Tricellina gertschi ( Forster & Platnick, 1981 )

Rix, Michael & Harvey, Mark, 2010, The spider family Micropholcommatidae (Arachnida: Araneae: Araneoidea): a relimitation and revision at the generic level, ZooKeys 36 (36), pp. 1-321 : 35-36

Tricellina gertschi ( Forster & Platnick, 1981)

Figs 7D , 23 G–H, 33D, 40–45, 212

Tricella gertschi Forster & Platnick, 1981: 266 , figs 1–2, 4–10, 14–15, 20–22 (holotype male from west of Cherquenco, Cautín province, Chile, in AMNH, not examined). Brignoli, 1983: 696.

Tricellina gertschi (Forster & Platnick) : Forster & Platnick, 1989 in Platnick, 1989: 166. Platnick et al., 1991: 5, figs 240–244. Platnick, 2009.

Material examined. CHILE: Región IX (de la Araucanía): Cautín: 4 km W. of Cherquenco, near Temuco , 28.IV.1961, L. Smith, 1♁, 6♀ ( AMNH). Malleco: Monumento Natural Contulmo, 31.I.1986, N. Platnick, T. Schuh, 1♀ ( AMNH) ; same data except 23.I.1985, N. Platnick, O. Francke, 1♀ ( AMNH). Región X (Los Lagos): Chiloé: Chiloé Island , 5 km N. of Quellon, 1.XII.1981, N. Platnick, T. Schuh, 1♁ ( AMNH) ; same data, 1♁, 5♀ ( AMNH). Llanquihue: 35 km NW. of Río Negro, 24.I.1986, N. Platnick, T. Schuh, 3♀ ( AMNH). Osorno : Termas de Puyehue , 25.XI.1981, N. Platnick, T. Schuh, 1♀ ( AMNH) ; same data except 24.XI.1981, 6♁, 15♀ ( AMNH) ; Volcán Osorno, 12.II.1985, N. Platnick, O. Francke, 1♀ ( AMNH). Palena: 25–27 km N. of Chaitén , 17.I.1986, N. Platnick, P. Goloboff, T. Schuh, 2♁, 6♀ ( AMNH) ; 70 km S. of Chaitén , 16.I.1986, N. Platnick, P. Goloboff, T. Schuh, 5♁, 35♀ ( AMNH) ; vicinity of Chaitén , 5–7.XII.1981, N. Platnick, T. Schuh, 1♀ ( AMNH) ; same data except 7.XII.1981, 12♁, 29♀ (AM- NHSEM♁ ♀) .

Remarks. Tricellina gertschi is the only species in the tribe Micropholcommatini known to occur in Chile, where it is relatively widespread (Fig. 212). Forster and Platnick (1981) discussed the similarities of T. gertschi to a number of Australasian micropholcommatid taxa, suggesting a possible close relationship to Raveniella hickmani , R. luteola and Guiniella tropica (then all placed in Textricella ). The original naming of ‘ Tricella ’ (a contraction of ‘ Textricella ’) and the associated discussion on relationships were based on the assumption that T. gertschi was closely related to Textricella parva Hickman (= Eterosonycha alpina Butler ) and other taxa now in the Textricellini ; an erroneous interpretation based largely on a homoplastic morphology of the abdominal respiratory system. Tricellina gertschi was also described by Forster and Platnick (1981: 266) as a likely haplogyne spider, with “paired spherical receptacula, of which one is membranous”; an interpretation which resulted in the inclusion of T. gertschi in a cladistic analysis of haplogyne taxa by Platnick et al. (1991). The second “membranous” receptaculum identified by Forster and Platnick (1981) is actually a distal series of coiled, membranous insemination ducts surrounding a central, posteriorly-directed fertilisation duct – a morphology shared with species of Austropholcomma ( Fig. 33 ). Tricellina is now known to be a typical, entelegyne micropholcommatine taxon, closely related to Austropholcomma from Australia.

Tribe Textricellini Hickman, 1945 , new rank

Textricellidae Hickman, 1945: 136 . Type genus Textricella Hickman, 1945 (= Eterosonycha Butler, 1932 ).

Diagnosis. Species of Textricellini can be distinguished from all other Micropholcommatidae by the presence of a modified, enlarged and sinuous flagelliform gland spigot on the posterior lateral spinnerets (the ‘textricellin FL gland spigot’) ( Fig. 46 ), usually visible only with a scanning electron microscope. With the exception of the basal species Tinytrella pusilla ( Forster, 1959) , species of Textricellini can also be distinguished from all other Micropholcommatidae by the presence of two or three peg teeth on the male cheliceral promargin ( Figs 47 A–B), and the presence of ornate, ridged cuticular sculpturing on the male pedipalpal patella ( Figs 47 C–D). The tribe can be further distinguished from all other Micropholcommatinae by the absence in all but a few taxa of a dorsal scute on both the male and female abdomen ( Figs 76 A–B). The ‘textricellin somatic gestalt’ (see Remarks, below) is also extremely distinctive and useful for identification.

Distribution. South-eastern and south-western mainland Australia, Tasmania, Lord Howe Island, Papua New Guinea, New Zealand and southern Chile. This distribution is largely congruent with a vicariant, Gondwanan biogeography (Fig. 217) (see Biogeography, below).

Included genera. Eterosonycha Butler ( Fig. 7E ) and the nine new genera Algidiella ( Fig. 7K ), Eperiella ( Fig. 7J ), Epigastrina ( Fig. 7F ), Guiniella ( Fig. 72 ), Normplatnicka ( Fig. 7I ), Raveniella ( Fig. 7G ), Rayforstia ( Fig. 7H ), Taliniella ( Fig. 7L ) and Tinytrella ( Fig. 7M ).

Remarks. While difficult to quantify empirically, species of Textricellini possess an extremely distinctive overall somatic morphology, or ‘gestalt’, unique among Micropholcommatidae (see Figs 7 E–M). This textricellin somatic gestalt was recognised in the traditional generic concept of ‘ Textricella ’ (see Forster 1959) and the old family concept of Textricellidae ( Platnick and Forster 1986), and is often so obvious that an experienced arachnologist can identify a spider as a textricellin without the use of a microscope.

Figures

Figure 7. The genera of Micropholcommatidae, illustrated with habitus photographs of representative male specimens. A–D tribe Micropholcommatini: A Micropholcomma caeligenum Crosby & Bishop B Pua novaezealandiae Forster C Austropholcomma florentine sp. n. D Tricellina gertschi (Forster & Platnick). E–M tribe Textricellini: E Eterosonycha aquilina sp. n. F Epigastrina fulva (Hickman) G Raveniella peckorum sp. n. H Rayforstia vulgaris (Forster) I Normplatnicka lamingtonensis (Forster)] Eperiella alsophila sp. n. K Algidiella aucklandica (Forster) L Taliniella nigra (Forster) M Tinytrella pusilla (Forster). N Patelliella adusta sp. n., tribe Patelliellini. O–P subfamily Taphiassinae: O Olgania excavata Hickman P Taphiassa robertsi sp. n. Q–R subfamily Gigiellinae: Q Gigiella milledgei sp. n. R Gigiella platnicki sp. n. Note that Guiniella tropica (Forster) is not illustrated.

Figure 23. Scanning electron micrographs of posterior median spinnerets of female (left) and male (right) Micropholcommatini: A–B Micropholcomma bryophilum (Butler) from near Marysville, Victoria (WAM T94453) C–D Pua novaezealandiae Forster from the Makarora Valley, New Zealand (AMNH) E–F Austropholcomma florentine sp. n. from the Florentine Valley, Tasmania (FMC) G–H Tricellina gertschi (Forster & Platnick) from near Chaitén, Chile (AMNH). Note the apparent loss of the anterior CY gland spigot in female Austropholcomma and Tricellina. Arrows denote the anterior, mesal direction.

Figure 33. Austropholcomma, Tricellina species, female cleared receptacula, dorsal view: A–B, paratype A. florentine sp. n. from the Florentine Valley, Tasmania (FMC) C paratype A. walpole sp. n. from Walpole-Nornalup National Park, Western Australia (WAM T94440) D T. gertschi (Forster & Platnick) from south of Chaitén, Chile (AMNH). Arrows indicate the trajectory of insemination ducts. Scale bar = 0.065 mm (65 µm).

Figure 46. The enlarged, sinuous textricellin flagelliform gland spigot: A–B scanning electron micrographs of posterior lateral spinnerets of male Normplatnicka lamingtonensis (Forster) (left) and male Raveniella luteola (Hickman) (right), showing the characteristic FL gland spigot.

Figure 47. Diagnostic characters of the derived Textricellini (i.e. all textricellin genera except Tinytrella), illustrated with scanning electron micrographs: A–B three peg teeth on the cheliceral promargin of male Normplatnicka lamingtonensis (Forster) (left) and male Rayforstia vulgaris (Forster) (right) C–D ornate, ridged cuticular microstructure on the pedipalpal patella of male N. lamingtonensis (left) and male Eperiella alsophila sp. n. (right).

Figure 72. Guiniella tropica (Forster) from Daulo Pass, Papua New Guinea (QMB S111): A allotype female habitus, dorsal view B holotype male cephalothorax, dorsal view C allotype female cephalothorax, antero-dorsal view. Note the very poor condition of the type specimens.

Figure 76. Raveniella peckorum sp. n. from Modong Nature Reserve, Western Australia. A, C holotype male (WAM T94549): A habitus, dorsal view C cephalothorax, anterior view. B, D allotype female (WAM T94550): B habitus, dorsal view D abdomen, ventral view.