Orthomorpha caramel, Likhitrakarn, Natdanai, Golovatch, Sergei I., Semenyuk, Irina, Efeykin, Boris D. & Panha, Somsak, 2019

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 caramel sp. nov. Figs 12 , 13 , 14

Type material.

Holotype ♂ (ZMUM Rd 4197), Vietnam, Gia Lai Province, Kon Ka Kinh National Park, forest near the village Krong, 14°18'03"N, 108°26'42"E, 600 m a.s.l., mixed tropical forest on slopes to a small stream, on tree trunk, daytime, 13.V.2017, I. Semenyuk leg.

Paratypes. 1 ♂ (ZMUM Rd 4198), same locality, together with holotype; 1 ♂ (ZMUM), same locality, 14°17'46"N, 108°26'41"E, 750 m a.s.l., disturbed forest with dominating bamboo on hills, on tree trunk, daytime 18.V.2017, all leg. I. Semenyuk.

Name.

A noun in apposition, to emphasize the general caramel colouration of the animals.

Diagnosis.

Using the latest key ( Likhitrakarn et al. 2011), distinguished from all known congeners by the tip of the solenophore being very faintly bifid, with a nearly smooth terminal lobe bearing a minute lobule at the base; in the gonopod structure it is similar to O. tuberculifera Likhitrakarn, Golovatch & Panha, 2011, but differs in the rather smooth and shining dorsal tegument devoid of tubercles, coupled with the particular colouration.

Description.

Length of holotype 36.5 mm (♂), width of midbody pro- and metazonae 2.8 and 4.2 mm, respectively. Paratype 31.5-34.5 mm long, 2.6-2.8 and 4.0-4.1 mm wide on midbody pro- and metazonae, respectively.

Colouration of live animals dark chocolate brown ( Fig. 12A ); metaterga, paraterga and epiproct caramel in colour; head, antennae and legs dark brownish; colouration in alcohol after one year of preservation chocolate brown or faded to light brownish ( Fig. 12 B–H ); metaterga, paraterga and epiproct caramel to light brownish in colour; legs and sterna light brown to pale yellow; head and antennae dark brownish to brown.

Clypeolabral region densely setose, vertigial region sparsely so; epicranial suture distinct. Antennae rather long ( Fig. 12A ), reaching the end of body segment 3 when stretched dorsally. In width, head <segment 3 = 4 <collum <segment 5 <2 <6-17, body gently and gradually tapering thereafter. Collum with three transverse rows of setae: 4+4 in anterior, 2+2 in intermediate, and 3+3 in posterior row; a slight furrow laterally in posterior 1/3; caudal corner of paraterga very narrowly rounded, slightly upturned, but not drawn behind rear margin ( Fig. 12B, C ).

Tegument shining, prozonae finely shagreened, metaterga rugose to rugulose, surface below paraterga finely microgranulate and rugulose. Postcollum metaterga each with two transverse rows of short, mostly abraded setae traceable only as insertion points, short wrinkles or minute tubercles: anterior (pre-sulcus) row with 2+2 mostly abraded setae traceable only as insertion points; posterior (postsulcus) row with 3+3 setae borne on minute tubercles or short wrinkles. Tergal setae long, slender, ca. 1/3 of metatergal length. Axial line rather clear, especially so on metazonae.

Paraterga very strongly developed ( Fig. 12 B–H ), mostly upturned, all lying below dorsum, set at ca. upper 1/4 of midbody height, nearly level with dorsum on segments 15-18, caudal corner always spiniform and narrowly rounded, extending beyond rear tergal margin; in lateral view, paraterga thinner in poreless segments and modestly enlarged in pore-bearing ones.

Paraterga 2 broad, anterior edge evidently convex, lateral edge with one larger incision in anterior 1/3, one smaller, but evident incision in the middle and a faint furrow at posterior 1/3; posterior edge oblique ( Fig. 12B, D, F ). Anterior edges of following paraterga strongly and regularly rounded, lateral edge with only one small, but evident incision in anterior 1/3, posterior edge clearly concave, especially strongly emarginate in segments 17-19 ( Fig. 12 F–H ). Calluses on paraterga 2-4 strongly delimited by a sulcus only dorsally, on following paraterga both dorsally and ventrally.

Ozopores evident, lateral, lying inside an ovoid groove at ca. 1/4 in front of caudal corner. Transverse sulcus usually distinct ( Fig. 12C, E, H ), complete on metaterga 5-18, incomplete and nearly wanting on segments 4 and 19, wave-shaped, rather shallow, nearly reaching the bases of paraterga, ribbed at bottom. Stricture between pro- and metazona rather wide and deep, beaded at bottom down to base of paraterga ( Fig. 12B, D, F ). Pleurosternal carinae complete crests with a sharp caudal tooth on segments 2-7(8), thereafter bulged anteriorly and with a small, sharp, caudal tooth on segments 8-10, the tooth gradually reduced into small, caudally roughly granulate crests until segment 12 ( Fig. 12C, E, H ). Epiproct ( Fig. 12F, G ) conical, flattened dorsoventrally, with two evident apical papillae; tip subtruncate; pre-apical papillae small, but evident, lying rather close to tip. Hypoproct pentagonal, setiferous knobs at caudal edge evident and well-separated.

Sterna sparsely setose, without modifications except for two rather large and long, fully separated, sternal cones between ♂ coxae 4 ( Fig. 12I, J ). A paramedian pair of evident tubercles in front of gonopod aperture. Legs long and slender, midbody ones ca. 1.2-1.4 times as long as body height, prefemora without modifications, ♂ tarsal brushes present until legs 15.

Gonopods ( Figs 13 , 14 ) simple. Coxa slender and long, with several setae distoventrally. Femorite ca. 2 times as long as prefemoral (= strongly setose) part. Femorite slender, suberect to slightly curved, “postfemoral” portion demarcated by an oblique lateral sulcus; solenophore moderately twisted and curved, tip of solenophore very faintly bifid, with a nearly smooth terminal lobe bearing a minute lobule at base; solenomere long and flagelliform, as usual.

Remarks.

The biology and behaviour of this species are very similar to those of O. vietnamica sp. nov. During field observations in May 2017, millipedes occurred mainly on tree trunks. Mating was also recorded, but no females were collected.

Figures

Figure 12. Orthomorpha caramel sp. nov., ♂ holotype A habitus, live colouration B, C anterior part of body, dorsal and lateral views, respectively D, E segments 10 and 11, dorsal and lateral views, respectively F-H posterior part of body, dorsal, ventral and lateral views, respectively I, J sternal cones between coxae 4, subcaudal and sublateral views, respectively.

Figure 13. Orthomorpha caramel sp. nov., ♂ holotype, right gonopod A, B lateral and mesal views, respectively C distal part, suboral view. Scale bars: 0.5 mm

Figure 14. Orthomorpha caramel sp. nov., ♂ holotype, right gonopod A, B mesal and lateral views, respectively C-G distal part, caudal, mesal, oral, submesal and subcaudal views, respectively.