Assessment of diversity of Odonata fauna in selected sites of Purba Barddhaman district, West Bengal, India

: Purba-Barddhaman, a newly emerged district of West Bengal was surveyed for listing its odonate diversity. The district is located in southern West Bengal, and two major rivers, Damodar and Ajay, run through it. It also has a lot of small rivers, perineal and seasonal water bodies, grasslands, marshes, and agricultural fields, making it a great place for odonates. Five different sites of the district were surveyed by direct search and opportunistic sighting methods for a period of two years (March 2021 to February 2023) and odonate diversity was listed. We have found a total of 47 species belonging to 35 genera and six families from this district. The most diverse family was Libellulidae, with 24 species. A few major findings from this study were Macrogomphus montanus , Platygomphus dolabratus , Lathrecista asiatica , Libellago indica , and Agriocnemis kalinga . This is the first systematic study of odonates from this district, and it illustrates the value of this densely populated district for further exploration due to its high agricultural fertility.


INTRODUCTION
The amphibiotic order Odonata, including dragonflies and damselflies, attracts a lot of attention due to the vibrant colours and exquisite flight patterns (Andrew et al. 2008).They are predominantly found in tropical subtropical and oriental regions, although a small number of species have also been found in the temperate zone, specifically in Japan and China (Kalkman et al. 2008) and are found in close proximity of freshwater body, including streams, lakes, marshes, or transient stagnant rainfall pools.They are hemimetabolous insects that go through three life cycle stages: a brief egg stage (a few weeks), the longest larval stage (ranging from months to year) (Stoks & Córdoba-Aguilar 2012), and finally reaching adulthood.Odonata larvae are aquatic and must go through several moult stages (e.g., 10 moults) before becoming terrestrial flying adults (Stoks & Córdoba-Aguilar 2012;Tiple et al. 2012) and their crucial role is notified in the food web and ecosystem as predators (both nymphs and adults).
Odonates are considered as excellent model for studying insect evolution and ecology due to their phenotype and ecological diversity (Tiple & Koparde 2015;Bybee et al. 2016) and reliable bioindicators (Tiple et al. 2013;Siddika et al. 2017).
Globally, 6,406 species in 693 genera of odonates have been reported (Paulson & Schorr 2023) of which, 498 species and 27 subspecies in 154 genera and 18 families are known from India (Babu 2019;Tiple et al. 2022).By recording approximately 22 species from Kolkata, Selys (1891) launched the study of Odonata in West Bengal and subsequently, Mitra (2002) reported 65 species from the District, Howrah and Kolkata.Srivastava & Sinha (1993) documented 178 species in West Bengal, (Srivastava 1993).Recent studies on the Odonata fauna of Purba Mednipur by Payra & Tiple (2019) and Pahari et al. (2019) recorded 49 and 45 species, respectively.Dwari & Mondal (2018) documented 17 species from the agricultural fields of the Howrah district and 63 Odonata species were reported from the industrial areas of Paschim Barddhaman district, by Nayak & Roy (2016, 2021).Paschim Medinipur was explored by Jana et al. (2021) and 19 species of damselflies were recorded.Odonata diversity of Chinsurah, Baidyabati and Purbasthali were documented by Ghosh (2022) with the finding of 40 species.Latest updated checklist of odonates of West Bengal consists of 240 species from 114 genera (Dawn 2021(Dawn , 2022)).

Study area
Burdwan district was bifurcated into two districts Purba and Paschim Barddhaman on 7April 2017.These two districts are topographically different.Paschim Barddhaman is predominantly arid region with dry deciduous forests, patchy grasslands and two major rivers Damodar and Ajay, whereas Purba Barddhaman extends towards the Gangetic delta, which is more humid and dominated by flat alluvial plainlands.Purba Barddhaman lies almost in the middle of southern West Bengal, consisting of several perennial freshwater bodies, adjacent to major rivers like the Ajay, Damodar, and Ganges and small streams like Khari, Kunur, Banka, Kana Damodar to name a few.Bibliographic data on odonata species implies no such comprehensive record or published checklist from Purba Barddhaman district (all the information were collected from www. purbabardhaman.nic.in.).
Purba Barddhaman district is encircled by six distinct districts: Murshidabad and Birbhum are located in the north, Nadia covers the east, and south is bounded by Hooghly and a portion of Bankura, and the west side by Paschim barddhaman.The district covers an area of approximately 5,432.69Km 2 and is located between 23 o 53′-22 o 56′ N and 88 o 25′-87 o 56′ E (purbabardhaman.nic.in).Annual rainfall ranges from 1,200 to 1,400 mm (Ruidas et al. 2021).
Five different sites (Image 1), which covers a significant part of the district and the district bordering areas, were surveyed for the study of Odonata distribution and abundance.The details of each site are described in the Table .1.

Sampling, Documentation, and Identification
Extensive field work was carried out from March 2021, to catalogue the diversity, distribution patterns of odonates in various niches and habitats at bordering areas of adjacent districts by potent described methodology.
The survey of odonate fauna was carried out throughout the year from March 2021 to February 2023.Data was gathered between 0700 h and 1400 h.Each of the sites were visited at least once in each month (2-5 hours of observation on each day).Each of the sampling area covered at least 1.5 km 2 (150 ha) of land or more.Among each of the study sites there were multiple small patches which were surveyed separately and samples were collected using proper labels (e.g., Site 1, pond 1 near XX village or river) and photographs of each of J TT those sites were taken along with co-ordinates using Angle Cam software.The sampling was conducted using the line transect approach (Burnham et al. 1980) and the opportunistic sighting method.For line transect method the lines were of a length of 0.5 to 1 km and number of lines varied from 2-5 in each site according to habitat and accessibility.Walking with uniform speed was used to cover the whole transect line, and all Odonata species on either side of the line were recorded.Photographs taken from a variety of viewpoints were used for documentation.Canon 80D and Nikon D500 cameras were used for taking photographs of individual sightings in field and collected samples.Collected photographic data as well as samples (both dry and wet) were assembled, and specified into monsoon, post monsoon, and pre-monsoon season.Odonate identification was primarily performed in the field with field identification guide, previous literatures describing Odonata species, and websites such as www.indianodonata.organd (Fraser 1933a(Fraser ,b, 1936;;Subramanian 2009).Some of the species which were difficult to identify instantly, so the cryptic specimens were captured by insect net.The damselflies were preserved in 70% alcohol in 5 ml plastic vials, and the dragonflies were collected in butter paper envelopes for further dry preservation.Dragonfly specimens were stretched with the help of insect pin to display all the key characters for identification.Identification was done with the help of taxonomic keys (Fraser 1933).Taxonomy and systematic arrangements were followed by Subramanian & Babu (2017).

RESULTS
The data from all of the sites revealed a total of 47 species, 35 genera, and six families.The sites chosen contained 32 species under the suborder Anisoptera and 15 species under the suborder Zygoptera.The Libellulidae family was found to be the most abundant (24 species).Together with the Libellulidae, other families were also found, including Coenagrionidae (11 species), Gomphidae (5 species), Aeshnidae (3 species), Platycnemididae (3 species), and Chlorocyphidae (1 species).The detailed record of the species along with its occurrence in different seasons and in different sites is listed in Table 1.

Suborder Zygoptera Selys, 1854 Family Chlorocyphidae Cowley, 1937 Libellago indica Fraser, 1928
Labrum dark brownish-yellow, abdomen 14-16 mm, black in colour with yellow markings on the sides of segments and broad mid-dorsal black stripes, differentiating it from Libellago lineata.Brown eyes.Black prethorax with citron yellow markings.Black thoracic segments with citron or greenish yellow markings.Legs are black, wings are hyaline, and the bases of all have a little amber tinge.Forewing's apical black patch is noticeably longer (See Image 4d).A small damselfly, possibly the smallest described from India to date, with an abdomen measuring about 13-14 mm and a hindwing measuring 8-11 mm.The superior anal appendages are longer than the inferior ones, and the male's tergum 2 is marked with a distinctive cobra hood-like pattern.The ground colour is bright yellow with black on the dorsum, yellow pterostigma, with a bright yellow tip.The males on the other hand are dark green coloured with a black line running through the dorsal side of the abdomen.The anal appendages on occasions appeared yellow or orangish-yellow and the thorax also had black line markings (Image 4a).

Suborder Anisoptera Selys, 1854 Family Gomphidae Rambur, 142 Platygomphus dolabratus Selys, 1854
Abdomen is about 41 mm.Bright yellow labium, labrum, and face.Fronts are completely yellow; vertex is black with a sizable yellow mark behind the ocelli; and the occiput is a bright yellow.Bottle-green eyes.Prothorax J TT is black on dorsum, sides yellow.Thorax is yellow with black markings.Wings hyaline that occasionally have a slight yellow hue.Legs are yellow with black markings.Anal appendages have a black border and are yellow or yellowish-brown in colour (Image 2e).

Macrgomphus montanus Selys, 1869
Length of abdomen, 45 mm.Black head with yellow markings.Labrum has two oval basal patches, as does the entire labium.Brown colored occiput.Unmarked prothorax is black in colour.Stripes are visible on the black thorax.Widely yellow sides with two neatly marked black lateral sutures.Hyaline, palely enfumed, brown wings with a tight reticulation.Dark blackish-brown legs.Black abdomen with yellow markings.The apical half of the divaricate, point-tipped anal appendages are thick at the base (Image 2a,b,c,d).

DISCUSSION
This is the first comprehensive study of odonate diversity to cover a significant portion of the Purba Barddhaman district, though there were some individual sighting reports from a few small pockets and another study that covered Purbasthali, within the district's territory (Ghosh 2022).We attempted to incorporate various types of habitats in this study, ranging from seasonal pools to perennial rivers, resulting in the listing of 47 species from 35 genera.Our results were in cohesion with the detailed report by Dawn (2022).
It reveals from the results (see Table .2) that the family Aeshnidae is noticed in Site 1, 2, 3, 4 but not in 5; out of which Anax indicus (Lieftinck, 1942) appeared to be a more common species and is noticed in Site 1, 2 & 3 site in monsoon period but Anax guttatus (Bermeister, 1839) and Gynacantha sp. in Site 3 during post monsoon period.Anax indicus was found mostly flying over small waterbodies and sometimes hanging from the leaves or branches of mango trees.Gynacantha sp. was found in the middle of Barddhaman town near an old house.

J TT
A total of 24 species belonging to Libellulidae family of Anisoptera were recorded from the study areas, making it the most abundant family.Pantala flavescens (Fabricus, 1798) and Urothemis signata (Rambur, 1842) are available in pre monsoon and monsoon period with P. flavescens mostly flying in good numbers at a height near waterbodies, whereas U. signata was mostly seen sitting atop small shrubby patches.Orthetrum sabina (Drury, 1770) was seen very commonly and across seasons, and on some occasions seen feeding on other Odonata species like Brachythemis contaminata (Fabricus, 1793) was often seen sitting on small hydrophytes in small and stagnant waterbodies.It often showed obelisk posture while sitting.Potamarcha congener (Rambur, 1842) was often seen sitting on wires or dry bamboo sticks.Crocothemis servilia (Drury, 1770) was very commonly found near waterbodies even in the banks of rivers and Diplacodes trivialis (Rambur, 1842) was often found sitting on the ground and feeding on mosquitos, mayflies and other small insects.Brachydiplax sobrina (Rambur, 1842) was found near waterbodies with loads of hyacinths and shady areas; Tramea basilaris (Palisot   (Drury, 1773) was not so common and was seen in grassy areas near waterbodies on a few occasions.Rhodothemis rufa (Rambur, 1842) and Rhyothemis variegata (Linnaeus, 1763) in Site 3, 4 ,5 and Site 2, 3, 4, respectively.Tholymis tillarga (Fabricus, 1798) was mostly found active during late afternoon and during daytime sitting in the shades.

J TT
Pseudocopera ciliata (Selys, 1863) of Platycnemididae family were found in monsoon only in Site 1 & 2. Eleven species of family Coenagrionidae are recorded of which Ischnura senegalensis (Rambur, 1842) and Agriocnemis pygmaea (Rambur, 1842) were found across seasons very commonly.Agriocnemis pygmaea was found mostly in shallow water patches sitting on vegetation.During premonsoon and monsoon Ceriagrion coromandelianum (Fabricus, 1798) and Ischnura rubilio (Selys, 1876) were noticed in all sites; whereas during monsoon and post monsoon period Pseudagrion rubriceps (Selys, 1876) was often observed guarding its mate or in tandem with the female and in very few occasions laying eggs on submerged twigs.Pseudagrion decorum (Rambur, 1842) was found near perennial waterbodies and small seasonal village ponds but Pseudagrion microcephalum (Rambur, 1842) was found near the Damodar River only.Other species like Agriocnemis kalinga Nair & Subramanian 2014, Amphiallagma parvum (Selys, 1876) were found in open water puddles and large waterbodies with grasses and other hydrophytes, whereas Ceriagrion cerinorubellum (Brauer, 1865) was found in shady areas and bushes.Ischnura nursei (Morton, 1907) was only found near Damodar River along with other damselflies like Agriocnemis pygmaea.
It appeared from the recorded data (Figure 2) of studied area that monsoon is the favourable period for completion of their life cycle, although they were noticed as well as were seen to breed throughout the seasons selectively.Highest percentage (85%) of species are recorded from Site 3 and 51.06%, 46.80%, 44.68%, & 31.91%from Site 4, 1, 2, & 5, respectively.
A possible limitation to the study is that many small pockets of the district which covers a number of other water bodies both seasonal and perennial were not surveyed, though we tried to cover as much area as possible.Future exploration of these sites and beyond can extend the list further and make the data even more robust.Seasonal variation of Odonata species and relative abundance in different locations are two other aspects that has to be investigated further.
The study overall sets a stepping stone for further studies related to the fascinating world of Odonates from this district and also advocates about greater possibilities of the district to have a secured place in the Odonata map of West Bengal.

Figure 1 .
Figure 1.Field site: Panel (a) shows the geographical location of PurbaBarddhaman district within India (shown as red dot).Panel (b) shows the centralised position of PurbaBarddhaman district in southern part of West Bengal (the boundary of the district is filled in red).Panel (c) shows the geographical location of five field sites.The sites are namely site 1 Katwa and surroundings, site 2 Bhatar, Karjana and surroundings, site 3 Barddhaman town and surroundings, site 4 Ausgram and surroundings, site 5 Jamalpur, Raina and surroundings.

Image 1 .
Different habitats from the sampling areas across five sites: The photographs show different habitats from the areas sampled across five different sites in Purba Bardhaman district.The habitats were diverse ranging from river banks to seasonal pools and canopy covered shrubland areas.All the photographs have the unique name code for each of the microhabitats along with the GPS location.Photographs were taken using Anglecam software.Photograph courtesy © Kushankur Bhattacharyya.Journal of Threatened Taxa | www.threatenedtaxa.org| 26 February 2024 | 16(2): 24775

Figure 2 .
Figure 2. Percentage of odonate diversity from different sites and in different seasons.The bar graphs in panel (a) shows percentage of odonates found in different field sites.S1, S2, S3, S4, S5 denotes Site 1, 2, 3, 4, 5, respectively.The bar graphs in panel (b) shows percentage of odonates found in different seasons.Each season is denoted by different colour These are Bar graphs plotting the respective percentages.The X axis shows locations (panel (a)), and seasons (panel (b)).The Y axis shows the percentage of occurrence of species from different locations and different seasons.

Table 1 . A brief description of selected study sites along with the co-ordinates and habitat types.
Seasonal marshes and water puddles, seven perennial ponds with low to moderate hydrophyte population, paddy fields, mango groves, Khori River bank and surrounding grasslands.