Nanometa gentilis Simon 1908
Creators: name: Álvarez-Padilla, Fernando
name: Kallal, Robert J.
name: Hormiga, Gustavo
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Tetragnathidae
Nanometa
Nanometa gentilis

description: meta gentilis Simon, 1908, by monotypy.
Eryciniolia Strand, 1912: 346. Type species: Linyphia purpura-punctata Urquhart, 1889. New synonymy.
Nediphya Marusik and Omelko, 2017. Type species: Nediphya lehtineni Marusik and Omelko, 2017. New synonymy.
DIAGNOSIS: The internal epigynal structures of Nanometa are similar to those found in Taraire from New Zealand. The copulatory ducts of Nanometa are modified as membranous sacs and separated from the spermathecae, giving the appearance of four receptacles (figs. 9H, 11C, 13E). The accessory glands found in Nanometa and Taraire were used to homologize the spermathecae; however, these accessory glands were not discussed in the description of Nediphya (Marusik and Omelko, 2017). Nanometa species can have the eyes in two (fig. 9G, I) or three rows (Marusik and Omelko, 2017: 1–4, 6–8). The AME are slightly reduced in N. purpurapunctata (fig. 26G, I), but that arrangement differs considerably from Nanometa lehtineni in dorsal view, in which the PLE are enlarged (Marusik and Omelko, 2017: figs. 1–4). The posterior edge of the epigynum in Nanometa never extends below the epigastric furrow (fig. 10A, B), in contrast to Taraire, where the posterior edge extends beyond the epigastric furrow (fig. 47A, B). Nanometa cymbial processes can be easily homologized with those of Pinkfloydia, Taraire, and Tawhai, in addition to many tetragnathids, such as Chrysometa Simon, 1894, Meta C. L. Koch, 1836, Metellina Chamberlin and Ivie, 1941, and Allende. The CEBP of Nanometa is basal to the paracymbium and usually bears one to several spines (figs. 7B, 8A, 10F, 23E, F), the CEMP is a cuticular fold distal to the CEBP either covered with normal setae (figs. 7D, 10E), armed with modified structures as in Pinkfloydia (Dimitrov and Hormiga, 2011: figs. 8A, 13H) or as a tiny cuticular fold in Nanometa lehtineni (Marusik and Omelko, 2017: figs. 38, 39). Nanometa males can be separated from those of Taraire, Tawhai, and Iamarra by the absence of basal embolic apophyses (figs. 49A–C, 54A–C, 59C, D) and by the conductor formed by a flat coiled sclerite with sclerotized margins and translucent middle section (fig. 10C); this structure is folded in the latter two genera (figs. 46A, B, 49A, 50B). Nanometa males can be further separated from other tetragnathids by the presence of a stridulatory organ on the booklung cuticle that probably interacts with several cusps on the retrolateral surface of coxa IV (figs. 20F, 26F, 30C). The small size is no longer a useful diagnostic feature for Nanometa with the addition of some of these new species (2.7– 9.5 mm).
DESCRIPTION: Female total length 2.3–8.8. Cephalothorax length 0.9–3.6, width 0.7–2.7. Carapace glabrous, background pale yellow to brown, cephalic region dark gray or brown, darker coloration tapering toward fovea, carapace margins outlined by the same pattern covering the cephalic region (figs. 9A, 18A, 36A). Fovea deep, triangular in shape or as a transverse line, carapace dorsal pits absent. Clypeus height 0.9–2.7 AME diameter, cuticle darker below median eyes and paler below lateral eyes (figs. 9G, 36I, J). AME slightly larger than PME; except in N. purpurapunctata, which has reduced AME. Lateral eyes juxtaposed on a tubercle (separated in N. purpurapunctata), one AME diameter apart from median eyes and approximately half that size. Chelicerae with few scattered setae, cuticle smooth, without ventral stridulatory ridges. Promargin with three teeth, retromargin with none to two, cheliceral denticles present. Endites longer than wide, dark brown, internal margins lighter in coloration. Labium rectangular, wider than long, colored as endites. Sternum yellowish to dark brown, trapezoidal in shape, wider between first two legs (figs. 9E, 18C, 21E). Abdomen dorsum covered with silvery guanine patches, background either brown or gray. Silvery guanine patches in small species cover the entire abdominal dorsum giving a shiny appearance; larger species’ patches are isolated in spots giving a less shiny appearance when alive (figs. 9A, 14A, 36A). Venter with a central dark longitudinal rectangle flanked by two parallel lines of guanine patches (figs. 9E, 18C, 20E) (pattern less conspicuous in Nanometa tasmaniensis: fig. 21E). Lateral surfaces with either a complete longitudinal area of guanine patches, or this area interrupted with a reticulated pattern either dark gray or dark brown (figs. 9C, 26C, 36E). Booklung covers without stridulatory organs, except in N. sarasini (fig. 14H). Spinnerets pale gray to brown, lighter pattern on internal surfaces. Leg formula 1-2-4-3; femur I length 1.1–6.9; first pair considerably larger, all leg segments from pale yellow to dark brown, decorated with transverse darkbrown lines or dark spots, except in N. fea which has all legs entirely dark brown (fig. 15C). Femora with few setae, other segments increasingly hirsute after tibiae. Macrosetae few and present on all segments except tarsus. Epigynum flat, rectangular in shape and wider than long; copulatory openings visible in ventral view and located laterally on the epigynal plate (figs. 10A, B, 11A, B, 14D); size and shape of these openings are species diagnostic. Copulatory ducts modified as membranous sacs that connect to spermathecae via two longitudinal sclerotized ducts (fig. 13E). Spermathecae sclerotization variable, but differentiated from the “copulatory sacs” by a cluster of accessory gland ducts (figs. 20H, 23C, D). Fertilization ducts short, well sclerotized, and originating near the cluster of accessory gland ducts (figs. 13E, 23C).
Male same as female except as noted. Total length 2.0–8.1. Cephalothorax length 1.0–3.2, width 0.8–2.0. Carapace dorsal coloration lighter than female. Clypeus height 1.0–1.5 AME diameter. Chelicerae slightly longer and narrower apically, dorsal cuticle smooth, becoming rugose toward ectal and apical surfaces (figs. 9I, 14I, 26I); ventral cuticle without stridulatory organs (fig. 21H). Abdomen pattern as in female but lighter. Legs: Femur I length 1.6–10.1. Coloration and patterns weaker than in female. Pedipalp: Tibia triangular in shape and usually longer than wide, 1.4–3.75 times, apical margin wider (figs. 13A, 19A). CEBP with one to three apophyses, paracymbium hook or finger shaped either hirsute or glabrous; CEMP small, apical portion as a rounded blunt apophysis; cymbial distal process variable in size and shape (figs. 13C, 15D, 29C). Tegulum donut shaped and compressed dorsoventrally. Embolus and conductor attachment membranous, at the center of the tegulum (figs. 13A, B, 22A, B). Conductor spirals clockwise, margins heavily sclerotized, middle section membranous and expandible (figs. 10C–F, 13A, B). Conductor apical apophyses of variable shape (figs. 10C, D, 19A–C, 23G, H).
COMPOSITION: Nanometa gentilis, N. trivittata, N. lagenifera, N. sarasini, N. purpurapunctata, N. tasmaniensis, N. fea, N. tetracaena, N. dutrorum, N. forsteri, and N. dimitrovi (all presented in the current paper), as well as the taxa formerly included in Nediphya: Nanometa hippai comb. nov., N. lehtineni comb. nov., N. lyleae comb. nov., and N. padillai comb. nov. Several small sized Nanometa species remain undescribed; the species diversity of the smaller species seems to exceed that of the larger (perhaps more conspicuous and frequently collected) taxa.
SYSTEMATICS: The monophyly of Nanometa is supported by the following morphological synapomorphies: branched median tracheal trunks (figs. 11D, 30D); males with a sclerotized ridge on the anterior part of the booklung cover, presumably part of a stridulatory organ with a plectrum on the fourth coxae consisting of small teeth (figs. 20F, 30C) (Forster and Forster, 1999; Álvarez-Padilla and Hormiga, 2011); absence of embolic apophysis; conductor morphology as a curved, flattened translucent disk, with an enlarged and folded margin that covers the embolus distal part (figs. 10C, D, 11E, F, 13C); and copulatory ducts modified as sacs (figs. 9H, 11C, 13E). Kallal and Hormiga’s (2018) recent phylogenetic analysis included both large and small Nanometa species and supported the monophyly of the genus. These authors also found Pinkfloydia to be sister to a clade with remaining nanometines, with good support (Kallal and Hormiga, 2018). The analysis of Dimitrov et al. (2017) suggested that Taraire (see description below) is sister to Nanometinae but with low support. Our analysis elaborates on that latter work, focusing on Nanometa and other tetragnathid taxa found in Australia, New Zealand, New Caledonia, and Papua New Guinea.
ETYMOLOGY: Simon did not explain this genus name, but very likely it means the dwarf Meta, a common etymological root in Tetragnathidae referencing the genus Meta.
DISTRIBUTION: Nanometa species are distributed throughout Australasia, and many seem to be endemic to the islands included in this region. Nanometa trivittata and N. dimitrovi are found only in eastern Australia; N. tasmaniensis is found only in Tasmania; Nanometa tetracaena and N. dutrorum are found in Tasmania and mainland Australia (fig. 37). Nanometa sarasini is endemic to New Caledonia; N. purpurapunctata, N. lagenifera, and N. dimitrovi are found only in New Zealand; and species from Papua New Guinea include N. fea, N. hippai, N. lehtineni, N. lyleae and N. padillai.
NATURAL HISTORY: Nanometa species build horizontal or vertical orb webs with open hubs in humid habitats, sometimes close to or over water bodies, such as streams. When resting, the front legs are stretched forward in a characteristic posture while the rear legs are directed caudally (figs. 1A, C, D, 2B, C, 3C, D) (Forster and Forster, 1999; and all authors personal obs.). They occur in climates ranging from equatorial tropics to temperate forests.
REMARKS: The genus Nanometa was erected by Simon (1908) to include a small tetragnathid species from Western Australia; until now, the genus has remained monotypic. In an unpublished manuscript, the late Ray F. Forster planned to describe at least 40 additional species from eastern Australia, New Zealand and New Caledonia among other Australasian islands, but he passed away before his work was finished. Urqu- hart (1891: 1951) erected the genus Erycina to accommodate a single species (Erycina violacea Urquhart, 1891) unaware that he had already described two conspecifics under two different names (Linyphia purpurapunctata Urquhart, 1889, and Linyphia nitidulum Urquhart, 1889). Urquhart’s new genus name was preoccupied in Lepidoptera, Mollusca, and Reptilia, and so Strand (1912) provided Ericyniolia as a replacement name for Erycina. Urquhart (1891) did not give a justification for erecting the new genus nor did he provide a diagnosis. Forster (1980) and Forster and Forster (1999) placed Ericyniolia within nanometines (as “Eryciniolinae” in the former and “ Nanometidae ” in the latter work). Our phylogenetic analysis places Ericyniolia purpurapunctata in a clade of Nanometa species (figs. 61–63), including the type species, N. gentilis. We circumscribe Nanometa as a monophyletic group that includes purpurapunctata, and thus Ericyniolia becomes a junior synonym of Nanometa (maintaining Eryciniolia as a separate genus would render Nanometa paraphyletic).
More recently, Marusik and Omelko (2017) erected the new genus Nediphya to group four tetragnathid species from Papua New Guinea. Only in the type species of Nediphya are both sexes known, with the remaining three species described from females only. Marusik and Omelko (2017: 205) placed Nediphya within Nanometinae based on the “complicated morphology of the copulatory organs.” They also considered that, based on the morphology of the copulatory organs, Pinkfloydia, Eryciniolia, “ Orsinome ” sarasini (= Nanometa tasmaniensis), and “ Orsinome ” lagenifera (= Nanometa lagenifera) could not be placed in Nanometinae. We agree with Marusik and Omelko’s (2017) assessment that the genitalia of Nediphya are very similar to those of “ Orsinome ” sarasini and “ Orsinome ” lagenifera (these latter two taxa now placed in Nanometa).
Marusik and Omelko (2017) provide no explicit phylogenetic arguments in neither their comments nor justification of higher taxa. The unusual eye pattern and spination of legs I and II of Nediphya are highlighted in their discussion, where they conclude that the similarities between Nediphya and Diphya do not reflect ancestry (and thus must be convergently evolved) and that genitalic morphology better resolves their phylogenetic affinity. We agree with this assessment and, although we do not have DNA sequence data for Nediphya, the genitalic morphology clearly suggests that this genus is part of the Nanometa clade. The eye arrangement of Nediphya in three rows with nonjuxtaposed lateral eyes is unusual in the genus Nanometa, but it should be noted that Nanometa purpurapunctata also has an atypical ocular arrangement (Bryant, 1933: fig. 33), with distantly separated lateral eyes. The eye pattern of the nanometine genus Pinkfloydia is also unusual, due to the enlarged PMEs on conspicuous tubercles (Dimitrov and Hormiga, 2011; Hormiga, 2017). Despite the unusual eyes, both Nediphya and Nanometa purpurapunctata have the typical genitalic morphology found in all Nanometa species.
The other peculiar character of Nepdiphya is the promarginal row of stiff setae on legs I and II (Marusik and Omelko, 2017). A similar arrangement can also be found in some Nanometa species (e.g., in N. purpurapunctata, N. dimitrovi, and N. tetracaena). Unfortunately, the tracheal morphology of Nediphya remains unknown, and the SEM image of the booklung cover of the only known adult male in the genus (Marusik and Omelko, 2017: fig. 22) does not reveal whether the typical sclerotized anterior margin is present (although the authors report the ridges as absent).
Three putative morphological synapomorphies support the inclusion of Nepdiphya in Nanometa. The first one is the absence in both genera of an embolic apophysis, which is present in the sister genus of Nanometa (Pinkfloydia) and in other tetragnathids such as Allende, Tawhai, Taraire, and Chrysometa. The second is the conductor morphology as a curved, flattened, translucent disk, with an enlarged and folded margin that covers the embolus distal part. Pinkfloydia has a conductor that resembles that of Allende and some Metainae have it not flattened, more sclerotized, and projected apically as it curves with the embolus (Álvarez-Padilla and Hormiga, 2011; Dimitrov and Hormiga, 2011). A third putative synapomorphy is the presence of copulatory ducts modified as sacs, which gives the internal female genitalia of Nanometa the appearance of having four chambers. In the absence of any evidence of synapomorphic support for a clade that would include all Nanometa species but not Nediphya, we synonymize the latter genus under the former.
description: Published as part of Álvarez-Padilla, Fernando, Kallal, Robert J. & Hormiga, Gustavo, 2020, Taxonomy And Phylogenetics Of Nanometinae And Other Australasian Orb-Weaving Spiders (Araneae: Tetragnathidae), pp. 1-107 in Bulletin of the American Museum of Natural History 2020 (438) on pages 1-107, DOI: 10.1206/0003-0090.438.1.1, http://zenodo.org/record/4613901