Perania nigra ( Thorell, 1890 )

Schwendinger, Peter J., 2013, A taxonomic revision of the spider genus Perania Thorell, 1890 (Araneae: Tetrablemmidae: Pacullinae) with the descriptions of eight new species, Revue suisse de Zoologie 120 (4), pp. 585-663 : 632-636

Perania nigra ( Thorell, 1890) Figs 21-23

Phaedima nigra Thorell, 1890: 310 (description of male and female).

Paculla nigra ( Thorell, 1890) . – Simon, 1894: 573 (transfer).

Perania nigra ( Thorell, 1890) . – Bourne, 1980: 256, figs 12-19 (designation of lectotype; redescription of types; transfer). – Lehtinen, 1981: 15-16, figs 6, 8-9 (designation of lectotype; redescription of types; transfer). – Platnick, 2013 (listing).

Perania pallida Thorell, 1890: 316 (description of juvenile), synonymised by Lehtinen, 1981: 15.

TYPES: MCSNG; Ƌ lectotype and 1 ♀ paralectotype; Indonesia, Sumatra, West Sumatra Province, Singalang (= Gunung Singgalang; about 0°23’S, 100°21’E) near Bukittinggi; VIII.1878; leg. Odoardo Beccari.

NEW MATERIAL EXAMINED: MHNG, sample Sum-00/08; 1 Ƌ, 2 ♀, 2 juveniles; Indonesia, Sumatra, West Sumatra Province, near Lake Maninjau, waterfall above Gasang Village (about 0°16’30”S, 100°13’50”E), 600-700 m; 12.II.2000; leg. P. J. Schwendinger.

DIAGNOSIS: Distinguished by a pair of low humps on “thoracic” portion of carapace in both sexes; males with relatively deep, paddle-shaped apex of embolus with a tiny, tooth-like, distad-directed embolic part; females with large anterior opisthosomal plate fused with pulmonary plate, and with internal chambers of spermathecae medially connected by a sclerotised bridge.

RE-DESCRIPTION: Small species; both sexes without clypeal process; a pair of low humps sitting on “thoracic” portion of carapace (Fig. 21A-D); cowpat-shaped tubercles on carapace low, indistinct; conical tubercles along lateral margins of carapace relatively large; anterior portion of fovea pitlike and wider than posterior portion. Males without cheliceral modifications; few conical setal bases prolaterally in distal half of tibia I, many prolaterally to ventrally over entire length of metatarsus I; anterior pair of ventrolateral plates largely free, only their posterior tips fused with margin of pulmonary plate; postgenital plate more or less completely fused to pulmonary plate; all microplates on posterior side of opisthosoma isolated; cymbium relatively short, with pointed apex (Fig. 22A, D); bulbus ovoid, with U-shaped transition to long and sigmoid embolus (Fig. 22A); apex of embolus deep and somewhat paddle-shaped, with a widely angular or lobate subterminal lamella and with a tiny, tooth-like, distad- FIG. 21

Perania nigra , male lectotype (A-C), female paralectotype (D-G). (A) Carapace, dorsal view. (B) Same, lateral view. (C) Carapace and chelicerae, anterior view. (D) Carapace, anterior view. (E) Upper anterior side of opisthosoma showing entire anterior plate fused with pulmonary plate. (F) Posterior portion of opisthosoma showing reduced preanal plate, ventral view. (G) Genital region showing oulines of vulva, ventral view. Scale lines 1.0 mm (A-B; C-G).

directed embolic part (Fig. 22B-F). Females with a rudimentary preanal plate (Fig. 21F) and with a large, clearly outlined anterior opisthosomal plate being widely fused with pulmonary plate (Fig. 21E); some opisthosomal microplates near dorsal scutum conical but only slightly elevated; vulva with a short and relatively narrow anterior collar (Fig. 23A, D); fused spermathecae with a deep V-shaped invagination in common anterior margin, ventral wall including a pair of short and wide internal chambers with thin or broken retrolateral walls and thick prolateral walls, both chambers connected to each other by a sclerotised median bridge; ventral wall of spermathecae between porepatches and internal chambers unpigmented (Fig. 23B, E); anterolateral sides of spermathecae with shallow trenches (Fig. 23C, F); porepatches large, extending far onto dorsal side of spermathecae (Fig. 23A, D); ventral wall of genital atrium with wide, slightly pigmented median zone flanked by transparent lateral zones (Fig. 23A-B, D-E).

FIG. 22

Perania nigra , male lectotype (A-C), new male (D-F). (A) Distal portion of left palp, prolateral view. (B, E) Apex of left embolus, proventral view. (C, F) Apex of right embolus, same view. (D) Distal part of left palp, proventral view. Scale line 1.0 mm.

VARIATION AND MEASUREMENTS: Carapace lengths in two males (three females) are 3.3 (3.2-3.5), carapace widths 2.3-2.5 (1.9-2.5); the types have the highest values. The male lectotype has a widely invaginated posterior margin of the dorsal opisthosomal scutum, the new male has a straight margin. In the male lectotype the postgenital plate is completely fused to the pulmonary plate, in the new male both plates are medially separated by a very thin membranous stripe. The lectotype has slightly larger tubercles along the lateral margins of the carapace, and more numerous conical setal bases in the distal half of tibia I, whereas the new male has fewer conical tubercles restricted to the distal quarter of tibia I. In the two new females the preanal plate is smaller (but also distinct) than in the female paralectotype.

REMARKS: The female paralectotype was not dissected, but the outlines of the spemathecae and of the ventral chambers are visible from under the cuticle of the pulmonary plate (Fig. 21G) and correspond to those of the vulvae of the newly collected females.

Bourne (1980: 256, fig. 19) called the small unpaired ventral plate of the female paralectotype a “postgenital plate”. This confusion probably results from the fact that this specimen has a slightly shrunk opisthosoma in which the median ventrolateral plates (lying between the postgenital and preanal plates) are not clearly visible. A comparison with newly collected females with firm opisthosomata clearly shows a small unpaired ventral plate (with a smooth surface) lying between a triangular pair of median ventrolateral plates and an oval pair of posterior ventrolateral plates (with

FIG. 23

Perania nigra , two females (A-C; D-F). (A, D) Vulva, dorsal view. (B, E) Same, ventral view. (C, F) Same, anterior view. Scale lines 0.5 mm (A-E; C-F).

granular surfaces). Therefore the median plate illustrated by Bourne is the moderately reduced preanal plate and not the postgenital plate. The postgenital plate is completely fragmented in all Perania females. Bourne (1980: 256, fig. 14) claimed that there are “no defined plates between pulmonary and anal plates” in the male lectotype of this species and did not illustrate a preanal plate in the corresponding figure although that is well-developed and clearly visible (as in all Perania males).

RELATIONSHIPS: The pair of humps posteriorly on the “thoracic” portion of the carapace and strong similarities in copulatory organs of males and females of P. armata show that P. nigra and P. armata are the closest relatives. Moreover both species share a complete anterior opisthosomal plate, which is more or less fragmented in other congeners. However, the presence of an entire anterior plate is probably plesiomorphic, as may be the presence of paired structures in and on the spermathecae of all Perania species from Sumatra.

DISTRIBUTION AND HABITAT: Perania nigra is known from two localities (about

15 km apart) in West Sumatra Province (Fig. 1, localities 28-29). The types of P. nigra

and the original types of P. armata (now lost) were allegedly all collected on Mt Singgalang (Fig. 1, locality 29). Thus both species may occur side by side, although that seems unlikely given their close relationship. The new specimens were collected from a fallen, partially rotten tree and from holes in a stream bank in a remnant patch of primary rain forest.