Research Article |
Corresponding author: Anh D. Nguyen ( ducanh410@yahoo.com ) Academic editor: Nesrine Akkari
© 2023 Anh D. Nguyen, Pavel Stoev, Lien T. P. Nguyen, Tam T. Vu.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Nguyen AD, Stoev P, Nguyen LTP, Vu TT (2023) A new species of Paracortina from a Vietnamese cave, with remarkable secondary sexual characters in males (Callipodida, Paracortinidae). ZooKeys 1149: 181-195. https://doi.org/10.3897/zookeys.1149.99651
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A new millipede species, Paracortina kyrang sp. nov., is described from a cave in Cao Bang Province, northern Vietnam. The new species is diagnosed by having an extraordinarily long projection on the head of males, reduced eyes, a gonocoxite with two processes, a long and slender gonotelopodite with two long, clavate prefemoroidal processes densely covered with long macrosetae apically, and with a distal, reverse, short spine on mesal side, and a rather sinuous distal part of the telopodite. This is the third species of the genus that is known from Vietnam. A brief comparison of some secondary sexual characters is made.
Biodiversity, cave fauna, northern Vietnam, southern China
The millipede order Callipodida is represented in South-east Asia by three extant families – Sinocallipodidae Zhang, 1993, Paracortinidae Wang & Zhang, 1993, and Caspiopetalidae Lohmander, 1931 (
A list of the hitherto described species of Paracortina
Here, we describe a new species of Paracortina from Ky Rang Cave, Cao Bang Province, Quang Hoa District, Quoc Toan commune, in northern Vietnam. The species is highly adapted to the cave environment and exhibits several somatic characteristics of troglobionts, such as reduced eyes, elongated legs and antennae, and lack of pigmentation on parts of the body.
All specimens were hand-collected from Ky Rang Cave, Cao Bang Province, Quang Hoa District, Quoc Toan commune, in northern Vietnam and preserved in 85–90% ethanol. All morphological characters were investigated with an Olympus SZX16 stereomicroscope. Gonopods were dissected for morphological examination and photographed. Colored images were taken using a Nikon SMZ800N microscope and NIS-Element BR v. 5.20.00 and stacked using Helicon Focus v. 7.0. Images were assembled into plates using Photoshop CS6. The terminology follows
Total DNA was extracted using Qiagen Dneasy Blood and Tissue Kits. A 680-bp fragment of the mitochondrial gene, cytochrome c oxidase subunit I (COI), was amplified and sequenced using a pair of universal primers, LCO1490 and HCO2198 (
The holotype, paratypes, and DNA vouchers were preserved in 90% ethanol and deposited at the Institute of Ecology and Biological Resources (IEBR), Hanoi, Vietnam.
Abbreviations: PT pleurotergite/s.
Order Callipodida Pocock, 1894
Family Paracortinidae Wang & Zhang, 1993
Holotype. 1 male (IEBR-Myr 921) Cao Bang Province, Quang Hoa District, Quoc Toan commune, Ky Rang Cave, 2.xi.2021, leg. Anh D. Nguyen.
Paratypes. 1 female, 1 juvenile (IEBR-Myr 932), 1 female (IEBR-Myr 935) same locality, but 17.iii.2022, leg. Anh D. Nguyen & D.D. Nguyen.
Non-types. 1 male, 1 male juvenile, 1 female juvenile (IEBR-Myr 954), same locality, but 16.x.2018, leg. Alexandre Faille.
The new species is well distinguished from all congeners by the strongly modified head in males bearing a unique apically bent projection. Body composed of 68–74 pleurotergites +telson, eyes reduced, composed of 19 or 20 ommatidia in two or three rows. Gonocoxa with an anterior long spiniform process (a), as long as ca 80% of telopodite stem, and a rather slender, much shorter, cephalad process (b). Process a with a cephalad lobe distally, process b about 1/3 the length of telopodite. Telopodite with two long, clavate prefemoroidal processes (cp), densely covered with long macrosetae apically. Telopodite long, slender, apically twisted laterad, with a distal, reverse, short spine. Distal part of telopodite rather sinuous, narrowed at the base, then smoothly widened at its top, to narrow sharply finally at the solenomere (sl) and parasolenomere (ps).
The new species can be keyed out into the first branch in Liu et al.’s (2015) key for identification of the species of Paracortina, with the clustering species having a pair of prefemoroidal clavate processes (cp) on the gonopods: P. thallina, P. stimula, P. leptoclada, P. voluta, P. serrata, P. viriosa, and P. carinata (all from southern China).
The species epithet “kyrang” is a noun in apposition for the type locality, Ky Rang Cave.
Male holotype : Length about 42 mm, width and height of midbody PT 2.3 mm and 2.2 mm, respectively; 68 PT+ telson.
Colour
: living specimens greenish white (Fig.
Head
(Figs
Antennae
(Figs
Width of PT: 6>7>>8–14>4>3>2>1. PT slightly broader than high; height of 10th PT: 2.19 mm, width 2.32 mm.
Collum
(Fig.
Below ozopores, midbody PT with 2+2 primary crests and 2+2 shorter and thinner secondary crests between primary crests, and 8–10 lower crests down to ventral pleurotergal edge (Fig.
Midbody pleurotergal setae 5+5, located at caudal edges of primary crests (Figs
Epiproct
(ep) (Fig.
Male leg-pairs 1 and 2 much shorter, with strong setae on ventral side of femorite and tibia, leg-pair 3 slightly shorter than following legs. Tarsi 1–3 1-segmented, and from tarsus 4 to ultimate pair 2-segmented; tarsal pads large until leg 26, then gradually thinner and eventually absent on subsequent legs. All legs ending with a rather slender, long, curved claw. Coxal sacs present from legs 3–26 (PT 16). Only coxae and tibia finely micropapillate ventrally (Fig.
Coxa 2 with a small anterior process and a posterior gonopore, the latter placed on a small cone (Fig.
Chaetotaxy:
Anterior setae | Posterior setae | |
Collum | 4+4 | 2+2 |
PT2 | 5+5 | broken |
PT3 | 5+5 | broken |
PT4 | broken | 5+5 |
PT5 | broken | 5+5 |
PT6-penultimate PT | 5+5 (rarely 6+5) |
Gonopods (Figs
Paracortina kyrang sp. nov., holotype A leg 7 in posterior view B leg 7 in anterior view C gonopods in posterior view D gonopods in anterior view. Abbreviations: st = short tubercle; rap = rounded anterior process; a = coxal process a; b = coxal process b; te = telopodite; cp = clavate prefemoroidal processes; sp = distomesal spine on telopodite; sl = solenomere.
Paracortina kyrang sp. nov., holotype A right gonopod in lateral view B right gonopod in ventral view C right gonopod in mesal view D solenomere in ventral view. Abbreviations: a = coxal process a; te = telopodite; cp = clavate prefemoroidal processes; sp = distomesal spine on telopodite; sg = seminal groove; sl = solenomere; ps = parasolenomere.
Females. Head unmodified (Fig.
The new species has a close genetic identity with Tetracion jonesi Hoffman, 1956 (Abacionidae) from 77.74% to 78.25%.
Ky Rang Cave is located in close proximity to Thang Hen Lake in Cao Bang Province, northern Vietnam, at the altitude of 1,000 m a.s.l. The cave entrance is wide, but the only passage is blocked by an artificial door made by the local residents. Because of it, the semi-light part of the cave is missing, and, on entry, the cave is immediately dark (Fig.
Currently, there are only three Paracortina species recorded in Vietnam: P. warreni Shear, 2000 from caves at Hong Mat (Hoa Binh), P. multisegmentata Stoev & Geoffroy, 2004 from Ngoc Lac (Thanh Hoa), and P. kyrang sp. nov. from Quoc Toan (Cao Bang) (Fig.
Cao Bang Province is located in a karst region of northern Vietnam and supports hundreds of caves varying in size and environmental parameters (
Most callipodids live in caves and rock crevices (
Head shape is often dimorphic in order Callipodida (
Some callipodidans have the size of the anterior pleurotergites in females and males differing, which allows for observer to determine the sex, even with the naked eye. Usually, in females, the second and third pleurotergites are enlarged, while in males this occurs in the sixth and seventh pleurotergites, where the gonopods are located. The enlargement of pleurotergites in both sexes corresponds to the maturation, when vulvae and gonopods become fully developed. This dimorphic character is observed also in the genus Paracortina. The PT 6 and sometimes PT 7 are strongly enlarged in males, but not in females – see P. chinensis, P. multisegmentata (
The work is supported by the Vietnam Academy of Science and Technology under the project NCXS01.04/23-25. We acknowledge Mai Van Thai, Dang Van Dong, and Nguyen Duc Hiep, all from IEBR, for their help in fieldwork. Alexandre Faille is sincerely thanked for kindly providing his specimens. Two reviewers, Dr William Shear (USA) and Dr Henrik Enghoff (Denmark), and the editor, Dr Nesrine Akkari (Austria), are acknowledged for their invaluable comments to improve the manuscript.
COI sequences of the new species
Data type: FAS file