Description
Ghatixalus magnus is a relatively large frog for the genus. The original description is of two large males with snout-vent lengths of 71.54 and 81.90 mm. The head is slightly wider than long. When looking at the head morphology the snout is rounded and greatly protrudes from the lateral profile and acutely rounded from the ventrally view. The canthus rostralis is rounded and the loreal region is obtusely flat. The nostrils are close to the tip of the snout, while the eye to nostril distance is just slightly smaller than the eye diameter. The distance between the eyes is greater than the length of the upper eyelid width. The pupils are horizontal and oval shaped. The tympanum is distinct and round and is almost twice as large as the distance from the eye to the tympanum. The distinct supratympanic fold extends from behind the outer canthus rostralis to just below the forearm. They have a single, median and subgular vocal sac present. The forelimbs are shorter than the hand length. The fingers are elongated, have a moderate dermal fringe, have webbing, and the fingertips are enlarged into truncate discs with circum-marginal grooves. The relative length of the fingers is 1 < 2 < 4 < 3, following the traditional method of finger numbering (II < III < V < IV following the Shubin and Alberch [1986] method). The single subarticular tubercles are prominent and round. However, the second subarticular tubercle on finger 2 is weakly developed. The hands also have supranumerary tubercles, prominent and elongated palmer tubercle. The hind limbs are long, with the thighs having a total length that is longer than the shanks. The feet have supernumerary tubercles and long, webbed toes. The webbing extends from the disc of toe 5 to above the subarticular tubercle of toe 4 and finally to the disc of toe 3. The relative lengths of the toes are 1 < 2 < 3 < 5 < 4. On the toes, there are single, well-developed subarticular tubercles.

The snout, upper eyelids, interorbital region, and anterior ventral part of the thigh have smooth skin. The sides of the head, back region of the tympanum, and the upper part of the flanks are granulated, and the dorsal parts of the forelimbs and hind limbs are finely granulated (Abraham et al. 2015).

Ghatixalus magnus can be differentiated from other Ghatixalus species of Western Ghats (G. variabilis and G. asterops) by the larger snout-vent length in the focal species; G. variabilis and G. asterops have shorter snout-vent lengths of 46.67 ± 2.0 mm and 41.93 ± 2.0 mm respectively. Additionally, the eye to nostril distance in G. magnus is about the length of the eye diameter, while the eye to nostril distance is shorter than the eye diameter in both G. variabilis and G. asterops. The anterio-ventral surfaces of the thighs in G. magnus are smooth and the posterior sides are areolate, while the full ventral surface of the thighs are areolate in both G. variabilis and G. asterops. Ghatixalus magnus has a larger distance from the tympanum to the eye, and the supratympanic fold extends from the posterior corner of the eye to below the level of the forearm, whereas the fold ends above the level of the forearm in both G. variabilis and G. asterops (Abraham et al. 2015).

The coloration of adults in life is a pale rusty-yellow on the dorsal side that has a reticulation of many small, irregular bright-yellow blotches. The lateral side is chocolate brown with cream-colored reticulations and purple-turquoise blotches on the groin. The tympanum and loreal region are pale yellow and a bright-yellow bands runs along the upper part of the tympanic fold down to the canthus rostralis and converges at the snout tip. The iris is a purple-grey color with many black venations. The limbs are rusty-yellow with dark brown cross-bands on the dorsal sides of thigh, forelimbs, and digits. The posterior side of the thigh is brown with randomly scattered yellow blotches. The feet and hands are a light turquoise blue with bluish-brown webbing and yellow disks (Abraham et al. 2015).

The coloration of adult preserved specimens is dark brown with dull-yellow blotches on the dorsal and lateral sides. On the lateral sides the blotches extend from the arms to the groin. The tympanum in a yellow-brown and the upper eyelid is grey. The ventral side is a brownish-grey, with the coloration being lighter at the throat and chest and darker near the posterior end. Lastly, the hands and feet are a pale blue color (Abraham et al. 2015).

Males have a sexual characteristic on their fingers where the nuptial pads on finger III are more pronounced than on finger II (using the Shubin and Alberch [1986] method). Late stage metamorphs and froglets maybe green on the dorsum (Abraham et al. 2015).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: India

View distribution map in BerkeleyMapper.

Ghatixalus magnus occurs in the highlands of the southern Western Ghats, India, between the Palakkad Gap and Shencottah Gap in the forested hill streams of Valparai and Parambikulam, Kadalar, Upper Manalar, and near Pandianthodu. This species was specifically found in the mid-montane rainforests at elevations between 1350 and 1800 meters ASL (Abraham et al. 2015).

Life History, Abundance, Activity, and Special Behaviors
Ghatixalus magnus is a widespread Rhacophorid species in the Western Ghats. The tadpole development takes place in months preceding summer when stream pool flow rates are slow (Abraham et al. 2015). Other Ghatixalus are foam nesting frogs as are closely related genera (Abraham et al. 2015).

Larva
The tadpole description is based off of one tadpole at stage 38. The body is large and depressed. The eyes are moderate sized, directed laterally, and are not visible in ventral view. The nares are an equal distance from the snout and eyes. The spiracle is sinistral and is located at ventrolaterally at the mid body. The tail musculature is well developed. The tail fin is high and pointed at the end with the upper fin being higher than the lower fin. The oval shaped oral disc is located anteroventrally and is laterally emarginated. There are many marginal papillae that frame the oral disc both ventrally and laterally, but they are absent from the upper labium. There are small submarginal papillae that cover the inner rim of the oral disc. The upper jaw is stretched into a wide U-shaped arch, while the lower jaw is V-shaped. The labial tooth row formula is 10(6 -10)/10(10) and helps to differentiate this species (Abraham et al. 2015).

The G. magnus tadpole can be differentiated, morphologically, by its large size, coloration and by labial tooth row formulas. Whereas G. magnus has a labial tooth formula of 10(6 -10)/10(10), both G. variabilis and G. asterops have formulas of 7(3 – 7)/6(1). Biologically, G. variabilis and G. asterops are adapted to rocky, montane streams and thus have a moderate oral sucker to help them attach to substrate, whereas G. magnus is found in stream pools within the rainforest during relatively dry months of the year, making it unlikely that the oral appendage is used for adhering to substrates (Abraham et al. 2015).

The coloration of live tadpoles is yellow-brown with golden iridophores that appear as small spots on the body and as large blotches on the tail. The ventral and ventrolateral sides of the body are a pale yellowish-brown color and less pigmented than the rest of the body. The eyes are golden-brown (Abraham et al. 2015).

Early descriptions of G. variabilis tadpoles by Annandale (1918) are very likely G. magnus (Abraham et al. 2015).

Tadpoles of the genus Ghatixalus have the greatest number of labial toothrows on both jaws in the family Rhacophoridae (Abraham et al. 2015).

Comments
The species authority is: Abraham, R.K., Mathew, J.K., Cyriac, V.P., Zachariah, A., Raju, D.V., Zachariah, A. (2015). A novel third species of the Western Ghats endemic genus Ghatixalus (Anura: Rhacophoridae), with description of its tadpole. Zootaxa 4048.1: 101-113.

Ghatixalus is a monophyletic clade that includes G. variabilis, G. asterops, and G. magnus. Based on Maximum-likelihood analysis of 12S, 16S, Rag-1, and RHOD gene sequences, G. magnus forms a strongly supported sister lineage to G. variablis and G. asterops (Abraham et al. 2015).

The species name “magnus” is Latin for “great”. This was chosen, as G. magnus is larger in size compared to other Ghatixalus species (Abraham et al. 2015).

References

Abraham, R.K., Mathew, J.K., Cyriac, V.P., Zachariah, A., Raju, D.V., Zachariah, A. (2015). ''A novel third species of the Western Ghats endemic genus Ghatixalus (Anura: Rhacophoridae), with description of its tadpole. .'' Zootaxa, 4048(1), 101-113.

Shubin, N.H., Alberch, P. (1986). ''A morphogenetic approach to the origin and basic organization of the tetrapod limb.'' Evolutionary Biology. Plenum Press, New York, 319–387.

Species Account Citation: AmphibiaWeb 2022 Ghatixalus magnus <https://amphibiaweb.org/species/8403> University of California, Berkeley, CA, USA. Accessed Dec 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Dec 2024.

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