Plutomurus jangamensis, Chang & Park, 2020

Chang, Gyudong & Park, Kyung-Hwa, 2020, Report on a new species of Plutomurus (Collembola, Tomoceridae) from a South Korean limestone cave, with notes on its DNA barcode, Zootaxa 4718 (1), pp. 108-122 : 111-117

Plutomurus jangamensis sp. nov.

(Korean name: Jang-am-jang-nim-gul-ga-si-tok-to-gi)

Figs 2–12

Type locality. Jangamgul cave (37°23′53.75′′N, 128°25′24.79′′E) ( Fig. 1 ), Jujin-ri , Pyeongchang-gun, Gangwondo, KOREA .

Type material. Holotype: female on slide, 25.x. 2018, 250m from entrance, leg. GD Chang, SA Peak, TK Lee . Paratypes: 36 specimens on slides, same data as holotype .

Additional material. 20 specimens in ethyl alcohol, same data as holotype but different collecting date as 18. xi. 2018, 8. xii. 2018 , and 16. ii. 2019.

Diagnosis. Body color completely white, or white with gray pigment speckles ( Fig. 2a ). Head without eyes. Prelabral chaetae 3–4 + 3–4. Claw inner teeth 1–2 on unguis and 4–10 on unguiculus. Hind leg with trochanteralfemoral organ with 30–35, 30–35 chaetae on trochanter and femur. Dental spines formula 3–4, IV–VI /1–4, I, 1–2, I, 2–3, I and one lateral macrochaetae on dens. Mucro with 2 basal, 1 intermittent, one apical and one subapical teeth.

Body ( Fig. 2a ). Body length up to 2.0 mm excluding antennae and furca (ranges 1.6–2.0mm). Body color completely white including antennae, ventral tube, legs and furca, or white with gray pigment speckles except antenna, ventral tube, ventral side of manubrium, mouth part area, and head vertex area.

Head ( Figs 5–7 ). Cephalic diagonal 0.4−0.7mm (average 0.5 mm), 0.25 times of body length. Antenna length 1.6–2.0 mm, as long as body length, 3–5 times length of cephalic diagonal. Head without eyes, and PAO under optical microscope. Prelabral and labral chaetae smooth: prelabral chaetae 3–4 + 3–4; labrum with 5, 5, 4 papillae and with 4 bended strong spine-like papillae on distal part of labrum ( Fig. 7 ). Maxillary outer lobe trifurcate with terminal hair (th), and dorso-lateral and ventral processes on palp; sublobal plate with 4 hair-like processes. Labial palp with five papilla (A–E); Papillae A without guard chaeta, Papillae B with 5 guard chaetae, Papillae C without guard chaeta, Papillae D with 4 guard chaetae, Papillae E with 6 guard chaetae ( Fig. 5 ). Maxillary head with three toothed-like structure with 6 lamellae ( Fig. 6 ; lamella 6 not shown). Lam. 1 feather-like shape with many inner filaments, much longer than others. Lam.2 and 4 fan-like shape, densely covered with denticles and hooks; Lam.3 short with cilia; Lam.5 with many inner filaments but without prominent basal beard-like projection ( Fig. 6 ). Labium with 19–22 proximal chaetae. Basomedial field with 17–19 smooth chaetae; basolateral field always with 5 chaetae (A3–A5 and L1–L2).

Legs ( Figs 8–10 ). Posterior face of hind tibiotarsus with 2 prominent spine-like chaetae on 1/2 and 4/5 position each, resulting in a 0, 0, 2 tibiotarsal spine formula on fore, middle and hind tibiotarsi ventrally ( Fig. 8 ). Hind legs with well-developed trochanteral-femoral organ with 30–35, 30–35 chaetae respectively, one chaeta of each much longer than the rest ( Fig. 9 ). Unguis on all legs with one unpaired inner tooth at one–third from the basal part (rarely 2; one at one-third, and the other at two-third from basal part). Unguiculus lanceolate, with 2 internal lamellae and both bearing 2–5 serrated shape teeth. Tenent hair acuminated, shorter than inner edge of unguis ( Fig. 10 ). Average ratio of unguis: unguiculus: tenent hair = foreleg, 2: 1: 1.1.

Ventral tube. Ventral tube with 30–35 + 30–35 anterior, 40–45 + 40–45 laterodistal, and (about) 45–50 posterior chaetae.

Tenaculum. Corpus with 1 smooth chaeta; rami with 4 + 4 teeth.

Furca ( Figs 11–12 ). Ratio manubrium: dens: mucro 2.6: 3.9: 1. Manubrium ventrally scaled and 10 lateral chaetae on each side; dorsal scale absent; each dorsal chaetal stripe with 150–200 chaetae of different sizes; distal corner with one chaeta on each side. Dental spines formula as 3–4, IV–VI /1–4, I, 1–2, I, 2–3, I ( Figs 11a & 11b ) with simple shape of spines. Small spines arranged in-a-row along with those normal spines present ( Fig. 11c ). Outer margin of basal segment of dens with one prominent thick, straight, and apically pointed spine-like macrochaeta. Mucro with one apical and subapical teeth. Subapical teeth more or less larger than apical teeth. One intermittent, two basal teeth present. Two dorsal lamellae running from subapical tooth; intermittent teeth placed on the outer lamella; outer lamella ending in outer basal tooth and inner lamella ending beside inner basal tooth ( Fig. 12 ).

Chaetotaxy. Head ( Fig. 3 ). 10 normal chaetae present on near the base of each antenna. Dorsally with 6 paired Mc on each half, respectively: 2 anterior (A 2, A 3), 2 interocular (Ps 2, S 4) and 2 postocular (Pa 2, Pa 5). Posterior margin with 5 blunt macrochaetae.

Body ( Figs 4a & 4b ). Dorsal macrochaetae formula on Th. II–Abd. V as 4, 1/2, 2, 4, 2, 3 on each half, respectively; Th. II with 2 medial and 2 posterior Mc. About 10–15 apically blunt macrochaetae on anterior side; Th. III with 1 posterior Mc.; Each of Abd. I–II with 2 posterior Mc., Mc. positions different between each segments; Abd. III with 2 anterior and 2 posterior Mc.; Abd. IV with 2 posterior Mc.; Abd. V with 3 posterior Mc. Dorsal bothriotrichal formula on Th. II–Abd. V as 2, 1/0, 0, 1, 2, 0 on each half, respectively. Pseudopore formula on Th. II–Abd. V as 1, 1/1, 1, 1, 1, 0. Micro-sensilla formula on Th. II–Abd. V as 1, 1/1, 1, 1, 1, 0 on each half, respectively.

Variable characters ( Table 2 & Fig 2a ). There were two types of body color: 18 of 37 specimens examined were completely white, whereas 19 had gray pigment. The number of prelabral chaetae showed 3 + 3 to 4 + 4 or mixed Prelabral chaetae form of both. The number of teeth on inner two lamellae of unguiculus vary from 4 to 10. The formula of dental spines also presented various forms, as 3–4, IV–VI /1–4, I, 1–2, I, 2–3, I (holotype form), 3–4, IV–VI /1, I, 2, I, 1–2, I, 1, I. In some specimens, the number of prelabral chaetae and the formula of dental spines on the left and right sides were different even in the same individuals.

4 + 4 3 + 3 3 + 4 (13 of 37 specimens) (11 of 37 specimens) (7 of 37 specimens) Dental spines formula 3–4, IV– VI /1–4, I, 1–2, I, 2–3, I (13 of 37 specimens) 3–4, IV– VI /1, I, 2, I, 1–2, I, 1, I (4 of 37 specimens) 3–4, IV– VI /1–4, I, 1–2, I, 2–3, I and 3–4, IV– VI /1, I, 2, I, 1–2, I, 1, I (10 of 37 specimens)

Etymology. The species is named after the cave (Jangamgul cave) in which it was collected.

Ecology. Specimens were collected from piles of bat guano in the Dark Zone with Constant Temperature (DZCT) ( Choi et al. 2011), on the third floor of the Jangamgul cave. This site maintains high soil humidity because of water trickling from several crevices, and this also keeps the humidity of guano high.

Distribution. Gangwon-do, South Korea (new species).

Remark. Plutomurus jangamensis sp. nov. is very similar to P. gul ( Yosii, 1966) in the general pattern of cephalic and body chaetotaxy, absence of eye, presence of pointed tenent hair, and number of lateral macrochaetae in basal segment of dens and number of mucronal intermediate tooth; however, the two species can be separated by the small spines arranged in-a-row along with dental spines (with in P. jangamensis sp. nov. vs. without in P. gul ) and body color (completely white or white with gray speckles in P. jangamensis sp. nov. vs. gray with dark gray speckles in P. gul ) ( Figs 2a & 2b ). Although the two species are diagnosable by reliable characteristics in species diagnosis, there are also individuals representing intermediate or mixed characteristics of both species, especially in body color, the formula of dental spines, or even the number of prelabral chaetae. Moreover, it was necessary to use another study to clarify whether these variants are all the same species. These results will be described in the molecular results section. This new species is also similar to P. marmorarius Yosii, 1967 described from a cave in Japan, with the presence of 4 + 4 prelabral chaetae. Of the 31 described species of Plutomurus , only P. marmorarius Yosii 1967 shares this character with the present new species ( Jordana et al. 2012), in contrast, 11 species had 3 + 3 prelabral chaetae, 19 species had 2 + 2 and one species is unknown. However, this new species clearly differs from P. marmorarius by the number of chaetae on tenaculum (1 in P. jangamensis sp. nov. vs. 5–6 in P. marmorarius ), the unguiculus teeth (2–5 in P. jangamensis sp. nov. vs. without in P. marmorarius ), and the outer macrochaetae on dens (1 in P. jangamensis sp. nov. vs. 2 in P. marmorarius ).

Figures

FIGURE 1. Jangamgul cave in Korea: a, Entrance zone; b, Blind end of the cave; c, Collecting site.

FIGURES 2–4. Plutomurus jangamensis sp. nov.: 2a, Habitus of new species and 2b, Plutomurus gul Yosii, 1966; 3, Head cheatotaxy; 4a, Picture of micro-sensillum (The arrow indicates micro-sensillum); 4b, Body cheatotaxy (Th. II–Abd. VI). Large empty circles represent macrochaetae; Black circles represent mesochaetae; Circles with a slash represent pseudopore; Circles with three lines represent bothriotricha; Comma-shape represent micro-sensilla.

FIGURES 5–7. Plutomurus jangamensis sp. nov.: 5, Labial palp; 6, Maxillary head; 7, Labrum (Arrows indicate prelabral chaetae). Scale bar: 0.05mm.

FIGURES 8–10. Plutomurus jangamensis sp. nov.: 8, Spine-like chaetae on hind leg; 9, Trochanteral-femoral organ in hind leg; 10, Claw. Scale bar: 0.05mm.

FIGURES 11–12. Plutomrus jangamensis sp. nov.: 11a, and 11b, Dental spines; 11c, Picture of small spines on dens; 12, Mucronal teeth (Scale bar: 0.05mm).

Tables

TABLE 2. Variations in prelabral chaetae and dental spines formula of P.jangamensis sp. nov.

Prelabral
chaetae
	4 + 4	3 + 3	3 + 4
	(13 of 37 specimens)	(11 of 37 specimens)	(7 of 37 specimens)
Dental
spines
formula
	3–4, IV– VI /1–4, I, 1–2, I, 2–3, I (13 of 37 specimens)	3–4, IV– VI /1, I, 2, I, 1–2, I, 1, I (4 of 37 specimens)	3–4, IV– VI /1–4, I, 1–2, I, 2–3, I and 3–4, IV– VI /1, I, 2, I, 1–2, I, 1, I (10 of 37 specimens)