Description

DESCRIPTION:

Ansonia kaochangensis is the first known limestone cave-dwelling toad species of the genus Ansonia. The snout-vent length ranges from 34.0 - 35.3 mm in females and 31.9 - 32.0 mm in males. The head is longer than it is wide. The snout is shorter than it is wide and extends past the lower jaw. The dorsal side of the snout is convex with a depression in the midline. The canthus rostralis is distinct, below which the nares open laterally. The distance between the nares is less than the snout length. The large eyes protrude beyond the jaw and their diameter is barely larger than the snout length. Along the outer margin of the upper eyelid, there is one row of small spinules. The supratympanic fold and parotoid gland are not present. The submandibular and mental regions have small tubercles, and the gular region ranges from roughly granular to slightly tuberculate. The tubercles on the back are small and low while the posttympanic region has large, isolated tubercles. The tubercles on the flanks are large, low, and wide. The abdomen is granular and coarse. The dorsal surface of the limbs are densely tuberculate and the ventral sides are coarsely granular. The pes and manus are weakly tuberculate. The outer palmar tubercle is raised and ovular. The fingers are long, slender, and follow the relative length formula I < II < IV < III. The fingertips are rounded and dilated but do not form discs. Basal webbing is present up to the proximal subarticular tubercles, which are distinct. The hind limbs are also long and slender, with the foot being longer than the tibia. The inner metatarsal tubercle is elongated and raised, while the outer metatarsal tubercle is somewhat smaller than the inner one, raised, and ovular. The relative toe lengths are I < II < III < V < IV and the webbing formula is I 1, II ½ – 2, III 1½ – 2, IV 2 – 2, V 1. The toe tips are dilated and rounded but do not form discs. The subarticular tubercles are weak (Grismer et al. 2017).

DIAGNOSIS:

Ansonia kaochangensis can be differentiated from other Ansonia species by its morphology and coloration. Compared to A. siamensis, A. khaochangensis males are larger, having a maximum snout-vent length of 32.0 mm compared to 28.0 mm in A. siamensis. Ansonia khaochangensis also differs from A. siamensis because of its visible tympanum, more extensive webbing on toes I and II, and coarsely granular abdomen, which is finely granular in A. siamensis. Except for A. siamensis and A. latiffi, A. kaochangensis differs from all other Ansonia species by lacking submandibular tubercles in males (Grismer et al. 2017).

COLORATION: (In life and/or in preservative)

In life, the dorsal surfaces of the head, body, and hind limbs are dark brown, as are the sides of the head and neck. The flanks, forelimbs, hands, and feet are orange-tan, while the ankle, knee, and elbow are a dull orange color. The immaculate venter is beige. The tubercles near the rictus, on the flanks, on the limbs, and in the postfemoral region are yellow. The brown coloration seems to match the limestone substrate of the karst habitat, indicating adaptation to this microhabitat (Grismer et al. 2017).

VARIATION: (if known)

Variations in coloration may include the hands and feet being light tan instead or a dull orange (Grismer et al. 2017).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Thailand

View distribution map in BerkeleyMapper.

The type locality is Phang Nga, Takua Pa District, Phang Nga Province, southern Thailand, which has an elevation of 91 m. The species is only known from the Khao Chang tower karst formation north of Phang Nga. This karst rises to an elevation of 125 m. Along its southeast face is the Phung Chang Cave, inside of which is where A. kaochangensis were found in recesses of the cave walls up to 3 m above the ground. Karst ecosystems have been known to promote speciation and can contribute to the evolution of varying lifestyles (see Life History).

Life History, Abundance, Activity, and Special Behaviors
Other Ansonia species are known from lotic environments and do not lay direct-developing eggs, but A. kaochangensis is unique because of its cave-dwelling life. No aboveground sources of water have been found near the type locality, so it is assumed that underground sources of water exist. The reproductive biology of A. kaochangensis is currently unknown (Gismer 2017).

At night, A. kaochangensis have been observed to leave the cave and climb the karst, climbing as high as 10 m above the forest floor (Gismer 2017).

Comments

PHYLOGENETIC RELATIONSHIPS:

Based on Maximum Likelihood and Bayesian inference analyses of 12S and 16S mtDNA, A. kaochangensis is sister to the clade containing A. inthanon, A. kraensis, and A. thinthinae, which are Ansonia species that are distributed north of Isthmus of Kra (Grismer et al. 2017).

Ansonia kaochangensis is nested within a clade of 14 other Ansonia species that are endemic to the Thai-Malay Peninsula (Grismer et al. 2017).

OTHER INTERESTING INFORMATION:

Sundaland is the region west of Wallace’s Line that includes Borneo, Java, Sumatra, hundreds of other small islands, and the Thai-Malay Peninsula south of the Isthmus of Kra. Indochina and Borneo are major sources of species colonization for species that immigrate to all areas of Southeast Asia. Speciation has particularly occurred in Borneo since the Miocene. Borneo is the origin of all Thai, Peninsular Malaysian, Sumatran and Philippine populations of Ansonia (Grismer et al. 2017).

References
Grismer, L.L., Wood Jr., P.L., Aowphol, A., Cota, M., Grismer, M.S., Murdoch, M.L., Aguilar, C., and Grismer, J. (2017). Out of Borneo, again and again: biogeography of the Stream Toad genus Ansonia Stoliczka (Anura: Bufonidae) and the discovery of the first limestone cave-dwelling species. Biological Journal of the Linnean Society, 120(2), 371-395. [link]

Species Account Citation: AmphibiaWeb 2024 Ansonia khaochangensis: Cave-dwelling Stream Toad <https://amphibiaweb.org/species/8652> 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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