Dermatohomoeus maliauensis Schilthuizen, Otani & Seip

Schilthuizen, Menno, Seip, Lilian A, Otani, Sean, Suhaimi, Jadda & Njunjic, Iva, 2017, Three new minute leaf litter beetles discovered by citizen scientists in Maliau Basin, Malaysian Borneo (Coleoptera: Leiodidae, Chrysomelidae), Biodiversity Data Journal 5, pp. 21947-21947 : 21947

Dermatohomoeus maliauensis Schilthuizen, Otani & Seip sp. n.

Materials

Type status: Holotype. Occurrence: recordedBy: A.Y.C. Chung; Momim Binti; J.L. Yukang; individualCount: 1; sex: male; lifeStage: adult; preparations: card-mounted; head, legs and genitalia dissected; disposition: in collection; Taxon: scientificName: Dermatohomoeusmaliauensis; order: Coleoptera; family: Leiodidae; genus: Dermatohomoeus; specificEpithet: maliauensis; taxonRank: species; scientificNameAuthorship: Schilthuizen, Otani & Seip; Location: continent: Asia; island: Borneo; country: Malaysia; stateProvince: Sabah; municipality: Tongod; locality: Maliau Basin, along the Seraya Trail and the Agathis Trail near the Ginseng Camp ; verbatimElevation: 670 m; Event: samplingProtocol: Winkler extraction of leaf litter; samplingEffort: 20 1-square-m units of leaf litter and soil; eventDate: 2005-03-06 /12; fieldNumber: S2; Record Level: institutionID: Forest Research Centre; institutionCode: FRCS; basisOfRecord: PreservedSpecimen Type status: Paratype. Occurrence: recordedBy: A.Y.C. Chung; Momin Binti; J.L. Yukang; individualCount: 1; sex: male; lifeStage: adult; preparations: card-mounted; head, legs, and genitalia dissected; coated for SEM; disposition: in collection; Taxon: scientificName: Dermatohomoeusmaliauensis; order: Coleoptera; family: Leiodidae; genus: Dermatohomoeus; specificEpithet: maliauensis; taxonRank: species; scientificNameAuthorship: Schilthuizen, Otani & Seip; Location: continent: Asia; island: Borneo; country: Malaysia; stateProvince: Sabah; municipality: Tongod; locality: Maliau Basin, along the Seraya Trail and the Agathis Trail near the Ginseng Camp ; verbatimElevation: 670 m; Event: samplingProtocol: Winkler extraction of leaf litter; samplingEffort: 20 1-square-m units of leaf litter and soil; eventDate: 2005-03-06 /12; fieldNumber: A9; Record Level: institutionID: Forest Research Centre; institutionCode: FRCS; basisOfRecord: PreservedSpecimen Type status: Paratype. Occurrence: catalogNumber: BOR/COL/14092 ; recordedBy: I. Njunjić; M. Schilthuizen; Taxon Expeditions; individualCount: 1; sex: female; lifeStage: adult; preparations: card-mounted; disposition: in collection; Taxon: scientificName: Dermatohomoeusmaliauensis; order: Coleoptera; family: Leiodidae; genus: Dermatohomoeus; specificEpithet: maliauensis; taxonRank: species; scientificNameAuthorship: Schilthuizen, Otani & Seip; Location: continent: Asia; island: Borneo; country: Malaysia; stateProvince: Sabah; municipality: Tongod; locality: Maliau Basin, near Studies Centre, along Seraya Trail, where stream enters the river ; verbatimElevation: 260 m; verbatimCoordinateSystem: decimal degrees; decimalLatitude: 4.7389; decimalLongitude: 116.9696; Event: samplingProtocol: Winkler, litter from basis of trees; samplingEffort: c. 15 l of leaf litter; eventDate: 2017-09-27; fieldNumber: TxEx-MBSC1wb; Record Level: institutionID: Universiti Malaysia Sabah; collectionID: Institute for Tropical Biology and Conservation, BORNEENSIS; institutionCode: UMS; collectionCode: BORN; basisOfRecord: PreservedSpecimen Type status: Paratype. Occurrence: catalogNumber: BOR/COL/14093 ; recordedBy: I. Njunjić; M. Schilthuizen; Taxon Expeditions; individualCount: 1; sex: female; lifeStage: adult; preparations: card-mounted; disposition: in collection; Taxon: scientificName: Dermatohomoeusmaliauensis; order: Coleoptera; family: Leiodidae; genus: Dermatohomoeus; specificEpithet: maliauensis; taxonRank: species; scientificNameAuthorship: Schilthuizen, Otani & Seip; Location: continent: Asia; island: Borneo; country: Malaysia; stateProvince: Sabah; municipality: Tongod; locality: Maliau Basin, near Studies Centre, along Seraya Trail, where stream enters the river ; verbatimElevation: 260 m; verbatimCoordinateSystem: decimal degrees; decimalLatitude: 4.7389; decimalLongitude: 116.9696; Event: samplingProtocol: Winkler, litter from basis of trees; samplingEffort: c. 15 l of leaf litter; eventDate: 2017-09-27; fieldNumber: TxEx-MBSC1wb; Record Level: institutionID: Universiti Malaysia Sabah; collectionID: Institute for Tropical Biology and Conservation, BORNEENSIS; institutionCode: UMS; collectionCode: BORN; basisOfRecord: PreservedSpecimen

Description

Length of body c. 1.4 mm (Fig. 6). Oval, 1.45x longer than wide, greatest width at the shoulders. Pronotum 2.0x wider than the head. Winged. Reddish brown, with yellow legs and antennae. Eyes large. Antennae slender, antennomere VII 1.5x as long as wide. Pronotal posterior angle not drawn out, only a very faint convex curve next to the rounded angles. Elytra sparsely pubescent, with distinct punctuation, here and there arranged into longitudinal rows. All punctures on the elytra connected by microreticulation.

Head: Eyes large, each with an estimated 40-50 ommatidia. Ratio of horizontal width of eye (measured in dorsal view and perpendicular to the longitudinal axis of the head) to distance between eyes: 1:4.4. A thin supraorbicular groove runs along the inner margin of the eyes and over the antennal insertion. Length of antennomere III 0.7 times the length of antennomere II. Antennomere IX slightly narrower than antennomere X. Antennomeres X and XI of equal width (Fig. 9). Punctuation (when viewed at 50x magnification) distinct, individual punctures spaced by 3-5 times their diameter (Fig. 7a). No microreticulation visible.

Pronotum: Broadest at the base. Pronotal posterior angle rounded, not drawn out, the pronotal basis near the posterior angle with only a very faint convex curve. Pronotum smooth, glossy, hairless, without any microreticulation but with very fine and sparse punctuation, punctures spaced at 3-5 times their diameter, nearly invisible at 50x magnification (Fig. 7b). A fine, continuous margin runs along the lateral and anterior margin.

Scutellum: Microsculptured as on pronotum.

Elytra: Broadest at the shoulders, roundly curved to apex. Elytra with distinct punctuation. Punctures separated by ca. 3x their own diameter, here and there arranged into longitudinal rows. All punctures connected by jagged horizontal striae that are spaced ca. 20 µm apart. Elytra with sparse hairs emerging from the punctures; these hairs are short, about as long as the width of antennomere III (Fig. 7c).

Aedeagus: Median lobe in dorsal view gradually narrowing towards the apex, terminally shaped into a broad, mushroom-shaped plate that is twice as wide as long (Fig. 8a). The apical angles of the ventral piece can be seen emerging on either side of this plate. Parameres reach the level of the basis of this plate. The dorsal surface of the terminal one-third of the median lobe is covered in coarse granules (only visible with scanning electron microscopy). In lateral view (Fig. 8b), the median lobe is basally strongly curved ventrad, but in the terminal one-third curved gently dorsad and flattened into the shape of a thin wedge.

Spermatheca: Not studied.

Diagnosis

As pointed out by Švec (2009), Dermatohomoeus species are often very similar externally and the male genitalia offer the only certain identification. The shape of the aedeagus separates D. maliauensis sp. n. from nearly all Dermatohomoeus species for which the male genitalia are known. One species with similar male genitalia is the widespread D. portevini (Champion, 1923). The size of the body and eyes, the microsculpture of the dorsum, and the shape of the pronotum indeed place the new species in the close vicinity of D. portevini . However, in D. portevini the median lobe of the aedeagus displays a bulge directly basal of the terminal plate ( Daffner 1988), which is not the case in D. maliauensis sp. n. Also, the 7th antennomere is broader in D. maliauensis. A second species with a similar aedeagus is D. bidentatus Švec & Cooter 2015 from Yunnan, China which, however, is characterised by the two lateral teeth at the terminus of the median lobe; moreover, it is nearly twice as large ( Švec and Cooter 2016). Another species that appears to possess similar external characteristics is D. terrenus (Hisamatsu 1985) from Korea and Japan. This species is thought to be parthenogenetic, as no males are known ( Park and Ahn 2007). D. terrenus differs from D. maliauensis sp. n. in having an 11th antennomere that is distinctly broader than the 10th and by transverse microsculpture on the pronotum, which is absent in D. maliauensis sp. n.

Etymology

Named after Maliau Basin Conservation Area in Sabah, Malaysian Borneo. This 30-km-wide circular depression, covered with montane forest on poor soils and surrounded by steep sandstone cliffs, is known as "Sabah's Lost World". It is the focal area for the Borneo work of Taxon Expeditions. The species epithet was selected during a naming ceremony in Maliau Basin Studies Centre on 6 October 2017, in which expedition participants as well as a large number of field centre staff and porters took part. As far as the authors are aware, this is the third animal species named for this under-explored area ( Disney 2016, Buhl 2009).

Distribution

Known only from two locations in the valley where the Maliau river flows out of Maliau Basin, located at 260 m elevation (Maliau Basin Studies Centre) and 670 m elevation (Ginseng Camp).