Biodiversity Data Journal :
Taxonomic Paper
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Corresponding author: Jeremy A. Miller (jeremy.miller@naturalis.nl)
Academic editor: Yasen Mutafchiev
Received: 02 Mar 2018 | Accepted: 26 Mar 2018 | Published: 03 Apr 2018
© 2018 Jeremy Miller, Christian Freund, Liselotte Rambonnet, Lianne Koets, Nadine Barth, Corné van der Linden, József Geml, Menno Schilthuizen, Richard Burger, Benoit Goossens
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Miller J, Freund C, Rambonnet L, Koets L, Barth N, van der Linden C, Geml J, Schilthuizen M, Burger R, Goossens B (2018) Dispatch from the field II: the mystery of the red and blue Opadometa male (Araneae, Tetragnathidae, Opadometa sarawakensis). Biodiversity Data Journal 6: e24777. https://doi.org/10.3897/BDJ.6.e24777
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Males of Opadometa are difficult to associate with conspecific females, and sex-matching errors may persist in the taxonomic literature. Recommended best practices for definitive sex matching in this genus suggest finding a male in the web of a female, or better yet, mating pairs.
A male Opadometa was observed hanging on a frame line of the web of a female Opadometa sarawakensis, a species for which the male was previously undescribed. This occurred during a tropical ecology field course held at the Danau Girang Field Centre in Sabah, Malaysia. A taxonomic description was completed as a course activity.
Borneo, tropical field course, spider, orb web, sexual size dimorphism
The cover of Koh and Ming’s 2014 field guide to the Spiders of Borneo was graced with a striking but at the time undescribed red and blue Opadometa species.
In 2018, students participating in a two-week tropical ecology field course offered by the Naturalis Biodiversity Center and Leiden University and hosted by the Danau Girang Field Centre (DGFC) in Sabah, Malaysia, found a mature male at the margin of the web of a red and blue Opadometa. The female spider matched Dzulhelmi et al.’s (2015) description of Opadometa sarawakensis. A survey of orb web-building spiders near DGFC found no other Opadometa species. The students resolved, along with lecturers and field station scientific staff, to describe the male and provide additional data on the female, as well as data on the ecology and behavior of the species, and submit their results in the form of a manuscript before the end of the course. This is the second contribution to spider taxonomy and natural history to be produced in this way (
Four species (plus eight subspecies) of Opadometa are currently cataloged (
Selected images from the legacy taxonomic literature depicting the male of purported Opadometa grata (according to the current
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Some authors have expressed skepticism that males and females of the two classical species are properly matched (e.g.,
Trails around the Danau Girang Field Center were surveyed for Opadometa and other medium to large orb weaving spiders during day and night searches. Webs were assessed for several characteristics: diameter, angle, number of radii, number of spirals, and height of hub from the ground. Vegetation density was assessed by counting stems at breast height in a circle around the web hub with a radius of 3 meters. Percent canopy cover above the hub was estimated using a photograph processed with ImageJ (
Specimens were fixed and stored in 70% denatured ethanol. For imaging, specimens were positioned using cotton wool in a petri dish. Images were taken with an iPhone SE illuminated with an LED head light mounted on a gooseneck clip. The iPhone was mounted on a second gooseneck clip with a magnetic base and stabilized with newspaper, tape and a tongue depressor (Fig.
The taxonomic publication featuring the original treatment of Opadometa sarawakensis was semantically enhanced with XML markup using GoldenGATE Imagine (
Opadometa sp. in
Opadometa sarawakensis Dzulhelmi & Suriyanti, in
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.
Opadometa sarawakensis Dzulhelmi & Suriyanti, 2015, left legs, prolateral view.
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.
Male Opadometa sarawakensis Dzulhelmi & Suriyanti, 2015 (DGFCW2018022300), illustrations of the palpus.
Female: For description and diagnosis of female, see
Female Opadometa sarawakensis Dzulhelmi & Suriyanti, 2015 (DGFCW2018022402), somatic morphology.
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.
Cymbial basal process (CBP) of male palp projects initially posteriorly (Fig.
Opadometa sarawakensis is known from lowland dipterocarp forest in Bako National Park, Sarawak and Maliau Basin, Sabah, Malaysia (
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.
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Web and forest characteristics | DGFCW2018022402 | DGFCW2018022611 |
Diameter (cm) | 29 | 35.7 |
Number of radii | 28 | 22 |
Number of spirals | 46 | 33 |
Angle above hub | 55 | 25 |
Angle below hub | 35 | 5 |
Hub height from ground (cm) | 150 | 153 |
Stem count (3 m radius) | 35 | 29 |
Percent canopy cover | 91 | 94 |
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.
Given the troubled history of matching sexes in Opadometa,
The evidence for matching sexes in O. sarawakensis presented here is behavioral (male at margin of female web) and faunistic (only one Opadometa species found in survey of orbweaving spiders). Another possible line of evidence would be DNA barcode sequences (
More work clearly needs to be done to sort out the distributions of the known Opadometa species. If our analysis based on the legacy of male descriptions is correct, and O. grata is limited to New Guinea (and possibly points East) while O. fastigata is found further West, this should clear up some of the confusion regarding the distribution, sex matching, and anatomical features found in this genus.
Joseph Koh and Fernando Alvarez Padilla provided constructive comments on the manuscript. Joseph Koh generously shared unpublished data and images. Thanks to Kalsum Yusah and Bakhtiar Effendi Yahya for facilitating the deposition of specimens at the Universiti Malaysia Sabah's Institute for Tropical Biology and Conservation, Borneensis (BORN). We thank the Naturalis Biodiversity Center and Leiden University for their support of the Tropical Field Course. Donat Agosti provided technical support with the markup of legacy taxonomic literature. Thanks to course participants Robin Labrujere, Sophie Maycock, Marta Ramirez, Tim Rietbergen, Serena Rivero, Annabelle de Vries (MSc students at Leiden University), Laura Verbeek (MSc student at Wageningen University), Isabela Pombo Geertsma (MSc student at the University of Amsterdam), Natasha Zulaikha (BSc student at University of Nottingham, Malaysia), Amanda Shia Kang Ping (research officer at HUTAN - Kinabatangan Orang-utan Conservation Programme), and Dr. Bakhtiar Effendi Yahya (Universiti Malaysia Sabah). Heartfelt thanks also to DGFC-Cardiff University Professional Training Year students Luke Davies, Max Lawson, Alex Rose, Aaron Sambrook, Jasmine Walker, Cardiff University PhD student Juan Manuel Aguilar Leon, University of California at Berkeley PhD student David Kurz, DGFC volunteer Layla Spicer, DGFC veterinarian Dr. Navaneetha Roopan, DGFC manager Peter Asun, and Leiden University MSc student and Tropical Field Course alumnus Sophie van der Hart. Thanks to editor Yasen Mutafchiev, Lyubomir Penev, and the Pensoft team for their extraordinary help with this manuscript. Special thanks to all the staff and families at the Danau Girang Field Centre.