Tetragnatha megalocera Castanheira & Baptista 2020, new species
Creators: name: Castanheira, Pedro De Souza
name: Baptista, Renner Luiz Cerqueira
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Tetragnathidae
Tetragnatha
Tetragnatha megalocera

description: Tetragnatha megalocera new species
(Figs 1–3, Map 2)
Type material. Type material. Holotype ♂. BRAZIL, Rio Grande do Sul: São Leopoldo: 25.IX.1987, C. J. Becker leg. (MCTP 0357). Paratypes: BRAZIL, Espírito Santo: Anchieta: CSV (Macega), 24.I.2009, sweeping, R. Baptista leg., 1 ♀ (UFRJ 1476); Rio de Janeiro: Cachoeiras de Macacu: Reserva Ecológica de Guapiaçu, Lagoa, 17.XII.2017, R. Baptista leg., 1 ♀ (UFRJ 1565); Mendes: Centro Marista São José das Paineiras (Sede), 22°30’35.1”S, 043°45’16.5”W, 551 m, 1.XI.2014, looking up, R. Baptista leg., 1 ♀ (UFRJ 1477); Rio Grande do FIGURE 1. Tetragnatha megalocera new species male holotype: A, dorsal habitus. B, lateral habitus. C, ventral habitus. D–G, left chelicera; D, upper view. E, inner view. F, lower view. G, outer view. H–J, left palp; H, mesal view. I, dorsal view. J, ventral view (paracymbium). Scale bars, A, B, C, 2 mm; D, E, F, G, H, I, J, 0.2 mm.
Sul: Cachoeira do Sul: Capão Grande, 27.VIII.1992, R. G. Buss leg., 4 ♂, 2 ♀, 2 immatures (MCTP 3374); idem, Porteira Sete, 12.IX.1992, R. G. Buss leg., 5 ♂, 4 ♀, 8 immatures (MCTP 3383); São Leopoldo: 01.IX.1986, C. J. Becker leg., 1 ♂ (MCTP 0333); idem, 1 ♂ (UFRJ 1481 ex MCTP 0333); Taquara: Morro da Pedra, 17.II.1995, A. D. Brescovit leg., 1 ♀ (IBSP 6735); Santa Catarina: Florianópolis: Parque do Córrego, 01.XI.2011, Alunos curso UFSC leg., 1 ♂ (IBSP 220810); São Paulo: Peruíbe: Estação Ecológica Juréia Itatins, 24°33’S, 47°13’02’’W, 14–18.xii.1998, A. D. Brescovit et al. leg., 1 ♀ (IBSP 22922); 16.XII.1998, A. D. Brescovit et al. leg., 1 ♂ (IBSP 22448); Ubatuba: Serra do Mar State Park, Núcleo Picinguaba, 29.X–02.XI.2008, R. Baptista leg., 1 ♀ (UFRJ 1482).
Additional material examined. BRAZIL, Espírito Santo: Anchieta: CSV (Macega), 24.I.2009, looking up, A. Pérez-González leg., 1 ♀ (UFRJ 1478); Cariacica: Duas Caras, 20.29159°S, 40.51949°W, 13.X.2005, T. Souza et al., 1 ♂ (IBSP 133175); Rio de Janeiro: Cachoeiras de Macacu: Reserva Ecológica de Guapiaçu, 09.IX.2018, looking up, G. O. Assunção leg., 1 ♂ (UFRJ 1517); Macaé: Terminal Cabiúnas (Mata da Fazenda), 15.III.2011, beating, R. Baptista leg., 2 ♀ (MNRJ 7517, lost); Terminal Cabiúnas (Mata do Gasoduto), 22.XI.2013, looking up, D. R. Pedroso leg., 1 ♀ (UFRJ 1479); 23.II.2016, looking up, D. R. Pedroso leg., 1 ♀ (UFRJ 1480); Rio Grande do Sul: Cachoeira do Sul: Capanezinho, 17.X.1992, R. G. Buss leg., 1 ♂ (MCTP 41481); idem, Cordilheira, 09.IX.1992, R. G. Buss leg., 1 ♂, 3 ♀, 1 immature (MCTP 3379); 2 ♂, 2 immatures (MCTP 3380); idem, Porteira Sete, 26.VIII.1992, R. G. Buss leg., 2 ♂, 2 immatures (MCTP 3384); 31.X.1992, R. G. Buss leg., 2 ♂, 1 ♀, 3 imma- tures (MCTP 41483); Guaíba: 14.VII.1995, A. A. Lise et al. leg., 1 ♂ (MCTP 6689); Nova Santa Rita: 23.V.2009, A. Oliveira leg., 1 ♂ (MCTP 37284); Novos Cabrais: 27.I.2010, R. G. Buss leg., 1 ♂ (MCTP 27885); São Francisco de Paula: Potreiro Velho, 05–08.XII.1996, A. A. Lise leg., 1 ♀ (MCTP 13952); São Leopoldo: 28.ix.1987, C. J. Becker leg., 1 ♂ (MCTP 0370); idem, 1 ♂ (MNRJ 7521 ex MCTP 0333, lost); Viamão: Est. Exp. Fitotécnica, 10.X.1995, A. A. Lise leg., 1 ♂ (MCTP 0816); São Paulo: Mongaguá: Sena Guaperuvi, 25.I.1966, Remé leg., 1 ♀ (MZUSP 4780); Peruíbe: Estação Ecológica Juréia-Itatins, 24°33’S, 47°13’2’ W, 26.IV–03.V.1999, A. D. Brescovit et al. leg., 1 ♀ (IBSP 24744); 26.IX–03.X.1999; A. D. Brescovit et al. leg., 1 ♀ (IBSP 25215); Ribeirão Grande: Parque Estadual de Intervales, 17.x.2002, M. O. Gonzaga leg., 1 ♀ (IBSP 58772); São Bernardo do Campo: Estrada do Mar, 07.II.1968, Biasi, Tammi & Boscheno leg., 2 ♂, 1 ♀, 1 immature (MZUSP 8214).
Etymology. The specific epithet “ megalocera ” is a greek word composed of “ megalo ” = large and “ ceras ” = horn, referring to the large hornlike tooth seen in the ventral row of the chelicera of males and females of this species.
Diagnosis. Tetragnatha megalocera new species shares with all species described below (except the female of T. renatoi new species) similar small-sized body, yellowish brown carapace, with thin darker line from eyes to the posterior rim, elongated and rather slender abdomen, with dorsum beige and covered by guanine spots (Figs 1A, B, 2A, B, 4A, B, 7A; 9A, B; 10A, B; 12A, B, 13A, B; Okuma 1992, fig. 21D, G). T. megalocera new species, T. chiyokoae new species, T. chauliodus and T. tenuissima differ from T. renatoi new species by a series of dark grey to black spots on each side of abdomen (Figs 1A, B, 2A, B, 7A; 9A, B; 10A, B; 12A, B, 13A, B; Okuma 1992, fig. 21D, G; Zhu et al. 2003, fig. 59B). Except for the males of T. renatoi new species, the other four species share a robust, elongated and pointed median tooth (T) (Figs 1D–G, 7B–D, 8D–G; 11C–F). T. megalocera new species and T. tenuissima may be set apart from T. chiyokoae new species and T. chauliodus by longer L2, almost adjoined to the basis of Gl (Figs 1E, F, 3B, 7C, D, 12D, E, 14B). Males of T. megalocera new species are diagnosed from T. tenuissima by male chelicerae with conspicuous swelling (S) at the basis of ‘a’, absence of ‘t’, AXu and Gu, much larger and more curved L2 placed close to the smaller Gl, and vestigial or much reduced L3 and L4 (Figs 1D, G, 9C–F). Females of T. megalocera new species share with T. vermiformis Emerton, 1884 similar external and internal genitalia, with short genital plate and two rounded spermathecae, on the edge of genital fold, bearing two lobes (Figs 2H, I, 3I; Castanheira et al. 2019, fig. 18H, I). They also share short and laterally bulged paturon with Gu slightly offset from the row and apart from U2 by large gap (Figs 2D, E, H; Castanheira et al. 2019, figs 18D–G, 19B). Females of T. megalocera new species are set apart by its vulva with two very rounded and massive spermathecae lobes, with poorly sclerotized and developed central membranous sac (Fig. 2I). They are also distinguished from all Tetragnatha by its massive horn-like L2 projected distal- and downward (Figs 2 D–G, 3C).
Description. Male (Holotype): Carapace yellowish brown, elongated and tapering toward the slightly elevated anterior rim, with parallel borders and thin brown line covering edges from the border of lateral eyes towards posterior rim (Fig. 1A, B). Fovea dusky with smooth strikes (Fig. 1A). Labium long and brown (Fig. 1C). Sternum light brown with darker contour (Fig. 1C). Posterior eyes evenly separate, AME centrally placed, almost touching, ALE smaller and located on edge of carapace (Fig. 1A). Legs yellowish brown with dusky patches on femur (Figs 1A–C). Paturon almost 4x longer than wide, about 80% as long as the carapace, well curved outwards, around 65° from median line of the body, thick and well carved on its external side near the apex, after the insertion of the excavated, thin, regularly bent and distally projected dorsal apophysis (a) bearing a conspicuous swelling (S) at its basis (Figs 1D–G, 3A, B). ‘t’ and AXu absent (Figs 1D, 3A). Upper row with five uneven teeth (Figs 1D, E, 3A): Gu absent; ‘sl’ small, straight, upward projected, three times shorter than ‘T’ and apart from it by a significant gap; ‘T’ thick, slightly pointed distal- and upward with very large basis and ‘rsu’ with three straight pointed teeth decreasing in size. AXl absent. Lower row with seven normal teeth and another two seemingly vestigial (Figs 1E, F, 3B): Gl and L2 very large, blade-shaped and bulky, distalward projected, both sharing the same basis near the fang; Gl smaller, thinner and with a thicker tip in comparison to L2, which is also more distalward curved; L3 and L4 vestigial with marked basis and located in a gap between L2 and L5; L5 and L6 normal, slightly decreasing in size, followed by a thicker and longer L7, ending in L8 and L9, both about the same size of L5 and L6. Cheliceral fang shorter than base, regularly and clearly bent downward, wavy and thinner at distal third, without cusps (Figs 1D–F, 3A, B). Abdomen long, cylindrical and slender, around 3.4x longer than carapace, and bit larger at basis (Fig. 1A–C). Dorsum pale beige, with six black spots in each edge, sparse dots of guanine, especially between the black spots and with contiguous lateral thick black stripe from the anterior rim toward spinnerets (Fig. 1B, C). Venter a little darker than dorsum, with some guanine spots placed in line near the border (Fig. 1C). Epiandrous heart-shaped with a clear central division with only four fusules in each side (Fig. 3H). Palps with median sized tibia, smaller than the elongated cymbium, which bears a large basis, a wide constriction at the middle, and distal third ventrally curved, ending in a wide point, cymbial tarsal organ wide, but not strongly developed (Figs 1H, I, 3D); tegulum roundish, two times wider than high (Figs 1I, 3D); conductor with one pleat, twisted, with thick edges enfolding over the embolus as a wide and projected pouch on its median portion and projected well beyond the embolus apex in a large hood-like pointed bulge, with short tail in ventral view (Figs 1H, I, 3D, E, G); embolus thick, originating near the cymbium basis, with a small downward initial portion, followed by a strong upward curve, then a gently curved terminal portion, tapering towards apex, which is pointed and hidden by the conductor (Fig. 1H–J); paracymbium elongated, downward slanted, tapering towards its divided notch, which bears a blunt mesal edge longer ectal edge; translucid lobe thin, medially placed, occupying more than 50% the paracymbium length, but not reaching its basis, nor its apex; knob large, longer than wide, sclerotized, with a round point basalward projected (Figs 1J, 3F).
Total length 7.3. Carapace 1.65 long, 0.91 wide. Abdomen 5.65 long, 0.59 wide. Left chelicera 1.3 long, 0.33 wide. Leg formula I–IV–II–III. Leg I: femur 6.66, patella 0.77, tibia 7.06, metatarsus 7.16 and tarsus 1.68. Leg II: patella + tibia 4.59. Leg III: patella + tibia 1.55. Leg IV: patella + tibia 4.39.
Female (Paratype UFRJ 1477): Carapace, endites, fovea, eyes, labium, and legs as in male (Fig. 2 A–C). Sternum as in male but with darker brown colour (Fig. 2C). Paturon wrinkled below the fang (Fig. 3C), straight, around 2,8x longer than wide and about half as long as the carapace (Fig. 2D, F), medially bulged on both sides, tapering towards the basis of fang, with its colour as in male (Fig. 2G). AXu absent. Upper row with seven teeth (Figs 2D, E, 3C): Gu very sclerotized, slightly displaced from the row and apart from the fang by a gap, directed upward, thinner but about as long as U2 and U3, with a pointed tip; U2–U7 straight, sharp and pointed, apart from Gu by a large gap. U2 larger but a bit shorter than U3, remaining teeth decreasing in size. AXl absent. Lower row with nine teeth (Figs 2E, F, 3C): Gl very short, laterally placed next to the basis of fang, strongly directed downward; L2 horn-like, massive, very elongated, bulky, strongly curved distal- and downward, with acute tip, placed transversally to the row; remaining teeth slightly projected distalward, decreasing in size; L3 elongated, blade-shaped and very sclerotized; L4–L9 still sclerotized, L7 and L8 fused sharing the same basis and thicker than L4–L6; L9 small but longer than the three tiny denticles placed between both rows but adjoined to remaining lower teeth. Cheliceral fang short, thick, slightly bent upward, abruptly tapering to its tip, with inner keel beginning at its middle portion (Figs 2D, F, 3C). Abdomen as in male, around 4.1x longer than the carapace, differing by abundant cover of guanine dots and lack of the first black spot on the dorsum (Fig. 2 A–C). Genital fold short, elevated, approximately 5.5x wider than long, thick and ending in concave and wide tip (Figs. 2H, 3I). Internal genitalia composed of two spermathecae with two massive dumbbell-like rounded lobes, with posterior lobes slightly smaller than the anterior ones and a poorly developed, small and transparent central membranous sac on the top of a median sized neck (Fig. 2I).
Total length 9.36. Carapace 1.83 long, 1.06 wide. Abdomen 7.53 long, 0.83 wide. Left chelicera 0.97 long, 0.37 wide. Leg formula I–II–IV–III. Leg I: femur 6.22, patella 0.61, tibia 5.20, metatarsus 7.01 and tarsus 1.35. Leg II: patella + tibia 4.35. Leg III: patella + tibia 1.18. Leg IV: patella + tibia 3.09.
Variation. Males (n = 20): total length, 5.67 – 7.90; females (n = 15): total length, 7.32 – 10.03. Male chelicerae vary in teeth conformation on the lower row; the holotype bears L3 and L4 as vestigial teeth while in other specimens, either L3, L4 or both teeth can be developed. On the other hand, we have observed that there is a fusion between the last few teeth in the cheliceral lower row of female; either L7–L8 or L8–L9 can be fused. There are also differences between the denticles located after them, varying in number (up to three) and position (normally adjoined to other teeth).
Natural History. This species seems to have lost the association to water bodies, being collected almost exclusively in the interior of forest remnants. Its tiny horizontal orb-web is usually placed on dead branches of trees and large bushes at middle distance (1–2 m) from soil during night. At least one of the web’s rays is firmly adhered to a stick. So, the whole web is bisected by the central stick, with all other rays converging to the hub, where the spider sat perfectly camouflaged (unfortunately, no photos are available).
Distribution. This species reaches from Anchieta, in the south-center of Espírito Santo state, through Macaé in the north and Mendes in the southwest of Rio de Janeiro state, São Bernardo do Campo in centre east and Ubatuba, Mongaguá in northeast São Paulo state, to São Leopoldo and Viamão in the northeast and Cachoeira do Sul in the south-center of Rio Grande do Sul state (Map 2).
description: Published as part of Castanheira, Pedro De Souza & Baptista, Renner Luiz Cerqueira, 2020, Notes on slender species of the long-jawed spider genus Tetragnatha (Araneae Tetragnathidae) with description of three new species, pp. 43-75 in Zootaxa 4768 (1) on pages 45-51, DOI: 10.11646/zootaxa.4768.1.4, http://zenodo.org/record/3777828