Apochinomma nitidum ( Thorell, 1895 )

Sankaran, Pradeep M., 2021, A review of the Indian species of Apochinomma Pavesi, 1881 and Corinnomma Karsch, 1880, synonymy of Castianeira quadrimaculata Reimoser, 1934, and a catalogue of the Indian corinnid fauna (Arachnida: Araneae), Zootaxa 5072 (6), pp. 541-559 : 543-548

Apochinomma nitidum ( Thorell, 1895)

Figs 2–5

Tyrrhus nitidus Thorell, 1895: 39 (subadult ♀).

Tyrrhus ambiguus Thorell, 1897: 238 (♂).

Apochinomma nitidum Simon, 1897b: 169 ; Gravely, 1931: 276 (immature ♀); Deeleman-Reinhold, 2001: 327, figs 482–485 (♂ ♀).

Apochinomma ambiguum Simon, 1897b: 169 .

Corinnomma rufofuscum Reimoser, 1934: 491 , fig. 14 (♀) syn. nov.

Type material. T. nitidus. Holotype subadult ♀ from MYANMAR: Tharrawaddy (=Tharrawaddi) (17°38’N, 95°46’E; 15 m a.s.l.), collector unknown, date unknown, repository NHM (register number unknown), not examined (illustrations of the male and female genitalia given in Deeleman-Reinhold [2001: figs 483–485] are diagnostic and were used for comparative purposes).

C. rufofuscum . Syntypes 2♀ from INDIA: Tamil Nadu: Nilgiri: Mudumalai (11°34’58.7’’N, 76°35’03.6’’E; 894 m a.s.l.), leg. J. Carl and K. Escher, 1926-1927, repository MHNG (no register number specified), examined based on photographs .

Other material examined. INDIA: Kerala: Thrissur, Chimmony Wildlife Sanctuary (10°25’06.80’’N, 76°32’07.25’’E; 709 m a.s.l.), 31 May 2013, leg. M.S. Pradeep, from ground, by hand: 2♀, 1 subadult ♂ (brown morph) ( ADSH2241 ); Kottayam, Pala, Areeppara in Edappady (09°42’35.62’’N, 76°42’48.42’’E; 27 m a.s.l.), 5 June 2017, leg. M.S. Pradeep, from ground, by hand: 2♀ (black morph) ( ADSH2242 ) .

Diagnosis. Within Apochinomma , A. nitidum is unique and differs from other known species by more closely arranged posterior eyes (vs. posterior eyes separated by>2x their diameter in other Apochinomma species ) and slightly recurved PER (vs. strongly recurved in other Apochinomma species ) (compare Fig. 2A–D with Haddad 2013 a: fig. 4A–B).

Redescription (brown morph). Female in alcohol ( Figs 2A–B , 3A–F ). Carapace, clypeus, chelicerae, sternum, scuta, sclerites brownish; eye region brownish, with black shades; endites and labium pale brownish; leg segments pale brownish to brownish, with black shades; palp segments pale brownish, with black shades; opisthosoma greyishblack; spinnerets greyish. Carapace rugose, clothed with fine white appressed hairs. Fovea longitudinal, straight ( Fig. 2A–B ). AME black. Clypeus height equal to one and half times AME diameter, provided with a few hairs. Cheliceral pro- and retromargins provided with series of hairs having slightly bent tips ( Fig. 3B ); promargin with three teeth, proximal slightly separated from median and distal that are closely spaced, median largest, proximal and distal small and subequal ( Fig. 3B ); retromargin with two equally sized teeth, proximal large, distal moderate ( Fig. 3B ). Endites with well-developed scopulae, anterior margin with serrula ( Fig. 3A , arrow 1). Sternum rugose, clothed with scattered long hairs, with coxal and intercoxal extensions; intercoxal extensions fused with carapace. Pedicel short, with collar ( Fig. 3E ). Opisthosoma tubular, with slight median constriction ( Fig. 2A–B ), clothed with fine hairs; dorsal scutum nearly oval, occupying anterior half of opisthosoma, unfused with collar ( Figs 2A–B , 3F ); epigastric scutum fused with collar ( Fig. 3E–F ); post-epigastric sclerites narrow ( Fig. 3E ); first lateral sclerite small, patch-like, second dot-like, inconspicuous ( Fig. 3F ). Femur III–IV provided with distoventral constriction ( Fig. 3C–D , arrows 2 & 3). Body length 6.85. Carapace length 3.45, width 1.93. Opisthosoma length 3.40, width 1.65. Eye diameters: ALE 0.09, AME 0.15, PLE 0.14, PME 0.12. Eye interdistances: AME–ALE 0.03, AME–AME 0.08, AME–PME 0.15, ALE–PLE 0.21, PME–PLE 0.17, PME–PME 0.20. Clypeus height at AMEs 0.22, at ALEs 0.19. Length of chelicerae 1.02. Measurements of palp and legs: palp 3.07 [0.87, 0.43, 0.63, 1.14], I 7.63 [2.05, 0.75, 1.87, 1.70, 1.26], II 7.28 [1.99, 0.75, 1.72, 1.66, 1.16], III 6.77 [1.86, 0.72, 1.54, 1.74, 0.91], IV 9.95 [2.68, 0.84, 2.46, 2.83, 1.14]. Leg formula: 4123. Spination of palp: femur do 2 v 5, patella pld 1 do 1, tibia do 2 rl 1 rld 1, tarsus plv 1 rl 1 rld 1 rlv 1; legs: femur I pld 1 do 3, II do 3, III–IV pld 2 do 3; patella I–IV spineless; tibia I plv 3 rlv 2, II plv 2 rlv 2, III pl 2 plv 2 rlv 1, IV pl 2 plv 3 rld 2 rlv 2; metatarsus I–II plv 2 rlv 2, III pld 2 plv 3 rld 1 rlv 3 vt 1, IV pld 3 plv 3 rld 3 rlv 3; tarsus I–IV spineless. Genitalia ( Fig. 3H–J ): epigynal plate triangular, weakly sclerotised, with convex posterior margin ( Fig. 3H–I ). Copulatory openings with laterally oriented, C-shaped rims, medially placed ( Fig. 3H–I ). Copulatory ducts short, as wide as long, initially directed dorsally before bending transversely towards midline, opening into anterior spermathecae II ( Fig. 3J ). Spermathecae I and II pear-shaped, contiguous, leaving small median separation ( Fig. 3J ). Fertilisation ducts small, diverging ( Fig. 3J ).

Black morph. Female in alcohol ( Figs 2D , 3G ). In all details like the female of brown morph except the following: carapace, eye region, clypeus, chelicerae, endites, labium, sternum black; scuta, spinnerets brownishblack; leg segments black to straw-coloured, with white bands, particularly on femora; palp segments black to straw-coloured; opisthosoma black, with broad transverse white bands. Opisthosoma pear-shaped, with slight distal constriction ( Fig. 2D ). Body length 6.83. Carapace length 3.38, width 1.96. Opisthosoma length 3.45, width 2.18. Eye diameters: ALE 0.10, AME 0.16, PLE 0.14, PME 0.13. Eye interdistances: AME–ALE 0.03, AME–AME 0.12, AME–PME 0.12, ALE–PLE 0.14, PME–PLE 0.10, PME–PME 0.16. Clypeus height at AMEs 0.19, at ALEs 0.17. Length of chelicerae 0.89. Measurements of palp and legs: palp 2.95 [0.84, 0.39, 0.59, 1.13], I 6.96 [1.89, 0.65, 1.76, 1.50, 1.16], II 6.65 [1.83, 0.68, 1.57, 1.52, 1.05], III 6.19 [1.71, 0.67, 1.41, 1.56, 0.84], IV 9.46 [2.51, 0.82, 2.31, 2.72, 1.10]. Spination of palp: tarsus pl 1 pld 1 plv 1 rld 1 rlv 1; legs: femur I pl 1 pld 1 do 2, II pld 1 do 2, III–IV pld 1 do 3; tibia I–II plv 3 rlv 3, III pl 2 plv 2 rld 2 rlv 2; metatarsus III pld 3 plv 2 rld 2 rlv 3 vt 1, IV pld 3 plv 4 rld 3 rlv 2 vt 1. Genitalia as in Figs 3K–L , 4A–B .

Male. For description and illustrations of the male, see Deeleman-Reinhold (2001). Colouration of subadult male brown morph in Fig. 2C .

Variation. Female (n=4): body length 6.27–6.85.

Justification of the transfer and synonymy of C. rufofuscum . Reimoser (1934) described C. rufofuscum based on female specimens collected from Tamil Nadu. Detailed examination of the syntypes of this species shows that it has all the diagnostic features of A. nitidum , including slightly recurved PER, elongate prosoma with a median constriction and oval opisthosoma ( Fig. 5A–B ). Further examination shows that C. rufofuscum shares features with A. nitidum as described and illustrated in Deeleman-Reinhold (2001: fig. 484): abdomen with small dorsal scutum, laterally oriented, C-shaped rims of copulatory openings and pear-shaped spermathecae I and II (compare Fig. 5C–D with Deeleman-Reinhold 2001: fig. 484). Based on these observations, I propose to consider C. rufofuscum as a junior synonym of A. nitidum .

Remarks. In contrast to Reimoser (1934), who mentioned only a single specimen of C. rufofuscum , the MHNG collection has two female specimens labelled as ‘type’; both represent the syntypes (P. Schwendinger, pers. comm.) ( Fig. 5A ). This is the first record of A. nitidum from India.

Note. The inclusion of A. nitidum in Apochinomma is doubtful, as the shape of its carapace, more closely positioned eyes and only slightly recurved PER are unique among other known Apochinomma species , indicating that A. nitidum may be a member of an unknown genus (C. Haddad, pers. comm.). However, this can only be confirmed after revising the Asian species of Apochinomma .

Figures

FIGURE 2. Apochinomma nitidum (Thorell, 1895), A–C brown morph, D black morph: A–B, D female habitus, dorsal views; C subadult male habitus, dorsal view. Scale bars: A–D = 2 mm.

FIGURE 3. Apochinomma nitidum (Thorell, 1895), A–F, H–J female brown morph, G, K–L female black morph: A female endites and labium, ventral view; B female left chelicera, ventroretrolateral view; C left femur III, retrolateral view; D left femur IV, retrolateral view; E female opisthosoma, ventral view; F same, retrolateral view; G female opisthosoma, retrolateral view; H epigyne without clearing, ventral view; I, K same after clearing, ventral view; J, L vulva, dorsal view.Abbreviations: C—collar; DS—dorsal opisthosomal scutum; DMS—dot-like median scutum; ES—epigastric scutum; LS—lateral sclerite; PES—postepigastric sclerite. Arrows indicate serrula of endite (1) and distoventral constriction on femur III–IV (2 & 3). Scale bars: A–B, H–L = 0.2 mm; C, G = 0.5 mm; D–F = 1 mm.

FIGURE 4. Apochinomma nitidum (Thorell, 1895), female black morph: A epigyne, ventral view; B vulva, dorsal view. Abbreviations: CD—copulatory duct; CO—copulatory opening; FD—fertilization duct; ST I—spermatheca I; ST II— spermatheca II. Scale bars: A–B = 0.2 mm.

FIGURE 5. Apochinomma nitidum (Thorell, 1895), syntype females of Corinnomma rufofuscum Reimoser, 1934: A habitus, dorsal and lateral views; B eye group, dorsal view; C epigyne of syntype female 1, ventral view; D epigyne of syntype female 2, ventral view; E labels from type bottle. Figures not to scale. © MHNG, Geneva.