed in pits ( Fig. 106A View Figure 106 ); femora IV with a single trichobothrium ( Fig. 106F View Figure 106 ); thick and cylindrical median and lateral tracheal trunks ( Fig. 105B View Figure 105 ); haplogyne system ( Fig. 107B–D View Figure 107 ); copulatory opening as a spiracle, more sclerotized than the surrounding cuticle ( Fig. 107A View Figure 107 ), displaced to the centre of the abdomen.

Description: Female: body length c. 5.0 mm. Ocular area higher than carapace lateral margins ( Fig. 106C View Figure 106 ). Sternum longer than wide projecting between the coxae; labium trapezoidal, wider than long, and rebordered ( Fig. 106B View Figure 106 ). Chelicerae divergent, anterior cuticle smooth as in the clypeal area ( Fig. 106C–E View Figure 106 ); boss present. Clypeus higher than two AME diameters. Eyes subequal in size; PME without canoe-shaped tapetum, with rhabdoms arranged in loops. PLE with canoe-shaped tapetum ( Levi, 1980: figs 156–161). Abdominal cuticle formed by small cylinders arranged in lines ( Fig. 105A, F View Figure 105 ). Tracheal spiracle located near the spinnerets, wider than long, with fewer than four accessory glands on each side ( Fig. 105B, D View Figure 105 ). ALS with c. 35 piriform spigots. PMS with two aciniform spigots between the cylindrical and minor ampullate silk gland spigots but without any aciniform spigots over the anterior surface ( Fig. 105C View Figure 105 ). Femora IV with a single trichobothrium ( Fig. 106F View Figure 106 ). Epigynum absent, copulatory opening spiracle-shaped, with both margins slightly sclerotized. Spermathecae well sclerotized and connected to a membranous sac that leads to the only copulatory opening ( Fig. 116B View Figure 116 ; Levi, 1980: figs 206, 207). Accessory gland openings in separate pits, concentrated near the copulatory ducts ( Fig. 107C, D View Figure 107 ).

Male: size and somatic morphology similar to the female. Epiandrous fusules immersed in a transverse depression and arranged in a single line. Lower margin of the epiandrous plate swollen ( Fig. 105F View Figure 105 ). Palpal patella without macrosetae; palpal tibia as wide as long ( Fig. 108B View Figure 108 ). Palpal femur length more than four times its width. Cymbium constricted in the middle ( Fig. 108C View Figure 108 ). Paracymbium-cymbium attachment membranous. Paracymbium longer than half the cymbium length, with distal apophyses ( Fig. 108D View Figure 108 ). Conductor-tegulum attachment well sclerotized, located at the centre of the tegulum ( Fig. 108A View Figure 108 ). Embolus tubular, without basal apophyses. Sperm duct spiralled, considerably enlarged on its middle section ( Levi, 1980: fig. 177).

Natural history: Pachygnatha has 40 described species and two subspecies described. Most species have a Holarctic distribution with some exceptions in South-East Asia, central and southern Africa ( Platnick, 2009). Adults of Pachygnatha do not build capture webs but juveniles construct a small orb web (4 to 6 cm in diameter), with 13 to 17 radii and open hubs although the web has never been photographed ( Levi, 1980: 50). Adults are found wandering in moist places on the ground, lack aggregate and flagelliform silk gland spigots, and the tarsal accessory claw is reduced. Juveniles have these gland spigots and their accessory claws are well developed ( Levi, 1980). Some aspects of the biology of Pachygnatha have been studied, such as a comparison and description of the life cycles of Pachygnatha degeeri Sundevall, 1830 and Pachygnatha clercki Sundevall, 1823 ( Alderweireldt & de Keer, 1990); the role of P. degeeri as an aphid predator ( Harwood, Sunderland & Symondson, 2005); and the sperm ultrastructure of Pachygnatha listeri Sundevall, 1830 ( Michalik et al., 2005). The female genital anatomy of P. autumnalis was descried by Dimitrov et al. (2007).

Taxonomy: The monophyly of Pachygnatha has never been tested. The taxonomy of the North American ( Levi, 1980), European and the Afrotropical species ( Bosmans & Bosselaers, 1994) has been revised. We have coded P. autumnalis Marx , in Keyserling, 1884 in the character matrix. Our diagnosis and description were based on this latter species and on the Pachygnatha species descriptions of Levi (1980) and Bosmans & Bosselaers (1994). Previous phylogenetic analyses have recovered Pachygnatha as sister to Glenognatha ( Hormiga et al., 1995; Álvarez-Padilla, 2007; Dimitrov & Hormiga, 2009). Both the morphology plus behaviour and the total evidence data sets recover this latter sister group relationship ( Figs 143 View Figure 143 , 144 View Figure 144 ).

TETRAGNATHA LATREILLE, 1804 View in CoL

( FIGS 1A, B View Figure 1 , 5D View Figure 5 , 109–113 View Figure 109 View Figure 110 View Figure 111 View Figure 112 View Figure 113 )

Type species: Tetragnatha extensa ( Linnaeus, 1758) . The type specimens of Aranea extensa are lost ( Levi, 1981).

Diagnosis: The genus Tetragnatha is diagnosed by the following features: PLE tapetum absent but PLE canoe-shaped tapetum present ( Levi, 1981: figs 20, 21); female lateral eyes on separate tubercles; cephalic fovea deep, divided in two pits ( Fig. 110D View Figure 110 ); smooth femoral trichobothrial shaft, arranged in an irregular line; and haplogyne genitalia ( Fig. 113D View Figure 113 ). In many species mature females have the copulatory opening displaced posteriorly relative to the epigastric furrow ( Fig. 111A, B View Figure 111 ).

Description: Female: body length variable 5.4 to 13.3 mm ( Levi, 1981). Femora IV trichobothrial shaft not branched ( Fig. 110E View Figure 110 ). Ocular area lower than carapace lateral margins ( Fig. 110B View Figure 110 ). Labium trapezoidal, wider than long, and rebordered ( Fig. 110F View Figure 110 ). Sternum longer than wide. Chelicerae divergent, anterior surface smooth and cheliceral boss present ( Fig. 110B View Figure 110 ). Clypeus slightly higher than one AME diameter. Abdomen cylindrical, covered with silver guanine patches. Booklung cuticle smooth. Tracheal spiracle located near the spinnerets. ALS with extensive field of piriform spigots ( Fig. 109B View Figure 109 ). PMS with three aciniform spigots between the cylindrical and minor ampullate silk gland spigots but without any aciniform spigots over the anterior surface ( Fig. 109D View Figure 109 ). PLS with c. 20 aciniform spigots arranged in roughly parallel lines, distal end of the aggregate spigots separated from the tip of the flagelliform spigot ( Fig. 109F View Figure 109 ). Epigynal plate absent, copulatory opening as a transverse spiracle ( Fig. 111A, B View Figure 111 ). Spermathecae with two chambers, walls well sclerotized ( Figs 111C–F View Figure 111 , 113D View Figure 113 ). Copulatory ducts short, well sclerotized and attached to a membranous sac ( Fig. 113D View Figure 113 ). Fertilization ducts absent. Spermathecae accessory gland ductiles evenly distributed over the spermatheca, but more concentrated in the chamber near the copulatory duct. Accessory glands immersed in individual pits ( Fig. 111E, F View Figure 111 ).

Male: body length 4.3 to 9.2 mm ( Levi, 1981); somatic morphology similar to that of the female, except chelicerae considerably larger and with distal apophyses ( Fig. 110A, C View Figure 110 ). PLS triplet reduced to nubbins ( Fig. 109E View Figure 109 ). Epiandrous plate well sclerotized, fusules distributed in two groups, individual fusules not immersed in pits ( Fig. 109C View Figure 109 ). Palpal patella with one macroseta. Palpal femora and tibia very long, more than four times its width ( Fig. 110A View Figure 110 ). Paracymbium cylindrical, longer than half the cymbium length, evenly covered with macrosetae, and with a basal apophysis. Paracymbium-cymbium attachment membranous ( Fig. 113A, D View Figure 113 ). Tegulum spherical ( Fig. 112A View Figure 112 ). Conductor-tegulum attachment well sclerotized, located on the centre of the tegulum ( Fig. 113A View Figure 113 ). Embolus tubular, without basal apophyses. Sperm duct spiralled and considerably enlarged in its middle section ( Fig. 113B, C View Figure 113 ).

Natural history: Tetragnatha is the most diverse genus in the family, with 325 described species and 15 subspecies that are distributed worldwide ( Platnick, 2009). These spiders usually build webs over the vegetation inside forests or along ponds and rivers. The orb architecture is very variable ( Fig. 5D View Figure 5 ; Levi, 1981: pl. 3) and some species do not build webs ( Okuma, 1990; Gillespie, 1991b). The biology of Tetragnatha species has received more attention than that of any other tetragnathid genus. The web building behaviours of several Tetragnatha species were described by Eberhard (1982). Some studies on the biology of Tetragnatha include those of habitat selection in several Nearctic Tetragnatha species ( Gillespie, 1987; Aiken & Coyle, 2000); the evolution, taxonomy, and biogeography of radiations of Tetragnatha species on the Hawaiian archipelago and Society Islands ( Blackledge & Gillespie, 2004; Gillespie, 1991 a, 1997, 1999, 2002; Pons & Gillespie, 2003; Vandergast, Gillespie & Roderick, 2004); venom composition ( Binford, 2001); the relationship of the ‘haplogyne’ type of genital anatomy and sperm priority in Tetragnatha extensa ( Austad, 1984; West & Toft, 1999); and sexual selection based on mating histories and body condition (Danielson- François & Bukowski, 2005).

Taxonomy: The taxonomy of Tetragnatha has received considerable attention and although a global taxonomic revision has never been attempted, several regional taxonomic revisions are available. The North American Tetragnatha species were revised by Seeley (1928), Chickering (1959), and Levi (1981). The species from Mexico, Central America, Jamaica, and Panama were revised by Chickering (1957a, 1957b, 1957c, 1962). The Hawaiian fauna has been studied by Gillespie (2003a, b, c). Some Tetragnatha species from the Far East of Russia were revised by Kurenshchikov (1994). The Australasian and Japanese Tetragnatha were revised by ( Okuma 1979, 1987, 1988a, b); this latter author also revised some of the African Tetragnatha ( Okuma, 1985) . Several of the Tetragnatha species from China have been illustrated ( Song et al., 1999). Finally the Tetragnatha species from paddy fields in Thailand and China have also been studied ( Vungsilabutr, 1988; Barrion & Litsinger, 1995; Zhu, Wu & Song, 2002). We coded Tetragnatha versicolor in the character matrix. Our diagnosis and description were based on this latter species plus the species

800 F. ÁLVAREZ-PADILLA and G. HORMIGA descriptions in Levi (1981). The morphology plus behaviour data set recovered Tetragnatha and Cyrtognatha as sister taxa ( Fig. 143A, B View Figure 143 ); however, when these data are combined with DNA sequences, Tetragnatha is sister to a clade that includes Glenognatha and Pachygnatha ( Fig. 144 View Figure 144 ).