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Rediscovery of Anisogomphus ceylonicus (Odonata: Gomphidae) based on its larva

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Anisogomphus ceylonicus (Hagen in Selys, 1878) is one of the rarest of the Sri Lankan Odonata. It was first discovered from Ramboda over 140 years ago based on a female specimen, which was originally described as Gomphus ceylonicus and later assigned to the genus Heliogomphus by F. C. Fraser. Almost a century later, Lieftinck (1971) collected an immature male and its exuvia of a clubtail dragonfly from Rambukpath Oya, 10 miles northwest of Hatton in 1962 and described as Anisogomphus solitaris. However, Bedjanič & van der Poorten (2013) recognized that H. ceylonicus is conspecific with A. solitaris, and thus reassigned it to the genus Anisogomphus. Since the discovery of the species, only these two records have ever been documented, despite odonatological surveys and numerous biodiversity explorations conducted on the island.
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35 TAPROBANICA VOL. 11: NO. 01
Rediscovery of Anisogomphus ceylonicus
(Odonata: Gomphidae) based on its larva
Anisogomphus ceylonicus (Hagen in Selys,
1878) is one of the rarest of the Sri Lankan
Odonata. It was first discovered from Ramboda
over 140 years ago based on a female specimen,
which was originally described as Gomphus
ceylonicus and later assigned to the genus
Heliogomphus by F. C. Fraser (Bedjanič & van
der Poorten 2013). Almost a century later,
Lieftinck (1971) collected an immature male and
its exuvia of a clubtail dragonfly from
Rambukpath Oya, 10 miles northwest of Hatton
in 1962 and described as Anisogomphus
solitaris. However, Bedjanič & van der Poorten
(2013) recognized that H. ceylonicus is
conspecific with A. solitaris, and thus reassigned
it to the genus Anisogomphus. Since the
discovery of the species, only these two records
have ever been documented (Bedjanič et al.
2014), despite odonatological surveys and
numerous biodiversity explorations conducted
on the island.
According to the taxonomic descriptions, the
adult A. ceylonicus can be distinguished by the
combination of characters including
characteristic wing venation, predominantly
black prothorax with yellow pyriform dorsal
spot, well-interrupted broad mesothoracic collar,
long narrow antehumeral stripe pointed at both
ends, isolated upper mesepisternal spot, middle
lateral yellow thoracic stripe interrupted, lateral
yellow markings on abdominal segments 13, a
dorsal basal yellow patch on abdominal segment
7 and the anal appendages of the male (Bedjanič
& van der Poorten 2013). The larvae can be
distinguished by the long movable hook, down-
curved palpus with faintly serrated inner surface,
characteristic shape of ligula, long dorso-
ventrally flattened third antennomere with long
setae and very short fourth antennomere (de
Fonseka 2000). Despite its placement in the
genus Anisogomphus, it should be noted that A.
ceylonicus differs considerably from other
Anisogomphus based on both adult and larval
characters (Lieftinck 1971, de Fonseka 2000)
and its generic placement needs to be reviewed.
Even though both sexes of the species as
well as the larval exuvia is descriptively known
(Lieftinck 1971), the available knowledge on the
species beyond its taxonomic descriptions, is
very limited. The emerging male collected in
1962 was collected in March from a stream in a
steep ravine with the riparian vegetation
consisting of bushes and some indigenous
vegetation and surrounded by tea and rubber
plantations (Brinck et al. 1971, Lieftinck 1971).
No other information on its habitat and habits is
known. A. ceylonicus is recognized as a globally
Critically Endangered species and the possibility
of it being extinct due to habitat degradation or
pollution has also been expressed as there were
no records of the species for over 50 years
despite some targeted surveys (Bedjanič et al.
2014, Bedjanet al. 2021).
As a part of an ongoing study on odonates in
the montane region of Sri Lanka, a field survey
was conducted in the foothills of Haputale
Mountains in February 2021. An unusual
gomphid larva was encountered during the
survey and field observations and subsequent
comparisons with taxonomic literature identified
it as a larva of A. ceylonicus. Thus, here we
report the third record of A. ceylonicus,
confirming living evidence of the species almost
six decades after its last documented record. The
observation presented here was recorded at
Nikapotha (6.7470 N, 80.9656 E. alt. 748 m
a.s.l.), between Beragala and Koslanda along
Colombo-Batticaloa highway, Badulla District,
Sri Lanka. The stream where the observation
was made (Fig. 1) had a moderate flow rate with
rocks and boulders. Semi disturbed riparian
vegetation with some herbaceous plants, shrubs
and trees, was present along the stream. It had
been partially blocked by the local community
using boulders to create a small pool with a
width of about 6 m, for washing and bathing.
The substrate of this area primarily consisted of
sand with some scattered pebbles and cobbles.
TAPROBANICA, ISSN 1800427X. May, 2022. Vol. 11, No. 01: pp. 3537, pl. 9.
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REDISCOVERY OF Anisogomphus ceylonicus
36 TAPROBANICA VOL. 11: NO. 01
Figure 1. Habitat of Anisogomphus ceylonicus at
Nikapotha; arrow indicates the microhabitat where
the larva was found.
A survey was conducted in the site on 3
February 2021. Odonates were recorded using
the visual encounter survey method and
potential micro-habitats were sampled for larvae
using a hand net. All odonate larvae collected
were examined in detail, photographed and
released back to the original location. Larval
identifications were based on Lieftinck (1971)
and de Fonseka (2000), and morphological
terminology follows Tennessen (2019).
The observed A. ceylonicus larva (Fig. 2)
represented an intermediate instar with the wing
sheath reaching the base of abdomen segment 3.
The larva was found near the stream bank under
some aquatic vegetation. The substrate at the
microhabitat of the observed larvae consisted of
sand (Fig. 1). Four Paragomphus larvae and two
Anax immaculifrons Rambur, 1842 larvae were
also recorded in the same habitat. The site was
revisited in April 2021, but no adults or larvae of
A. ceylonicus were observed even though early
instar Paragomphus larvae were abundant.
Description of larva: Sandy brown in
colour with black eyes and a dark abdomen tip.
Prementum (Fig. 2B) longer than the maximum
width. Palpus down curved with faintly serrated
inner margin and less than half the length of
movable hooks. Movable hooks long and
gradually curved ending with a sharply pointed
apex. Ligula concave with a distinct anterior
directed tooth in the middle. A dense ridge of
setae along the margin of the ligula. Antenna
with four antennomeres and the third
antennomere elongated and covered with long
setae (Fig. 2C). Legs are covered in sandy
brown setae. Fore and mid tibiae with apical
triangular burrowing hooks. Abdomen (Fig. 2D)
widest in the middle. A faint dark pattern on
either side of the mid dorsal carina of the
abdomen. Minute dorsal spines and small lateral
spines on abdominal segments 7, 8 and 9.
Epiproct and cerci are of equal length and
paraprocts slightly longer. Cercus with a straight
outer margin and outward curved inner margin
forming a tapering apex. Paraproct also with a
straight outer margin and a curved inner margin
but with a less tapering apex compared to the
cerci. Epiproct is with a slightly tapering
rounded apex.
The morphological characters of the
observed larva match well with the description
and diagrams of A. ceylonicus exuvia by
Lieftinck (1971). The distinct shape of the
ligula and features in the antennae clearly
support its identification compared to the larvae
of other Sri Lankan gomphids (de Fonseka
2000). The habitat and elevation of the location
also agree with the limited information that has
been reported by previous authors. The new
locality reported here is about 45 km southeast
of the type locality of the species and is located
on the southeastern slope of the central
highlands of Sri Lanka (Fig. 3).
Based on the limited records available, it
seems that the species inhabits semi disturbed
streams with a sandy substrate in montane and
sub-montane habitats between the elevations of
300-900 m. It is possible that the species may
occur in suitable habitats across the highlands of
Sri Lanka even though occurrence records are
extremely rare. As the emerging male was
collected in March 1962 (Lieftinck 1971) and
the present observation of intermediate instar
larva was made in February, the species is likely
on the wing at least in March and April, which is
the period prior to the beginning of the
southwestern monsoon in Sri Lanka. Based on
the observations presented here, it seems that A.
ceylonicus can tolerate some aquatic pollution
caused by detergents and soap at least in its early
larval stages. However, further studies are
required to understand how water quality affects
its larval development and emergence.
Anisogomphus ceylonicus is one of the few
Odonates of Sri Lanka with no photographic
records of a living specimen available hitherto.
The present observation provides the first
photographs of a live A. ceylonicus larva and the
most recent documentation of the species. These
observations, coupled with previous work
(Lieftinck 1971, Bedjanič & van der Poorten
2013), provide an improved understanding of the
species, which might enable further targeted
surveys to be made. Extensive surveys in
SUMANAPALA ET AL. 2022
37 TAPROBANICA VOL. 11: NO. 01
potentially suitable habitats, especially in
February, March and April, incorporating both
adult and larval survey techniques, might yield
further records of the species. Any such records
would add crucial information on the biology
and ecology of this globally Critically
Endangered species and support its conservation
in the future.
Figure 3. Distribution of Anisogomphus ceylonicus
in Sri Lanka; historical records (orange), new locality
record (red)
Acknowledgements
We express our gratitude to Rufford Foundation
grant (No. 26652-1) for funding the survey. We
also thank Devaka Weerakoon (University of
Colombo, Sri Lanka) and the Butterfly
Conservation Society of Sri Lanka for their
support.
Literature cited
Bedjanič, M., R.A. Dow, and A.P. Sumanapala
(2021). Anisogomphus ceylonicus. The IUCN
Red List of Threatened Species 2021:
e.T200030437A173365264. Accessed on 24
February 2022.
Bedjanič, M., N. van der Poorten, K. Conniff, and
A. Salamun (2014). Dragonfly Fauna of Sri
Lanka: Distribution and Biology with Threat
Status of its Endemics. Pensoft, Sofia: 321pp.
Bedjanič, M. and N. van der Poorten (2013). On
the synonymy of two enigmatic endemic
clubtails from Sri Lanka (Anisoptera:
Gomphidae). Agrion, 17 (2): 4447.
Brinck, P., H. Andersson, and L. Cederholm
(1971). Report No. 1 from the Lund
University Ceylon Expedition in 1962.
Entomologica Scandinavica Supplementum 1.
Munksgaard, Copenhagen: 34pp.
De Fonseka, T. (2000). The Dragonflies of Sri
Lanka. Wildlife Heritage Trust. Colombo:
303pp.
Lieftinck, M.A. (1971). Odonata from Ceylon.
Reports from the Lund University Ceylon
Expedition in 1962. Vol. 1. Entomologica
Scandinavica Supplementum, 1: 188207.
Tennessen, K.J. (2019). Dragonfly Nymphs of
North America: An Identification Guide.
Springer, Cham: 620pp.
Submitted: 10 Sep 2021, Accepted: 4 May 2022
Section Editor: Tosaphol S. Keetapithchayakul
A.P. Sumanapala 1,2, T. Ranasinghe 2 & D.
Sumanapala 2,3
1 Department of Zoology & Environment Sciences,
University of Colombo, Sri Lanka
E-mail: apsumanapala@gmail.com
2 Butterfly Conservation Society of Sri Lanka, 762/A,
Yatihena, Malwana, 11670, Sri Lanka
3 Faculty of Graduate Studies, University of Sri
Jayewardenepura, Sri Lanka
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