Monographis condorensis, Huynh, 2020

Huynh, Cuong, 2020, Three new species of penicillate millipedes from the Con Dao Islands of southeast Vietnam (Diplopoda, Lophoproctidae and Polyxenidae), Zootaxa 4759 (1), pp. 1-30 : 14-18

Monographis condorensis new species

Fig. 11–16

Material examined: Type specimens. Adult ♂ holotype ( QMS 109020), 2 adult ♂ paratypes ( QMS 109021–22), 5 adult ♀ paratypes ( QMS 109023–27) from Vietnam, Ba Ria-Vung Tau Province, Con Dao Islands, Con Son Island, leaf litter from So Ray old fruit plantation, 8.691263°N, 106.588949°E, elevation 223 m; on 25th July 2015 (collected by C. Huynh).

Diagnosis: Differs from congeners in having dense, long trichomes. Body length over 3.5 mm. Antennomere VI with 24–29 sensilla forming a triangular shape, setiform sensillum located in the anterior position, conical sensillum absent. Labrum asetose smooth, with long slender setae in the anterior margin. Telotarsus with posterior lateral process shorter than half length of the claw, anterior lateral process and lamella process present, anterior setiform process longer than the claw.

Description: Colour and trichome patterns dark grey on both sides with contrasting light green medial band on dorsal surface of the body. Body covered with dense, long trichomes. Caudal bundle black-silver ( Fig. 11 ). Holotype male body 3.5 mm; paratypes: males 3.5–3.6 mm, females 3.8–4.5 mm; caudal bundle in both sexes same length (0.9 mm). Head: Each side 8 ommatidia: 4 dorsal, 4 lateral (1 anterior, 2 medial and 1 posterior). Vertex with 2 posterior trichome groups and a large medial gap. Each group with 2 rows: Anterior row curved slightly, on an oblique angle with large trichome sockets in central position, gradually reducing the size at both ends; posterior row with large sockets; a narrow medial space between these rows. Holotype posterior trichome groups with 18 sockets (L) and 19 (R) sockets in anterior rows, posterior rows with 5 sockets both sides ( Fig. 12A ) (Paratypes showed that variation is common in this species, regardless of sex, ranging from 14–22 sockets in anterior rows, 2–6 in posterior rows). Trichobothria typically thin, sensory hairs with narrow cylindrical funicles; trichobothria equal in socket size forming an isosceles triangle with equal distance ab and bc ( Figs.12E and 13A ) (trichobothrium a located in posterior position of the head capsule, trichobothrium b in lateral position, trichobothrium c in anterior position). Antennae: Eight antennomeres, 4 sensory cones, typical characteristics of Polyxenidae . Antennomere VI with 24–29 bacilliform sensilla ( Figs. 14A, B and C ). Holotype with 26 bacilliform sensilla forming a triangular shape (3 thick and 23 thin bacilliform sensilla), setiform sensillum located in anterior position, conical sensillum absent. Antennomere VII with 2 thick bacilliform sensilla (T, Ta and Tp), setiform sensillum (s) located in between these two sensilla (T), conical sensillum (c) located next to Tp ( Figs. 15A and B ). Clypeo-labrum: Holotype, labrum posterior margin with 10 setae, setae equal in length to labrum width (Setae on the paratypes ranged from 10–11 in both sexes). Labrum surface smooth and asetose, labrum posterior margin has a row of minute backward-pointing setae. Lateral lamella and single broad lamella each side median cleft, 20 slender setae, pair at the base, present on anterior margin of each side of labrum ( Fig. 12G ) (The number of these anterior slender setae varies among paratypes, ranging from 18–24 on each side. ( Fig.13C )). Gnathochilarium: Lateral palp 1.25 times medial palp; 11 conical sensilla on the lateral palp and 22 on the medial palp. Same in holotype and paratypes ( Figs. 12F and 13D ). Trunk: Body with 10 tergites, 9 pleural projections, and a telson excluding caudal bundle. 13 pairs of legs. Collum (tergite 1) with lateral protuberances 4–6 trichome sockets each side. Other tergites with pair of pleural projections located in anterolateral positions. The tergal trichome socket arrangements typically have 2 broad oval shapes, slightly enlarged in lateral position, with the posterior row straight slightly to the centre, an intermedial gap between these rows ( Figs. 12C and 13B ). Holotype, collum with 73 sockets each side, lateral protuberance 5 (L) and 4 (R) sockets ( Fig.12B ) (Paratypes ranged 65–78 sockets in the collum and lateral protuberances 4–6 sockets). Tergite 2 had a similar structural pattern with the posterior row slightly longer and 73 (L) and 71 (R) trichome sockets ( Fig.12C ), the patterns are similar to characteristic large gaps. Tergite 10 is the exception with these trichome sockets being smaller and denser, a narrow space exists between the lateral rosette trichome sockets and posterior row. Trichome sockets of this tergite are over 100 and the tergite 10 of the holotype was counted 115 (L) and 112 (R) sockets ( Fig.12D ). Legs: Leg segmentation following Manton (1956). Legs 1 and 2 without trochanter, leg 1 without tarsus 1. Chaetotaxy (setae on leg articles): coxa 1 and 2: 2 setae, coxae 3–13: 2–4 setae; pre-femur, post-femur, tibia with 1 seta, except femur with 1–4 setae, tarsus 1 and 2 with a spine ( Fig. 16A ). Coxa, pre-femur and femur with biarticulated seta and ridged funicle ( Fig.16B ). 1–3 smaller biarticulated setae in posterior position of femur, some also on penis ( Fig. 16C ). Post-femur and tibia distally with setiform seta ( Fig. 16D ). The spine on tarsus 2 is sharply pointed and twice as long as ( Fig.16F ) the spine in the antero-sternal position of tarsus 1 ( Fig. 16E ). There 4 spines in tarsus 1 from the holotype. The posterior edge of the last sternite had 4 setae similar to those present on the coxa and the number of these setae are the same in the holotype and paratypes. Telotarsus-Claw: Claw slender with anterior lateral process and posterior lateral process less than half length of the claw; the anterior setiform process is longer than the claw; lamella process is present ( Fig. 16G ). Sex organs in the male: A pair of penes on coxae 2 and 2 pairs of coxal glands are located on the 8th–9th coxal plates. Telson: Dorsal ornamental trichome sockets symmetrically arranged on both sides of telson; 25 (L) and 29 (R) sockets of trichomes a on each side of the telson in the holotype (paratypes with 14–29). Trichome a sockets form 2 rows, top row with small sockets, bottom row with larger sockets. Socket of trichome b and 3 large sockets trichomes c with protruding base: c1, c2 and c3, forming triangular shape located in ventroposterior positions in each arrangement. Circular indentation d apparent each side near the exterior side of trichomes c ( Fig. 12H ). Caudal bundles: Similar to congener ( Huynh & Veenstra 2015, 2018c) ( Fig. 13E ) and is classified as the caudal bundle type I arrangement ( Condé & Nguyen Duy-Jacquemin, 2008). Caudal trichomes with a series of 2–6 backward hooks.

Remarks: Monographis condorensis n. sp. has a longer body, with dense, long trichomes that are dark grey, which differs from the yellowish-brown colour seen in live specimens of other Monographis species. The number of sensilla (24–29) on the antennomere VI also differs from congeners that have fewer sensilla (12–20 (Nguyen Duy- Jacquemin and Condé, 1967)) forming a triangular shape. A row of the slender setae present on lamellae along the anterior margin of the labrum. Morphological and genetic differences indicate that M. condorensis is a new species. An updated diagnosis of genus Monographis is also required based on the morphology of all described species. The arrangement of the sensilla on antennomere VI divides Monographis into 2 groups: 1) forming a crescent shape and 2) triangular shape ( Huynh & Veenstra, 2018c). Monographis condorensis n. sp. belongs to group 2 with sensilla arranged in a triangular shape, which is found in M. dongnaiensis , M. queenslandica , M. tamoyoensis and M. yunnanensis ( Huynh & Veenstra, 2015) . The differences between M. condorensis n. sp. and other species in the group are the presence of setae on lamellae along the anterior margin of labrum, which is a character absent in the group; a large number of sensilla on antennomere VI (>24 sensilla) and the claw structure (the claw is slender in structure with a shorter posterior lateral process, and the anterior setiform process is longer than the claw). All these characteristics make M. condorensis a distinctively new species in Monographis .

Etymology: The name of Monographis condorensis refers to the old name of Con Dao Archipelago as Pulo

Condore in southeast Vietnam, where this species was first found.

Figures

FIGURE 11. Monographis condorensis n. sp. showing the body cover with dense, long trichomes.

FIGURE 12. Holotype Monographis condorensis n. sp., A. Head capsule with 8 ommatidia on each side, the posterior vertex trichome group (pv) and 3 sockets of trichobothria (trichobothria a, b and c); B. Collum (co) and lateral protuberances (Lp) showing the arrangement of trichomes sockets; C. T2: Tergite 2; D. T10: Tergite 10—the last tergite; E. Trichobothria a, b and c (right hand side) showing the sensory hairs and sockets; F. Gnathochilarium: the lateral palp (LP) with 11 sensilla and medial palp (MP) with 22 sensilla; G. Clypeo-labrum showing a smooth surface, asetose, with setae along both anterior edges. H. Dorsal ornamental trichome sockets of trichome a (a), trichome b (b), trichome c (c) and the circular indentation d (d).

FIGURE 13. SEM images of Monographis condorensis n. sp., A. Dorsal view of the head capsule, showing 8 ommatidia and trichobothria a, b and c; B. Dorsal view of the body, co: Collum, Lp: lateral protuberances and pp: pleural projection, T2: tergite 2 and T3: tergite 3; C. Clypeo-labrum showing the smooth surface and asetose (l), s: setae along anterior edges, Se: posterior setae, bse: a minute backward-pointing setae; D. Right gnathochilarium showing the lateral palp (LP) with 5 sensilla and 6 sensilla sockets, 22 sensilla on the medial palp (MP); E. Bare caudal bundle in the female showed 2 distinctive structures: caudal trichome sockets (cts) which include barbate trichome sockets (bts) in the middle of the bundle, forming a dorsal single bundle, nest trichome sockets (nts) forming 2 ventral bundles; these bundles are separated by the trichome socket-free tissue (tsft); T: telson; F. Leg articles and arrows indicate spines which are typical characters of Monographis.

FIGURE 14. Monographis condorensis n. sp., A. SEM images of antennomeres VI, VII and VIII with 4 sensory cones (sc), showing the arrangement of sensilla on antennomeres VI and VII; B. Antennomere VII with 2 thick sensilla (T), setiform sensillum (s) between them and a conical sensillum (c) located in posterior position; C. Antennomere VI with a group of 29 thin sensilla forming a triangular shape followed by a setiform sensillum.

FIGURE 15. Holotype Monographis condorensis n. sp., A. Antennomeres VI, VII and VIII with sensory cones (sc), showing the arrangement of sensilla on antennomeres VI and VII; B. Antennomere VII with 2 thick sensilla (Ta (anterior) and Tp (posterior)), setiform sensillum (s) between them and a conical sensillum (c) located next to Tp; antennomere VI with a group of 26 sensilla (23 thin sensilla (t) and 3 thick sensilla (★)) forming a triangular shape followed by a setiform sensillum (s).

FIGURE 16. Holotype Monographis condorensis n. sp., A. 2nd leg showing seven leg articles (co: coxa, pf: pre-femur, fe: femur, pof: post-femur, tib: tibia, T1: tarsus 1, T2: tarsus 2, c: claw) and sex organ—penis (P); B. Biarticulated seta present on the coxa, pre-femur, the distal edge of femur and the posterior edge of the last sternite; C. Similar smaller version of this seta present in the middle of the femur; D. Seta on tibia; E. Smaller spine on tarsus 1; F. Larger spine on T2; G. Telotarsus—claw structures (SEM image of one specimen) and a drawing of the telotarsus from the holotype (lateral view), p: posterior lateral process, a: anterior lateral process, c: claw, l: lamella process and s: anterior setiform process.