Description

Originally written under the species Ingerana charlesdarwini: This is a small to medium sized frog species from the Dicroglossidae family. Females are slightly larger than males with snout-vent length ranges from 29.16 - 33.19 mm while males ranged from 24.54 - 28.74 mm. The head is relatively longer in males than in females and females have heads that are as wide as they are long while males have heads that are wider than they are long. In the dorsal and lateral view, the snout is bluntly rounded. Its nostrils are located closer to the snout tip than the eyes, and their proximity to the snout is more pronounced in males. It has relatively large eyes. The distinct and exposed tympanum is smaller than the eye and relatively smaller in males than females. It has a well developed supratympanic fold, from the posterior corner of the eye to the jaw angle, in the form of a thick and fleshy ridge. Ingerana charlesdarwini has short upper arms that are less than a quarter of the snout-vent length. The relative lengths of the unwebbed, swollen-tipped fingers are III = I > IV > II. The finger discs do not have circummarginal grooves, and the fingers have well-developed subarticular tubercles. The thighs are slightly longer than the tibia and the feet. For males, the thigh is slight shorter relative to females. The toes have well-developed subarticular tubercles with swollen tips and terminal discs that lack circummarginal grooves. Their relative toe lengths are IV > III > V > II > I and they have reduced toe webbing with a formula of I½ – 1II½ – 2III1 – 2IV2 – 1V (Chandramouli 2017).

Ingerana charlesdarwini is most notably characterized by its lack of lingual papilla, which distinguishes it from members of the genus Liurana, and its possession of vomerine teeth. From other species found on the Andaman Islands, I. charlesdarwini can be distinguished by dorsal coloration, nostril location, toe webbing, and by the presence of an outer metatarsal tubercle. More specifically, from Fejervarva andamanensis, I. charlesdarwini is diagnosed by the latter having dark dorsal coloration that matches the lateral body. The lack of a dorsal “W” pattern in some color morphs and less toe webbing distinguishes I. charlesdarwini from Limnoncetes hascheanus. The nostrils in I. charlesdarwini are positioned laterally, which distinguishes the focal species from Fejervarva cancrivora, as well as I. charlesdarwini having less toe webbing and a small outer metatarsal tubercle (Chandramouli 2017).

Ingerana charlesdarwini has three known color morphotypes. The first type has a dull brown body coloration with a bright orange “butterfly” pattern on the dorsum just posterior to the head and another orange spot in the sacral region. There are also weak black subocular spots. The limbs do not have barred patterning. The second type can change the intensity of body coloration based on moisture. The overall body coloration is light tan (dry) to dark brown (wet) with black bars on the limbs, a weak “W” shaped pattern on the mid-dorsum, and weak orange spots, which darken in water, just posterior to the head and on the mid-body. Some specimens have a mid dorsal strip that runs from the snout to the cloaca. The third type is distinctly bright creamy white with brown dorsal patches and possess a thin creamy white mid-dorsal strip and two white distinct subocular spots. Males of morph 2 and 3 have a dark gular vocal sacs (Chandramouli 2017).

Variation of this species includes three basic color morphs (see above) and sexual dimorphism with females being larger and having heads that are as wide as long while males have heads that are wider than long. Additionally, the placement of the nares is closer to the snout in males than in females, males have a relatively smaller tympanum, and males have relatively shorter thighs than females (Chandramouli 2017).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: India

View distribution map in BerkeleyMapper.

Ingerana charlesdarwini is endemic to the subtropical and tropical moist lowland forests (Das et al. 2004) of the Andaman Islands of India, located in the Bay of Bengal. It has specifically been found at Mount Harriet National Park on South Andaman Island, Saddle Peak National Park on North Andaman Island, Little Andaman Island, Rutland Island, Long Island, Havelock Island, Neil Island, Tarmugli Island, Alexandria Island, and Redskin Island. As of 2018, the species has not been recorded on the nearby Nicobar Islands. The species has been found in an elevational range of 39 - 600 m asl (Chandramouli 2017, Harikrishnan and Vasidevam 2018).

Life History, Abundance, Activity, and Special Behaviors
Ingerana charlesdarwini is an arboreal species of subtropical to tropical moist lowland forests (Das et al. 2004) that breed in water-filled cavities formed by plants. Males were found calling during the day and night near breeding sites, which included tree holes, large water-filled leaves, and other small, stagnant water bodies (Das et al. 2004, Harikrishana and Vasidevam 2018). During the day, individuals could also be found on the forest floor in the leaf litter (Harikrishana and Vasidevam 2018)

Trends and Threats
Although I. charlesdarwiniis not uncommon, it is listed as “Critically Endangered” by the IUCN Red List because its extent of occurrence is less than 100 km², its area of occurrence is less than 10 km², and it is threatened by habitat loss due to timber harvesting and clear cutting (Das et al. 2004).

The species can be found in at least two protected area, Mount Harriet National Park and Saddle Peak National Park, which are both protected by Indian national legislation. However, land and water conservation are still needed to protect this species (Das et al. 2004).

Comments
Ingerana charlesdarwini was originally placed in the Ingerana genus based on morphology. At the time of its description, it was tentatively placed in the genus Rana but it was noted that it was allied with Ingerana. After the genus Ingerana was reviewed and redefined, it was proposed that I. charlesdarwini was a member of the sister genus, Liurana. However, Das (1998), explicitly stated in his species description that I. charlesdarwini differed from all Liurana by lacking a lingual papilla. For this reason, and because I. charlesdarwini is geographically close to the type species of the Ingerana genus, I. charlesdarwini was provisionally placed in Ingerana until a more fine resolution taxonomic investigation could clarify its placement (Chandramouli 2017).

Phylogenetic analysis in 2022 by Garg and colleagues revealed the species Ingerana charlesdarwini is nested within the genus Minervarya.

The species epithet is in honor of the father of evolution, Charles Darwin (Das 1998).

References

Chandramouli, S.R. (2017). ''Rediscovery and redescription of a little known insular endemic frog, Ingerana charlesdarwini (Das,1998) (Amphibia: Anura: Dicroglossidae) from the Andaman Islands, Bay of Bengal.'' Alytes, 33(1-4), 47-54. [link]

Das, I. (1998). ''A remarkable new species of ranid (Anura: Ranidae), with phytotelmonous larvae, from Mount Harriet, Andaman Island.'' Hamadryad, 23(1), 41-49.

Das, I., Dutta, S., Vijayakumar, S.P. (2004). “Ingerana charlesdarwini”. The IUCN Red List of Threatened Species 2004: e.T58571A11805014. http://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T58571A11805014.en. Downloaded on 18 March 2019.

Garg S, Chandrakasan S, Gokulakrishnan G, Gopika C, Das I, and Biju SD. (2022). "The curious case of Charles Darwin’s frog, Rana charlesdarwini Das, 1998: Phylogenetic position and generic placement, with taxonomic insights on other minervaryan frogs (Dicroglossidae: Minervarya) in the Andaman and Nicobar Archipelago." Vertebrate Zoology, 72, 169–199.

Harikrishana, S., Vasidevam, K. (2018). ''Amphibians of the Andaman & Nicobar Islands: distribution, natural history, and notes on taxonomy.'' Alytes, 36(1-4), 238-265. [link]

Species Account Citation: AmphibiaWeb 2022 Minervarya charlesdarwini: Charles Darwin's Frog <https://amphibiaweb.org/species/5504> 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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