Alloproctoides consonensis, 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 : 4-10

Alloproctoides consonensis new species

Figs 2–8 , 9B .

Material examined: Type specimens. Adult ♂ holotype ( QMS 109011), 5 adult ♀ paratypes ( QMS 109015– 109019), 3 adult ♂ paratypes ( QMS 109012–109014) from Vietnam, Ba Ria-Vung Tau Province, Con Dao Islands, 8.706281°N, 106.590703°E, elevation 20 m; rainforest leaf litter in Ong Dung Beach, Con Son Island, 26th July 2015 (Collected by C. Huynh).

Diagnosis: Adults 1.6–2.2 mm in length. Ommatidia absent. Antennomere VI with conical sensillum located in posterior position, with 2 long thick bacilliform sensilla, and 4 short thin bacilliform sensilla arranged diagonally, not arranged in a transverse row as in Alloproctoides remyi . Gnathochilarial medial palp with 58 sensilla (males), 18 sensilla (females)—not as in A. remyi with 38 (males) and 18 (females).

Description: Head light orange, lateral margins dark reddish-brown. Body light orange, with contrasting white pleural trichomes, and lighter coloured caudal bundle ( Fig. 2 ). Holotype male body length 1.7 mm (Paratypes: males 1.6–1.9 mm, females 1.9–2.2 mm). Male caudal trichome bundle narrower in width, bundle slightly longer (0.6 mm) than in female (0.5 mm). Head: Ommatidia absent. Vertex with two posterior trichome groups and a large medial gap. Each trichome group has 2 rows: anterior row, curved slightly, on an oblique angle with larger sized trichome sockets in the middle, and small sockets on both ends; posterior row with 1–2 trichome sockets; a narrow medial space between these 2 rows. Holotype with posterior trichome groups with 15 sockets (Left: L) and 14 sockets (Right: R) in the anterior rows; 2 sockets (L) and 1 socket (R) in the posterior rows ( Fig. 3A ) (Paratypes with 12–15 sockets in the anterior rows and 1–2 in the posterior rows ( Fig. 4A )). Trichobothria: Trichobothrium b, largest socket located closest to the edge of the head capsule in lateral position, trichobothrium a, medium size socket located furthest from the edge of head capsule, trichobothrium c, smallest socket located anterior to sockets a and b. ( Figs. 3E , 4C ). Antennae: 8 antennomeres, 4 reduced sensory cones, antennomeres VII and VIII equal in length ( Figs. 5A , 6A ) as is typical of Lophoproctidae . Antennomere VI with 2 long thick bacilliform sensilla (T): Ta located in anterior position, Tp located in posterior position. Conical sensillum (c) of antennomere VI located next to Tp, 4 short thin bacilliform sensilla (st) arranged diagonally located anterior to Ta ( Figs. 5C , 6C and 6D ). Antennomere VII with 2 long thick bacilliform sensilla: Ta shorter than Tp. Setiform sensillum (s) of antennomere VI located distal and between Ta and Tp, a conical sensillum located in posterior position next to Tp ( Fig. 5B ) (Two conical sensilla apparent in some non-holotype specimens, Fig. 6B ). Clypeo-labrum: with 11 setae (holotype), shorter than labrum width (paratypes with 10–12). Labrum posterior margin setose: 4–6 rows tiny backward facing setae. Thick marginal lamellae located on labrum anterior edge, with 2 linguiform processes in median cleft between lamellae ( Figs. 3G , 4D ). Gnathochilarium: medial palps with 58 sensilla (paratypes: males with 56–58, females with 18 sensilla) ( Figs. 3F , 4E and 4F ). Trunk: Body with 10 tergites, 9 pleural projections, and telson excluding caudal bundle. 13 pairs of legs ( Fig. 4B ). Collum (Tergite 1): Trichome sockets in 2 oval shapes laterally, large medial gap. Lateral protuberances with small number of trichome sockets each side ( Fig. 4A ). Tergites: Other tergites with pair of pleural projections located anterolaterally. Holotype with 49 (L) and 46 (R) trichome sockets on the collum. Lateral protuberances with 9 (L) and 8 (R) trichome sockets ( Fig. 3B ) (Paratypes with 46–58 sockets, lateral protuberances with 6–9). Tergites 2–10 have 2 latero-posterior oval groups of trichome sockets with a few sockets extended on both ends and these groups separated by a large medial gap ( Fig. 4A ). Holotype, tergite 2 with 50 (L) and 47 (R) trichome sockets ( Fig. 3C ), tergite 10 with 43 (L) and 40 (R) trichome sockets ( Fig. 3D ) (Paratypes, tergite 2: 54–66 sockets, tergite 10: 34–46). Legs: Leg segmentation following Manton (1956). Legs 1, 2 without trochanter; leg 1 without tarsus 1. Chaetotaxy (setae on leg articles): Holotype; coxa 1: 3 pubescent oval setae, coxa 2: 4, coxae 3–13: 2–5; pre-femur and post-femur: 1 pubescent oval seta; femur: 2 pubescent oval setae, one smaller located in ventromedial position ( Figs. 7A, 7B and 7C ) (Paratypes, female 3–6 setae on femur ( Fig. 8C )); tarsus 2 with spine ( Fig. 7D ). Holotype, last sternite: 6 pubescent oval setae (Paratypes with 4–6 sockets). Male sex organs: 2 penes on second coxa, coxal glands absent. Telotarsus–Claw: Simple slender structure, claw (c) with two small processes called the laterodorsal denticles (ldd) equal in length and a small spine located in the ventral position of the claw called the basal denticle (bd) ( Figs 7E , 8D ). Telson: Dorsal ornamental trichome sockets symmetrically arranged on both sides of telson. Holotype with 7 sockets of trichome a (Paratypes with 6–8 trichome a); single trichome b, two large protruding basal sockets trichome c: c 1 and c 3 (c 2 absent) ( Fig. 3H ). Caudal bundles: Male, single caudal bundle, uniform sized sockets carrying caudal trichomes. Female, two caudal bundles: main dorsal structure, similar to male, 2 laterosternal structures with finer nest trichome sockets ( Figs 8A and 8B ). (These caudal structures are commonly found in Lophoturus species ( Lophoproctidae ) ( Huynh and Veenstra, 2018b) and Monographis species ( Huynh and Veenstra, 2018c) and are classified as a caudal bundle Type I by Condé and Nguyen Duy-Jacquemin (2008)).

Remarks: Alloproctoides consonensis n. sp. was similar in appearance, to all species in the genus having the same characteristic sensilla morphology on antennomere VI. There is some variation in the arrangement of sensilla when comparing Alloproctoides species, for example, A. consonensis n. sp. is similar to A. remyi in the number and arrangement of short thin bacilliform sensilla on the antennomere VI. However, A. consonensis has 4 or sometimes 5 short thin bacilliform sensilla, with sockets on an acute angle placed parallel in anterior position to the long thick bacilliform sensillum ( Fig. 9B ). In contrast, A. remyi has 5 short thin bacilliform sensilla, 4 located in similar positions to those of A. consonensis n. sp. and one sensillum located in ventral position, in relation to the long thick bacilliform sensillum (Ta) ( Fig. 9C ). The number of sensilla on the gnathochilarium can also be used to differentiate between these two species: In males, A. remyi has 38 sensilla ( Fig. 9C ), A. consonensis n. sp. has 56–58 sensilla ( Fig. 9B ), and 18 sensilla in females of both species ( Figs. 9B and 9C ). Alloproctoides consonensis n. sp. and A. dawydoffi have the same arrangement of the sensilla, but these sensilla are positioned on a slightly different angle. The short thin bacilliform sensilla forming a transverse row in A. dawydoffi ( Fig. 9A ) compared to A. consonensis n. sp., which has a row of sensilla on an acute angle. If based solely on the arrangement of sensilla, Alloproctoides species from Con Dao Islands may have been identified as A. dawydoffi , a species found only on mainland Vietnam.

Etymology: The species is named Alloproctoides consonensis n. sp. as they were found on Con Son Island, Con Dao Archipelago, Vietnam.

Additional information about the genus Alloproctoides (Lophoproctidae) : The lectotype and paralectotype of Alloproctoides dawydoffi Attems, 1938 , collected from Nha Trang, Khanh Hoa Province, Vietnam, were deposited in the National Museum of Natural History (Paris, France) by Nguyen Duy-Jacquemin and Condé (1967). This was the type specimen of Alloproctoides remyi Marquet and Condé, 1950 , from Mauritius. These type specimens have not been found in the museum’s collection records. At present, there is only a single slide mounted adult female, with 13 pairs of legs, a handwritten label including ‘24 St. Denis * Alloproctoides simulans ♀ 13 H TYPE’ and a printed label ‘ Alloproctoides dawydoffi ( Attems, 1938) M. Nguyen Duy’. This slide has a whole mount of a female with both antennae missing, embedded in Canada balsam. In this current study, which included collecting trips to Mauritius and Vietnam, specimens of A. dawydoffi (collected from Dinh Mountain (Nui Dinh), Ba Ria–Vung Tau Province, Vietnam) and A. remyi (collected from Sir Seewoosagur Ramgoolam Botanical Garden, Pamplemousses District, Mauritius) were plentiful. Many specimens from these two species have been slide mounted, creating a collection of neotypes now deposited in the Queensland Museum along with type specimens of A. consonensis . The purpose of neotypes of A. dawydoffi (QMS 10935–36 for males, QMS 10937–38 for females) and A. remyi (QMS 10939–40 for males, QMS 10941–42 for females) is to include them in the species records of genus Alloproctoides for future study, along with their genetic information (GenBank accession numbers: A. dawydoffi : MH729070 for 18S and MH737734 for COI; A. remyi : MH729071 for 18S and MH737735 for COI). In the genus Alloproctoides , morphological similarities can make correct species identification a challenge, particularly if using only the number and arrangement of sensilla on antennomere VI to distinguish between them. In the future, species identification will be easier with this new species being designated a species rather than subspecies; the subspecies Alloproctoides dawydoffi sineligulatus needs to be elevated to species level as Alloproctoides sineligulatus .

Figures

FIGURE 2. An image of a live specimen of Alloproctoides consonensis n. sp.

FIGURE 3. Holotype male, Alloproctoides consonensis n. sp., A. Head capsule showing the posterior vertex trichome sockets (pv) and sockets of trichobothria a, b and c; B. Collum (co) with lateral protuberances (Lp), C. Tergite 2 (T2) and D. Tergite 10 (T10), all show trichome socket patterns; E. Trichobothria a, b (thin, funicular, cylindrical structures) and c (claviform funicle) F. Left gnathochilarium (♂); G. Clypeo-labrum, 11 setae posteriorly, with setose surface and a pair of linguiform processes (lp); H. The ornamental trichome sockets, located dorsally above the caudal bundle, with 7 trichomes a, one b and 2 trichomes c (c1 and c3).

FIGURE 4. SEM images of Alloproctoides consonensis n. sp., A. Dorsal view of the head capsule, showing the vertex area (V), the posterior vertex trichomes group (pv), the trichobothria (tr); co: collum, the lateral protuberance (Lp); T2: tergite 2 and the associated pleural projections (pp), the medial gap (mg); B. Ventral view; C. Trichobothria a, b and c: Trichobothrium b, largest socket located closest to the edge of the head capsule in lateral position, trichobothrium a, medium size socket located furthest from the edge of head capsule, trichobothrium c, smallest socket located anterior to sockets a and b; D. Clypeo-labrum showed the setose surface and a pair of linguiform process (lp), E. Gnathochilarium in male showing 45 sensilla on the medial palp (some sensilla missing, the total numbers usually 56–58); F. Gnathochilarium in female with 18 sensilla.

FIGURE 5. Holotype Alloproctoides consonensis n. sp., A. Antennomeres VI, VII and VIII with 4 reduced sensory cones (sc), showed the arrangement of sensilla on antennomeres VI and VII; B. Sensilla on antennomere VII: Two long thick bacilliform sensilla (T), Ta—shorter (anterior) and Tp (posterior), setiform sensillum (s) between them and a conical sensilla (c) located in posterior position; C. Sensilla on antennomere VI: Two long thick bacilliform sensilla (Ta and Tp), a conical sensillum (c) located in posterior position. Four short thin bacilliform sensilla (st) located on an acute angle near Ta. (Arrows indicated sensilla from B (article VII) and from C (article VI))

FIGURE 6. SEM images of Alloproctoides consonensis n. sp., A. Antennomeres VI, VII and VIII with four reduced sensory cones (sc), showing the arrangement of sensilla on antennomeres VI and VII; B. Antennomere VII with two long thick bacilliform sensilla, Ta and Tp, setiform sensillum (s) between them and two conical sensilla (c) located in posterior position; C. Antennomere VI with two long thick bacilliform sensilla (Ta and Tp), a conical sensillum located in posterior position; the arrangement of four short thin bacilliform sensilla (st); D. Another angle of antennomere VI, showing the arrangement of the short thin bacilliform sensilla and st2 (damaged).

FIGURE 7. Holotype Alloproctoides consonensis n. sp., A. 2nd leg showing seven leg articles (co: coxa, pf: pre-femur, f: femur, pof: post-femur, tib: tibia, T1: tarsus 1, T2: tarsus 2, c: claw) and sex organ—penis (P); The chaetotaxy (setae on leg articles): B. A pubescent oval 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 and distal edge of the post-femur; D. Spine on tarsus 2; E. Telotarsus—claw structures (lateral view), laterodorsal denticles (ldd), basal denticle (bd) and claw (c).

FIGURE 8. SEM images of Alloproctoides consonensis n. sp., A. Male caudal bundle structure, showing the uniform trichome sockets; B. Bare caudal bundle in the female showing 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 sockets free tissue (tsft); C. Leg segments and chaetotaxy (setae on leg articles); D. Claw showing simple structures, laterodorsal denticles (ldd), basal denticle (bd) and claw (c). (ct: caudal trichome, ots: ornamental trichome sockets, pps: pleural projection sockets)

FIGURE 9. Comparison of arrangements of the short, thin bacilliform sensilla on antennomere VI from A. Alloproctoides dawydoffi, B. A. consonensis n. sp. and C. A. remyi (white arrow indicating the main difference between B and C); gnathochilaria of A. dawydoffi and A. consonensis n. sp. with the same number of sensilla (male with 58, female with 18 sensilla), A. remyi showing similarity to female with 18 sensilla and different to male with 38 sensilla.