Journal of Threatened Taxa | www.threatenedtaxa.org | 26 July 2020 | 12(10): 16272–16278
ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print)
#6110 | Received 07 May 2020 | Final received 30 June 2020 | Finally accepted 06 July 2020
Records of two toads Duttaphrynus scaber and D. stomaticus (Amphibia: Anura: Bufonidae) from southeastern India
S.R. Ganesh 1 , M. Rameshwaran 2, Naveen A. Joseph 3#, Ahamed M. Jerith 4 & Sushil K. Dutta 5
1 Chennai Snake Park, Rajbhavan Post, Chennai, Tamil Nadu 600022, India.
2 Reptile Conservation of India (RCI), No: 9/98, Dr. Chelladurai Nagar, Krishnapuram Post, Tirunelveli, Tamil Nadu 627011, India.
3 National Troopers for Conservation of Nature (NTCN), 3/79 C, East Street, Mudivaithanenthal, Thoothukudi, Tamil Nadu 628102, India.
4 M.Sc Wildlife Biology, Govt. Arts College, Udhagamandalam, Tamil Nadu 643001, India.
5 Assam Don Bosco University,Tapesia Gardens, Kamarkuchi, Sonapur, Tepesia, Assam 782402, India.
# - deceased
1 firstname.lastname@example.org (corresponding author), 2 email@example.com, 3 firstname.lastname@example.org, 4 email@example.com, 5 firstname.lastname@example.org
Abstract: We document two toad species Duttaphrynus scaber and D. stomaticus from southeastern India, in the Coromandel Coastal Plains. Owing to incorrect data presented in previous reports denoting the occurrence of these toad species, their occurrence in the said region has remained obscure. Our results, presented here, on both the species are based on morphological data from 15 preserved voucher specimens and direct field observations made by the authors in situ. In this work, we report D. scaber from Chengelpet and D. stomaticus from Thoothukudi. We revisited these places after studying the labeled specimens in Chennai Snake Park Trust Museum, to confirm their occurrences in the respective region and provide natural history notes based on our field observations.
Keywords: Chengelpet, Coromandel Coast, field sighting, India, morphology, toad, Thoothukudi (Tuticorin).
In amphibians, much of the diversity in the Indian peninsula is concentrated in the Western Ghats hill range (Biju 2001; Dinesh et al. 2009; Gururaja 2012), a global biodiversity hotspot covered with evergreen forests (Bossuyt et al. 2004). Other ecoregions in peninsular India are either under-surveyed or are depauperate in amphibian diversity (Dutta 1997; Daniels 2005; Gururaja 2012). Toads including species from the Indian peninsula were subjected to both morphological (Manamendra-Arachchi & Pethiyagoda 1998; Dubois & Ohler 1999) and molecular (Bocxlaer et al. 2009) reviews. But much of the above-mentioned studies better represent material from the Western Ghats and studies on toad species from southeastern India are largely lacking (Srinivasulu et al. 2013). Apart from the better-known, Common Indian Toad D. melanostictus (Schneider, 1799), two other species—the Dwarf Toad D. scaber (Schneider, 1799) and the Marbled Toad D. stomaticus (Lütken, 1864)—have been reported from the Coromandel Coastal Plains (Dutta 1997; Daniel 2002; Daniels 2005; Srinivasulu et al. 2013). Both morphological (Dubois & Ohler 1999) and molecular (Bocxlaer et al. 2009) studies revealed that D. scaber, D. stomaticus, and D. melanostictus all fall into different species groups of their own.
The type locality of Duttaphrynus stomaticus is Assam (Boulenger 1891; Dutta 1997). It is also known throughout the Indo-Gangetic floodplains from Aravallis up to Bengal, through the Terai belts of Nepal and Siwalik foothills and on to other places in northeastern India. South of this vast area, D. stomaticus is known from the Seoni Hills and Chota Nagpur Plateau and on to Salsette / Bombay in the Konkan Coast and eastwards in the Deccan Plateau (Dutta 1997; Daniel 2002; Deuti et al. 2014; Frost 2020). Further south, reports based on old museum collections (Dutta 1997) and a recent field sighting (Sondhi 2009) exist. Recently, Srinivasulu et al. (2013) recommended further studies on southern Indian D. stomaticus populations due to conflicting views about its presence there and some misidentified reports that were later falsified. They even mentioned the population referred to by Dutta (1997) from Tirunelveli Plains as Duttaphrynus cf. stomaticus.
Duttaphrynus scaber was first described from ‘Orientali India’ (= eastern India; Dutta 1997). It had, in fact, starting from the description of its synonym from Trivandrum (= Bufo fergusoni), has been better reported from western India, and not the eastern part of the peninsula (Frost 2020). In the adjacent island of Sri Lanka, D. scaber has remained relatively better-studied (Bogert & Senanayake 1966; Manamendra-Arachchi & Pethiyagoda 1998; Jayawardena et al. 2017), compared to India. Recently, Padhye et al. (2013) reported it from northern Western Ghats, based on both morphological and molecular data. But unfortunately, past reports of this species from Kadayam in southern Western Ghats foothills (Vijayakumar 2002), Chengelpet (Das & Martin 1998), and Mayiladuthurai (Ganesh & Chandramouli 2007; Nath et al. 2012) in Coromandel Coastal Plains were missed, although historical reports from nearby localities were mentioned (Boulenger 1892; Rao 1915). Puducherry was also added as another coastal plains site record for D. scaber (Seshadri et al. 2012 read with Srinivasulu et al. 2013).
Thus, reports from southeastern India of D. scaber fall short due to lack of voucher material (see Ganesh & Chandramouli 2007; Nath et al. 2012) while that of D. stomaticus falls short due to lack of recent field sightings with ample morphological descriptions (see Dutta 1997; Sondhi 2009). Adding on to this, some works have, sadly, confused the identities of D. scaber and D. stomaticus, again from the Coromandel Coastal Plains (Seshadri et al. 2012). All these factors, cumulatively, led Srinivasulu et al. (2013) to revisit such reports that were not based on collected voucher specimens accompanied with ample morphological description notes as well as recent field sightings in situ. The problem is further confounded by reports based on misidentifications (see Srinivasulu et al. 2013). In this paper, we present further records of D. scaber and D. stomaticus from southeastern India. Thus, though described in the 19th century, and often reported in many studies across the country (Dutta 1988, 1997), their occurrence in southeastern India, in the Coromandel Coastal Plains have remained murky. To fill up this lacuna, we describe the morphology and provide field observations for these two species based on both live and preserved materials originating from Coromandel Coastal Plains, in southeastern India.
We conducted visual encounter surveys (Crump & Scott 1994) for collecting primary field data, both day and night. The sighted live individuals were gently restrained and examined, briefly measured and photographed in situ to enable unambiguous species identification, seen in light of publications dealt with by Srinivasulu et al. (2013). They were soon released after recording data and were not preserved and deposited in museums due to the want of permits. The preserved specimens already present in museum holdings were examined in detail. Measurements were recorded to the nearest mm using vernier calipers (least count 0.1mm). Morphological features were documented using a magnifying hand lens (X 5 optical zoom). Measurement protocols and morphometric nomenclature followed Dutta & Manamendra-Arachchi (1996). Colouration notes of live individuals were taken during field work and based on photographs taken there on. Photographs were taken using Canon Powershot SX-130IS model camera and some are reproduced here as photographic vouchers. Coromandel Coastal Plains Ecoregion definition follows Everard (2018). Habitat type classification follows Champion & Seth (1968). Museum abbreviation CSPT refers to Chennai Snake Park Trust, Chennnai, India. Geo-coordinates and elevation values were extracted from Google Earth software.
Duttaphrynus stomaticus (Lütken, 1864)
(Marbled Toad: Image 1)
Taxonomic history: This species was originally described as Bufo stomaticus by Lütken (1864). The type locality of this species is ‘East India’ (restricted to Assam, fide Boulenger 1891) and the type specimens are currently untraceable (Dutta 1997). There are currently three subjective junior synonyms (Dutta, 1997; Frost, 2020) namely: Bufo pantherinus (non Boie) Anderson, 1871, Bufo andersoni Boulenger, 1883 (type loc. Ajmere, Rajputana), Bufo andersonii Murray, 1884 (type loc. Thatta & Joongshai in Sind) and Bufo stomaticus peninsularis Rao, 1920 (type loc. Wattekole, Coorg, Mysore; status: incertae sedis). Bocxlaer et al. (2009) revised its generic allocation as Duttaphrynus stomaticus.
Material examined (n=7): CSPT/A-21, three adult males and four adult females, date and collector unknown, all collected from Tuticorin (8.764˚N & 78.136˚E; 5m), Coromandel Coastal Plains, peninsular India.
Description: Small to medium-sized toad; skin fairly smooth, often with blunt pustules; no ridges on top of head; tympanum ½ the size of eye, visible; parotid glands bean-shaped; fingers free; toes 35-45% webbed; relative finger lengths: 1=2<4<3; relative toe lengths: 1<2<5<3<4. Measurements (range in mm, juvenile’s data in parenthesis): Snout to vent length: 35.0-43.0 (26.0), body width: 8.0–11.5 (5.0), axilla-groin distance: 20.0–24.5 (14.5), head length: 11.5–12.5 (8.5), head width: 7.0–8.0 (5.5), head depth: 4.0–8.5 (3.0), humeral length: 4.0–5.0 (2.5), radio-ulnar length: 4.0–5.0 (2.5), carpal length: 3.0–4.5 (2.0), femoral length: 7.0–8.5 (4.5), tibia length: 5.0–6.5 (3.5), metatarsal length: 4.5–6.0 (3.5), eye diameter: 2.0–3.0 (2.0), tympanum diameter: 0.5 (0.5), eye to nostril distance: 2.5–3.0 (2.0), eye to tympanum distance: 2.5–3.0 (2.0), eye to lip distance: 1.0 (0.5), internarial distance: 1.0–1.5 (0.5), interocular distance: 3.5–4.5 (2.5). Colouration: Dorsum dull ruddy brown, light yellow or dark brownish grey, with yellowish random wavy white spots and patterns; adult males with yellow, single, mid-gular vocal-sac; venter off-white with some dark markings; eyes yellow with a horizontally oval, black pupil.
Field observations: On 5 and 6 April 2015, we conducted night surveys (20.00–04.00 h) in Tuticorin for a total of 40 man hours (8hr x 5men). A total of five sightings, consisting of three adult males and two adult females were obtained. Individuals were sighted actively foraging on land, near paddy fields dotted with coastal scrub belts and grasslands. These short term observations require further field surveys to add more to our knowledge on the natural history of D. stomaticus in Tuticorin (also see Sondhi 2009).
Duttaphrynus scaber (Schneider, 1799)
(Dwarf Toad: Image 2)
Taxonomic history: This species was first described as Bufo scaber Schneider, 1799 (type loc. ex orientali India). As this nomen was confused with Bufo scaber Daudin, 1803 (a synonym of Bufo melanostictus Schneider, 1799), it was also considered as a synonym of D. melanostictus till resurrection by Dubois & Ohler (1999). Again, Dubois & Ohler (1999) also synonymized the nominate taxon Bufo fergusonii Boulenger, 1892 (type locality - Trevandrum on the Cavalry Parade Ground) with Bufo scaber Schneider, 1799 (non Daudin, 1802). Bocxlaer et al. (2009) revised its generic allocation as Duttaphrynus scaber (also see Bogert & Senanayake 1966; Jayawardena et al. 2017).
Material examined (n=8): CSPT/A-19 four adult males, two subadult males and two adult females, date and collector unknown, all collected from Chengelpet (12.727˚N & 79.975˚E; 115m), Coromandel Costal Plains, peninsular India.
Description: Small-sized toad, with a rather depressed body, flat head, blunt snout and fairly slender limbs; skin very rough and warty with numerous pustules both dorsally and ventrally, larger pustules tipped with black keratinized point endings; distinct bony ridges on top of head; tympanum subequal to eye, visible; parotid glands rounded; fingers free; toes <25% webbed; relative finger lengths: 1=2<4<3; relative toe lengths: 1<2<3<5<4. Measurements (in mm): Snout to vent length: 40.0–47.0, body width: 8.0-11.5, axilla-groin distance: 19.0–26.0, head length: 12.5–14.0, head width: 8.0–9.0, head depth: 4.5–6.0, humeral length: 3.5–4.5, radio-ulnar length: 4.0–5.5, carpal length: 4.0–5.0, femoral length: 7.0–8.5, tibia length: 5.0–6.0, foot length: 5.0–6.5, eye diameter: 2.0–3.0, tympanum diameter: 1.0, eye to nostril distance: 3.0–3.5, eye to tympanum distance: 2.5–3.0, eye to lip distance: 1.5, internarial distance: 3.0–3.5, interocular distance: 3.5–4.0. Colouration: Dorsum dull ruddy brown, light yellow or dark brownish black; venter dirty white with some brownish minute specklings; adult males with yellow, single, mid-gular vocal sac; eyes yellow with a horizontally oval, black pupil.
Field observations: From diurnal (09.00–16.00 h) field surveys in Chengelpet by the first author during August 2013 and February 2014, for a period of 50 man hours, this species was sighted commonly. A total of 12 sightings consisting of six adult males (identified based on nuptial pads and gular sacs), four adult females and two juveniles (unsexed) were obtained. The toads were observed resting underneath rocks, debris and inside stone piles.
The current report of both the preserved voucher specimens and recent field observations attest to the fact that in deed both D. scaber and D. stomaticus are present in southeastern India. This means that three different species groups – D. melanostictus group, D. scaber group and D. stomaticus group are widely distributed in India (Dubois & Ohler 1999; Bocxlaer et al. 2009), with at least one species in each group. Recent records of D. scaber from northern Western Ghats by Padhye et al. (2013) stressed the fact that precise records are more from the Western Ghats, including historical record of Trevandrum (Boulenger 1892) and their report from Thrissur. As recent publications from southeastern India (Ganesh & Chandramouli 2007; Nath et al. 2012) are not based on voucher specimens, authors in general have not been unequivocal about the reports of D. scaber from southeastern India. The same holds true for D. stomaticus as well. In this case, despite it being absent in the adjacent and closely-affiliated Sri Lanka (Manamendra-Arachchi & Pethiyagoda 1998), previously this species has been reported from Tuticorin and Tirunelveli in the far south of India by Dutta (1997). Dutta (1997) in his compilation of exhaustive museum specimens of Indian frogs lodged worldwide reported D. stomaticus from Tuticorin and Tirunelveli based on Carnegie Museum specimens. But for this record, D. stomaticus has not been convincingly reported from anywhere in southern India (Srinivasulu et al. 2013). Our specimens studied here conformed to the topotypical D. stomaticus population (fide Choudhury et al. 2001; Jayaditya Purkayashta pers. comm.).
For a long while, only D. melanostictus has been thought to be the common species of toad widespread across India (Dutta 1997). Dutta (1988) provided scores of records of two more congeners–the same ones reported here–D. scaber and D. stomaticus from eastern peninsular India. Most records of D. stomaticus from peninsular India are scarce, e.g., in the Circar Coast (Dutta 1988; Mahapatro & Dash 1991), in the Konkan Coast (Daniel 2002), in the Deccan plateau (Srinivasulu & Das 2008) and in Western Ghats (Rao 1920). Most records are from the Northwestern Frontier (Sharma et al. 2011) and the Indo-Gangetic Plains (Grosjean & Dubois 2005), and eastwards to type locality–Assam and the northeast India in general (see Ahmed et al. 2009). Similarly, reports of D. scaber from India are from the Western Ghats (Boulenger 1892; Satyamurti 1967; Vijayakumar 2002; Ganesh & Asokan 2010; Padhye et al. 2013) and the Eastern Ghats (Thurston 1888; Satyamurti 1967; Srinivasulu & Das 2008; Ganesh & Asokan 2010; Ganesh et al. 2018), Deccan (Donahue & Daniel 1966), while a few reports exist from the Circar Coast (Dutta 1988) and Coromandel Coast (Rao 1915; Das & Martin 1998; Ganesh & Chandramouli 2007; Nath et al. 2012; Seshadri et al. 2012 read with Srinivasulu et al. 2013). A series of preserved specimens of both these species from southern India (Coimbatore, Srivilliputhur, Madurai near the Western Ghats foothills and Tuticorin near the coast) has been reported (Ganesh et al. 2020). But it has not been corroborated by field surveys that these toads exist in the regions mentioned. This work supplements existing records of D. scaber and D. stomaticus with voucher specimen descriptions and/or field observations made from under-reported areas in southeastern India.
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