Orsinome, THORELL, 1890

Álvarez-Padilla, Fernando & Hormiga, Gustavo, 2011, Morphological and phylogenetic atlas of the orb-weaving spider family Tetragnathidae (Araneae: Araneoidea), Zoological Journal of the Linnean Society 162 (4), pp. 713-879 : 791-794

ORSINOME THORELL, 1890

( FIGS 5A, B , 91B, D , 96–104 )

Type species: Orsinome vethii ( Hasselt, 1882) . The type specimen depository of Pachygnatha vethii is unknown to us.

Diagnosis: Orsinome species can be distinguished from other tetragnathids by the following combination of characters: femora IV with trichobothria ( Fig. 101G ); female chilum present; copulatory ducts well sclerotized and coiled; copulatory openings inside a common chamber on the centre of the epigynal plate ( Figs 102A–D , 104E ); male cephalothorax ocular area higher than lateral margins ( Fig. 101B, D ); embolus base resting on the subtegulum ( Fig. 104A ); and having the dorsobasal process of the cymbium made of a cuticular fold that extends to the middle of the cymbium ( Fig. 103C ).

Description: Female: body length c. 14.0 mm. Femora IV trichobothrial shaft not branched ( Fig. 101G ). Ocular area lower than carapace lateral margins ( Fig. 101B ). Labium trapezoidal, wider than long and rebordered. Sternum longer than wide ( Fig. 101C ). Anterior surface of chelicerae smooth; boss present ( Fig. 101F ). Secondary eyes with canoe-shaped tapetum. Eyes subequal in size, lateral eyes slightly smaller, juxtaposed, and on a tubercle. Clypeus almost twice one AME diameter. Abdomen cylindrical, covered with silver guanine patches ( Murphy & Murphy, 2000: fig. 10). Booklung cuticle smooth ( Fig. 100A ). Tracheal spiracle near the spinnerets. Median tracheae not ramified, longer than half the lateral tracheae length, with leaf-shaped tips ( Fig. 100A, C ). ALS with an extensive field of piriform spigots ( Fig. 100B ). PMS with three aciniform spigots between the cylindrical and minor ampullate silk gland spigots but without any aciniform spigots over the anterior surface ( Fig. 100G ). PLS with c. 22 aciniform spigots arranged in roughly parallel lines, distal end of the aggregate spigots embracing the tip of the flagelliform spigot ( Fig. 100D ). Epigynal plate flat, copulatory openings ventrally orientated. Spermathecae walls weakly sclerotized ( Figs 100B , 104E ). Copulatory and fertilization ducts coiled, longer than the spermatheca length with well-sclerotized cuticle. Accessory concentrated near the duct junction, accessory glands acorn-shaped and in individual pits ( Fig. 104B–F ).

Male: size and somatic morphology similar to that of the female, except the chelicerae are considerably larger, with a massive median apophysis on the internal margins ( Fig. 101H ). PLS triplet reduced to nubbins. Epiandrous plate well sclerotized, fusules immersed in a transverse groove with their bases wider than the fusule shaft ( Fig. 100F ). Palpal patella without macrosetae. Palpal femora very long, more than four times its width. Tibia length twice its width. Paracymbium shorter than half the cymbium length, curved, with swollen distal margin ( Fig. 103F ). Cymbial dorsobasal process fused to the cymbium more than two thirds of its length ( Fig. 103C, D ). Tegulum roughly oval, with an ectal depression produced by the displaced subtegulum ( Fig. 104A, B ). Conductor parts well sclerotized, attachment to tegulum membranous ( Fig. 104C, D ). Embolus base rectangular and longer than wide, located between tegulum and cymbium. Embolus displaced between the tegulum and cymbium with its distal part resting on the subtegulum ( Fig. 104A ). Embolus approximately as long as the cymbium, thin and well sclerotized ( Fig. 104C ). Sperm duct with more than five coils ( Fig. 104B ).

Natural history: Orsinome includes 17 described species distributed in the South-East Asian tropics and Madagascar ( Thorell, 1890; Chrysanthus, 1971; Zhu et al., 2003). They build horizontal webs, with c. 20 spirals, c. 13 radii, and open hubs ( Fig. 5C ). Their webs are found over the water between the rocks, and over vegetation along rivers.

Taxonomy: Two species are included in this analysis, Orsinome cf. vethi and ‘ Orsinome ’ sarasini Berland, 1924 , but the results of our analysis suggest that they are not congeneric. The first species belongs to the leucaugines, whereas ‘ Orsinome ’ sarasini belongs to Nanometinae ( Fig. 144 ). The taxonomic status of ‘ O. ’ sarasini should be revised when a larger taxonomic sample of these Australasian lineages is studied in more depth. A new genus name is required for this lineage of species from New Caledonia, South-eastern Australia, and Tasmania ( Urquhart, 1891; Berland, 1924). ‘ Orsinome ’ sarasini differs from the taxa in Nanometinae by the following characteristics: distal end of aggregate spigots embracing the distal end of flagelliform spigot ( Fig. 96C ); paracymbium cylindrical, longer than half the cymbium length and with a basal apophysis ( Fig. 97E ); and median tracheae not ramified ( Fig. 97F ). All other studied morphological

794 F. ÁLVAREZ-PADILLA and G. HORMIGA features are similar to Nanometa sp. and ‘ Nanometinae sp.’ ( Figs 91B, D , 96–99 ). The relationships of Orsinome to other Leucauginae genera are unresolved by the data set of morphology plus behaviour ( Fig. 143A, B ); however when these data are combined with DNA sequences O. cf. vethi is placed as sister to Tylorida ( Fig. 144 ).

Figures

Figure 5. Webs of tetragnathids and outgroup taxa: A, Opadometa sp. from Chiang Mai, Thailand (65 cm horizontal) (DSCN3876). B, hub detail. C, Orsinome cf. vethi from Bang Lang National Park, Thailand (95 cm horizontal) (DSCN4297). D, Tetragnatha versicolor from Virginia, USA (65 cm horizontal) (DSCN3180). E, Tylorida striata from Khao Luang National Park, Thailand (35 cm horizontal) (DSCN4091). F, Parasteatoda sp. from Chiapas, Mexico (25 cm horizontal) (DSCN7996).

Figure 91. Nanometa sp. and ‘Orsinome’ sarasini genital anatomy illustrations: A, Nanometa sp. palp expanded. B, ‘Orsinome’ sarasini, pedipalp expanded. C, Nanometa sp. cleared epigynum ventral view. D, ‘Orsinome’ sarasini cleared epigynum ventral view.

Figure 96. ‘Orsinome’ sarasini abdomen: A, male booklung cuticle. B, anterior lateral spinnerets. C, posterior lateral spinnerets. D, tracheal spiracle posterior view. E, posterior median spinnerets. F, median tracheae tips. G, epiandrous fusules. All images from SEMFAP050.

Figure 97. ‘Orsinome’ sarasini cephalothorax: A, male dorsal view. B, female dorsal view. C, female chelicera. D, male chelicera. E, female tangential view. F, male coxa IV dorsal view. G, female sternum. H, male tangential view. All images from SEMFAP050).

Figure 98. ‘Orsinome’ sarasini epigynum: A, lateral view. B, ventral view. C, spermatheca. D, dorsal view. E, accessory glands. F, lateral view. All images from SEMFAP050.

Figure 99. ‘Orsinome’ sarasini male pedipalp: A, mesal view. B, apical view. C, ventral view. D, dorsal view. E, ectal view. F, cymbial ectobasal process. All images from SEMFAP050.

Figure 100. Orsinome cf. vethi abdomen: A, female booklung cuticle. B, anterior lateral spinnerets. C, tracheal system dorsal view. D, posterior lateral spinnerets. E, median tracheae bifurcation. F, epiandrous fusules. G, posterior median spinnerets. All images from SEMFAP040.

Figure 101. Orsinome cf. vethi cephalothorax: A, female dorsal view. B, female tangential view. C, female sternum. D, male tangential view. E, cheliceral paturon base. F, female chelicera. G, female femur IV dorsal view. H, male chelicera. All images from SEMFAP040.

Figure 102. Orsinome cf. vethi epigynum: A, posterior view. B, dorsal view. C and D, copulatory and fertilization ducts. E, spermatheca accessory glands. F, abdomen cuticle gland ducts. All images from SEMFAP040.

Figure 103. Orsinome cf. vethi male pedipalp: A and B, conductor. C, dorsal view. D, mesal view. E, ventral view. F, ectal view. All images from SEMFAP040.

Figure 104. Orsinome cf. vethi genital anatomy illustrations: A, cleared male pedipalp bulb dorsal view. B, ventral view. C and D, pedipalp expanded. E, epigynum cleared ventral view.

Figure 143. Strict consensus trees of parsimony analyses of the morphological and behavioural data set presented in Appendix 2: A, strict consensus cladogram of the five cladograms of minimal length obtained under equal weights of 1033 steps (consistency index = 26, retention index = 58); the consensus tree is ten steps longer. Bremer support values are given under the nodes. B, strict consensus of 11 optimal cladograms obtained with implied weights at concavities 1 to 100; the consensus tree is 101 steps longer than the equal weighted optimal cladograms. Symmetric resampling support values above 51% are given under each node. See text for additional details.

Figure 144. Preferred optimal cladogram from the study of Álvarez-Padilla et al. (2009). This tree is based on a combined analysis, using direct optimization methods, of multigene DNA sequences and the morphological and behavioural data set presented in Appendix 2. The single most parsimonious tree was 54 536 steps when all the data were analysed simultaneously. Numbers under each node correspond to the node numbers in Table 1 where all support values are plotted and the synapomorphies mapped.