Sreeni's Golden Backed Frog

A fairly large frog when compared with co-occurring golden-backed species, male Indosylvirana sreeni have a snout-vent length of 30 - 69 mm, while females range from 42 - 80 mm. The small head is longer than wide and appears flat from the dorsal view. In the dorsal view the snout is sub-elliptical, from the ventral view it appears rounded, and from the side it somewhat protrudes. The snout is longer than the length of the horizontal diameter of the eye. The prominent canthus rostralis is rounded. The nostrils are oval, have a flap of skin on the lateral side, and are positioned closer to the snout tip than the eye. The loreal region is concave and vertical. The distance between the eyes is flat and wider than the width of the upper eyelid but narrower than the internarial distance. The eyes are set such that the distance between the posterior sides is 1.3 times greater than the distance between the anterior sides of the eyes. The tympanum is three-fourths the size of the eye. There is a pineal ocellus on the anterior edge of the eye. Males have two indistinct vocal sacs located on the posterior and lateral side of the throat (Biju et al. 2014, Ganesh and Arumugam 2015). The forelimbs are thin and short, shorter than the hand length. The long fingers have a relative length of I = II < IV < III and expand at the tips to wide, pointed, flat discs that have lateroventral grooves. The fingers also have dermal fringes and single, prominent, oval, subarticular tubercles. The hands have two moderately developed and distinct palmar tubercles and at the base of each finger there are distinct supernumary tubercles. Males have a single, thick, velvety, oval nuptial pad on finger I and weak humeral glands on the pre-axial side of the upper forelimb. The hind-legs are long and thin with the shank being longer than the thigh and the thigh being about the same length as the foot. The relative toe lengths are I < II < III < V < IV and the toes have discs similar to the fingers. The toes are webbed with a formula of I1-2II1-2+III1-2+IV2-1V. There is a dermal ridge or fringe on toe V that continues as a granular projection from the base of the toe to the knee. There are subarticular tubercles on all toes that are prominent and oval. The inner metatarsal tublercle is distinct and short while the prominent outer metatarsal tubercle is rounded. When adpressed, its hind-legs reach the tympanum (Biju et al. 2014, Ganesh and Arumugam 2015).The skin is shagreen on the dorsal surface of the forelimbs, and belly. The snout, loreal region, and sides of the head are shagreened to granular while the dorsum and flanks are shagreen to sparsely granular. The upper eyelids, dorsum, sides of the body, thighs, tibia, tarsus, anal region are granular. The dorsum, sides of the body, tibia and tarsus also have horny spinules. A prominent dorso-lateral fold starts at the posterior corner of the eye and runs the length of the body. The ventral part of the throat is smooth and there is a round rictal gland on a level with the jaw posterior to the corner of the mouth (Biju et al. 2014, Ganesh and Arumugam 2015).Indosylvirana sreeni can be distinguished from other golden-backed frogs of peninsular India by its size, sub-elliptical snout, prominent yellow dorso-lateral folds, shagreen to sparsely granular dorsal skin, and webbing on the second toe that doesn’t reach the first tubercle on the inside of the toe. More specifically, having a sub-elliptical snout differentiates I. sreeni from I. flavescens, I. manga, and I. montanus. Having shagreen to sparsely granular dorsal skin differentiates I. sreeni from I. caesari, I. indica, and I. magna. Having webbing on the second toe that only reaches the first subarticular tubercle differentiates I. sreeni from I. caesari, I. indica, I. magna, and I. montanus. Additionally, having an interorbital space about equal to the length of the horizontal diameter of the eye differentiates I. sreeni from I. caesari, I. flavescens, I. indica, I. magna, and I. montanus. And having a tympanum that is smaller than the horizontal diameter of the eye differentiates I. sreeni from I. indica. Lastly, I. magna has a larger snout-vent length than I. sreeni (Biju et al. 2014). In life, I.sreeni is golden to bronze to pale brown dorsally with prominent yellow dorso-lateral folds from the anterior of the eye to the posterior trunk. Males are darker laterally, while females are dorsolaterally uniform. The tympanic area is light greyish-brown while the tympanum itself is light brown. The upper lip has a yellowish-white stripe that extends through the rictal gland to the insertion above the arm. The lower flanks, forelimbs, and dorsal surfaces of the thigh, tibia, and foot are light brown with brown spots. There are reticulated light yellowish-brown patches on the light grey anterior part of the thigh. Specimens from the Eastern Ghats also display a pattern of dark barring on the limbs. The whole ventral side of the frog is greyish white. The webbing is dark grey with minute specks. Its eyes are generally dark red-brown with a circular black pupil. The nuptial pad in males is cream to straw-colored (Biju et al. 2014, Ganesh and Arumugam 2015).In preservation, the dorsal surface fades to greyish-brown, dark brown markings are muted to grey-brown, and the flanks become light brown. The tympanic area and tympanum retain the same coloration. The stripe found on the upper lip that extending across the rictal gland becomes white-grey. The limbs are a light grey-brown with grey spots. The reticulated patches on the anterior portion of the thighs become light greyish-brown on a dark grey background. Ventrally, the body is greyish-white, and the legs and feet are yellowish-brown. The webbing of the toes turns dark grey with tiny speckles (Biju et al. 2014). Females are larger than males and commonly have uniformly colored dorsolateral regions while males display darker bilateral coloring. Patterning on the skin also varies between individuals. Some individuals display almost black banding on limbs. Some have also been found with brown-speckled dark grey-brown underbellies. The amount of granulation on the skin also varies from shagreen to sparsely granular (Biju et al. 2014, Ganesh and Arumugam 2015).The species authority is: Biju, S.D., Garg, S., Mahony, S., Wijayathilaka, N., Senevirathne, G., Meegaskumbura, M. (2014). ''DNA barcoding, phylogeny and systematics of Golden-backed frogs (Hylarana, Ranidae) of the Western Ghats-Sri Lanka biodiversity hotspot, with the description of seven new species.'' Contributions to Zoology, 83(4), 269-335.Indosylvirana sreeni is a member of the genus Indosylvirana, which consists of twenty-five species of Hylarana frog endemic to India, Sri Lanka, and Southeast Asia (Oliver et al. 2015). These frogs are also called the Golden-backed Frogs. Based on Maximum Likelihood, Maximum Parsimony, and Bayesian Inference analyses of the mitochondrial genes,16S, COI, and Cytb, I. sreeni is closely related to species in the Indosylvirana flavenscens group. More specifically, I. sreeni is sister to I. indica. The clade including I. screeni, I. indica, and I. caesari is sister to the clade containing I. magna and I. flavescens (Biju et al. 2014) The species epithet, “sreeni” was named after a Dr. K.V. Sreenivasan, who was a supportive figure to S.D. Biju, the first author of the original description of the species (Biju et al. 2014).Indosylvirana sreeni was first named Hylarana sreeni in its original description (Biju et al. 2014). Prior to its description, I. sreeni was thought to be a population of Hylarana temporalis (Biju et al. 2014).At the time of its description, I. sreeni was the only known species of the Indosylvirana flavescens group to be found in both the northern and southern sides of the Palghat gap (Biju et al. 2014).

Indosylvirana sreeni is found in southern India, in both the eastern and western Ghats at elevations of 100 - 1500 m above sea level in the states of Kerala and Tamil Nandu. Specifically, it has been found in Kerala at Chathankod, Pandimotta, Gavi, Thekkady, Munnar, Nelliyampathy, Parambikulam, and Siruvani and in Tamil Nandu at Kiriparai, Sirumalai, Kolli hills, and Shevaroy hills (Yercaud). This distribution is oddly disjointed with the species missing from Nilgiris and the northerly hills of the Central Western Ghats (Biju et al. 2014, Ganesh and Arumugam 2015).Indosylvirana sreeni inhabits aquatic habitats in both primary and secondary forest, favoring perches near fast-moving streams and the surrounding areas. But can also be found in ponds and, rarely, in trees or under logs (Biju et al. 2014, Ganesh and Arumugam 2015).

Indosylvirana sreeni is highly aquatic but known to perch on rocks or on the edge of stream banks of perennial fast flowing streams. During the breeding season, it has been found lying eggs in shallow, peripheral areas of streams (Biju et al. 2014). In the Eastern Ghats, during the monsoon and post-monsoon season, the species could be found in many microhabitats including on the ground, in leaf litter, under logs, on plants, on rocks, in trees, in streams, and in ponds. However, the species was much more likely to be in streams than in ponds (Ganesh and Arumugam 2015). The call of I. sreeni was recorded in the Eastern Ghats portion of the range in July during the day at temperatures of 20.8oC from a distance of 1.5 m from the calling frog. It is complex and fairly long, lasting 3.87 – 11.30 seconds. Roughly transposed, its sound approximates to “cruck...cruck...cru-cru-cruck”. The call consists of 5 – 12 short single notes and two types of double notes: a short double note that was repeated 0 – 5 times or two, long, multi-pulsed notes. The call interval ranged from 545 – 3117 ms and had a dominant frequency of 1.89 kHz with a power peak between 96.7 – 101.2 dB. The short single notes have one pulse lasting 6 – 69 ms, a dominate frequency of 1.03 – 2.24 kHz, and peak power of 76.1 – 97.4 dB. The short double note portion of the call last 30 – 97 ms with the first note lasting 8 – 30 ms and the second note lasting 15 – 39 ms. The notes are always produced together. The long, multi-pulse double notes lasted 457 – 760 m. The first note lasted 250-457 ms, consisted of 18 – 27 pulses, had a pulse rate of 0.06 – 0.07 pulses per second, a dominant frequency of 1.72 – 1.89 kHz, and a peak power of 94.7 – 101.2 dB. The second note lasted 183 – 437 ms, consisted of 9 – 27 pulses, had a pulse rate of 0.04 – 0.06 pulses per second, a dominant frequency of 1.89 kHz, and a peak power of 90.9 – 94.6 db (Ganesh and Arumugam 2015). Females have white ova with a pigmented pole (Biju et al. 2014). In Sirumalai, Shevaroys, and Kolli I. sreeni can be found living sympatrically with various Fejervarya species and in Sirumalai it can also be found with species of Indirana. In the Western Ghats, the species co-occurs with I. flavescens (Ganesh and Arumugam 2015).

Indosylvirana sreeni has not been evaluated by IUCN Red List but is one of the more widely distributed species of Indosylvirana in the Western Ghats (Biju et al. 2014). However, because of its limited and disjoint range, it may be a candidate for protection in the Southern Eastern Ghats (Ganesh and Arumugam 2015).In the Eastern Ghats, Ganesh and Arumugam (2015) observed two I. screeni killed by vehicles and one instance of anophthalmia, a rare birth defect wherein the frog develops only one or neither of its eyes. Further study is needed to provide information on the frequency, magnitude, and long-term effects of roadway mortality in this species.

Indosylvirana sreeni, also known as Sreeni's golden-backed frog, is a species of frog in the family Ranidae found in Southern Western and Eastern Ghats in the states of Kerala and Tamil Nadu, India, at elevations of 100 to 1500 meters.