Orthomorpha rotundicollis (Attems, 1937)

Likhitrakarn, Natdanai, Golovatch, Sergei I., Semenyuk, Irina, Efeykin, Boris D. & Panha, Somsak, 2019, Review of the millipede genus Orthomorpha Bollman, 1893 (Diplopoda, Polydesmida, Paradoxosomatidae) in Vietnam, with several new records and descriptions of two new species, ZooKeys 898, pp. 121-158 : 121

Orthomorpha rotundicollis (Attems, 1937) Figs 3 , 4 , 5

Pratinus rotundicollis Attems, 1937: 118 (D).

Pratinus rotundicollis - Attems 1938: 217 (D); 1953: 179 (R).

Pratinus tuberculatus Attems, 1937: 119 (D). Synonymized by Likhitrakarn et al. (2011).

Pratinus tuberculatus - Attems 1938: 219 (D).

Orthomorpha rotundicollis - Jeekel 1963: 265 (M); 1964: 361 (M, D); 1968: 56 (M); Hoffman 1973: 363 (M); 1977: 700 (M); Golovatch 1998: 42 (M, D); Enghoff et al. 2004: 38 (M, R); Likhitrakarn et al. 2011: 61 (D).

Orthomorpha tuberculata - Jeekel 1963: 265 (M); 1964: 361 (M, D); 1968: 56 (M); Hoffman 1977: 700 (M); Golovatch 1998: 42 (M, D); Enghoff et al. 2004: 39 (M, R).

Old records.

Vietnam, Lam Dong Province, Lang Biang Mountain, Tram Hanh (=Arbre-Broye), 1,500 m; Dalat, 1,500 ( Attems 1937, 1938); Laos, Xiangkhoang Province, Xiangkhoang Plateau, Xiang Kuang ( Attems 1953).

New material examined.

1 ♂ (yellow morph, ZMUM Rd 4215), Vietnam, Dong Nai Province, Cat Tien National Park, 11°25'37"N, 107°25'39"E, 140 m a.s.l., lowland monsoon tropical forest with dominating Lagerstroemia calyculata and Afzelia xylocarpa , on bush, daytime, 7.X.2016; 1 ♂ (yellow morph, ZMUM Rd 4217), same locality, under log, daytime, 6.V.2015; 1 ♂ (red morph, ZMUM Rd 4218), same locality, on forest floor, daytime, 10.V.2015; 1 ♂ (red morph, ZMUM Rd 4221), same locality, on bush, daytime, 3.VI.2015; 1 ♂ (red morph, ZMUM Rd 4222), same locality, on tree trunk, night time, 29.06.2015; 1 ♂ (red morph, ZMUM), same locality, hilly area with mainly bamboo forest, 11°22'50"N, 107°13'16"E, 110 m a.s.l., in leaf litter, daytime, 29.VI.2017; 1 ♂ (red morph, ZMUM), same locality but light open forest with highly dominating L. calyculata , 11°24'51"N, 107°22'34"E, 130 m a.s.l., on tree trunk, daytime, 20.09.2016; 1 ♂ (red morph, ZMUM), same locality, 11°27'09"N, 107°21'57"E, lava cave, on excrements of Hipposideros sp.; 2 ♂, 1 ♀ (red morph, ZMUM Rd 4216), same locality, on concrete floor between huts in headquarters of National Park, 11°25'16"N, 107°25'39"E, 120 m a.s.l., night time, 4.I.2015; 1 ♀ (red morph, ZMUM Rd 4219), same locality, 11°25'37"N, 107°25'39"E, 140 m a.s.l., lowland monsoon tropical forest with dominating Lagerstroemia calyculata and Afzelia xylocarpa , on tree trunk, daytime, 20.V.2015; 1 ♀ (yellow morph, ZMUM), same locality, on bush, night time, 14.VI.2015; 1 juv. (ZMUM Rd 4223), same locality, on tree trunk, night time, 9.VII.2015; 4 ♂, 2 ♀ (white form, ZMUM), Vietnam, Dong Nai Province, Thac Mai waterfall and hot spring area, 11°06'12"N, 107°24'24"E, grassy recreation area near pond, in leaf litter, daytime, 01.VI.2018, all I. Semenyuk leg.

Descriptive notes.

Length 29.0-38.5 mm (♂) or 31.5-40.5 mm (♀), width of midbody pro- and metazonae 2.3-2.8 and 3.5-4.3 mm (♂) or 2.8-3.3 and 3.6-4.9 mm (♀), respectively.

Colouration in alcohol, after one year of preservation, blackish to black-brown ( Fig. 3 A–F ), paraterga and epiproct orange-yellow to light yellow; legs and sterna light yellow to light brown; antennae yellowish to dark brownish distally ( Fig. 3A ). Colour polymorphism evident, colouration of paraterga generally ranging from white or yellow to red in one and the same population (see also below under Remarks).

Antennae rather long ( Fig. 3A ), projecting behind (♂) or reaching (♀) body segment 3 when stretched dorsally. Collum with caudal corner of paraterga dentiform, pointed, directed caudally, but not drawn past rear margin. Paraterga 2 broad, anterior edge rounded, lateral edge with two small incisions in anterior 1/3. Lateral edge of following paraterga with a small incision in anterior 1/3 ( Fig. 3A, C, F ) and caudal corner fully pointed, beak-like and slightly curved mesad, strongly produced behind rear tergal margin ( Fig. 3 A–G ). Pleurosternal carinae complete crests with a sharp caudal tooth on segments 2-4, followings segments 5-10 each with an evident sharp denticle caudally, the latter gradually reduced to a small tooth until segment 15 (♂, ♀) ( Fig. 3B, D, E ). Epiproct ( Fig. 3 E–G ) with evident apical papillae directed ventrocaudally.

Legs long and slender, midbody ones ca. 1.3-1.4 (♂) or 0.9-1.0 (♀) times as long as body height, ♂ tarsal brushes present on legs of segments 2-10, thereafter gradually thinning out until segment 16.

Remarks.

This species has recently been redescribed ( Likhitrakarn et al. 2011), based on type material, and it is widespread from Luang Prabang Province, northern Laos to Cat Tien National Park, southern Vietnam ( Fig. 19 ). The fresh specimens agree nearly fully with the available descriptions, except for the ♂ tarsal brushes being present until legs 10-14 vs. legs 5, and the pleurosternal carinae represented by small teeth gradually reduced until segment 15. These variations, as well as colour morphs, are certainly not more than infraspecific (cf. Likhitrakarn et al. 2011). One variety, subrotundicollis var. nov., is more disjunct morphologically, but not genetically, and is treated separately below.

The biology and behaviour of this species, referred to as Orthomorpha sp., has recently been described in detail in Cat Tien National Park ( Semenyuk and Tiunov 2018). Millipedes are abundant almost throughout the year with a slight decline in the dry season (winter and early spring). Juveniles start swarming in the rainy season, mainly on logs or other decaying wood debris, also in suspended soil in tree holes. Swarms are active mostly in the night but can often be seen also in the daytime. Juveniles of later instars do not swarm, but still tend to group.

Figures

Figure 3. Orthomorpha rotundicollis (Attems, 1937), ♂ from Cat Tien National Park A, B anterior part of body, dorsal and lateral views, respectively C, D segments 10 and 11, dorsal and lateral views, respectively E-G posterior part of body, lateral, dorsal and ventral views, respectively H, I sternal cones between coxae 4, subcaudal and sublateral views, respectively.

Figure 4. Orthomorpha rotundicollis (Attems, 1937), left gonopod A, B mesal and lateral views, respectively. Scale bar: 0.5 mm.

Figure 5. Orthomorpha rotundicollis (Attems, 1937), left gonopod A, B lateral and mesal views, respectively C-F distal part, suboral, oral, sublateral and submesal views, respectively.

Figure 19. Distributions of Orthomorpha species (nine species or varieties, excluding the pantropical anthropochore O. coarctata (de Saussure, 1860 )) recorded in Vietnam. Open triangle O. hydrobiologica Attems, 1930 Filled circle O. scabra Jeekel, 1964 Open circle O. scabra, grandis var. nov., O. scabra Jeekel, 1964 and O. rotundicollis (Attems, 1937) Crossed square O. rotundicollis, subrotundicollis var. nov., O. caramel sp. nov. and O. vietnamica sp. nov. Filled Inverted triangle O. glandulosa (Attems, 1937) Opened Inverted triangle O. scabra Jeekel, 1964 and O. scabra, grandis var. nov. Open diamond O. glandulosa (Attems, 1937) and O. hydrobiologica Attems, 1930 Filled diamond O. glandulosa (Attems, 1937) Open square O. arboricola (Attems, 1937) and O. rotundicollis (Attems, 1937) Filled square O. rotundicollis (Attems, 1937) and O. coarctata (de Saussure, 1860).