Metabus

Álvarez-Padilla, Fernando, 2007, Systematics of the spider genus Metabus O. P. - Cambridge, 1899 (Araneoidea: Tetragnathidae) with additions to the tetragnathid fauna of Chile and comments on the phylogeny of Tetragnathidae, Zoological Journal of the Linnean Society 151 (2), pp. 285-335 : 297-302

METABUS O. P.– CAMBRIDGE, 1899

( FIGS 3A–E , 4A–E , 9A–E , 10D , 11A , 12–15 )

Metargyra F. O. P.- Cambridge, 1903: 444, pl. 42, f. 15- 16. New synonymy.

Type species: Metabus gravidus O. P.– Cambridge, 1899, type fixed by monotypy.

Etymology: O. P.– Cambridge (1899: 298) did not explain the etymology of Metabus , this genus name means resembling or having the quality of Meta .

Diagnosis: Metabus species can be distinguished from all other tetragnathid genera by the following combination of characters: epigynum flat, well sclerotized and with a rectangular atrium ( Figs 12C , 13B , 15B ); male pedipalp conductor longer than wide, and apically projected ( Figs 12J , 13–15G ); femur IV without trichobothria; and leg I more than four times the body length.

Description

Female: Medium- to small-sized spiders, total length from 4.7 to 8.1. The smallest specimens belong to M. debilis and the largest to M. ocellatus . Carapace usually light in colour, cephalic region slightly elevated and lighter than thoracic region, except in M. ocellatus , in which the cephalic region is darker. Thoracic region margins delineated in dark brown, fovea shallow and curved. Sternum triangularshaped, dark in colouration and projecting between coxae IV. AME and PME subequal in size, larger than the lateral eyes. Lateral eyes juxtaposed and on a tubercle. Clypeus height 1.0–1.4 × AME diameter. Secondary eyes with canoe-shaped tapetum. Anterior surface of chelicerae smooth ( Fig. 12B ), three prolateral and four retrolateral teeth. Labium rebordered, wider than long. Endites rebordered, longer than wide. Leg formula I> II> IV> III, femora without trichobothria, legs I and II considerably longer than the others (2.30 and 2.06 times body length, respectively). Booklung cover smooth. Abdomen oval with silver guanine patches. Spinnerets of M. ocellatus ( Fig. 9A–C ), ALS with c. 90 piriform spigots. PMS with three aciniform spigots between the cylindrical and the minor ampullate spigots, mAP nubbin present. PLS aciniform field with c. 25 spigots, aggregate spigots embracing the flagelliform, cylindrical spigots peripheral. Female copulatory openings inside grooves that run along the sides of the epigynal atrium ( Fig. 4A, B ). Copulatory ducts long, weakly sclerotized and entering the spermathecae near the fertilization duct origin region ( Fig. 4C, D ). Spermathecae also weakly sclerotized, and longer than wide. Fertilization ducts well sclerotized, long and coiled ( Fig. 12E, F ). Accessory gland openings evenly distributed on the spermathecae surface ( Fig. 4E ).

Male: Total length from 2.2 to 7.3. The smallest specimens belong to M. debilis and the largest to M. ocellatus . Abdomen oval, somatic morphology as in female ( Fig. 12G ). Anterior surface of chelicerae smooth ( Fig. 12H ). One line of epiandrous fusules anterior to a sclerotized plate, posterior plate margin enlarged ( Fig. 9E ). Pedipalp patella with one macroseta. Palpal tibia 2.8–3.2 times longer than wide with two mesal rows of trichobothria. Cymbial basal process absent (except in M. ocellatus ), distal cymbial macrosetae enlarged. Tegulum oval, longer than wide and ventrally protruding ( Fig. 3A ). Spermatic ducts coiled several times ( Fig. 12L ). Subtegulum displaced laterally ( Fig. 3E ). Embolus base longer than wide, embolus filiform. Conductor longer than wide, originating ventrally ( Fig. 3A ), attachment with the tegulum membranous.

Natural history: M. ocellatus builds individually differentiated webs on a communal framework attached to various vegetation points over running water. These spiders share a communal retreat during the night, emerging at day to build individual webs. Prey is not shared among colony members and agonistic behaviour is displayed to defend their webs from other individuals ( Buskirk, 1975a, b; Uetz & Craig, 1997). M. ebanoverde spiders span their webs on open spaces and across small rivers. The largest orb found was 92 cm in diameter ( Fig. 10D ), the support threads were heavily reinforced and longer than the orb diameter. Some spiders were found under dry leaf clusters with the legs I and II extended and in contact with the support threads. Several individuals were collected above the branches that connected the solitary webs as in some Tetragnatha species , suggesting a possible communal behaviour. The web of M. ebanoverde has c. 12 radii and a relatively dense sticky spiral ( Fig. 10D ). The shape of the web is roughly polygonal resembling that of Tetragnatha species.

Composition: Four species: Metabus ocellatus ( Keyserling, 1864) , M. debilis (O. P.- Cambridge, 1889), M. ebanoverde and M. conacyt .

Phylogenetics: Two unambiguous synapomorphies support the monophyly of Metabus : conductor apex curved apically (66-1) ( Fig. 3A ), and absence of trichobothria on the fourth femora (27-1). A cladistic analysis that includes Okileucauge species is recommended to explore Metabus generic limits further, and to test hypotheses about the evolution of the fourth femoral trichobothria complex within ‘leucaugines’. Both taxa have similar genitalia and lack trichobothria on the ectal surface of the femora IV ( Tanikawa, 2001; Zhu et al., 2003).

Distribution: Neotropical, from southern Mexico to French Guiana and Dominican Republic ( Fig. 11A ).

Nomina dubia: Metabus fuegianus ( Simon, 1902: 26) is proposed as a nomen dubium because the holotype ( Meta fugiana Simon, 1902 ) is an immature specimen.

METABUS OCELLATUS ( KEYSERLING, 1864) COMB. NOV.

( FIGS 3A–E , 4A–E , 9A–E , 11A , 12 )

Tetragnatha ocellata Keyserling, 1864: 149 pl. 7 f. 7–9 (syntypes of in BMNH, examined).

Argyroepeira ocellata Keyserling, 1893: 336 pl. 17 f. 248.

Metabus gravidus O. P.– Cambridge, 1899: 299 pl. 37 f. 7 (female holotype in BMNH, examined). - Archer 1963: 17. – Nentwig, 1993: 122 f. 141a. New synonymy.

Meta gravida (O. P.– Cambridge, 1899): F. O. P.- Cambridge, 1903: 446. – Petrunkevitch, 1925: 109 f. 19–21 (transferred back to Metabus by Archer, 1963).

Leucauge ocellata ( Keyserling, 1864) : Petrunkevitch, 1911: 356.

Diagnosis: M. ocellatus can be distinguished from other Metabus species by the following combination of characters: body length between 6.5 and 8.1 mm, cephalothorax margins rebordered with thick dark lines ( Fig. 12A, G ); epigynum atrium longer than wide, anterior margin slightly curved ( Fig. 12C, D ); cymbial basal process spine-shaped ( Fig. 12I ), conductor slightly curved and with a single distal apophysis ( Fig. 12I–K , arrow).

Description: Female from Prusia, Chiapas, Mexico (FAP0093). Habitus as in Figure 12A . Total length 8.1. Cephalothorax 3.1 long, 2.5 wide, 0.8 high. Sternum 1.1 long, 1.3 wide. Chelicerae surface smooth and same colour as the cephalothorax ( Fig. 12B ). Abdomen oval, pattern as in Figure 12A . 6.5 long, 4.4 wide, 4.7 high. AME diameter 0.20, ALE 0.20, PME 0.15, PLE 0.15. Clypeus height 1.8 × AME diameter. AME separation 0.8 × AME diameter, AME–ALE separation 1.1 × AME diameter, PME separation 1.3 × PME diameter, PME–PLE separation 1.4 × PME diameter. Leg I length 31.6, leg II 18.2, leg III 8.5, leg IV 12.9, pedipalp 3.9. Epigynum as in Figure 12C, D . Spermathecae anteriorly projected; fertilization ducts with many coils ( Fig. 12E ).

Male from Prusia, Chiapas, Mexico (FAP0092). Habitus as in Figure 12G . Chelicerae anterior surface smooth ( Fig. 12H ). Total length 7.3. Cephalothorax 3.5 long, 2.9 wide, 0.8 high. Sternum 1.4 long, 1.4 wide. Abdomen oval 4.5 long, 2.1 wide, 2.3 high. AME diameter 0.22. ALE 0.18. PME 0.18. PLE 0.16. Clypeus height 1.4 × AME diameter. AME separation 0.6 × AME diameter. AME–ALE separation 1.1 × AME diameter. PME separation 1.5 × PME diameter. PME–PLE separation 1.7 × PME diameter. Leg I length 34.0, leg II 18.1, leg III 7.6, leg IV 12.5, pedipalp. 2.9. Pedipalp tibia 2.8 times longer than wide. Pedipalp as in Figure 12I–L .

Variation: Female total length 6.5–8.1, cephalothorax length 2.8–3.1. Male total length 5.2–7.3, cephalothorax length 25–3.5.

Distribution: Southern Mexico to Colombia and French Guiana ( Fig. 11A ). This species can be found from sea level up to 2700 m elevation. Most of the specimens studied were collected at higher altitudes (1100-2700 m).

Figures

Figure 3. A–E, male genital anatomy of Metabus ocellatus. A, pedipalp ventral view. B, ectal view. C, dorsal view. D, apical view. E, mesal view. F, Leucauge venusta male pedipalp.

Figure 4. A–E, female genital anatomy of Metabus ocellatus. A, epigynum ventral view. B, caudal view. C, spermatheca dorsal view. D, fertilization and copulatory ducts. E, accessory gland openings. F, Leucauge venusta spermatheca dorsal view.

Figure 6. A, female genital anatomy of Allende patagiatus mating plug. B–C, A. longipes. B, epigynum caudal view. C, dorsal view. D–E, A. nigrohumeralis. D, fertilization and copulatory ducts. E, accessory gland openings. F, Chrysometa saladito spermatheca lateral view.

Figure 9. Spinnerets. A–E, Metabus ocellatus. A, female ALS. B, female PMS. C, female PLS. D, male PLS. G, epiandrous fusules. F–H, Allende longipes. F, female ALS. G, female PMS. H, female PLS. I–J, A. nigrohumeralis. I, male PLS. J, epiandrous fusules. K–O, Mollemeta edwardsi. K, female ALS. L, female PMS. M, female PLS. N, male PLS. O, epiandrous fusules.

Figure 10. Photos of webs: A, Allende puyehuensis. B, Chrysometa acinosa. C, Mollemeta edwardsi. D, Metabus ebanoverde. Scale lines 10 cm. Photos A–C from Puyehue National Park, Chile. Photo D from Ebano Verde Scientific Reserve, Dominican Republic. (Photos A to C by G. Hormiga).

Figure 11. Distribution maps: A, Metabus species, Central and northern South America. B, Allende species, Chile. C, Chrysometa species, Chile. D, Mollemeta edwardsi, Chile.

Figure 12. Metabus ocellatus. A, female habitus. B, female frontal view. C, epigynum ventral view. D, caudal view. E, central view cleared. F, dorsal view cleared. G, male habitus. H, male frontal view. I–L, male pedipalp. I, ectal view. J, ventral view. K, mesal view. L, cleared L. Scale bars 0.2 mm, except in habitus 1 mm.

Figure 13. Metabus debilis. A, female habitus. B, epigynum ventral view. C, caudal view. D, ventral view cleared. E, dorsal view cleared. F–G, male pedipalp. F, ectal view. G, ventral view. H, mesal view. Scale bars 0.2 mm, except in habitus 1 mm.

Figure 14. Metabus ebanoverde. A, female habitus. B, epigynum ventral view. C, caudal view. D, ventral view cleared. E, dorsal view cleared. F–G, male pedipalp. F, ectal view. G, ventral view. H, mesal view. Scale bars 0.2 mm, except in habitus 1 mm.

Figure 15. Metabus conacyt. A, female habitus. C, epigynum ventral view. C, caudal view. D, ventral view cleared. E, dorsal view cleared. F–G, male pedipalp. F, ectal view. G, ventral view. H, mesal view. Scale bars 0.2 mm, except in habitus 1 mm.