Research Article |
Corresponding author: Tosaphol Saetung Keetapithchayakul ( keetapithchayakul.ts@gmail.com ) Academic editor: Jan van Tol
© 2024 Tosaphol Saetung Keetapithchayakul, Quoc Toan Phan.
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:
Keetapithchayakul TS, Phan QT (2024) Description of the larva of Platycnemis phasmovolans Hämäläinen, 2003 (Odonata, Platycnemididae), with a key to the larvae of the subfamily Platycnemidinae from the Sino-Japanese and Oriental regions. ZooKeys 1221: 1-18. https://doi.org/10.3897/zookeys.1221.138079
|
The final instar larva of the rare species Platycnemis phasmovolans Hämäläinen, 2003 is described and illustrated here for the first time, including a new distribution record from Vietnam. The larva of P. phasmovolans differs from that of congeneric species by distinct morphological features, including the presence of four setae on the palpal lobe of the labium, the presence of lateral spines on abdominal S5–9, and a long terminal filament on the caudal lamella. We also provide a key to species for the known larvae of the subfamily Platycnemidinae in the Sino-Japanese and Oriental regions.
Biological notes, Coenagrionoidea, damselfly, identification key, new record, Platycnemidini, Vietnam, Zygoptera
The genus Platycnemis Burmeister, 1839, comprising 11 recognized species (
The larvae of Platycnemidinae display a variety of morphological traits that are essential for species identification and add to our understanding of evolutionary relationships within the subfamily (
Final instar larvae were collected from headwater streams of the North Central Region of Vietnam using D-frame nets and sorted manually with sieves. The larvae were transported to the laboratory and reared in plastic containers until they reached adulthood. They were fed Aedes larvae and provided with toothpicks as substrates to support emergence. Identification of the emerged adults was based on
The descriptions of the larval mandibular formula, generic characteristics, and distinctive surface features of the larvae follow
S1–10 abdominal segments 1–10
A1–7 antennomeres 1–7
Vietnam • 1 exuviae: 1 ♂ (collected as last stadium larva, reared in laboratory); 27 Jul. 2024; 18°59'24.4"N, 104°50'17.8"E; elevation 266 m a.s.l.; Yen Khe Commune, Con Cuong District, Nghe An Province; T.S. Keetapithchayakul leg.; ZCDTU. • 7 late stadium larvae: 1 ♂ (F-0), 1 ♀ (F-0), 1 ♂ (F-1), 2 ♀♀ (F-1), 1 ♂ (F-2), 1 ♀ (F-2); 27 Jul. 2024; same site and collector as above; ZCDTU. • 2 early stadium larvae: 1 ♂, 1 ♀; 27 Jul. 2024; same site and collector as above; ZCDTU.
(based on 1 male (exuviae) and 1 female (F-1)) Habitus (Fig.
Head
: broad in dorsal view, roughly a strongly squashed pentagon in outline, with hind margin strongly excavated; bearing scattered simple setae; labrum flattened ventrally, outline with convex corners flanking central anterior concavity, with minute tubercles on distal half and basal glabrous; frons and vertex strongly raised with prominent ocelli; compound eyes narrow and rounded protruding postero-laterally; occiput with dense minute tubercles and scattered simple setae, convex in outline, anterior occiput with low raised prominences just behind margin of eyes (Fig.
Compound eyes and mouth parts of Platycnemis phasmovolans larva A genae B left maxilla, dorsal view C left maxilla, lateral view D right mandible, ventro-internal view E right mandible, internal view F left mandible, internal view G left mandible, ventro-internal view. Arrow indicates row of spines and setae.
Thorax : narrower than head, with scattered simple setae, papilliform setae, and white spots. Prothorax dorsally flattened; lateral angles acute, projecting sharply at postero-lateral corners; posterior margin gently keeled midline, forming subtle ridge across posterior border, rounding at lateral edges. Synthorax robust, slightly elongated; mesepisternum with pronounced lateral keels defining boundary with mesepimeron; keels slightly raised, forming well-defined ridge; dorsal surface of mesepisternum with faint longitudinal ridges, aligned parallel to midline; mesinfraepisternum slightly convex; wing pads pale with glabrous, parallel, anterior and posterior wing pads reaching to distal margin of S6; legs almost flat and long; femora thin with dark band on posterior side, row of spiniform setae and scattered simple setae; tibial comb with scattered setae and a few tridentate setae; two claws simple with pulvilliform empodium.
Abdomen
: cylindrical, slender, narrowing caudally, scattered simple setae, minute tubercles and white spots; abdominal terga with pale longitudinal line, posterior margin with pair of pale black spots; abdominal sterna smooth; abdominal pleura flatted on S2–S9, with scattered simple setae, and row of spiniform setae and simple setae on lateral margin, lateral spines on abdominal S5–S9 (S9≥S8≥S7>S6>>S5) (Fig.
Vietnam • 4 ♂♂; 21 May 2024; 18°59'24.4"N, 104°50'17.8"E; elevation 266 m a.s.l.; Yen Khe Commune, Con Cuong District, Nghe An Province; Q.T. Phan leg.; ZCDTU. • 3 ♂♂, 2 ♀♀; 27 Jul. 2024; same site and collector as above.
China • 1 ♂ 26–31 May 2020; 25°18'36.0"N, 107°54'00.0"E; Maolan National Nature Reserve, Guizhou, Libo County, Province, Ruibin Song observer.
Male (Fig.
Female (Fig.
This description agrees almost exactly with
Lao PDR: Bolikhamsai Province, Kaew Neua Pass area (
The larvae of P. phasmovolans inhabit forest pools, which are small, shallow bodies of water formed by rainwater or slow-moving streams (Fig.
This study presents the first description of the larva of P. phasmovolans, bringing the total number of documented larval descriptions for Platycnemis species from Asia to four: P. echigoana by
Asian Platycnemis species can be distinguished from their European congeners by the presence of four palpal setae on the labial lobe, as opposed to three setae in European species (
The distribution of Platycnemis may be restricted by its preference for specific habitats, such as pristine forests and limestone caves (as observed in China). The species appears to be restricted to regions where such conditions occur (Fig.
Recent records have expanded the known distribution of P. phasmovolans to Vietnam, approximately 80 km from the type locality in Laos (Fig.
Currently, data on P. phasmovolans is significantly lacking, leading to its classification as “Data Deficient” by the IUCN (
The subfamily Platycnemidinae in the Sino-Japanese and Oriental regions includes 16 species in two tribes: Coperini (Copera, 5 species) and Platycnemidini (Matticnemis, 1 species; Platycnemis, 6 species; and Pseudocopera, 4 species) (
1 | Caudal lamellae with frilled borders | 2 (Coperini: Copera) |
– | Caudal lamellae with elongate and smooth borders | 4 (Platycnemidini) |
2 | Number of fringe filaments less than 20; short, fringe filaments stout basally; sometimes poorly fimbriated | C. chantaburii [Indochina region] |
– | Number of fringe filaments more than 20; long, fringe filaments stout or narrow basally | 3 |
3 | Slender, fringe filaments stout basally; spiky, jagged appearance (Fig. |
C. marginipes [Oriental region] |
– | Hair-like, slightly curved fringes, very narrow basally; wavy appearance (Fig. |
C. vittata [Oriental region] |
4 | Palpal lobe with three palpal setae; moderately produced ligula; well-developed protuberance on occipital margin; body shorter than 1.3 × length of caudal gills | 5 (Pseudocopera) |
– | Palpal lobe with four palpal setae; strongly produced ligula; poorly-developed protuberance on occipital margin; body at least as long as 1.5 × length of caudal lamellae | 7 (Platycnemis) |
5 | S8–9 without lateral spines | Ps. rubripes [Sino-Japan region] |
– | S8–9 or S9 with lateral spines | 6 |
6 | Caudal lamellae length longer than 0.8× body length; with one pair seta on the terminal filament of the caudal lamellae; with lateral spine on S9 | Ps. ciliata [Oriental region] |
– | Caudal lamellae length shorter than 0.8× body length; without one pair seta on the terminal filament of the caudal lamellae; with lateral spine on S8–9 | Ps. annulata [Sino-Japan region] |
7 | S5–9 with lateral spines | Pl. phasmovolans [Indochina region] |
– | S7–9 with lateral spines | 8 |
8 | Postocular lobe rounded; shallow posterior lobes | Pl. sasakii [Sino-Japan region] |
– | Postocular lobe angulated; deep posterior lobes | 9 |
9 | Ligula with small median cleft; terminal filaments on apex of caudal gills long | Pl. echigoana [Sino-Japan region] |
– | Ligula without median cleft; terminal filaments of caudal gills short or absent | Pl. phyllopoda [Sino-Japan region] |
The authors express their gratitude to the editor (Jan van Tol) and referees, including Albert G. Orr, and Matti Hämäläinen for their valuable feedback and insightful suggestions. We also thank Ruibin Song for providing crucial information on the distribution and reference photos of Platycnemis phasmovolans from China. Special thanks are extended to Nguyen Tu Minh Hoang for his assistance with photography during the field trip. Our appreciation also goes to Ho Viet Hieu and Nguyen Huy Hung (Duy Tan University) for supplying mosquito larvae. Lastly, we are deeply grateful to Akihiko Sasamoto, Xin Yu, Sungbin Cho, and Guo-Hui Yang for their invaluable suggestions on genus Platycnemis.
The authors have declared that no competing interests exist.
No ethical statement was reported.
This study received partial support from the International Dragonfly Fund through the second author.
Conceptualization: TSK, QTP. Investigation: QTP, TSK. Methodology: QTP, TSK. Project administration: QTP. Resources: TSK. Visualization: QTP. Writing – original draft: TSK, QTP. Writing – review and editing: TSK, QTP.
Tosaphol Saetung Keetapithchayakul https://orcid.org/0000-0001-7565-4701
Quoc Toan Phan https://orcid.org/0000-0002-3154-6546
All of the data that support the findings of this study are available in the main text.