Description
Mercurana myristicapalustris is a medium-sized frog with an average snout-vent length of 36.1 mm in males and 65.1 mm in females. The snout is protruding and round from the lateral view. This species has an indistinct canthus rostralis, obtusely concave loreal region, horizontal and oval pupil, lightly distinct round tympanum, slight supratymapnic fold beginning at the eye and ending at the shoulder, and small vocal sack. Mercurana myristicapalustris has weakly-developed vomerine teeth and no lingual papilla. The skin is finely granulated and the ventral surface is coarsely granular. The fingers are unwebbed and the toes are 3/4th webbed. The 4th finger is strongly bifid and all fingers have well developed and distinct discs (Abraham et al 2013).

Mercurana, which could potentially be confused with Beddomixalus, differs from the latter in the following characters: presence of vomerine teeth and lingual papilla (vs. absence); symphysial knob not sharply pointed (vs. sharply pointed); no stripe on the dorsolateral margin (vs. pale distinct stripe on the dorsolateral margin); canthus rostralis indistinct (vs. rounded); toes 3/4th webbed (vs. half/moderately webbed); finger discs large (vs. moderate); subarticular tubercle on finger IV bifid (vs. rounded); oviposited eggs mixed with mud in shallow pit (vs. eggs openly scattered on ground substrates; Abraham et al 2013).

In life, the overall body color of breeding males is rusty-brown speckled with black dots. There are a few yellow blotches on the dorsum and the axillary underside of the arms is white with yellow blotches. The upper-arms and hands are yellowish. The flanks are white with a yellow groin. The upper lip is whitish, as is the ventral surface, the anterior and posterior boarder and ventral surface of the thighs. Hindlimbs are unmarked. There is no vent fold. The iris is silvery-brown with a yellowish tint. When non-breeding, males have a pale yellowish-brown dorsum with black specks. Females have a pale greenish-yellow dorsum and white ventral surface.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: India

View distribution map in BerkeleyMapper.

Mercurana myristicapalustris is known only from the western foothills and valleys of the Agasthyamalai Hills in the Southern Western Ghats in Kerala state in India. The species occurs mostly in lowland Myristica swamp forests found here, between elevations of 100m and 300m ASL (Abraham et al 2013).

Life History, Abundance, Activity, and Special Behaviors
Mercurana myristicapalustris adults are arboreal and inhabit low-elevation Myristica swamp forests. Their breeding behavior is remarkably similar to that of Beddomixalus bijui, in terms of large male aggregations at breeding sites during the pre-monsoons, and oviposition on the swamp floor. Vocalizing males call from atop perches inside the Myristica swamp forest with standing water or intermittent streams, at 2-5m height from the forest floor. As the night progresses, the males make their way slowly towards the forest floor, where competition for space is greater and physical combat between males has been observed (Abraham et al 2013, 2018).

A male and female in amplexus were observed descending to the swamp floor, from the base of a shrub. On reaching the ground, the pair moved into the leaf litter where both individuals slowly changed color, becoming almost inconspicuous on the forest floor. The female was seen digging into the slushy soil and ovipositing into the resulting shallow burrow in the mud, following which she mixed the semiterrestrial eggs with muddy soil. Digging and mixing was aided by employing her well-developed hindlimb webbing. Ensuing oviposition, the pair moved away from the oviposition site (Abraham et al 2013, 2018).

The eggs are non-pigmented and early embryonic development occurs in wet mud after pre-monsoon showers. Free-living aquatic tadpoles metamorphose in lowland swamps (Abraham et al 2013).

Trends and Threats
Information on trends in abundance is currently unknown, but expected to have declined from its original population strength. Much of the natural habitat, including the Myristica swamp ecosystem within the historical range of the species has been converted to monocultures of paddy rice fields, rubber, oil palm, teak and Acacia plantations. This greatly reduces the abundance of the species in most parts of its original range. Additionally, since the reproduction of the species is intricately linked with the early pre-monsoon showers, the recent abrupt nature of rains would clearly impact survival of eggs and early stage tadpoles, in turn affecting population recruitment. Urgent studies are needed to study the threats caused by habitat destruction, pollution and climate change (Abraham et al 2013).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Climate change, increased UVB or increased sensitivity to it, etc.

Comments
Species Authority: Abraham R. K., Pyron R. A., Ansil B. R., Zachariah A., Zachariah A. (2013) Two novel genera and one new species of treefrog (Anura: Rhacophoridae) highlight cryptic diversity in the Western Ghats of India. Zootaxa 3640(2): 177-199. doi:10.11646/zootaxa.3640.2.3

Mercurana myristicapalustris is a recent addition to the family Rhacophoridae and represents an ancient, independent clade, which is sister to the clade containing the Sri Lankan and Indian-Chinese-Indochinese radiations of bushfrogs (Pseudophilautus + Raorchestes; Abraham et al 2013).

The genus name is derived from ‘Mercury’ as a tribute to the late Freddie Mercury, the iconic lead singer of the British rock band Queen, whose vibrant music inspired the authors, in combination with Rana (Linnaeus, 1758), a suffix commonly used for many frog taxa (Abraham et al 2013).

The specific epithet, a combination of the words ‘Myristica’ for the nutmeg family, and ‘palustris’, which is Latin for swampy, emphasizes the Myristica swamp forest habitat of this frog, which is a fragile and threatened habitat type of the Western Ghats (Abraham et al 2013).

This species was featured as News of the Week on December 10, 2018:

Described in 2013, Mercurana myristicapalustris is a rare frog species that has a limited range, inhabiting the once-widespread evergreen Myristica swamp forests of the Western Ghats of India. Abraham et al. (2018) report an extensive investigation into the reproductive behavior and larval development. Reproducing during the short pre-monsoon season, this frog displays a mixture of prolonged and explosive breeding, with males using acoustic and physical defenses of calling perches while advertising to females with a complex repertoire. Once in axillary amplexus, the larger-sized female carries the male to a low point in the leaf litter where she digs a shallow burrow in the loamy soil in which to lay eggs. After water accumulates in the nest and surrounding area, motile larvae emerge from the jelly capsule indicating that hypoxia is a trigger for larval emergence. The authors hypothesize that the species is limited to this short window of reproduction because the low oxygen and high acidity of the swamp water requires larval development to be fast and to occur early in the monsoon season. Because the species is highly dependent on Myristica swamp environments, which are critically endangered, they are especially at risk from climate change. (Written by Ann T. Chang)

References

Abraham RK, Mathew JK, Raju DV, Rao R, Zachariah A (2018). ''Reproduction and metamorphosis in the Myristica Swamp tree frog, Mercurana myristicapalustris (Anura: Rhacophoridae).'' PeerJ, 6(e5934). [link]

Abraham, R. K., Pyron, R. A., Ansil, B. R., Zachariah, A., Zachariah, A. (2013). ''Two novel genera and one new species of treefrog (Anura: Rhacophoridae) highlight cryptic diversity in the Western Ghats of India.'' Zootaxa, 3640(2), 177-199.

Species Account Citation: AmphibiaWeb 2018 Mercurana myristicapalustris: Myristica Swamp Treefrog <https://amphibiaweb.org/species/8003> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

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

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