Xim trenzado Ibarra-Núñez & Chamé-Vázquez & Maya-Morales 2021, gen. et sp. nov.
Creators: name: Ibarra-Núñez, Guillermo
name: Chamé-Vázquez, David
name: Maya-Morales, Julieta
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Linyphiidae
Xim
Xim trenzado

description: Xim trenzado gen. et sp. nov.
urn:lsid:zoobank.org:act: 62BE28C7-8A47-4053-B6CD-EA2F7E5EA83B
Figs 1–5
Diagnosis
Monotypic genus, see genus diagnosis.
Etymology
The specific epithet is a noun in apposition taken from the Spanish word meaning ‘braided’, referring to the interweaved macrosetae on the femur I of the male.
Type material
Holotype MEXICO • ♁; Chiapas, Municipio de Unión Juárez, Ejido Talquián; 15°05′15″ N, 92°05′56″ W; 2010 m a.s.l.; 4 Mar. 2009; Maya, Ibarra, López and Sentíes leg.; tropical montane cloud forest, in low understory; beating; ECOTAAR-005030.
Allotype
MEXICO • ♀; same collection data as for holotype; ECOTAAR-005030.
Paratypes MEXICO • 1 ♂, 1 ♀; same collection data as for holotype; 22 Jan. 2009; Maya, Ibarra, López and Sentíes leg.; ECOTAAR-004936 • 1 ♂, 1 ♀; same collection data as for preceding; AMNH • 1 ♂, 1 ♀; same collection data as for preceding; 4 Feb. 2009; CNAN • 1 ♂, 1 ♀; same collection data as for preceding; CAS • 1 ♂, 1 ♀; same collection data as for preceding; 18 Mar. 2009; MNHN AR16055 • 1 ♂, 1 ♀; same collection data as for preceding; MACN • 1 ♂, 1 ♀; same collection data as for preceding; 1 Apr. 2009; USNM • 1 ♂, 1 ♀; same collection data as for preceding; 15 Jul. 2009; Maya, Ibarra and López leg.; ZMB Arach 49468.
Other material
MEXICO • 2 ♂♂, 8 ♀♀, 1 subadult ♂, 1 subadult ♀, 1 juv.; Chiapas, Municipio de Unión Juárez, Ejido Talquián; 15°05′15″ N, 92°05′56″ W; 2010 m a.s.l.; 22 Jan. 2009; Maya, Ibarra, López and Sentíes leg.; tropical montane cloud forest, in low understory; beating; ECOTAAR-004937 • 1 ♂; same collection data as for preceding; 4 Feb. 2009; ECOTAAR-004950 • 1 ♀, 2 juvs; same collection data as for preceding; ECOTAAR-004949 • 6 ♂♂, 6 ♀♀, 1 subadult ♂, 2 juvs; same collection data as for preceding; ECOTAAR-004952 • 6 ♂♂, 7 ♀♀, 5 subadult ♂♂; same collection data as for preceding; ECOTAAR-004974 • 2 ♂♂, 6 ♀♀, 2 subadult ♂♂, 1 subadult ♀, 2 juvs; same collection data as for preceding; 4 Mar. 2009; ECOTAAR-005029 • 1 ♀; same collection data as for preceding; 18 Mar. 2009; ECOTAAR-005063 • 6 ♂♂, 2 ♀♀, 2 subadult ♂♂; same collection data as for preceding; 1 Apr. 2009; ECOTAAR-005177 • 1 ♀; same collection data as for preceding; ECOTAAR-005183 • 1 ♀; same collection data as for preceding; 12 Aug. 2009; Maya, Ibarra, López and Chamé leg.; ECOTAAR-005435 • 1 ♂; same collection data as for preceding; hand collecting; ECOTAAR-005438 • 1 ♂; same collection data as for preceding; 15°05′38″ N, 92°06′06″ W; 2044 m a.s.l.; 5 Feb. 2009; beating; ECOTAAR-004962 • 1 ♀; Chiapas, Municipio de Motozintla, Cerro Boquerón; 15°13′55″ N, 92°18′22″ W; 2332 m a.s.l.; 27 Feb. 2015; Campuzano, Montaño and Moreno leg.; tropical montane cloud forest, in low understory; beating; ECOTAAR-011462.
Description
Male HABITUS. Carapace, chelicerae and endites light brown with some suffused grey on thoracic part, labium and sternum brown, distal half of labium light brown. Legs, coxae to femora yellow-cream with distal half of femur I and II light-brown, tibiae to tarsi yellow brown. Opisthosoma light brown with sparse yellow spots and slender yellow chevrons on the rear half of dorsum (Fig. 1 A–C, G).
MEASUREMENTS. Total length 1.68. Carapace 0.71 long, 0.59 wide.
PROSOMA. Carapace with conical post-ocular lobe, about as high as clypeus in lateral view, apex crowned with few hairs. Eye diameters and interdistances: AME 0.039, ALE 0.052, PME 0.039, PLE 0.039, AME–AME 0.026, AME–ALE 0.065, PME–PME 0.065, PME–PLE 0.065; AER in frontal view almost straight, slightly recurved, PER in dorsal view almost straight, slightly recurved. Clypeus 0.13 high with few short setae below AME. Chelicerae with five promarginal (Fig. 1G) and four retromarginal teeth; lateral face of chelicerae with scaly striae, widely and evenly spaced. Sternum 0.40 long, 0.44 width, produced between coxae IV posterior tip truncated; coxae IV 1.4 times their width apart (Fig. 1C).
OPISTHOSOMA. Elliptical, slightly narrowed towards posterior end (Fig. 1 A–C).
LEGS. Femur I with distal half modified, bent ventrad, prolaterally enlarged, with hemispherical bulge about three quarters from femur base (Figs 1 A–B, 4A–F). Distal, prolateral side of femur I with two longitudinal, parallel series of conspicuous macrosetae beginning at femoral turn, finishing at base of the hemispherical bulge (Fig. 4 A–G). Dorso-lateral series of macrosetae composed of nine, spaced, erect, macrosetae gently curved, ventro-lateral series composed of 18 (17 on right femur I) macrosetae closely spaced, recumbent, strongly curved, interweaved forming a braid (Fig. 4 A–G). Tibiae I to II without dorsal macrosetae, tibiae III with one very short, proximal dorsal macroseta, tibiae IV with one short proximal, dorsal macroseta, without distal, dorsal macroseta; metatarsi and tarsi without macrosetae. Leg formula: 1423. Legs measurements: I 2.52 (0.70, 0.21, 0.61, 0.58, 0.42), II 2.36 (0.71, 0.19, 0.57, 0.53, 0.36), III 1.80 (0.56, 0.16, 0.38, 0.43, 0.27), IV 2.49 (0.66, 0.17, 0.56, 0.68, 0.42); TmI 0.40, TmIV absent.
PALPUS. Distal half of femur ventrally slightly enlarged; tibia with conspicuous plate-like, slanting, higher than long, prolateral apophysis pointed in distal corner (Figs 1B, 2 A–D, F–G); with a small, rounded, distal retrolateral apophysis touching paracymbium (Fig. 2C, E–F); with one retrolateral trichobothrium (Figs 2F, 4I), lacking on prolateral side (Fig.2D).Cymbium with deep retrolateral groove wider in proximal part (Fig. 2C, F–H), with an elongated, prolateral, basal process touching palpal tibia (Fig. 2 A–B, D–E, G) and a large slanted, pointed dorsal process with retrolateral face slightly concave, glabrous from apex till retrolateral cymbial groove, its prolateral face convex and hirsute as most of cymbium (Figs 1B, 2A, C–D, F–H). Alveolus nearly as long as cymbium. (Figs 2B, E, 3A). Paracymbium large with scale-like papillae, connected to cymbium by a membrane, longer than wide (wider distally), about half as long as cymbium, extended proximally to fit the RTA, distally overlapping proximal part of tegulum and about half of subtegulum, with few small setae near base and tip forming a straight hook touching retrolateral cymbial groove (Figs 2 B–C, E–F, 3A). Subtegulum ectal to tegulum. Tegulum elliptical, with scale-like papillae, slightly sclerotized at mesal border, with small membranous protegulum in distal-mesal corner (Figs 2 B–C, E–F, H, 3A); sperm duct with tight kink in tegulum (Fig. 3A). Suprategulum curved, continuous with tegulum, visible on prolateral side of alveolus, touching the cymbium, distally turned retrolaterally and ending in a short distal suprategular apophysis, concealed in ventral view by embolic membrane and distal part of protegulum. (Figs 2 A–B, D–E, H–I, 3A–B). Radix as long as cymbium, with a spiral tailpiece and heavily sclerotized distal part with a serrated radical ridge (Figs 2 A–B, D–E, H–I, 3B), ending in a short spine-like anterior radical process, at origin (in a slightly closed angle) of a very short, straight, less sclerotized embolus, directed proximally (Figs 2B, E, H–I, 3B). Column arising from suprategulum, with embolic membrane developed as an ectal outgrowth from column, both visible among tegulum, tailpiece and radix (Figs 2E, H–I, 3B).
Female
HABITUS. Carapace, chelicerae and endites light brown with some suffused grey on thoracic part, a narrow diffuse grey band on border of thoracic part, labium and sternum brown. Legs yellow cream, slightly darker from distal half of femur (I and II) or tibiae (III and IV) to tarsi. Opisthosoma yellow cream on the dorsum with a diffused central longitudinal light brown stripe over the 4/5 anterior part, sides and venter light brown; epigastrium and spinnerets yellow-cream (Fig. 1 D–F, H).
MEASUREMENTS. Total length 1.73, carapace 0.75 long, 0.59 wide.
PROSOMA. Carapace similar shape to male, except a lower and rounded post-ocular lobe, about half the clypeus height in lateral view, with few sparse hairs (Fig. 1E). Eye diameters and interdistances: AME 0.052, ALE 0.052, PME 0.039, PLE 0.039, AME–AME 0.026, AME–ALE 0.078, PME–PME 0.052, PME–PLE 0.065; AER in frontal view almost straight, slightly recurved, PER in dorsal view almost straight, slightly recurved. Clypeus 0.143 high. Chelicerae with five promarginal (Fig. 1H) and four retromarginal teeth. Sternum 0.44 long, 0.44 width, produced between coxae IV, posterior tip truncated; coxae IV 1.4 times their width apart (Fig. 1F).
OPISTHOSOMA. Elliptical (Fig. 1 D–F). Trachea desmitracheate.
LEGS. Femur I without prolateral macrosetae. Legs I to IV with one proximal, dorsal macrosetae on each tibia (longer than those of male), without distal, dorsal macroseta; metatarsi and tarsi without macrosetae. Leg formula 1423. Legs measurements: I 2.90 (0.82, 0.23, 0.69, 0.69, 0.47), II 2.77 (0.77, 0.21, 0.64, 0.68, 0.47), III 2.18 (0.62, 0.18, 0.43, 0.56, 0.39), IV 2.80 (0.79, 0.19, 0.66, 0.71, 0.45). TmI 0.377, TmIV absent.
EPIGYNUM. With large ventral plate with scattered hairs, with anterior semicircular concavity (ACV) whose rear margin forms a sclerotized border (Fig. 5A, G–H). Dorsal plate in ventral view small, rectangular and transverse, occupying only posterior border of epigynum, with a big anterior lobe, flush with ventral plate, ovoid and slightly wider than long, with a narrowing forming a neck at the level of anterior end of copulatory opening slits, where the anterior lobe joins the ventral plate (Fig. 5 A–B, G). Ventral and dorsal plates slightly darker than venter; anterior lobe of dorsal plate yellow-whitish, membranous in appearance (Figs 1F, 5G). Copulatory openings as narrow slits between ventral plate and anterior lobe of dorsal plate (Fig. 5 A–B, G). Spermathecae visible ventrally through integument (Figs 1F, 5G). In dorsal view, copulatory duct wide and very short, connected to an asymmetrical, u-shaped, oblong spermatheca with one mesal and one ectal branch, both branches of spermatheca anteriorly directed, ectal branch longer and larger than mesal one, which is almost round (Fig. 5 C–F, H). Spermathecae covered by numerous small glandular pores, with bigger pores in base of ectal branch (Fig. 5 C–F). Fertilization duct barely visible, arising from postero-mesal part of ectal branch and posteriorly oriented (Fig. 5H).
Subadult morphology
Subadult males show enlarged palpal cymbium, palpal tibia with a dorsal protuberance corresponding, in position and shape, to forthcoming prolateral apophysis; carapace with a low post-ocular conical lobe, similar in height to that of adult females; femur I with distal half enlarged and bent to ventral side (less than in adult males), with one series of 9–10 prolateral recumbent macrosetae pointing distally (not interweaved among them), and some subadult males with another series of 2–3 macrosetae located dorsally to first series. In subadult females, carapace shows the post-ocular area slightly higher than the ocular area, and the epigastrium slightly swollen.
Variation
Males (n = 6). Same color pattern as holotype. Total length 1.49–1.68. Carapace 0.67–0.73 long, 0.56– 0.60 wide, clypeus 0.12–0.16 high. AME diameter 0.039 –0.052, ALE 0.039 –0.052, PME 0.033 –0.039, PLE 0.033 –0.039, AME separation 0.026 –0.039, AME–ALE separation 0.052 –0.078, PME separation 0.052 –0.078, PME–PLE separation 0.065 –0.078. Sternum 0.38–0.51 long, 0.41–0.52 wide. Coxae IV separation 0.13–0.19. Leg total length: I 2.34–2.57, II 2.27–2.57, III 1.75–2.00, IV 2.31–2.62. Females (n = 6). Same color pattern as allotype. Total length 1.57–1.91. Carapace 0.67–0.76 long, 0.57–0.62 wide, clypeus 0.10–0.17 high. AME diameter 0.039 –0.052, ALE 0.039 –0.052, PME 0.039 –0.039, PLE 0.039 –0.039, AME separation 0.013 –0.039, AME–ALE separation 0.052 –0.078, PME separation 0.052 –0.065, PME–PLE separation 0.052 –0.078. Sternum 0.40–0.44 long, 0.43–0.48 wide. Coxae IV separation 0.14–0.21. Leg total length: I 2.61–290, II 2.48–2.75, III 1.97–2.29, IV 2.55–2.84.
Distribution and ecology
Known only from a small area in the south of Chiapas State, Mexico, the type locality and from Cerro Boquerón, Municipio de Motozintla. One male and one female of this species were collected for the first time by pitfall trap (in January and March 2007, respectively) in a year-round sampling for soil spiders in the type locality. Two years later (2009), when sampling the understory vegetation in the same locality, numerous specimens of both sexes were collected by beating low understory, showing that this species is associated normally to low understory vegetation and was found accidentally on the soil in 2007 (Ibarra-Núñez et al. 2011; Maya-Morales et al. 2012; cited as “ Erigoninae sp1”). They were collected from January to August but were more abundant during the dry and cold season (January to beginning of March), when adult numbers were about twice that of juveniles. Human disturbances also affect negatively the abundance of this species (Maya-Morales et al. 2012). Other surveys for spiders were made later in three other cloud forests in the same mountain range (Sierra Madre de Chiapas), but only one female of this species was collected in the nearest of the three studied localities (Cerro Boquerón, 27 km distance from the type locality, by beating low understory). This makes Xim trenzado gen. et sp. nov. a micro-endemic species, and consequently highly vulnerable to habitat destruction.
Remarks
In the ventral plate of the epigynum of Xim trenzado gen. et sp. nov., the anterior semicircular concavity (Fig. 5A, G) is very similar to that of Tutaibo velox (Keyserling, 1886) as described and illustrated by Miller (2007: 179, fig. 138f).
description: Published as part of Ibarra-Núñez, Guillermo, Chamé-Vázquez, David & Maya-Morales, Julieta, 2021, A new spider genus (Araneae: Linyphiidae: Erigoninae) from a tropical montane cloud forest of Mexico, pp. 97-116 in European Journal of Taxonomy 731 on pages 102-110, DOI: 10.5852/ejt.2021.731.1207, http://zenodo.org/record/4452265