Rhacophorus lateralis Boulenger, 1883

Biju, S. D., Kamei, Rachunliu G., Mahony, Stephen, Thomas, Ashish, Garg, Sonali, Sircar, Gargi & Suyesh, Robin, 2013, Taxonomic review of the tree frog genus Rhacophorus from the Western Ghats, India (Anura: Rhacophoridae), with description of ontogenetic colour changes and reproductive behaviour, Zootaxa 3636 (2), pp. 257-289 : 271-274

Rhacophorus lateralis Boulenger, 1883

Small Tree Frog (Das and Dutta 1998)

( Figures 1A, D–E , 2B , 3, 3C–E , 6B , 7A–G ; Tables 1–3)

Original name and description. Rhacophorus lateralis Boulenger, 1883 , Description of new species of reptiles and batrachians in the British Museum. Annals and Magazine of Natural History, Series 5, 12:162. Name-bearing type. Holotype, NHM 1947.7. 2.8.38 (ex BMNH 1882.2.10.75), by monotypy, an adult male, collected by Beddome. Type locality. “Malabar”, India. Current status of specific name. Va li d n a m e, a s Rhacophorus lateralis Boulenger, 1883 .

Other material studied/observed. KARNATAKA: Kodagu district, Virajpet, Lakunda Estate, ZSI A 9071 (adult female), collected on 19 July 1998, ZSI A9072 (adult female), collected on 29 July 1998; Honey Valley Estate, SDBDU 2011.84 (adult male), collected by SDB on 13 June 2011; Chikmagalur district, Bhadra Wildlife Sanctuary, SDBDU 2011.1420 (adult female), collected by SDB on 20 June 2010; Bygoor Estate, SDBDU 2010.330–2010.331 (two adult males), collected by RS on 26 June 2010; Kudremukh National Park, SDBDU 2011.1421 (adult male), collected by SDB on 11 August 2009. KERALA: Idukki district, Periyar Tiger Reserve, ZSI/SRS VA 245 (sex not known); Wayanad district, Kalpetta, SDBDU 395–398 (four adult males), collected by SDB on 12 July 2002 and SDBDU 40114 (adult female), collected by SDB on 12 July 2002, SDBDU–712 (two adult males), collected by SDB on 15 July 2004; Kurichiyarmala, SDB personal observation (adult male), (not collected) on 12 July 2002; Mananthavady, SDBDU 6302–6303 (two adult males), collected by SDB on 15 July 2002; Sulthanbathery, SDBDU 204 (adult male), collected by SDB on 11 August 2003.

Diagnosis. Rhacophorus lateralis can be distinguished from known congeners by the following combination of characters: (1) small male adult size (SVL 28.2–35.0 mm); (2) body slender; (3) green or dark brown dorsal skin, presence of a distinct metallic yellow or light yellow lateral stripe that commences from the snout, running over the upper eyelids to the groin and terminating in the inguinal region; (4) finger and toe discs well developed (FD III 1.6 ± 0.2 mm, FW III 0.6 ± 0.1 mm, N = 14, male; TD IV 1.4 ± 0.1 mm, TW IV 0.6 ± 0.1 mm, N = 14, male); (5) webbing moderate between fingers, reaching below the distal subarticular tubercle on either side of finger III; (6) webbing on toes moderate, reaching up to distal subarticular tubercle on either side of toe IV ( Figure 7 F, G ).

Comparison. Rhacophorus lateralis is unique in having green or brown dorsal skin colouration with two golden yellowish lateral lines from the nostrils running over the eyelids and along the sides of the body to near the vent.

Das (2000) provided a description of this species based on a fresh collection of two female specimens. We here provide a redescription of the holotype male for completeness of the taxonomic revision of historic name bearing types.

Description of holotype (all measurements in mm): Medium sized frog (SVL 35.0); head width subequal to length (HL 9.7; HW 9.8; MN 9.3; MFE 7.1; MBE 3.5); outline of snout in dorsal and ventral view oval, snout (SL 4.2) longer than horizontal diameter of eye (EL 3.1); loreal region obtuse, canthus rostralis distinct; nostril oval and closer to tip of snout than eye (NS 1.1; EN 2.5); interorbital area (IUE 3.9) wider than upper eyelid (UEW 2.0); distance between posterior margins of eyes (IBE 9.2) less than two times the distance between anterior margins of eyes (IFE 5.6); Tympanum ( TYD 1.7) distinct, rounded, its distance to eye (TYE 0.6) approximately one third of tympanum diameter, supratympanic fold indistinct, from posterior corner of upper eyelid to near the shoulder; pineal ocellus absent; vomerine ridge horizontal, near anterior corner of choanae; space between the two ridges is less than the length of the ridge; tongue notched; median lingual process absent. Forearm (FAL 5.8), shorter than hand (HAL 9.3); dermal fringe on outer border of forelimbs present; fingers with dermal fringes; finger discs with distinct circummarginal grooves, third finger disc two times wider than finger (FD III 1.2; FW III 0.5); webbing moderate, on finger I up to subarticular tubercle; finger II, to subarticular tubercle (inner) and above the subarticular tubercle (outer); finger III, to above the first subarticular tubercle on both sides; finger IV, up to second subarticular tubercle; relative length of fingers: (I <II <IV <III); subarticular tubercles prominent, oval, all present; prepollex distinct, oval; one palmar tubercle, oval, indistinct; nuptial pad well developed. Hind limbs moderately long, shank length (SHL 16.3) longer to thigh (TL 15.0), and foot length (FOL 11.9); distance from heel to tip of toe IV (TFOL 20.7); thick dermal fringe from base of pad of toe V extends along lateral edge of tarsus to heel where it develops into broad flange with lateral projecting calcar on lateral edge of heel; webbing medium, webbing on toe I, well above subarticular tubercle; toe II, to well above subarticular tubercle (inner) and base of disc (outer); toe III, well above distal subarticular tubercle (inner) and up to distal subarticular tubercle (outer); toe IV, reaching the third subarticular tubercle on either side of toe; and toe V, up to second subarticular tubercle; relative length of toe: I <II <III <V <IV; finger discs with distinct circummarginal grooves, fourth toe disc 2.4 times wider than toe (TD IV 1.2; TW IV 0.5); subarticular tubercles prominent, oval, all present; inner metatarsal tubercle distinct, oval; outer metatarsal tubercle, supernumerary tubercles and tarsal tubercle absent.

Skin of snout and between eyes smooth, upper eyelids shagreened; anterior and posterior parts of back shagreened, dorsal parts of forelimb, thigh and shank are smooth ( Figure 7A ); ventral side, throat, chest smooth, belly shagreened, posterior part of belly granular, forelimbs smooth, thigh granular, ( Figure 7B ); a conspicuous squarish dermal fold above the anal opening.

Colour of holotype. In preservation. Dorsal side light brown, ventral side light grey, thigh darker than belly and chest, hand, feet and webbing dark grey ( Figure 7 ). A light grey stripe that commences above the nostrils, runs over the upper eyelids on either sides of the body, terminating in the inguinal region. In life. This species shows considerable variation in dorsal colour ( Figure 3C–E ).

Secondary sexual characters. Male, nuptial pads present; female, eggs large (diameter 2.5 ± 0.3 mm, N = 30, single egg clutch), unpigmented (based on SDBDU 40114, SDBDU 2011.1420).

Variation. Measurements of two female and 14 male specimens, including holotype, are given in Table 2. Considerable variation is seen in the dorsal colouration of this species: SDBDU 40114, dorsally light green, a pair of golden yellow stripes commences above the nostrils to vent margined with florescent blue, lateral side of the body and margins of thigh light reddish, limbs with inconspicuous bluish cross bands, webbing dark grey ( Figure 3D ); SDBDU 2011.84, brown with scattered inconspicuous spots, lateral line golden yellow with dark brown margins, lateral side light yellowish red, ventral side light grey, limbs with darker cross bands, webbing dark grey ( Figure 3E ); SDBDU 395, greenish with broken lateral yellow line margined with light blue ( Figure 3C ). For additional colour variations in life see Dinesh et al. (2010), Goel & Goel (2010) and Molur & Molur (2010).

Distribution and natural history. Rhacophorus lateralis is currently known from multiple localities in Chikmagalur and Kodagu districts of Karnataka, and Idukki and Wayanad districts of Kerala ( Figure 6B ). For complete list of specific localities refer to Table 1. All populations were found in disturbed habitats, either in coffee plantations close to forest patches or in disturbed secondary forests. The calling microhabitat preference in all populations was about 1.5 m above the ground, usually on leaves. It is likely that R. lateralis is restricted to the north of Palghat Gap in its distribution (see discussion section). All collections in the present study were made between 19:00 to 20:00 hours.

Remarks. Rhacophorus lateralis was originally described on the basis of a single specimen by Boulenger (1883). Wolf (1936) provisionally placed the species in the synonymy of Rhacophorus malabaricus which was subsequently rejected by Inger & Dutta (1987 "1986") and Biju (2000). After the original description another specimen was collected by W. M. Daly in 1892 from “Koppa, Mysore” and deposited (under the number 13565) in the Indian Museum (= Zoological Survey of India, Kolkata, [Sclater 1892a]). Sclater (1892a) described the species distribution range as “Mysore and Malabar”. The historical locality “Koppa, Mysore” was however overlooked by subsequent workers. The location of the Koppa specimen is not known and is presumably lost (SDB personal observation). After more than 100 years Biju (2000) and Das (2000) reported this species from Kerala and Karnataka, respectively. Later the species was subsequently reported from different parts of the Western Ghats in Kerala and Karnataka (Bennet et al. 2000; Dinesh et al. 2010; Goel & Goel 2010; Molur & Molur 2010).

Figures

FIGURE 1. A – G. Leaf nest types and multimale mating in the Western Ghats Rhacophorus. A – C. Leaf nest types. A. Type 1: Single leaf rolling— Rhacophorus lateralis; B – C. Type 2: Multiple leaves nest— R. calcadensis, R. malabaricus, R. pseudomalabaricus; D – G. Multimale mating. D – E. R. lateralis on vegetation. F. R. malabaricus on vegetation. G. R. malabaricus on ground.

FIGURE 2. A – D. Photographs showing colour and marking of juveniles and adults in the Western Ghats Rhacophorus. A. R. calcadensis; B. R. lateralis; C. R. malabaricus; D. R. pseudomalabaricus.

FIGURE 3. A – H. Rhacophorus of the Western Ghats. A – B. R. calcadensis; C – E. R. lateralis; F – G. R. malabaricus; H. R. pseudomalabaricus.

FIGURE 6. A – D. Distribution maps of the four Rhacophorus species in the Western Ghats. A. R. calcadensis; B. R. lateralis; C. R. malabaricus; and D. R. pseudomalabaricus. Positioning of symbols is approximate; see Table 1 for coordinates.

FIGURE 7. A – G. Holotype of Rhacophorus lateralis NHM 1947.7. 2.8. 38 (ex BMNH 1882.2.10.75), from " Malabar ": A. dorsal view; B. ventral view; C. lateral view of head; D. ventral view of hand; E. schematic illustration of webbing on hand; F. ventral view of foot; G. schematic illustration of webbing on foot.