Porrhomma cambridgei Merrett, 1994

Růžička, Vlastimil, 2018, A review of the spider genus Porrhomma (Araneae, Linyphiidae), Zootaxa 4481 (1), pp. 1-75 : 16-18

Porrhomma cambridgei Merrett, 1994

Figs. 13A–F .

Linyphia (?) oblonga O. Pickard-Cambridge, 1871 — O. Pickard-Cambridge (1871): p. 433 (descr. ♀); preoccupied, replaced by Merrett (1994).

Microneta oblonga — Simon (1884): p. 441. Porrhomma oblongum — F. O. Pickard-Cambridge (1894): p. 102, Pl. II, Fig. 4 (♀, descr. ♂). considered a synonym of P. oblitum ( O. Pickard-Cambridge, 1871) by Millidge & Locket (1952: p. 71). P. cambridgei Merrett, 1994 — Merrett (1994): p. 318, Figs. 1–4 (redescr. ♀); replacement name for P. oblongum ; removed from

synonymy of P. oblitum , contra Millidge & Locket (1952).

Material examined. CZECHIA: Bohemian Karst , Srbsko , 2 May 1999, 1 ♀, 5 July 2000, 2 ♀, leg. et coll. L. Kubcová. Liteň, 7 Mar –12 Apr 2011, 2 ♀, leg. A. Tenčík. Vápenný Podol, Podolská and Páterova Caves , 22 May – 18 Nov 2003, 1 ♀; Moravian Karst , Harbešská Cave, 15 Aug 2008, 1 ♂ 1 ♀, leg. R. Mlejnek. Horka nad Moravou, 6 Mar–13 Nov 2008, 2 Ƌ 6 ♀, leg. V. Laška & I . H. Tuf. Jenišovice-Zalažany, Mravín , 18 Apr 2014 –29 Sep 2015, 5 ♂ 6 ♀; Pardubice-Polabiny, 28 Apr–23 Sep 2015, 1 ♀, leg. V. Růžička & J . Dolanský ( IECA). Moravský Krumlov, Rokytná, 27 Apr 2002, 1 ♀, leg. V. Bryja (CVB).

Diagnosis. Small species (CW <0.60 mm), Fe I–II without dorsal spines, AP has the form of a bird head, Sshaped ascending parts of copulatory ducts. It is closely similar to P. oblitum , but it can be distinguished by depigmented body and reduced eyes ( Fig. 13A ).

Description. ♀ (from Horka nad Moravou, Czechia, 21 Aug–2 Oct 2008). Carapace pale yellow, 0.57 mm wide, eyes reduced, PME–PME = 2.3 ( Fig. 13A ). Abdomen pale. Fe without dorsal spines, Fe I with one prolateral spine. Ti I–II with one retrolateral spine. Tm Mt I = 0.39, Mt I/CW = 0.87. Ascending parts of the ducts are Sshaped. Spermathecae are formed behind the ascending part of the ducts ( Figs. 13C–F ).

Ƌ (from Jenišovice-Zalažany, Mravín, Czechia, 18 Apr 2014 – 29 Sep 2015). Embolus of middle length with a narrow velum. AP has the form of a bird head ( Fig. 13B ).

Variation. Ƌ ♀. Carapace 0.56–0.59 mm wide. Ti I sometimes with one prolateral spine. Tm Mt I = 0.39–0.41, Mt I/CW = 0.84–0.89 (n = 8) ( Růžička et al. 2011; sub P. aff. myops ).

Comments. O. Pickard-Cambridge (1871) described that the species Linyphia (?) oblonga is characterised by “eyes very small”. Based on vulva structure, Millidge & Locket (1952) synonymised this microphthalmic form with Porrhomma oblitum . Finally, Merrett (1994) removed it from synonymy with P. oblitum and revalidated it as a separate species P. cambridgei . Genitalia are indistinguishable from those of P. oblitum . The species is clearly characterised by femora I and II without dorsal spines, cephalothorax width <0.58 mm and reduced eyes. I found no intermediate form between P. cambridgei and P. oblitum .

Ecology. The species was collected on tree bark in the Bohemian Karst ( Thaler et al. 2003), in detritus in this karst region, and in conglomerate terrains in southern Moravia. Other specimens were found in grasslands ( Merrett 1994). However, the reduced eyes suggest that this species lives mainly in subterranean habitats. Růžička & Dolanský (2016) and Růžička et al. (2011, sub. P. aff. myops ) documented the occurrence of this species in sandy marlite terrain, alluvial soils and in karst terrain (unpubl.) at a depth of 35–140 cm. Finally, P. cambridgei was collected in two karst caves at a depth of 60 m.

Global distribution. Europe among southern England, northern Italy and the Czech Republic after Hänggi (1999), Zingerle (1999), Harvey et al. (2002), van Keer et al. (2016), Arachnologische Gesellschaft (2017), and this paper. See Fig. 14 .

Figures

FIGURE 1. Porrhomma cambridgei from Jenišovice-Zalažany, Mravín, Czechia. Female habitus. Scale bar, 0.1 mm.

FIGURE 2. A–B, Porrhomma pygmaeum, male palp. A, retrolateral view. B, prolateral view. Abbreviations: AP, anterior process of the embolic plate; DSA, distal suprategular apophysis; E, embolus; EM, embolic membrane; EP, embolic plate; PA, posterior apex of the embolic plate; PT-OP, protegulum, outer process; PT-IM, protegulum, inner membrane; ST, subtegulum; T, tegulum. Scale bar, 50 µm.

FIGURE 3. A–B, Porrhomma microphthalmum, male palp. A, retrolateral view. B, prolateral view. Abbreviations as in Fig. 2. V, velum. Scale bar, 50 µm.

FIGURE 4. Porrhomma microps. Female vulva coloured by chlorazol black, dorsal view. Abbreviations: A, appendix; MS, main sack; SL, side loop of the copulatory duct. Scale bar, 0.1 mm.

FIGURE 13. A–F, Porrhomma cambridgei from Horka nad Moravou, Czechia; except B, Jenišovice-Zalažany, Mravín, Czechia. A, ♀ carapace, frontal view. B, embolic section. C, epigynum. D–F, vulva, ventral, caudal and dorsal. Scale bars, 0.1 mm.

FIGURE 14. Global distribution of Porrhomma cambridgei.