Micrathena shealsi Chickering, 1960

Argañaraz, Carina I. & Rubio, Gonzalo D., 2011, The spider Micrathena shealsi Chickering, 1960 (Araneae, Araneidae): description of the male, with new data on its geographic distribution, Zootaxa 3104, pp. 52-58 : 53-54

Micrathena shealsi Chickering, 1960

( Figs. 1–18 ; Map 19)

Micrathena shealsi Chickering, 1960a: 8 , figs. 13–17 (Holotype female from Sunchal, Argentina, deposited in Invertebrate Zoology Collection of Museum Comparative Zoology—MCZ 23053, not examined).

Micrathena shealsi: Levi, 1985: 458 , figs. 74–78; Platnick, 2011.

New records. ARGENTINA: Jujuy: Yala (24º07'13''S, 65º27'24''W, 1888m.a.s.l.), 20 May 1983 (P. Goloboff), 1 female (MACN-Ar 25178); Calilegua, Parque Nacional Calilegua, Seccional Aguas Negras (23º45'43.3''S, 64º51'04.7''W, 605m. a.s.l.), 27–31 January 2009 (M. Izquierdo, L. Zapata & M. Akmentis), 1 male (MACN-Ar 27850); same loc., near Monolito (23º40'27''S, 64º54'01''W, 1714m.a.s.l.), 19 October 2009 (G. Rubio & M. Pocco), 1 female (MACN-Ar 27851). Salta: Quebrada de San Lorenzo, site 1 (24°42'51.84"S, 65°31'6.96"W, 1833m.a.s.l.), 26–28 April 2006 (G. Rubio, J. Corronca, B. Cava, V. Olivo & A. González-Reyes), 2 females (MACN-Ar 27852); same loc., site 2 (24°43'9.60"S, 65°30'56.40"W, 1691m.a.s.l.), same date (same leg.), 6 specimens (IEBI); same loc., site 3 (24°43'16.80"S, 65°30'39.00"W, 1587m.a.s.l.), same date (same leg.), 1 specimen (IEBI); same loc., site 4 (24°43'17.04"S, 65°30'25.80"W, 1575m.a.s.l.), same date (same leg.), 2 specimens (IEBI); same loc., site 5 (24°43'16.32"S, 65°30'7.92"W, 1560m.a.s.l.), same date (same leg.), 7 specimens (IEBI); road to El Carmen, site 1 (24°31'13.36"S, 65°21'4.02"W, 1547m.a.s.l.), same date (same leg.), 2 specimens (IEBI); same loc., site 2 (24°30'33.30"S, 65°20'27.13"W, 1587m.a.s.l.), same date (same leg.), 1 specimen (IEBI); same loc., site 3 (24°30'15.84"S, 65°20'11.40"W, 1516m.a.s.l.), same date (same leg.), 2 specimens (IEBI). Tucumán: Cochuna (27°19'19.97"S, 65°55'38.01"W, 1162m.a.s.l.), 25 March 2011 (C. Argañaraz), 1 male (MACN-Ar 27853); same loc., 0 9 April 2011 (C. Argañaraz & G. Rubio), 4 males, 6 females (MACN-Ar 27854), and 1 male (MACN-Ar 27856); monument to El Indio (27° 2'54.24"S, 65°40'8.76"W, 1065m.a.s.l.), 21 February 2011 (G. Rubio & L. Acosta), 1 sub-adult male (MACN-Ar 27855).

Diagnosis. Males of M. shealsi ( Figs. 1–7 , 9–15 ) resembles M. bifida (Taczanowski) from Peru by general habitus, and by the palp bearing a tegulum lobe in ectal view ( Levi 1985: figs. 45, 47) but it can be distinguished from it by the palpal morphology ( Figs. 5–7 , 9–13 ) ( M. shealsi has a distinctive shape of the median and terminal apophyses, Fig. 6 , 10 ). Females of M. shealsi differ from congeners by the absence of a scape on the epigynum ( Fig. 16 ) and by the ventral coloration (light sternum, and depigmented median area of the abdomen venter: Levi 1985). Micrathena shealsi was erroneously taken as “ M. nigrichelis with scape of epigynum torn off” ( Levi 1985). However, these species can be easily separated by the above-mentioned chromatic pattern ( Levi 1985), and by the dimensions of the cephalic region (smaller in M. shealsi ); the latter feature is also present in males.

Description. Male from Cochuna, Tucumán (MACN-Ar 27856): Carapace orange (in nature—Fig. 18) or yellowish (in alcohol), black on sides and with a blackish longitudinal strip starting near the posterior eyes towards thoracic groove ( Figs. 1 , 18 ). Very shallow dimples on each side of thoracic groove. Chelicerae pale yellow. Sternum and coxae light yellow, with dark pigment near the articulation. Legs orange-brown, first pair darker. Coxa I with hook, femur II with groove ( Figs. 14–15 ). Tibia I-II with macrosetae; ventral side of femur II with row of 8–9 spines. Abdomen longer than wide, rectangle-shaped, without humps; yellowish-white dorsally (slightly orange in nature) with three black marks on each side, one dark median longitudinal strip on posterior two thirds; end of abdomen black; venter between epigastric furrow and spinnerets pale yellow, spinnerets and the rest of venter black-grayish ( Fig. 3 ). Palp with reddish-brown general color ( Figs. 17–18 ). Body total length from AME to tip of abdomen 5.51; carapace length 2.10, width 1.47; sternum length 0.91, width 0.52; abdomen length 3.57, width 0.98. Leg formula I/IV/II/III. Leg lengths (I/II/III/IV): femur 2.03/1.78/1.12/2.17; patella 0.64/0.58/0.38/0.49; tibia 1.54/1.22/0.63/1.20; metatarsus 1.15/1.12/0.56/1.33; tarsus 0.63/0.63/0.35/0.66; total leg 5.99/5.33/3.04/5.85. Female (Holotype, MCZ 23053): See Chickering (1960a: 8, figs. 13–17). Internal genitalia as in figure 8.

Variation. Males (n=6): Body total length 4.83–5.51; carapace length 2.03–2.17, width 1.4–1.5; sternum width 0.50–0.56; abdomen length 3.01–3.57, width 0.87–1.05. Total leg (I/II/III/IV) 5.98–6.12/5.28–5.37/3.01–3.11/ 5.85–6.04.

Natural history ( Figs. 17–18 ). Males of M. shealsi were found in most cases on the upper periphery of the female webs, hanging from a silk line. In only one case, a male was found in a small orb-web located under the female site. Females of M. shealsi sometimes build their web near other female webs, forming groups (of 2 to 5 individuals) in the lower stratum of vegetation, no higher than 60 cm. In such cases males were not observed. Ongoing ecological research (G. D. Rubio, unpublished) suggests that this species is strongly associated with the Yungas rainforest habitat.

Geographic distribution ( Fig. 19 ). Micrathena shealsi was only known from the type locality “Sunchal, Argentina ” ( Chickering 1960a). Although Levi (1985) assigned this locality to Salta Province, “Sunchal” in the latter does not fall within the rainforests region ( Fig. 19 ); in contrast, “Sunchal” or “El Sunchal” in Tucumán Province, seems more likely for a rainforest-dwelling spider. New records here provided reveal that M. shealsi has an extensive distribution in the Yungas, corresponding to the higher altitudinal belt (~ 1700 m.) of the mountain forests and rainforests from Tucumán, Salta and Jujuy Provinces ( Fig. 19 ).

Figures

FIGURE 19. Locality records of Micrathena shealsi Chickering 1960 (blue squares), and extent of the Yungas ecoregion (green area) in northwestern Argentina (from Brown et al. 2006). The type locality is either Sunchal, Salta Province (solid circle) or El Sunchal, Tucumán Province (open circle). Inset: location of the map area in South America.

FIGURES 1 – 8. Micrathena shealsi Chickering 1960. 1 – 7, male from Cochuna, Tucumán (MACN-Ar 27856); body view (1, dorsal; 2, front; 3, ventral; 4, lateral), and palpal morphology (5, prolateral; 6, ventral; 7, retrolateral). 8, female (cleared epigynum, ventral). Abbreviations: a = terminal apophysis; c = conductor; e = embolus; m = median apophysis; pm = paramedian apophysis; sr = seminal receptacles; t = tegulum. Scale bars: (1, 3 – 4) 1 mm; (2) 0.5 mm; (5 – 8) 0.2 mm.

FIGURES 9 – 18. Micrathena shealsi Chickering 1960. 9 – 11, left palp (9, prolateral; 10, ventral; 11, retrolateral); 12 – 13, expanded left palp (12, prolateral; 13, retrolateral); 14, coxal hook; 15, groove on the second femur; 16, epigynum (ventral); 17 – 18, habitus in nature (Cochuna, Tucumán, 2011). Abbreviations: a = terminal apophysis; c = conductor; e = embolus; m = median apophysis; p = paracymbium; pm = paramedian apophysis; t = tegulum; y = cymbium. Scale bars: (9 – 16) 0.2 mm.