Metabus, O.Pickard-Cambridge, 1899

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 : 776-779

METABUS O. P.- CAMBRIDGE 1899 ( FIGS 4B , 61–65 )

Type species: Metabus ocellatus ( Keyserling, 1864) . The syntype series of Tetragnatha ocellata consists of two males and seven females from Bogota ( Colombia), deposited at the Natural History Museum , London (examined) .

Diagnosis: Metabus species can be distinguished from all other tetragnathid genera by the following combination of characters: leg I more than four times the body length; femur IV without trichobothria ( Fig. 62C ); epigynum flat, well sclerotized and with a rectangular atrium ( Fig. 63A, B ); spermathecae weakly sclerotized ( Figs 63C , 65C ); fertilization ducts coiled over the copulatory ducts ( Fig. 63B ); CEDP longer than half the cymbial width and parallel to the cymbium longitudinal axis; conductor longer than wide and apically projected ( Fig. 64B ).

Description: Female: body length c. 14.0 mm. Cephalothorax fovea formed by two short transverse grooves ( Fig. 62A ). Ocular area lower than carapace lateral margins ( Fig. 62F ). Labium trapezoidal, wider than long and rebordered. Sternum longer than wide ( Fig. 62G ). Anterior surface of chelicerae smooth; boss present ( Fig. 62E ). Secondary eyes with canoe-shaped tapetum. Eyes subequal in size, lateral eyes slightly smaller, juxtaposed, and on a tubercle. Clypeus more than one AME diameter high. Abdomen covered with silver guanine patches. Booklung cuticle smooth ( Fig. 61B ). Tracheal spiracle near the spinnerets, almost without accessory glands ( Fig. 61F ). Median tracheae not ramified, with leaf-shaped tips and shorter than half the lateral tracheae length ( Fig. 61C–E ). ALS with c. 70 piriform spigots. PMS with three aciniform spigots between the cylindrical and minor ampullate silk gland spigots but without any aciniform spigots over the anterior surface. PLS with c. 20 aciniform spigots roughly arranged in two parallel lines; distal end of the aggregate spigots embracing the distal end of the flagelliform spigot ( Álvarez-Padilla, 2007: fig. 9A–C). Epigynal plate flat ( Fig. 63A, B ). Copulatory openings ventrally orientated with the shape of longitudinal grooves located under the atrial edges ( Fig. 65C ). Spermathecae walls weakly sclerotized. Copulatory ducts more than half the spermathecae length but less than its total length, cuticle weakly sclerotized. Fertilization ducts well sclerotized, coiled around copulatory ducts ( Figs 63C–E and 65C ). Accessory glands ducts in individual pits, concentrated over spermatheca-fertilization duct junction ( Fig. 63C, F ).

Male: size and somatic morphology similar to that of the female, except that legs I and II are considerably longer. Epiandrous plate well sclerotized, fusules immersed in a transverse groove with bases wider than fusule shaft. Posterior margin of the epiandrous plate thicker than the anterior margin ( Fig. 61G ). PLS triplet reduced to nubbins ( Álvarez-Padilla, 2007: fig. 9D). Male palpal patella with one macroseta. Paracymbium hook-shaped, without apophyses and considerably shorter than cymbium length ( Fig. 64A ). Tegulum roughly ovoid, with an ectal depression produced by the displaced subtegulum ( Fig. 64B ). Conductor rigid, with sclerotized edges, although some parts are weakly sclerotized. Conductor-tegulum attachment membranous, originating at the ventral edge of the tegulum ( Fig. 65A, B ). Embolus base rectangular, longer than wide ( Fig. 65A ). Embolus flexible and weakly sclerotized. Sperm duct path convoluted, with several coils ( Fig. 65D ).

Natural history: This genus includes four species with a Neotropical distribution. Metabus ebanoverde Álvarez-Padilla, 2007 , builds horizontal webs with open hubs, fewer than ten radii, and fewer than 20 spirals ( Fig. 4B ), but other Metabus species seem to have denser webs ( Lopardo et al., 2004: fig. 16). Metabus ocellatus ( Keyserling, 1864) builds communal orb webs over ponds and shares a communal retreat during the night ( Buskirk, 1975a: fig. 1, 1986; Uetz & Craig, 1997). This communal behaviour has not been reported for any other species in the family. The web building behaviour of M. ocellatus was described by Eberhard (1982). The communal behaviour of M. ocellatus has been described and discussed by Buskirk (1975b).

Taxonomy: Metabus has recently been revised and its monophyly tested ( Álvarez-Padilla, 2007). Synapomorphies for Metabus include the conductor apex curved apically and the absence of trichobothria on the fourth femora. In that study Metabus was sister to a clade that included L. venusta and L. argyra ( Álvarez-Padilla, 2007: fig. 9B). Okileucauge Tanikawa, 2001 species are very similar to Metabus in their genital anatomy and somatic morphology, i.e. both genera lack femoral trichobothria. However, a previous phylogenetic analysis proposed that Metabus and Okileucauge were not sister taxa; instead Metabus was hypothesized to be sister to a clade that included Leucauge , Okileucauge , Tylorida , and Mesida ( Tanikawa, 2001; Fig. 8B ). The morphology plus behaviour data set did not resolve Metabus sister taxa relationships with either Tylorida or Orsinome ( Fig. 143A ). When these data are combined with DNA sequences Metabus come out as sister to a clade that includes Orsinome and Tylorida ( Fig. 144 ).

Figures

Figure 4. Webs of tetragnathids: A, Mesida argentiopunctata from Noosa National Park, Australia (37 cm horizontal) (Leuc004b). B, Metabus ebanoverde from Ébano Verde Natural Reserve, Dominican Republic (72 cm horizontal) (DSCN7567). C, Meta menardi from Zealand, Denmark (15 cm horizontal, photograph by Nikolaj Scharff). D, Metleucauge eldorado from California, USA (40 cm horizontal). E, Mollemeta edwardsi from Puyehue National Park, Chile (50 cm horizontal). F, Nanometa sp. from Lamington National Park, Australia (18 cm horizontal) (DSCN0492). Photographs (D) and (E) by Gustavo Hormiga.

Figure 8. Allende nigrohumeralis abdomen: A, tracheal system dorsal view (arrows pointing upwards correspond to lateral trachea and downward pointing arrows median trachea; trachea follow the same arrangement on all images). B, lateral tracheae cuticle. C, tracheal spiracle posterior view. D, detail of tracheal spiracle. E, median trachea tip. F, epiandrous fusules (arrow). Images of tracheal system (SEMFAP058), epiandrous fusules (SEMFAP057).

Figure 61. Metabus ocellatus abdomen: A, cuticle of the abdomen, close up of median lateral section. B, booklung external cuticle. C and D, median tracheae tip. E, tracheal system dorsal view. F, tracheal spiracle posterior view. G, epiandrous fusules. All images from SEMFAP036.

Figure 62. Metabus ocellatus cephalothorax: A, female dorsal view. B, male dorsal view. C, female femur IV ectal view. D, male chelicera. E, female chelicera. F, female tangential view. G, female cephalothorax ventral view and sternum. H, male tangential view. All images from SEMFAP036.

Figure 63. Metabus ocellatus epigynum: A, ventral view. B, posterior view. C, spermatheca dorsal view. D, spermatheca lateral view. E, copulatory and fertilization ducts. F, accessory glands. All images from SEMFAP036.

Figure 64. Metabus ocellatus male pedipalp: A, mesal view. B, ventral view. C, dorsal view. D, cymbial dorsobasal process. E, pedipalp dorsal view. F, embolus and conductor. All images from SEMFAP036.

Figure 65. Metabus ocellatus genital anatomy illustrations: A, and B, male pedipalp expanded. C, cleared epigynum dorsal view. D, pedipalp bulb 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.