Opadometa sarawakensis Dzulhelmi & Suriyanti, 2015

Miller, Jeremy A., Freund, Christian, Rambonnet, Liselotte, Koets, Lianne, Barth, Nadine, van der Linden, Corne, Geml, Jozsef, Schilthuizen, Menno, Burger, Richard & Goossens, Benoit, 2018, Dispatch from the field II: the mystery of the red and blue Opadometa male (Araneae, Tetragnathidae, Opadometasarawakensis), Biodiversity Data Journal 6, pp. 24777-24777 : 24777

Opadometa sarawakensis Dzulhelmi & Suriyanti, 2015

Opadometa sp. in Koh and Ming 2014: p. 259-260.

Opadometa sarawakensis Dzulhelmi & Suriyanti, in Dzulhelmi et al. 2015: p. 102-103, figs 5-13. (Link to treatment on Plazi)

Materials

Type status: Other material. Occurrence: catalogNumber: DGFCW2018022300 ; recordedBy: Jeremy Miller and Christian Freund; individualCount: 2; sex: 1 male, 1 female; lifeStage: adult; Taxon: scientificName: Opadometasarawakensis Dzulhelmi & Suriyanti, 2015; Location: country: Malaysia; stateProvince: Sabah; locality: Danau Girang Field Centre trails ; verbatimElevation: 23 m; decimalLatitude: 5.41619; decimalLongitude: 118.0426; Event: eventDate: 2018-02-23; Record Level: institutionID: Universiti Malaysia Sabah; collectionID: Institute for Tropical Biology and Conservation, Borneensis; institutionCode: UMS; collectionCode: BORN; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: catalogNumber: DGFCW2018022402 ; recordedBy: Jeremy Miller, Christian Freund, Liselotte Rambonnet, Lianne Koets, Natasha Zulaikha, and Jozsef Geml; individualCount: 1; sex: female; lifeStage: adult; Taxon: scientificName: Opadometasarawakensis Dzulhelmi & Suriyanti, 2015; Location: country: Malaysia; stateProvince: Sabah; locality: Danau Girang Field Centre trails ; verbatimElevation: 23 m; decimalLatitude: 5.40999; decimalLongitude: 118.04204; Event: eventDate: 2018-02-24; Record Level: institutionID: Universiti Malaysia Sabah; collectionID: Institute for Tropical Biology and Conservation, Borneensis; institutionCode: UMS; collectionCode: BORN; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: catalogNumber: DGFCW2018022611 ; recordedBy: Jeremy Miller and Christian Freund; individualCount: 1; sex: female; lifeStage: adult; Taxon: scientificName: Opadometasarawakensis Dzulhelmi & Suriyanti, 2015; Location: country: Malaysia; stateProvince: Sabah; locality: Danau Girang Field Centre trails ; verbatimElevation: 22 m; decimalLatitude: 5.41623; decimalLongitude: 118.04273; Event: eventDate: 2018-02-26; Record Level: institutionID: Universiti Malaysia Sabah; collectionID: Institute for Tropical Biology and Conservation, Borneensis; institutionCode: UMS; collectionCode: BORN; basisOfRecord: PreservedSpecimen

Description

Male: from Sabah, Malaysia (DGFCW2018022300). Prosoma uniform orange. Eight eyes in two rows, with the medians closer together than to the laterals; posterior median eyes oriented slightly toward the front; lateral eyes touching. Sternum dusky orange, darker posteriorly. Chelicerae orange, enlarged, diverging distally, armed in front and basolaterally with strong macrosetae; macrosetae absent from frontal-basal region (Fig. 3); with 2 promarginal and 2 smaller retromarginal teeth. Legs without macrosetae; femur of legs I and IV orange, distal segments darker; legs II and III overall dark (Fig. 4a); femur IV with row of very long prolateral trichobothria along entire length (Fig. 3a, b).

Abdomen gray dorsally with silvery patches and an anteriodorsal dark spot, black posteriorly and ventrally with two posteriolateral and one ventral orange spot, with a small anteriolateral black spot and a larger posteriolateral black spot, which joins with the black ventral marking.

Palpal trochanter, femur, and tibia very long (Fig. 3c). Cymbial basal process projects posteriorly, tip curved retrolaterally. Paracymbiuim (P) thick basally with curved distal projection. Tegulum (T) somewhat bulbous. Conductor (C) envelops embolus, thick basally, tapering through spiral path, with basal secondary apophysis (CSA) (Fig. 5).

Female: For description and diagnosis of female, see Dzulhelmi et al. (2015) (also available on Plazi’s treatmentBank here). Our observations of females from DGFC largely agree with the description in Dzulhelmi et al. (2015) (Figs 4b, 6, 7). We would only add that we observed a light distal brush on tibia II in addition to the heavy brushes found on tibiae I and IV (Figs 4b, 6).

Measurements

Male (DGFCW2018022300): Total length 2.8; carapace length 1.4, width 0.9; abdomen length 1.4, width 0.9, height 0.9.

Female (DGFCW2018022300): Total length 6.2; carapace length 3.6, width 2.4; abdomen length 5.0, width 2.8, height 2.7.

Female (DGFCW2018022402): Total length 8.1; carapace length 3.4, width 2.7; abdomen length 7.6, width 4.2, height 4.2.

Female (DGFCW2018022611): Total length 5.0; carapace length 3.5, width 2.1; abdomen length 4.4, width 2.6, height 2.6.

Diagnosis

Cymbial basal process (CBP) of male palp projects initially posteriorly (Fig. 5c), distinguishing it from males illustrated from New Guinea and New Hebrides (presumably true O. grata ; Fig. 1a, b, c, d, g) in which the CBP extends almost retrolaterally from the cymbium before curving distally; distinguished from males illustrated from further West in Southeast Asia (presumably true O. fastigata ) by the length of the CBP, which is shorter and more gradually curved in O. sarawakensis (Fig. 5c) than in O. fastigata (Fig. 1e, f, h). Opadometa males further distinguished by the base of the chelicerae, which project forward with large distally oriented macrosetae in O. fastigata (Fig. 1j, k); absent in the male of O. sarawakensis (Fig. 3c, d), which is naked at the base of the chelicerae, and also apparently absent in O. grata , although the lateral view of male Opadometa from New Guinea and points East has never been illustrated (but see Fig. 1i). The male chelicerae of O. sarawakensis (Fig. 3d) and O. grata (Fig. 1i) are divergent distally, not divergent in O. fastigata . Males of O. sarawakensis may be further distinguished from those of O. fastigata by the orientation of the posterior median eyes (Fig. 3c), which are set further back in O. fastigata and are oriented slightly posteriorly in lateral view (Fig. 1k). The secondary conductor apophysis (SCA) in O. sarawakensis (Fig. 5a, b, d) appears to be shorter than in either O. grata (Fig. 1b, c, g) or O. fastigata (Fig. 1e, h). At 2.8, the total length of the male of O. sarawakensis appears to be intermediate between O. fastigata (1.86-2.06; Ono 2011) and O. grata (3.2-3.5; Kulczyński 1911, Chrysanthus 1963).

Distribution

Opadometa sarawakensis is known from lowland dipterocarp forest in Bako National Park, Sarawak and Maliau Basin, Sabah, Malaysia ( Dzulhelmi et al. 2015), Danau Girang Field Centre, Sabah, Malaysia, and wooded areas and disturbed forest in Brunei ( Koh and Ming 2014).

Ecology

Trails around the Danau Girang Field Center were surveyed for Opadometa and other medium to large orb weaving spiders during day and night searches. Opadometa sarawakensis was the largest orb-weaver encountered after Nephila (2 juveniles in the 10-12 mm size range; no adult Nephila were encountered during the survey, although they have been seen at other times); no other Opadometa species were encountered. Opadometa sarawakensis build open-hub webs with an inflection point so that the top half is more steeply inclined than the bottom half. The specific angles were quite different between the two webs measured (Fig. 8, Table 1). Webs are moderately open with relatively few radii and spirals, especially compared to the dense webs of Nephila . All Opadometa we encountered were found during the day with spiders either at the hub or web margin; night searches failed to discover any additional Opadometa . Despite dedicated searches over the few days and nights available, Opadometa seem to be quite rare in the forest of Danau Girang in February 2018. The Danau Girang Field Center is located within the Lower Kinabatangan Wildlife Sanctuary, a narrow network of lowland riparian and riverine forest patches and corridors along the Kinabatangan River, surrounded by oil palm plantations.

Sexual size dimorphism

Sexual size dimorphism in Opadometa is extreme. The male-female pair found together (DGFCW2018022300) have a female/male size ratio of 2.2, meaning the female is more than twice the total length of the male.