Description
Pseudophilautus decoris are tiny grey-brown tree frogs with stout bodies and rough skin that live in Sri Lanka. The snout-vent for adult males is 18.3–20.6 mm and 19.0–23.9 mm for females. Its head is dorsally flat head. Its snout is pointed in the lateral aspect with a snout angle of approximately 90º. The internarial space is either concave or flat. The canthal edges can be rounded or sharp. The loreal region and interorbital space are concave. The tympanum is vertically oval and distinct. The supratympanic fold is prominent. Cephalic ridges are absent. There is no pineal ocellus or vomerine ridge, but there is a presence of a rounded lingual papilla. The dorsal surface is heavily tuberculated. The snout, interorbital area, side of their head, dorsum, and flank all have glandular warts. The skin is not co-ossified with the skull. The throat ranges from granular, warty, to roughly granular. The chest and belly are visibly granular and rough. The males have inner vocal slits but no nuptial pads. The dorsal surface of the forelimb, hindlimb and foot have glandular warts. The ventral surface of the thigh is granular but not rough. The posterior edge of the lower arm has an undulating dermal fold and fringe. The palms have supernumerary tubercles. The fingers have lateral dermal fringes and rudimentary webbing. On the foot, a tarsal fold and distinct calcar are present as well as a sheath-like, undulating fringe on the posterior edge. Their toes are medially webbed (Manamendra-Arachchi and Pethiyagoda 2005).

The combination of lingual papilla, crossbars on limbs, a tarsal fold, and a distribution in Rakwana hills, Morningside Forest Reserve, Sri Lanka differentiate P. decoris from other anurans. More specifically, P. decoris can be differentiated from most other Sri Lankan Pseudophilautus by the presence of a tarsal fold and partial webbed toes. Pseudophilautus decoris resembles P. extirpo (an extinct species), but may be distinguished by P. decoris having a smaller body size, tarsal tubercle, tarsal fold, lower-arm fold, visible tympanum, narrower snout angle of ~90º, and webbed fingers. Pseudophilautus decoris also closely resembles P. schmarda but P. decoris has lingual papilla, a snout angle of ~90º, a sheath-like undulating fold on posterior margin of lower arm and foot, and crossbars on limbs, while P. schmarda has no lingual papilla, a wider snout angle, a row of distinct tubercles on posterior margin of lower arm and foot, blotches on limbs, and the presence of horny spinules on dorsum in males that is absent in P. decoris. From P. cavirostris, the characteristics that differentiates P. decoris are the presence of lingual papilla, a snout angle of ~90º, half webbed toes, and the absence of vomerine ridge. Pseudophilautus cavirostris has a vomerine ridge, a wider snout angle, fully webbed toes, and lacks lingual papilla (Manamendra-Arachchi and Pethiyagoda 2005). Pseudophilautus singu and P. tanu also resemble P. decoris. However, P. decoris lacks tubercles on the upper eyelid and has a pointer snout, tarsal tubercle, a tarsal fold, and dermal fringes and webbing of the fingers that differentiate it from P. singu. From P. tanu, P. decoris has a pointer snout, tarsal tubercle, tarsal fold, and dermal fringes and webbing of the fingers that differentiates them (Meegaskumbura et al. 2009)

In life, P. decoris is described as having a grey-brown color on the dorsal portion of the head and symmetrical black markings on its occipital. The upper lip is grey-brown and dark brown. Its loreal region is grey-brown with dark brown bands. The canthal edge and the tympanic region are dark brown, while the tympanum is grey-brown. The lower area of the supratympanic fold is black. The dorsal side of its body is grey-brown, with yellowish-golden shoulder patch, a red-brown patch at the middle, and two black lines that run from the upper flank to the middle of the back. Its flank is grey-yellow with some dark brown markings. The inguinal zone and anterior thigh are light blue, with the anterior thigh having wide, dark brown bands. Its ventral surface is ashy yellow with black dots, with light yellow granules on the dark green-black lower abdomen. The underside of thigh, shank, and foot are ashy black with white spots (Manamendra-Arachchi and Pethiyagoda 2005).

In preservative, the dorsal surfaces of the head, body, and flanks are dark brown with light brown and ashy patches. The loreal and tympanic regions are dark brown with ashy spots, while the tympanum has dark brown and ash color. The upper lip is dark brown with white spots. The throat, vocal sacs, chest and abdomen are pale yellow with black dots. The margins of the throat are dark brown with white spots. The dorsal and lateral portions of the forelimb are dark brown with black crossbars. The inguinal zone is dark brown. The dorsal surface of the thigh and shank are dark-brown with ashy-brown crossbars. The posterior region of the thigh is dark brown, and the underside of the thigh is pale yellow. The dorsal surface of the foot has a dark brown color with ashy patches. The digit webbing is dark brown (Manamendra-Arachchi and Pethiyagoda 2005).

There is no tadpole stage in this species and froglets have adult coloration (IUCN 2016).

Few variations have been recorded in this species (Manamendra-Arachchi and Pethiyagoda 2005).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Sri Lanka

View distribution map in BerkeleyMapper.

Pseudophilautus decoris is only found in the Morningside Forest Reserve in the southwest of Sri Lanka at an elevation of 1060 meters near Rakwana. The species occupies a limited range of about 49 km². The habitat includes closed canopy forest with high humidity and loose, moist soils, but the species can also be found on cardamom plantations within forest and close to water (Manamendra-Arachchi and Pethiyagoda 2005; IUCN 2016). The habitat is categorized as wet zone highlands (Surasinghe 2009).

Life History, Abundance, Activity, and Special Behaviors
Excluding breeding, P. decoris is entirely arboreal. Females occupy lower branches of the understory than males (Bahir et al. 2005).

In a breeding studying of 17 species of Pseudophilautus, one mating event for P. decoris was observed. Based on that observation and inferences from the other species, it was determined that P. decoris reproduces via direct development and has a wholly terrestrial lifecycle. Reproductive activity in captive breeding experiments coincided with periods of high rainfall and/or mist, indicating the need for high ambient humidity (Bahir et al. 2005).

Breeding females have visible ova through their transparent ventral skin (Bahir et al. 2005).

Males vocalize at night from low shrubs 0.3 – 2.0 m above the ground (Manamendra-Arachchi and Pethiyagoda 2005) throughout the year and during the daytime, but activity is highest at night, especially during heavy rains. Receptive females seeks out males and engage in axillary amplexus. The mating pair then moves to the ground while in amplexus where their dorsal and lateral coloration adjusts to resemble the leaf litter. While still in amplexus, the female digs a nest in the ground to deposit her eggs by initially excavating a cavity with her forelimbs, scooping 3 – 9 scoops per hand before switching. She then enters the hole and uses her snout and hindlimbs to enlarge and shape the cavity by rotating her body 60 – 180º. Amplexus lasts between 1.5 – 29.5 hours and results in 6 – 155 eggs being deposited. Eggs are 3.7 – 5.7 mm in diameter amd intolerant to desiccation (Bahir et al. 2005).

After ovipositing the eggs, the female mixes them with dirt and leaf litter using the same method as cavity excavation while the male returns to his perch. Mixing the egg is speculated to increase aeration of each individual egg by separating them from each other. Mixing also better distributes the sperm and allows the eggs to absorb moisture from the soil. The female then uses her hands to cover the eggs with more soil and leaf litter and abandons them to develop. The embryo retains some characters that are associated with aquatic free-swimming tadpoles while in the egg but hatch directly into fully developed froglets (Bahir et al. 2005).

Juveniles can be found on the leaf litter through the year but are more abundant when there is heavy rainfall (Bahir et al. 2005).

Trends and Threats
Pseudophilautus decoris has an IUCN threat status of “Critically Endangered” (IUCN 2016). At the time of the species description the recommended threat listing was “Endangered” (Manamendra-Arachchi and Pethiyagoda 2005), however, the status was upgrade as the records of this species at Pituwala were later proven to be a different species. As such, P. decoris had a reduced extent of occurrence of only 49 km² and all the individuals were only known from a single location. Additionally, there is a decline in the extent and quality of its habitat outside of Morningside Forest Reserve due to the encroachment of cardamom plantations, human settlements, and firewood collection. Lastly, the population trend is declining (IUCN 2016).

Pseudophilautus decoris has a very narrow distribution, making it extremely vulnerable to habitat loss and fragmentation. Agricultural practices such as crop cultivation (cardamom, rubber, tea) contribute to habitat degradation due to loss of trees and shrub cover that this arboreal species relies on. Environmental pollution is also a byproduct of agricultural practices. Use of agro-chemicals such as pesticides and fertilizers and their subsequent contamination of the environment could result in deformed individuals and affect physiological performance (Surasinghe 2009).

As of 2009, Sri Lanka has not had any confirmed cases of amphibian mortality attributed to Chytrid fungi, but its tropical environment resembles other areas where the fungi is impacting amphibian populations, making this a potential threat to P. decoris (Surasinghe 2009).

Climate change is another current and future threat to P. decoris, modifying vegetation and habitat structure, as well as alterations in moisture regiments. The species requires high humidity and is reliant on the moisture the cloud-born mist brings. More specifically, P. decoris eggs are intolerant to desiccation (Surasinghe 2009).

Morningside Forest Reserve is the largest remnant forest in Sri Lanka and is a World Heritage site and UNESCO-MAB Biosphere Reserve. Pseudophilautus decoris is found in the reserve and in the forest reserves along the eastern margin of Morningside Forest Reserve. Furthermore, a long-term monitoring study has been set up in in area occupied by the species to restore critical habitat. However, studies of the species’ population size, distribution, trends, life history, ecology, and threats are still need (IUCN 2016).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Urbanization
Subtle changes to necessary specialized habitat
Habitat fragmentation
Predators (natural or introduced)
Climate change, increased UVB or increased sensitivity to it, etc.

Comments
The species authority is: Manamendra-Arachchi, K. Pethiyagoda, R. (2005). “The Sri Lankan shrub-frogs of the genus Philautus Gistel, 1848 (Ranidae: Rhacophoridae), with description of 27 new species.” Raffles Bulletin of Zoology, Suppl 12, 163–303

The species was moved into the genus Pseudophilautus following a phylogenetic examination of the family Rhacophoridae and its various genera and sub genera including Pseudophilautus and Philatus. The study utilized nuclear sequences of brain derived neurotrophic factor (BDNF), proopiomelanocortin, recombination activating gene 1, tyrosinase, and rhodopsin, as well as the mitochondrial genes for partial 12s and 16s ribosomal RNA and the complete valine tRNA. The subsequent molecular analysis suggested the reorganization of the existing phylogeny of the Rhacophoridae family such as the moving the species that were once in the Philautus genus but endemic to Sri Lanka into Pseudophilautus including Pseudophilautus decoris (Li et. al 2009).

Pseudophilautus decoris is morphologically most similar to P. schmarda, P. cavirostris, and P. extirpo (now extinct; Manamendra-arachchi and Pethiyagoda 2005), but is phylogenetically grouped as a sister species to P. mittermeiere based on Bayesian, Maximum Likelihood, and Maximum Parsimony criteria of 12s rRNA and 16s rRNA partial mtDNA sequences. The next most closely related species is P. singu and then P. tanu. Cyt-B was also used to determine percent divergence between sister taxa resulting in P. decoris having a divergence of 5.5, 18.5, and 22.6 from P. mittermeieri, P. singu and P. tanu, respectively (Meegaskumbura et al. 2009).

The original etymology for “Pseudophilautus” is of Greek origin with “Philautus” meaning “one who loves himself” based in part based on the literary character Phylautus, and “Pseudo” meaning “false” (Manamendra-arachchi and Pethiyagoda 2005).

The species epithet “decoris” is Latin for “adorned, elegant, or beautiful” and reflects the patterning on the dorsal side of the species, which can be more elaborate or ornamental in nature (Manamendra-arachchi and Pethiyagoda 2005).

References

Bahir, M. M., Meegaskumbura, M., Manamendra-Arachchi, K., Schneider, C. J., and Pethiyagoda, R. (2005). ''Reproduction and terrestrial direct development in Sri Lankan shrub frogs (Ranidae: Rhacophorinae: Philautus).'' The Raffles Bulletin of Zoology, 12, 339-350. [link]

IUCN SSC Amphibian Specialist Group 2016. “Pseudophilautus decoris.” The IUCN Red List of Threatened Species 2016: e.T58834A89262191. https://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T58834A89262191.en. Downloaded on 08 February 2020.

Li, J., Che, J., Murphy, R. W., Zhao, H., Zhao, E., Rao, D., Zhang, Y. (2009). ''New insights to the molecular phylogenetics and generic assessment in the Rhacophoridae (Amphibia: Anura) based on five nuclear and three mitochondrial genes, with comments on the evolution of reproduction.'' Molecular Phylogenetics and Evolution, 53(2), 509-522. [link]

Manamendra-Arachchi, K., and Pethiyagoda, R. (2005). ''The Sri Lankan shrub-frogs of the genus Philautus Gistel, 1848 (Ranidae: Rhacophorinae), with description of 27 new species.'' Raffles Bulletin of Zoology, Supplement 12, 163-303.

Meegaskumbura, M., Manamendra-Arachchi, K., Pethiyagoda, R. (2009). ''Two new species of shrub frogs (Rhacophoridae: Philautus) from the lowlands of Sri Lanka.'' Zootaxa, 2122(1), 51–68. [link]

Surasinghe, T. D. (2009). ''Conservation and distribution status of amphibian fauna in Sri Lanka.'' Biodiversity, 10(1), 3-17. [link]

Species Account Citation: AmphibiaWeb 2020 Pseudophilautus decoris: Elegant Shrub Frog <https://amphibiaweb.org/species/6508> University of California, Berkeley, CA, USA. Accessed Dec 28, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 28 Dec 2024.

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