Journal of Threatened Taxa Journal of Threatened Taxa | www.threatenedtaxa.org | 26 May 2019 | 11(7): 13875–13885

Ceriagrion chromothorax sp. nov. (Odonata: Zygoptera: Coenagrionidae) from Sindhudurg, Maharashtra, India

Shantanu Joshi¹ & Dattaprasad Sawant²

¹National Centre for Biological Sciences, Tata Institute of Fundamental Research, Rajiv Gandhi Nagar, Kodigehalli, Bengaluru, Karnataka 560097, India.
²Grant Medical College & Sir JJ Group of Hospitals, Noor Baug, Mazgaon, Mumbai, Maharashtra 400008, India. 

¹shantanu@ifoundbutterflies.org (corresponding author), ²dattaprasad.101@gmail.com

Abstract: Ceriagrion chromothorax sp. nov. is described from Western Ghats, India, based on six males and one female collected from Sindhudurg District of Maharashtra.

Keywords: Damselfly, Devgad, new species, Sindhudurg Marsh Dart, taxonomy, Western Ghats.

Introduction

Ceriagrion is a diverse and widespread genus of damselflies (Zygoptera) within the family Coenagrionidae with 51 species (Schorr & Paulson 2018).  This genus consists of many closely related species, which are difficult to diagnose without thorough examination of the prothorax and male genital ligula (Asahina 1967; Dijkstra 2005).  Asahina (1967) provided a review of this genus from the Oriental region, which still remains the most complete account.

Four species of Ceriagrion are currently known from the Western Ghats of India (Fraser 1933a; Subramanian & Babu 2017; Subramanian et al. 2018).  Here we describe a fifth species—Ceriagrion chromothorax sp. nov. from Vimaleshwar, Sindhudurg District, Maharashtra.  This species is morphologically similar to Ceriagrion coromandelianum (Fabricius, 1798), and C. indochinense Asahina, 1967, but can be distinguished from them by its chrome yellow synthorax, structure of the prothorax, and the shape of caudal appendages.

Materials and Methods

The new species was first photographed in August 2017.  Subsequently, DS collected three males in August- and September 2017, a copula along with two more males was collected in August 2018.  The collected specimens were examined using Leica (Leica Microsystems, Germany) stereomicroscopes for close up imaging.  Multiple images were stacked to generate greater depth of field; scale bars were added using Leica Application Suite (Leica Microsystems, Germany) or ImageJ (Schneider et al. 2012).

The general morphological terms are following Garrison et al. (2010), and Riek & Kukalova-Peck (1984) was referred for wing venation terminology, along with Kennedy (1920) for genital ligula and Asahina (1967) for prothorax.

The holotype has been pinned, while the two paratypes were preserved in ethanol.  Specimens are deposited at the Research Collections, National Centre for Biological Sciences, Bangalore.

The following abbreviations are used in the text: FW = fore wing, HW = hind wing, Ax & Px= antenodal and postnodal nervures, Pt= pterostigma, S1:S10= first to last abdominal segments.

Ceriagrion chromothorax sp. nov.

(Images 1a,b, 2a,b, 3a,b,c, 4a)

urn:lsid:zoobank.org:act:78B8744D-467C-4B5E-A393-73BDE57A6BC9

Common name: Sindhudurg Marsh Dart.

Holotype: Male (NCBS-BB921), 4.viii.2017, Vimaleshwar, Devgad, Sindhudurg District, Maharashtra, India, (16.4330N & 73.3950E; elevation ~27m), Dattaprasad Sawant leg.

The locality and collector of the following allotype and paratypes are same as holotype, except date of collection.

Allotype: Female (NCBS-BH969), 16.viii.2018.

Paratypes: 2 males (NCBS-BB922, NCBS-BB923), 27.ix.2017; 1 male (NCBS-BH970, collected in copula with allotype female), 16.viii.2018; 2 males (NCBS-BH971, NCBS-BH972), 19.viii.2018.

Etymology: The name ‘chromothorax’ is given for the bright yellow (=chromo) thoracic coloration (Image 1).

Description of holotype male (Images 1–5)

Head: Labium dark brown; labrum, anteclypeus, postclypeus, postfrons yellow, upper half of antefrons brown, rest yellow.  Vertex and postocular lobes pale yellow; eyes olive green.
Prothorax (Image 4): Yellow; anterior lobe with paired black marking dorsally, extending from the anterior border of latero-medial lobes; posterior lobe of the prothorax flat at the anterior border and medially, raised at the posterior border and laterally; posterior border trilobate; the posterior border of the central lobe not straight.

Synthorax (Images 1&2a): Mesostigmal plates: lateral carina shaped half-hexagon, pointed anteriorly; anterior carina robust, broader at the meeting point with lateral carina; lateral carina not extending beyond acrotergite; posterior carina rudimentary not extending even halfway from lateral carina to median pit; mesostigmal lamina raised; remus large; anterior carina and anterior 1/3rd of lateral carina black.  Synthorax bright yellow in live individuals, due to the flash used while photographing dorsum appears olive green in some individuals; slightly darker on dorsum paler yellow ventrally, black spots at the posterior end of meta and mesopleural sutures, small black spot at the junction of mesepimeron and metepisternum, 45 degrees from metastigma.  Mesocoxa and metacoxa dull with faint pruinescence.  Legs bright yellow, gradually pale brown towards the claws; small black dot at base of femur on the posterior side; base of the claws black; femur and tibia with large black spines. Metascutum and mesoscutum yellow with slight pruinescence.
Wings (Image 2b): Hyaline; Ax 2, Px: FW= 11, HW= 10. Pt: dark brown, slightly darker in HW, spanning just more than one cell; arculus lying at the level of second Ax; petiolated from anal vein; radial vein arising at the level of nodus.

Abdomen (Image 2a): Bright yellow; S2–6 posterior border dorsally faint brown; S7–8 faint brown dorsally, S9–10 dark brown; dorsum of S10 black, extended at the anterior border.

Genital ligula (Image 5): Description of genital ligula mainly based on paratype; genitalia was not dissected from the holotype to keep the specimen intact, but the holotype genitalia was observed under the microscope after relaxing the specimen to confirm characters described here.  Laterally, ventral half of first segment one black, rest pale brownish-yellow; anterior 1/4th of second segment black, continued as dark brown; black medial marking faintly visible in ventral view; third segment bi-lobed, folded internally with brown apex, and darker terminal fold; apex of terminal segment visible between the two lobes in ventral view, lateral margins of lobes straight till midway and expanded thereon.

Caudal appendages (Image 3): Cerci longer than paraprocts, broader at base; the apex pointed, curved ventrally and inwards, ending in a black spine often not visible in lateral view (Images 3 & 4); laterally paraprocts appear conical or blunt apically depending on the angle; apex inwardly curved, ending in a spine as seen in ventral and dorsal views; cerci dark brown covered densely with yellow setae especially at the inwardly curved apical spine.  Apex of paraprocts black, base pale brown; both covered with setae.

Measurements (in mm): abdomen + anal appendages = 37.2, HW= 21.5, FW= 22.5, genital ligula= 2.1, cerci= 0.5.

Variation in paratype males

Px: FW: 11–12, HW: 10–11. The paratypes and holotype show slight variation in the brown markings on dorsum of S5–10, particularly evident living specimens.  In some males, the markings are only restricted to the posterior half of segments.  Due to the angle and the position of paraprocts the caudal appendages appear slightly different in paratype males (Image 4c&d).

Description of allotype female (Image 6–7, 10)

Head: Pale olive, frons with paired black spots at the ventral border; vertex and occipital area pale brown; eyes olive green, blue at dorsum in live individuals; faint greenish-yellow in the pinned specimen.

Prothorax (Image 6): Propleuron with a black marking laterally; anterior lobe with a paired black stripe darker at the posterior border; anterior border of anterior lobe raised, bilobed; medial lobes more rounded than in male; posterior lobe tri-lobed similar to the male.

Synthorax (Image 10): Mesostigmal plates similar to male; yellow, except a conspicuously black and large depression below mesostigmal plates; lateral carina slightly curved; anteriorly curved towards the junction with lateral carina on both sides, anterior carina black; rest of the synthorax pale greenish yellow, darker dorsally, especially the mesepisternum.  Legs: coxae white; dorsal 2/3rd of femur dirty white, rest pale brown; posterior face of femur dark brown, broader at the ventral margin; tibia and tarsus pale brown; legs covered with black spines.

Wings: Similar to male, hyaline, with black venation, basal veins dark brown; pterostigma dark brown, quadrate; Px: FW: right=10, left=11, Ax: 2 in all wings.

Abdomen (Image 10): S1 pale brown, S2–5 yellow; laterally and ventrally posterior 1/3rd of S5 and S6–10 pale brown; S2–7 and S9 with black marking at the posterior margin, darker sequentially, S7 with a black marking at the anterior margin; S8 black latero-dorsally, anterior half of S9 black laterally; S10 pale with faint dark brown markings at the anterior margin dorsally.

Caudal Appendages (Image 7): Cerci brown, stylus dark brown, valve pale brown; cerci laterally flattened, curved inwards approximately 45 degrees, covered with yellow setae; stylus simple reaching to half the length of cerci posteriorly, in lateral view; slightly tapering in the middle, slightly expanded at the apex.

Differential diagnosis

Ceriagrion chromothorax sp. nov. is similar to C. coromandelianum, and C. indochinense, the latter has not been recorded from India but could possibly occur in the northeast.  The above three species share the character of yellow or olivaceous thoracic and abdominal coloration, but they differ with respect to the shape of their anal appendages, structure of prothorax and mesostigmal plate. Ceriagrion fallax, occurs in northern India but not in western India, it is similar to the three above-mentioned in terms of the yellow abdominal coloration, but is readily distinguishable using the following characters: a) S7–10 extensively black, b) shape of posterior lobe of prothorax and mesostigmal plates, and c) shape of anal appendages.

Ceriagrion chromothorax males can be distinguished from C. coromandelianum and C. indochinense by: a) shape and length of cerci and paraprocts (paraprocts shorter than cerci in C. chromothorax, while longer than cerci in the two latter species, Fig. 2, Images 3,4,10), b) shape of the prothorax and mesostigmal plates (Images 4; Fig. 2), and c) completely yellow thorax (Image 1–2: green in C. coromandelianum and C. indochinense (Image 8).  The genital ligula is similar in these three species, but in C. chromothorax the third segment is conspicuously bi-lobed (Image 5b&c).

Ceriagrion chromothorax is very similar to C. indochinense in the following characters: a) thoracic coloration, b) larger size (in relation to C. coromandelianum) and shape of paraprocts; but these two species differ most conspicuously in the structure of the mesostigmal plate of the thorax.  The caudal appendages of C. chromothorax, although similar to C. indochinense, can be differentiated by the longer cerci, and the inwardly curved, apical spine of the paraprocts.  The structure of mesostigmal plates is unique in C. chromothorax, especially the shape of the lateral carina (Fig. 1).  The posterior lobe of the prothorax in C. chromothorax differs in shape from C. coromandelianum and C. indochinense (the posterior margin of medial lobe is straight, not curved, posterior margin of lateral lobes less curved (Images 4,10 & Fig. 1).

Ceriagrion chromothorax is a larger species with a slimmer abdomen as compared to the widespread C. coromandelianum.  Cerci are almost as long as paraprocts in C. chromothorax, while cerci are much shorter than paraprocts in C. coromandelianum (Fig. 2).  These two characters along with the shape of the mesostigmal plates can be used to separate these two sympatric Cerigarion species.  The female of this species is more difficult to distinguish from C. coromandelianum, and is also similar to another co-occurring species, C. olivaceum.  Females of these three species have olive green thorax and pale brown abdominal coloration; however, the female of C. chromothorax can be distinguished from similar Ceragrion species by: a) shape of its mesostigmal plates (especially the lateral carina, Image 6), and b) dark markings at the posterior border of S2-7 (Image 9).

Habitat, habits and notes on congeneric species

A total of 14 visits were made to the type locality by DS, from July 2017 to November 2018.  Two individuals of C. chromothorax were first observed in July 2017, in the bushes near a banyan tree (Ficus benghalensis) at a weir dam (locally known as ‘Bandhara’) on a stream (Image 11).  On two subsequent visits conducted on 4 and 10 August two males were observed, the holotype male (Images 2–4) was collected on fourth.   On the next visit to the same locality on 27 September 2017, DS observed three C. chromothorax males out of which two were preserved as paratypes (with no sign of the female).  In the month of November and December no individuals of C. chromothorax were observed, while density of C. coromandelianum increased.  More than 15 males were observed along with three copulae on 16 August 2018, one copula was collected, from which the female allotype is described. C. chromothorax was observed at an additional locality in Wada Village (Image 12), Sindhudurg District, Maharashtra (GPS coordinates: 16.443946, 73.392725), approximately two kilometers from the type locality.  Habitat where the species was observed in Wada was an isolated muddy pond, surrounded by rice paddy fields and coconut plantations around it.  Four males, but no females were observed at the pond on 18 August 2018

Both the type locality and the other locality at Wada (Image 12) are seasonal.  Water starts building up from June with the start of monsoon.  July-September the water levels remain high, aquatic vegetation is most abundant during this period (see Image 11a).  From the end of September water levels start reducing, high fluctuations in water levels can be seen during this period dictated by infrequent storms and rain.  February onwards there was almost no flowing water (see Image 11b&g, Image 12), with only a few puddles left along with some odonate species such as Amphilagma parvum and Tramea sp.

Four Ceriagrion species, viz., C. cerinorubellum (Brauer, 1865), C. olivaceum (Laidlaw, 1914), C. rubiae (Laidlaw, 1916), and C. coromandelianum were observed co-occurring with C. chromothorax at the type locality.  All five Ceriagrion species were observed simultaneously from July–September, whilst October–November onwards only C. coromandelianum and C. cerinorubellum were present.  C. chromothorax males were observed aggressively interacting with C. coromandelianum, C. cerinorubellum, Pseudagrion rubriceps,and Pseudagrion malabaricum.  C. chromothorax males were observed feeding six times, following prey species were observed: a) a small white moth, b) a teneral Pseudagrion microcephalum, and c) C. coromandelianum (on four separate occasions).  This species prefers aquatic vegetation/grasses along the edges and wasn’t observed in the deeper parts of the water body.

Discussion

Ceriagrion is a genus of small to medium-sized generally brightly coloured damselflies with 51 species found across Africa, Asia and Australia and with a single representative in Europe.  Most species are widespread, but certain groups have incredible cryptic diversity, which remains understudied especially in Asia.  One such group comprises seven species (including C. chromothorax), which are found in mainland southern and southeastern Asia and are similar in appearance, having yellow abdominal coloration together with a yellow or olive thorax.

Of the seven species C. coromandelianum is undoubtedly the most widespread.  In Western Ghats two ‘yellow’ Ceriagrion occur: C. coromandelianum and C. chromothorax sp. nov. (C. chromothorax being the only endemic representative of the genus in Western Ghats and India).  Ceriagrion coromandelianum, C. fallax, and C. indochinense are widespread, whilst C. nigroflavum, C. melanurum, and C. pallidum have comparatively restricted distributions.  Ceriagrion nigroflavum is closely related to C. fallax with which it occurs in Myanmar, Thailand and Laos.  Although C. nigroflavum appears to be widely distributed, it is the only Asian Ceriagrion whose female remains unknown (Dow 2010).  In addition, it is known from only a handful of specimens with no records since 1952.  Ceriagrion pallidum was described from Laos and remains poorly known.  Although, Fraser (1933b) mentions it as “similar to C. azureum and C. olivaceum” (two very different species), this species resembles immature or teneral coloration in C. coromandelianum and C. indochinense (Farrell 2016).  Ceriagrion melanurum, another species similar to C. fallax, is distributed in China including Taiwan, the Korean Peninsula and Japan.

This description of a new species from the Western Ghats, a reasonably well studied region in terms of Odonata, is surprising and suggests that it has been misidentified as C. coromandelianum in the field by previous workers.  This is the first new Ceriagrion species to be described from Asia in more than 50 years (Schorr & Paulson 2018).  The type locality of this species is a non-protected area rich in odonate diversity, with more than 60 odonate species (Dattaprasad Sawant, pers.comm. 28 March 2019). 

For figure & images – click here

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