Description

Adult Morphology

Nyctibatrachus kumbara is a medium to large size frog with a snout-vent length range from 42.8 to 47.4 mm. It has a wide head with a round snout, round canthus rostralis, and a concave loreal region. The large eyes have rhombus shaped pupils. The subocular gland is conspicuous while the tympanum blends in with its body. It has wrinkled skin. There are no pineal ocellus, outer metatarsal, supernumerary tubercles, or tarsal tubercles. Femoral glands are present in males. It has finger and toe discs. There is no webbing on fingers, but webbing is present on the toes. The third finger and fourth toe discs both have a dorso-terminal groove cover. The groove cover of the finger disc is notched distally while the cover of the fourth toe disc is bifurcated distally. The order of finger length from shortest to longest is 1, 2, 4, 3. The order of toe length from shortest to longest is 1, 2, 5, 3, 4 (Gururaja et al. 2014).

Larval Morphology

The larvae of N. kumbara at Gosner Stage 25 have a long, robust, oval body shape with a body length range of 13.8 - 20.2 mm. The the lateral view, the body is depressed. The body is wider than high. Their powerful tail length ranges from 39.0 to 56.9 mm. They are characterized by having large, dorsally positioned eyes that are directed dorsolaterally. They have a small oral disc width ranging from 2.0 to 3.3 mm with complete marginal papillae that is rounded at the tip. Larvae do not have keratodonts. The dorsal fin is taller than the ventral fin (Priti et al. 2021).

Adult Diagnosis

There are several traits that can be used to distinguish adult N. kumbara from other species in the genus. Nyctibatrachus karnatakaensis is the only member of the genus that is larger; N. jog, N. kempholeyensis, N. shiradi, N. sanctipalustris, and N. vrijeuni are all smaller than N. kumbara. The dorso-terminal groove cover of the fourth toe of N. karnatakaensis, N. shiradi, N. sanctipalustris, and N. vrijeuni are notched or rounded distally, rather than being bifurcated distally. Nyctibatrachus sanctipalustris and N. vrijeuni have no groove covers on their third finger. Nyctibatrachus kempholeyensis and N. shiradi have less webbing and N. karnatakaensis has more webbing than N. kumbara. Nyctibatrachus jog and N. karnatakaensis have finger and toe discs that are more developed as well as smoother dorsal skin with glands that are more conspicuous (Gururaja et al. 2014).

Larval Diagnosis

Nyctibatrachus kumbara larvae can be distinguished from other species through their size and horizontal band between the trunk and tail. They are larger than many other larvae from other frog species, such as Nyctibatrachus jog and N. kempholeyensis. The horizontal stripe on N. kumbara can be used to distinguish it from N. kempholeyensis who does not have a horizontal band (Priti et al. 2015).

Adult Coloration

The dorsal side of adult N. kumbara is primarily a muddy brown color with distinct patterning. The sides of N. kumbara head are lighter than its dorsal surface. Their dorsum has two brick red dorsolateral bands, with darker coloration on the lateral edges, extending from the eyes to its vent. In between the dorsolateral bands is a lighter shade of brown with three horizontal bands located between its eyes, anterior of shoulders, and posterior of shoulders. Nyctibatrachus kumbara has golden yellow irises and cream colored subocular glands, ear regions, and nuptial pads on its first fingers. They have black bars paired with larger brown bars on their forearms. Nyctibatrachus kumbara possess a clear throat lined with black spots. Its chest, belly, and the anterior part of its thighs are clear. The femoral glands, located posterior of its thighs ventrally, are a light yellow color (Gururaja et al. 2014).

Larval Coloration

Overall, N. kumbara larvae are light brown with a tail that is a slightly lighter brown. The eyes are black. There are black spots on the tail, dorsal fin, and ventral fin and a black horizontal band between their trunk and tail. The oral disc is white (Priti et al. 2015).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: India

View distribution map in BerkeleyMapper.

Nyctibatrachus kumbara has been found in the central Western Ghats mountain range, located near the western coast of Karnataka State in south India at elevations around 550 - 600 m above sea level. More specifically, they have been found in the perennial streams of evergreen and semi-evergreen forests as well as Myristica swamps in the Tunga, Sharavathi, Aghanashini, and Bedthi river basins (Gururaja et al. 2014).

Life History, Abundance, Activity, and Special Behaviors
Nyctibatrachus kumbara are a nocturnal species with little activity seen during the day besides occasional calls (Gurunaja et al. 2014).

Like many frogs of their genus, N. kumbara are found near the edges of slow moving freshwater streams with a sandy substrate that flow through stilted roots, such as Myristica tree species. Small rocks and boulders allow for the creation of shallow, sandy puddles that are also shown to be inhabited by the frog. Low lying roots and branches over a sandy stream allow for ideal egg laying conditions and provide a muddy substrate for males to cover fertilized eggs. The color of adult dorsums mimics its environment of muddy areas filled with leaf litter (Gurunaja et al. 2014).

Since tadpoles were found in both monsoon and post-monsoon season, the species is thought to breed year-round (Priti et al. 2021).

The courtship ritual for N. kumbara occurs during low light conditions in the evening and nighttime. The male begins by identifying a suitable egg laying location under low hanging branches, roots, or leaves, which are 6.33 ± 0.52 cm above slow-moving, sandy bottom streams. When found, the male begins to produce its mating call to attract a female in the dark environment (Gurunaja et al. 2014).

Nyctibatrachus kumbara exhibits two types of calls: one with a single “tok” note and one with double “tok” notes. The single note call has a duration of 0.07 - 0.20 seconds, a fundamental frequency of 581 - 620 Hz, and a peak frequency of 956 - 1581 Hz. The double note call has a duration of 0.39 - 0.53 seconds, a fundamental frequency of 538 - 671 Hz, and a peak frequency of 1232 - 1724 Hz. Double calls were heard more often when females were nearby. Males produce these advertisement calls mainly at night, but calls can also be infrequently heard from crevices along the sides of streams during the day. Calls are produced year-round but are most prevalent during nights in the monsoon season (June - October). The external vocal sac does not dilate during the call (Gururaja et al. 2014). Like most anuran species, only males N. kumbara produce mating calls with no records of female recordings in any Nyctibatrachidae family species (Willaert et al. 2016).

After spotting an approaching female, a male stands on their hind legs and touches, with his forelimbs, the branches above. The female then moves face-to-face with the male and mimics the stance by standing and touching the branches that the male has made contact with (Gurunaja et al. 2014). It is thought that males and females initiate a tactile contact during courtship to determine the size of their mate in low light conditions (Willaert et al. 2016).

After contact, the female moves close to the male and the male engages in axillary amplexus. After about five minutes, the female reaches up and touches the spot on the branch that was touched before mating and rotates into a handstand touching her cloaca to the spot on the branch. The pair stay in this position briefly with the male vigorously shaking his hind limbs. He then dismounts but remains facing towards her, providing balance to the handstand. The female deposits between four to six eggs in a single clutch in about six seconds. The eggs are spherical with separate white and black hemispheres and measure 3.98 ± 0.1 mm in diameter. The eggs are loosely placed with separation between them (Gurunaja et al. 2014).

Nyctibatrachus kumbara demonstrates a unique method of parental care. After ovipositioning, the female moves away, but stays within 30 cm of the site. The male confirms the location of the eggs before spreading mud on the egg clutch. The male repeats this 14 - 15 times to ensure that all of the eggs are covered with mud. This process will take an average of 12 minutes per egg clutch. It has been hypothesized that this mud-packing serves to protect against desiccation or to camouflage the pigmented eggs. At the time of the species description, it was the only species of frog known to exhibit this type of parental care (Gururaja et al. 2014).

Sometimes males will call next to mud-covered egg clutches, and females will oviposit next to these clutches (Gururaja et al. 2014).

Nyctibatrachus kumbara larvae are stream-dependent and found in the shallow, slow moving water near the edges of streams. They are diurnal and have been seen scraping at leaf debris. They hide underneath leaf debris or the sandy substrate of the stream when approached. There has been no observation of N. kumbara tadpoles showing any schooling or cannibalistic behaviors (Priti et al. 2015).

Nyctibatrachus kumbara larvae are sensitive to water temperature, and their abundance declines with warmer waters: their preferred temperature range is 21 - 25 °C. They are also affected by the amount of dissolved oxygen in the water, occurring in water with 3 - 8 mg/L (Priti et al. 2021).

Research suggests that there is niche partitioning in the form of spatial heterogeneity between Nyctibatrachus larvae of N. kumbara, N. jog, and N. kempholeyensis. These species are sympatric, and different tadpole species were found in different regions of the stream (Priti et al. 2021).

Trends and Threats
As of 2022, the IUCN Red List has not assessed N. kumbara. However, the limited range of the species could make it a conservation priority. Myristica swamps were once widespread in the Western Ghats but now have a patchy distribution due to anthropogenic activities (Priti et al. 2015). The conversion of swamps into farmland is one of most common methods of habitat loss, but water diversion and damming also contribute (Ranganathan et al. 2021). This could disturb Nyctibatrachus tadpoles who depend on these streams and are sensitive to change, with consequences for both the tadpoles and the adult frogs (Priti et al. 2015). However, some of the swamps have been considered to be the sacred home of local deities for centuries and thus have been conserved, specifically Kathalekan forest, located in the central Western Ghats mountain range. These sacred groves provide habitat protection for N. kumbara as their historic range has been greatly reduced (Chandran et al. 2010).

Possible reasons for amphibian decline

General habitat alteration and loss
Intensified agriculture or grazing
Drainage of habitat
Dams changing river flow and/or covering habitat

Comments

Phylogenetic Relationships

Maximum likelihood analysis of mitochondrial 16S rRNA show that N. kumbara is part of the Nyctibatrachus sanctipalustris group, which includes N. dattatreyaensis, N. karnatakaensis, N. sanctipalustris, N. shiradi, and N. vrijeuni. Nyctibatrachus kumbara is sister to the rest of the species in the clade (Gururaja et al. 2014).

Etymology

The specific epithet “kumbara” comes from the Kannada language, and is the name of a community known for making pottery. This name is a reference to the frog’s method of parental care (Gururaja et al. 2014).

References

Chandran, S.M.D., Rao, G.R., Gururaja, K.V., Ramachandra, T.V. (2010). “Ecology of the Swampy Relic Forests of Kathalekan from Central Western Ghats, India.” Bioremediation, Biodiversity and Bioavailability 4 (Special Issue I), Global Science Books, 54-68. [link]

Gururaja, K. V., Dinesh, K. P., Priti, H., Ravikanth, G. (2014). “Mud-packing frog: A novel breeding behaviour and parental care in a stream dwelling new species of Nyctibatrachus (Amphibia, Anura, Nyctibatrachidae).” Zootaxa, 3796(1), 33-61. [link]

Priti, H., Gururaja, K. V., Aravind, N. A., Ravikanth, G. (2021). “Influence of microhabitat on the distribution of three endemic Nyctibatrachus species (Nyctibatrachidae) from the Western Ghats, India.” Biotropica, 53(6), 1475-1485. [link]

Priti, H., Gururaja, K. V., Ravikanth, G. (2015). “Morphology, natural history and molecular identification of tadpoles of three endemic frog species of Nyctibatrachus Boulenger, 1882 (Anura, Nyctibatrachidae) from Central Western Ghats, India.” Journal of Natural History, 49(43-44), 2667-2681. [link]

Ranganathan, P., Ravikanth, G., Aravind, N. A. (2021). “A review of research and conservation of Myristica swamps, a threatened freshwater swamps of the Western Ghats, India.” Wetlands Ecology and Management, 30, pages171–189 [link]

Willaert B, Suyesh R, Garg S, Giri VB, Bee MA, Biju SD (2016). "A unique mating strategy without physical contact during fertilization in Bombay Night Frogs (Nyctibatrachus humayuni) with the description of a new form of amplexus and female call." PeerJ, 4, e2117. [link]

Species Account Citation: AmphibiaWeb 2022 Nyctibatrachus kumbara: Kumbara night frog <https://amphibiaweb.org/species/8224> 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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