Micrathena ruschii ( Mello-Leitão, 1945 )

Alvarenga, Alessandra Da Silva De, Magalhaes, Ivan L. F., Fonseca, Rodrigo Nunes Da & Pérez-González, Abel, 2020, Rectifying the identities of the males of two Micrathena species (Araneae Araneidae), with report of the first case of intersexuality in the genus, Zootaxa 4808 (1), pp. 151-164 : 155-162

Micrathena ruschii ( Mello-Leitão, 1945)

( Figs 2 , 3 , 4A , 5 )

Acrosoma ruschii Mello-Leitão, 1945: 266 , figs. 7–9. [First synonymized with Micrathena triangularis by Levi 1985: 512, revalidated by Magalhães & Santos 2011]

Micrathena cicuta Gonzaga & Santos, 2004: 332–334 , figs. 1–5. [Synonymy established by Magalhães & Santos 2011]

Micrathena ruschii: Magalhães & Santos 2011 [partim, only the females specimens examined]: 46–48, [males, figs. 17–19, misidentified after this work].

Type material: Acrosoma ruschii Mello-Leitão, 1945 : Female lectotype MNRJ 2566 and three female paralectotypes MNRJ 4255 , from Santa Tereza [19º55’S 40º35’W, 655 m a.s.l.], Espírito Santo, Brazil. Examined by ILFM, destroyed in the MNRJ fire of September 2, 2018.

Micrathena cicuta Gonzaga & Santos, 2004 : Female holotype IBSP 36322 from Área de Relevante Interesse Ecológico Floresta da Cicuta , Volta Redonda [22º31’S 44º7’W, 390 m a.s.l.], Rio de Janeiro, Brazil. Not examined, destroyed in the Butantan fire of May 2010.

Male-female association: Since 2011, three male specimens (listed below; Figs 2 , 3 , 4A ) have been observed and collected on webs of females of Micrathena ruschii in Parque Municipal Atalaia, Macaé , Rio de Janeiro State. The neighbor-joining dendrogram based on a COI fragment ( Fig. 1 ) confirms the conspecificity of male (A6) and female (A5) of M. ruschii collect ed in Macaé (with 94% bootstrap support) and with a female of M. ruschii collect ed in Itatiaia, Rio de Janeiro (99% bootstrap support). The male of M. rusch ii described in Magalhães & Santos (2011) from Parque Nacional do Itatiaia, Itatiaia, Rio de Janeiro, Brazil, should be considered a misidentification and the specific identity of this specimen remains unknown (see Discussion below for details).

Diagnosis: Males of M. ruschii are similar to other species of the plana group (sensu Magalhães & Santos 2012) in having a rounded thoracic region, an abdomen with two dark bands in the lateral sides ( Fig. 2A ), and a drop-shaped projection in the terminal apophysis ( Fig. 4A : tap). They can be further diagnosed by the combination of an acuminate tip of the terminal apophysis ( Fig. 4A : ta, vs. rounded in most other species), a rounded margin of the rim of the median apophysis [ Fig. 4A : m, vs. more square or hook-shaped in e.g. M. triangularis (C.L. Koch) or M. excavata (C.L. Koch) ], and a slender paramedian apophysis [ Fig. 4A : pm, vs. widened in e.g. M. brevispina (Keyserling) ].

For the female diagnosis, see Gonzaga & Santos (2004).

Description: Male from Macaé, Rio de Janeiro, Brazil (UFRJ 1519), Figs 2 A–C, 3, 4A. Carapace rounded, thoracic fovea a shallow, rounded pit. Coxal hook present, small. Leg macrosetae: ~7 macrosetae apically on femur I, ~4 apically on femur II, 1 retrolaterally on patellae I–II, 1 proventrally on tibia I. Abdomen rectangular, slightly wider anteriorly, tubercles absent. Coloration: carapace orange, with brown orange bands on lateral sides. Sternum, labium, endites and chelicerae orange. Legs brownish orange. Abdomen dorsum brownish cream, brown on the sides and posterior end, with two faint transverse markings; venter brownish cream with brown pigment on the sides and posteriorly to the spinnerets. Total length 4.63. Carapace length 2.04, width 1.63. Abdomen length 2.84, width 1.34. Leg I: femur (fe) 1.81, patella (pa) 0.55, tibia (ti) 1.24, metatarsus (mt) 1.07, tarsus (ta) 0.52. II: fe 1.49, pa 0.50, ti 0.90. III: fe 0.90, pa 0.31, ti 0.50. IV: fe 1.85, pa 0.38, ti 0.97, mt 1.10, ta 0.51. Genitalia ( Figs 3 , 4A ). Palpal tibia unmodified. Paracymbium large, bilobed, otherwise unmodified. Median apophysis large, composed of a large, bent, rounded rim; a gently curved lobe; and a sclerotized basal projection partially fused to the radix. Paramedian apophysis digitiform. Conductor folded, sclerotized; lobe absent. Terminal apophysis partially fused to the embolus and covering most of it, sclerotized, ending in a sharp tip, and bearing an unsclerotized drop-shaped projection. Embolus short, ending in a broad tip.

Female described by Gonzaga & Santos (2004).

Material examined: BRAZIL. Rio de Janeiro: Macaé, Parque Municipal Atalaia , 7.vii.2011 , A. Alvarenga leg., 1 ♂ 1 ♀ ( MACN-Ar 41526 ). Same locality, 18.vi.2012 , A. Alvarenga leg., 1 ♂ 1 ♀ ( MNRJ). Same locality, 10.i.2010, J. M. Guimarães, 1 intersexual individual and 1 ♀ ( MACN-Ar 41529 , IFM-1948 voucher). Same locality, 9.vii.2010, biology class students leg ., 1 ♀ ( UFRJ 1518 ). Same locality, 26.vi.2009, R. L. C. Baptista and biology class students leg ., 1 ♂ ( UFRJ 1519 ) .

Variation (in mm and average between parentheses).—Males (n=3): total length 4.58–4.71 (4.64), carapace length 1.93–2.04 (1.99), femur I length 1.81–1.90 (1.84).

Intersexual specimen: One specimen (MACN-Ar 41529) was interpreted as a case of intersexuality ( Fig. 5 ). This specimen has a morphological pattern similar to a normal male: a rounded carapace with the thoracic fovea in the form of a shallow rounded pit and a rectangular abdomen which is slightly wider anteriorly. It also exhibits a typical male coloration. However, the pedipalps are not fully developed (not showing any sclerites of the functional male palp) and resemble those of females but with the tarsus slightly elongated. Also, this specimen displays a sclerotized plate in the place of the female epigynum, but the plate is rudimentary and does not exhibit the morphological complexity of a fully developed epigynum. The leg spination is more reminiscent of that of females than that of males. The poor degree of development of the palps and epigynum support our classification that this is a case of intersexuality. This agrees with the intersexuality definition adopted by Roberts & Parker (1973) who considered intersex as cases in which, although parts of the spider may be predominantly female and other parts predominantly male, the distinction is less definite because certain organs, such as palps and epigynum, may be very poorly developed.

Micrathena lata Chickering, 1960

( Figs 4B, C ; 6 )

Micrathena lata Chickering, 1960: 5 , figs. 8–12; Levi, 1985 [partim, only the females]: 565, figs. 608–612 [males, figs. 613– 615, misidentified after Magalhaes et al. 2017]

Type material: Micrathena lata Chickering, 1960 . Female holotype ( MCZ 21788) from Teresópolis [-27.747555° -48.919398°], Rio de Janeiro, Brazil [with no date of collection given]. Not examined.

Male-female association: The male has been associated to Micrathena lata because it clearly belongs to the militaris group due to the possession of projections in the palpal tibia, laterally projecting paracymbium, and lack of a macroseta in the palpal patella (see Magalhães & Santos 2012), and Micrathena lata is the only species of this group that occurs in the Atlantic Forest and is still known only by the female. Males and females have not been collected together but come from nearby localities (Puerto 17 de Octubre and San Javier, both in Misiones, Argentina, apart by ~ 225 km).

Diagnosis: Among species of the militaris group, the male of M. lata resembles most those of Micrathena furcata (Hahn) and Micrathena reimoseri Mello-Leitão due to the large S-shaped embolus and the abdomen with two lateral dark bands. It differs from these two species by the more angled coils of the embolus ( Fig. 4B : e, vs. gently curved in the other species), by the distally expanded terminal apophysis ( Fig. 4B : ta, vs. even width throughout) and by the folded shape of the embolic membrane ( Figs. 2 , 6 : em, vs. absent).

For the female diagnosis, see Levi (1985).

Description: Male from Puerto 17 de Octubre, Misiones, Argentina (MACN-Ar 3866), Figs. 4B, C ; 6 . Carapace oval, thoracic fovea a shallow, rounded pit. Coxal hook absent. Leg macrosetae absent, except for a few thin, stiff setae on the venter of tibiae I–II. Abdomen trapezoidal, widest posteriorly, with two posterior folds resembling tubercles. Coloration: carapace light brown, with brown bands on lateral sides. Sternum, labium, endites and chelicerae cream. Legs brownish cream, except for light brown dorsum of femur I. Abdomen dark brown with a longitudinal, light brown median stripe on dorsum. Total length 3.44. Carapace length 1.42, width 1.03. Abdomen length 2.00, width 1.10. Leg I: fe 1.14, pa 0.37, ti 0.77, mt 0.70, ta 0.49. II: fe 1.14, pa 0.37, ti 0.69. III: fe 0.73, pa 0.24, ti 0.38. IV: fe 1.16, pa 0.28, ti 0.67, mt 0.67, ta 0.41. Genitalia ( Figs 4 B–C, 6). Palpal tibia with an apical, unbranched projection. Paracymbium large, bilobed, laterally projecting, otherwise unmodified. Median apophysis reduced to a lobed, unsclerotized basal projection partially fused to the radix. Paramedian apophysis absent. Conductor hookshaped, sclerotized; lobe rounded, membranous, covering the conductor in prolateral view. Terminal apophysis unfused to the embolus, large, membranous, distally broadened. Embolus long, S-shaped with acute loops, bearing a translucent membrane along most of its length; embolic membrane with a folded projection near the apex of the embolus.

Female described by Levi (1985).

Material examined: ARGENTINA. Misiones: Puerto 17 de Octubre [currently Puerto Libertad], De Carlo, Schiapelli, Viana & Galiano coll., X/1953, 1 ♂ ( MACN-Ar 3866 ); San Javier, 1 ♀, without further information ( MACN-Ar 33832 ) .

Figures

FIGURE 1. Sequence similarity among selected Micrathena COI sequences inferred using the neighbor-joining method. Nodal support estimated with bootstrap (1000 replicates) shown next to the branches.

FIGURE 2. Micrathena ruschii from Brazil, Rio de Janeiro, Macaé, habitus. A–C, male. A, dorsal. B, lateral. C, ventral. D, female, dorsal. Scale bars, 1 mm.

FIGURE 3. Micrathena ruschii from Brazil, Rio de Janeiro, Macaé, male left palps. A, prolateral. B, Subretrolateral. C–D, male (UFRJ 1519). C, retrolateral. D, prolateral, clove oil cleared. Scale bars, 0.1 mm.

FIGURE 4. Male left palps. A, Micrathena ruschii from Brazil, Rio de Janeiro, Macaé (UFRJ 1519), prolateral. B, Micrathena lata, male from Argentina, Misiones (MACN-Ar 3866), prolateral. C, same, retrolateral, detail of paracymbium. Scale bars = 0.1 mm. Abbreviations: bp = basal projection of the median apophysis, c = conductor, cl = conductor lobe, cy = cymbium, e = embolus, em = embolic membrane, l = median apophysis lobe, m = median apophysis rim, pm = paramedian apophysis, r = radix, ta = terminal apophysis, tap = terminal apophysis projection, ti = tibial projection, tp = tegular projection.

FIGURE 5. Micrathena ruschii, intersexual individual from Brazil, Rio de Janeiro, Macaé (MACN-Ar 41529, IFM-1948 voucher). A, habitus, ventral. B, anterior legs and carapace, subanterior. C, ventral. D, palps, dorsal view. E, right palp, sublateral. F, genital opening, ventral. Scale bars, 1 mm (A–C); 0.5 mm (D); 0.1 mm (E–F).

FIGURE 6. Micrathena lata, male from Argentina, Misiones (MACN-Ar 3866). A, habitus dorsal. B, habitus lateral. C–G, left palp. C, prolateral. D, embolus, apical. E, retrolateral. F, prolateral, clove oil cleared. G, details of embolus. Scale bars, 1 mm (A, B); 0.1 mm (C–F); 0.05 mm (G). Abbreviations: c = conductor, cl = conductor lobe, e = embolus, em = embolic membrane, ta = terminal apophysis.