Glomeridesmus siamensis sp. nov.

Wesener, Thomas, Wongthamwanich, Nattarin & Moritz, Leif, 2021, Description of the first species of Glomeridesmida from Thailand (Diplopoda, Glomeridesmida, Glomeridesmidae), ZooKeys 1024, pp. 137-156 : 137

publication ID	https://dx.doi.org/10.3897/zookeys.1024.63678
publication LSID	lsid:zoobank.org:pub:EF866ABA-11B1-4C18-B269-6B8DD97EC83B
persistent identifier	https://treatment.plazi.org/id/2AB443F1-DFF4-5118-AE52-60106B9D2694
treatment provided by	ZooKeys by Pensoft
scientific name	Glomeridesmus siamensis sp. nov.
status

Treatment

Glomeridesmus siamensis sp. nov. Figures 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7

Material examined.

Holotype: 1 M, ZCSWU Myr D 000011 ( THAI11 ), Thailand, Krabi Province, N. of Krabi Town, western aspect of Tiger Cave temple (Wat Tham Suea), overgrown rocks next to rubber plantation, 08°07'23.8"N, 098°55'18.9"E. leg. 27.VII.2017, Wesener , Wongthamwanich , Nawanetiwong , Moritz. GoogleMaps

Paratypes: 1 immature M, ZFMK MYR 10301 View Materials , same data as holotype; 1 F, ZFMK MYR 10302 View Materials GoogleMaps ; 5 juveniles, ZCSWU Myr D 000012-16 ; 4 juveniles, ZFMK MYR10303-10306 , same data as holotype GoogleMaps .

Etymology.

Siamensis, noun in apposition, after the type locality in Thailand.

Diagnosis.

Small (5-7 mm) dark grey glomeridesmid with white legs (Fig. 1A, B View Figure 1 ). Antennae short (Figs 1A, B View Figure 1 , 2A-C View Figure 2 ). Coxal pouches starting at leg 9, all walking legs with apical spines and paronychium (Figs 3A-F View Figure 3 , 4A-C View Figure 4 ). Last pleurite posterior margin well-rounded in female. Male sensory leg, podomere 1 with a conspicuous excavation on its mesal margin, not known from other Glomeridesmus (Fig. 3G, H View Figure 3 ). Male telopods unique: Inner horns slender, widely separated, a character only shared with G. indus Carl, 1942. Telopod, podomere 2 rectangular, with a unique, strongly elongated and slender process protruding between movable (podomere 4) and immovable finger (process of podomere 3) (Fig. 5A, B View Figure 5 ). Podomere 3 with a slender immovable projection and podomere 4 forming a long movable finger. Immovable finger long and visibly laterally in G. siamensis sp. nov. (Figs 1C View Figure 1 , 5A, B View Figure 5 ), in contrast to South American species such as G. spelaeus Iniesta & Wesener, 2012 and G. arcostriatus Mauriès, 2020, where it is hidden in lateral view. Lamellae linguales of gnathochilarium fused with one another, but with a transverse suture towards mentum, lamellae with two central setae at margin and two lateral setae more posteriorly in G. siamensis sp. nov. (Fig. 6A View Figure 6 ), while all four setae are marginal in G. spelaeus (compare Iniesta et al. 2012).

Description.

Based on male holotype ( ZCSWU Myr D 000011) and female paratype ( ZFMK MYR 10302 View Materials ) .

Measurements: Largest adult female (20+ AS tergites, 35+1 leg pairs): length: ~ 6 mm; width (midbody): 1.0 mm. Male (19+ AS tergites, 33+1+ T leg pairs, holotype male): length: ~ 5 mm; width (midbody): 0.9 mm; immature (?) male (19+ AS tergites, 32+1+ T,): length: ~ 4 mm, width: 0.8 mm.

Colour in ethanol: Tergites and dorsal side of head grayish-brown (Fig. 1 View Figure 1 ), legs, antennae and ventral side whitish (Fig. 1A, B View Figure 1 ).

Head: General shape typical for the family (Figs 1D, E View Figure 1 , 2C View Figure 2 ). Epicranium glabrous; frons, clypeus and labrum with several isolated setae (Fig. 2C View Figure 2 ). Antennae widely separated by a distance slightly longer than twice width of first antennomere (Fig. 1A, E View Figure 1 ). Antennae and organ of Tömösváry both surrounded by individual cuticular rims, both on an elevated plateau (Fig. 2D View Figure 2 ). Genae (area below the antennae) almost non-existent, with incisura lateralis. Undivided basal joint of mandible large and visible in dorsal view.

Antennae consisting of seven joints, each covered with numerous setae. Size of joints 1 = 2 = 3 = 4 = 5> 6 (Fig. 2A View Figure 2 ). Apical disc carrying four long apical cones; sensilla basiconica apparently absent (Fig. 2B View Figure 2 ).

Tömösváry organs as large as antennal base, of well-rounded oval shape, interior covered by a sclerotized plate; surrounded by cuticular rim and several very short setae (Fig. 2C, D View Figure 2 ).

Gnathochilarium with very broad gula (hypostoma). Cardines very small, separated from basal part of gnathochilarium. Proximal fourth of mentum towards gula distinctly elevated, transverse suture visible between mentum and lamellae linguales. Lamellae linguales fused to one another, not separated by a longitudinal suture, apically with four long setae, central pair at apical margin, lateral two setae located more posteriorly. Whole surface of gnathochilarium covered with few, isolated setae. Stipites laterally without sclerotized ledge. Stipites apically with 2 extra-long setae (Fig. 6A View Figure 6 ). Stipites lateral palpi slender, carrying 4 slender sensory cones; inner palpi very wide, carrying 12-15 long, tube-shaped sensory cones interspersed between long cuticular fibres (Fig. 6B View Figure 6 ). Central pads (modified central palpi of lamellae linguales) large, mesally pointing towards and touching one another, in ventral view covered with numerous long, tube-shaped sensory cones and long cuticular fibers (Fig. 6B View Figure 6 ). Basally of central pads on endochilarium with two parallel rows of 9 sensory cones along median furrow (Fig. 6C View Figure 6 ).

Mandible: Basal joint massive, undivided (Figs 1D, E View Figure 1 , 2C View Figure 2 ). Apical joint (mandibular gnathal lobe) damaged during preparation, but with long slender external tooth and a long condylus. Inner tooth 4-combed. Seven rows of pectinate lamellae, large intermediate area covered by scale-like spines. Additional intermediate area located at a lower level next to molar plate with more elongated spine-plates. Molar plate plane, without indentations or grooves, margins entirely surrounded by thick membranous fringes (Fig. 6D View Figure 6 ).

Trunk: Collum (tergite 1) wider than head, shape similar to following tergites (Fig. 1A View Figure 1 ).

Tergites 2-19 (20) very thin, difficult to distinguish from one another. Width from tergite 1 to 8 gradually increasing, then decreasing to last tergite (Figs 1A, B View Figure 1 , 7A View Figure 7 ). Each tergite bearing 6-8 longitudinal striae. Distances between striae increasing towards posterior margin. Surface of tergites with sparse isolated setae (Fig. 7A, B View Figure 7 ). Tergite 11 onwards posterior-lateral edge pronounced into a sharp-edged tip, becoming a longer and spine-like process at tergite 17. Limbus (posterior margin of tergite) smooth, without any structures. Endotergum (underside of posterior margin of tergite) smooth area without any specific structures (Fig. 7C View Figure 7 ). Posterior margin of tergite 19 and 20 with several short teeth (Fig. 7D View Figure 7 )

Pleurites of rectangular shape, posterior margin overlapping first third of subsequent pleurite (Fig. 7B View Figure 7 ), wider than long. Pleurites similar to one another, but last pleurite on posterior margin with a well-rounded central indentation, providing space for the movements of the last leg.

Legs: In all except first coxae fused with stigmatic plates (typical for Glomeridesmida , Wesener et al. 2014) (Figs 3A-H View Figure 3 , 4A-C View Figure 4 ). Starting at coxo-stigmatic plate 9 (male holotype) or 11 (female paratype), every second coxa up to pair 21 (male) or 25 (female) apically with an eversible coxal pouch posteriorly of prefemur (Fig. 4B View Figure 4 ).

Leg-pair 1 with a well-rounded elliptical sternite visible in oral view. Femur 1.5 × longer than wide, tarsus slender and elongated,>7 times longer than wide (Fig. 3A View Figure 3 ). Apical half of tarsus without any spines or setae, except 1 or 2 apical spines, claw and paronychium (Fig. 3A, B View Figure 3 ).

Leg 2 (male) femur 1.7, tarsus>10 × longer than wide (Fig. 3C View Figure 3 ). Tarsus in apical half without any spines or setae except for single apical spine, claw and paronychium (Fig. 3D View Figure 3 ).

Legs 3-32 similar to first legs, e.g. midbody leg femur 1.8, tarsus>7 times longer than wide. Tarsus with 1 or 2 apical spines, claw and paronychium (Fig. 3D View Figure 3 ).

Penultimate leg with coxosternite narrow, with stigma opening and sternal part located below (instead of lateral to) of coxal part. Femur slightly longer than prefemur, 1.3 × longer than wide, tarsus shorter,>7 × longer than wide, apically with claw, apical spine and paronychium (Fig. 3E, F View Figure 3 ).

Ultimate leg pair (sensory leg) modified, consisting of a free large sternite, fused coxa-stigmatic plates plus 3 podomeres (Fig. 3G View Figure 3 ). First podomere with a conspicuous mesal bend. Last two podomeres extending postero-laterally (confused with telopod by pre-1941 authors). Podomere 3 apically with a large, long spine, longer than the podomere (Fig. 3H View Figure 3 ). Both legs widely separated from one another, connected by large sternite. Coxa-stigmatic plates large, almost as long as all 3 podomeres combined (Fig. 3G View Figure 3 ).

Anal shield: glabrous, with a well-rounded edge. Subanal plate located behind last pair of legs, large and hyaline.

Sexual characters: Female: second coxae on posterior side with prominent ovipositors protruding back to leg pair 5. Coxa protruding mesally as a short lobe. Ovipositors basally supported by an undivided plate (sternite?) (Fig. 4C View Figure 4 ). Ovipositor with a basal part consisting of 21 or 22 segments of (eversible?) half-rings, each carrying isolated setae in a regular distance to each other. Half rings anteriorly and posteriorly interrupted by two different, much slender tubes, also consisting of half-rings, running along the whole length of the ovipositor. Apical part of ovipositor with opening surrounded by four larger plates, each arising out of a tube of rings. All four plates covered by longer setae (Fig. 4D View Figure 4 ).

Male: second coxa with gonopore located mesally (Fig. 3C View Figure 3 ). Gonopore flanked by two sclerotized, plates resembling an open bivalve shell. Apical part of both plates with 2 or 3 longer setae (Fig. 5C View Figure 5 ).

Male telopod consisting of syncoxite with inner horns and 4 podomeres (Figs 1C View Figure 1 , 5A, D View Figure 5 ). Syncoxite covering basal podomeres laterally and in anterior view, medially rising into a smooth glabrous process. Process apically with two long inner horns; horns basally fused, completely separating more apically, diverging and running parallel to one another. Each horn apically slightly widening and spoon-shaped. Whole surface of horns sparsely covered by isolated, minute setae (Fig. 5D View Figure 5 ).

Telopod podomere 1 largest and most massive.

Podomere 2 wide, rectangular, apically with a large membranous area and mesally with a long and slender process. Membranous area well rounded, consisting of several inverse membranous folds. Slender process strongly elongated, as long as podomere 2, protruding between movable and immovable finger, inner surface excavated (Fig. 5A, B View Figure 5 ).

Podomere 3 long and slender, only 1/3 of width of podomere 2, inserting laterally on podomere 2. Posterior-lateral aspect of podomere 3 in apical part with slender, finger-shaped and well-rounded process called immobile finger, which makes up ca. half the length of podomere 3, inner surface of immobile finger excavated. Length of podomere 3, without immobile finger, 2 times longer than wide, with few isolated setae at margins in apical half (Fig. 5A, B View Figure 5 ). Immobile finger protruding up to 3/4 of length of podomere 4, called mobile finger (Fig. 5A, B View Figure 5 ).

Mobile finger (podomere 4), articulated to podomere 3 at base of immovable finger (Fig. 5A, B View Figure 5 ), slender and glabrous, 5 × longer than wide, posteriorly with an excavated area; at apex with a single long spine reaching 2/3 of length of immobile finger

Immature male.

The immature male has the same number of tergites, but one walking leg pair less than the mature male. The immature male is almost 1/3 shorter than the mature male. Coxal pouches starting at leg pair 9 as in mature male. Last pleurite with small well-rounded indentation at posterior margin. Telopod only slightly different from mature male: process of podomere 2 shorter, podomere 3 and 4 slenderer, immobile finger almost protruding up to apical end of movable finger.

Ecology.

All specimens were collected by hand in the morning during rainy season in Krabi province, the second reported area for Glomeridesmida in Thailand (the first in Shelley 2011). They were found in a karst landscape covered with evergreen forest (Fig. 8A, B View Figure 8 ) in soils at a depth of 10-20 mm near horizontal roots on a partially overgrown rock. Despite numerous attempts, no Glomeridesmus was discovered outside the less than 30 × 30 centimeter of habitat, showing that their distribution might be dependent on some unknown microhabitat requirements. The habitat was a flat area on a western aspect (Fig. 8C View Figure 8 ). Average air temperature and relative humidity during observation was approximately 29 °C and 85%, respectively. The specimens were fast moving (at least as fast as Chordeumatida ), capable of bending their flexible body 180° to quickly change directions. Furthermore, the male holotype carried an ‘amphoromorph’ fungus on one of its legs (Fig. 3B View Figure 3 ).

Additional locality data of unidentified Glomeridesmus from Thailand.

2 imm. F; NHMD ; Chiang Mai Province, Doi Suthep N. P.; Konthathan (Montha Than waterfall?); 600-700 m; leg. NHMD, 30.ix.1981 . 1 imm. F.; NHMD ; Chiang Mai Province, Doi Suthep N. P.; Montha Than; 600-700 m; leg. NHMD, 26.ix.1981 . 1 juv.; NHMD ; Doi Suthep, 1150 m; Lok. 3a; 29/9.1958; Birgit Degerbøl leg. Zool. Mus. Kbh. 1/7 59. Doi Suthep, 11-1200 m . 1 juv. (16 pairs of legs); NHMD ; Doi Suthep , No. Kasens DSal; 14/9.1959, Birgit Degerbøl leg., Zool. Mus. Kbh. 1/7 59. 1 mature F (with nemertini parasite); NHMD ; Doi Suthep, No. sigteprøve (= sifting sample) 3a?; 2/8.1958, Birgit Degerbøl leg., Zool. Mus. Kbh. 1/7 59 . 1 juv. (8 pairs of legs); NHMD ; Doi Suthep , 1150 m; No. Lok. 3a; 29/9.1958; Birgit Degerbøl leg., Zool. Mus. Kbh. 1/7 59 .