Porrhomma rakanum Yaginuma & Saito, 1981

Růžička, Vlastimil, 2018, A review of the spider genus Porrhomma (Araneae, Linyphiidae), Zootaxa 4481 (1), pp. 1-75 : 58

Porrhomma rakanum Yaginuma & Saito, 1981

Figs. 51A–E .

Porrhomma rakanum Yaginuma & Saito, 1981 — Yaginuma & Saito (1981): p. 33, Figs. 1–4 (descr. ♂ ♀).

Material examined. JAPAN. Porrhomma rakanum , paratypes No. 3–4, Rakan-ana Cave, Koya , Nomura-cho , Ehime Prefecture, 28 Nov 1968, 2 ♂, Masataka Yosida ; paratypes No. 15–19, Rakan-ana Cave, Koya, Nomuracho , Ehime Prefecture, 28 Nov 1968, 5 ♀, Masataka Yosida (ASJ).

Diagnosis. Among four species of the magnum -group, P. ohkawai and P. rakanum are characterised by absent eyes. P. rakanum differs from P. ohkawai by the presence of only two dorsal spines on Fe I. It was recorded exclusively in caves in Japan.

Description. Male holotype. Carapace pale, 0.65 mm wide, eyes absent or almost absent. Abdomen pale. Fe I with two dorsal spines and one prolateral spine, Fe II with one dorsal spine. Ti I–II with one retrolateral spine. Tm Mt I = 0.29, Mt I/CW = 1.92 ( Yaginuma & Saito 1981).

Embolic section characteristic for magnum -group. AP shorter than broad, the space between AP and PA quite open. Velum with pigmented margin ( Fig. 51A ).

♀ (from Rakan-ana Cave, Japan, 28 Nov 1968). Epigynum with lateral wings ( Fig. 51B ). Copulatory ducts very long, with ascending and descending parts. Main sacks oriented upwards, appendices narrowed, oriented towards the abdominal wall ( Figs. 51C–E ).

Ecology. Known exclusively from caves.

Global distribution. Recorded only in the Rakan-ana Cave in Ehime Prefecture, Shikoku Island , Japan. See Fig. 52 .

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 51. A–E, Porrhomma rakanum from Rakan-ana Cave, Japan. A, embolic section. B, epigynum. C–E, vulva, ventral, caudal and dorsal. Scale bars, 0.1 mm.

FIGURE 52. A record of Porrhomma rakanum. Rakan-ana Cave, Ehime Prefecture, Shikoku Island, Japan.