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Frogs of Borneo

Frogs of Borneo

Frogs of Borneo

Frogs of Borneo

Frogs of Borneo

Frogs of Borneo

Frogs of Borneo

Frogs of Borneo

Frogs of Borneo

Frogs of Borneo

Frogs of Borneo

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Ansonia kanak

These tadpoles occur on rock faces within strong currents of cascades in hillside streams at elevations of 250–820 m a.s.l. Many other anuran species occur syntopically (see Matsui et al. 2020). Tadpoles escape temporarily to areas with moderate currents, such as pools between cascades, only when disturbed.
  • Family:
    Bufonidae
  • Genus:
    Ansonia
  • Ecomorph:
    exotrophic, lotic, rheophilous, suctorial
  • Waterbody Type:
    flowing
  • Water Column:
    rock surface
  • Feeding Type:
    feeding, hard surface grazer, omnivorous, rasping
  • Size:
    22 mm
  • Development:
    larva, tadpole
  • Adult:
    Ansonia
    kanak

Coloration

Dorsal coloration brown with darker areas; the roof of the braincase between the eyes and the region overlying the vertebral column densely pigmented. A light crossbar is present at the head-trunk transition. A diffuse, broad dark band extends laterally from flank to flank, forming a saddle. Small, loosely scattered golden pigment cells are present below the eyes, on the dorsum, and laterally at the flank-venter transition. Dense dorsal pigmentation continues onto the muscular portion of the tail. Tail fins pigmented along their margins.

Snout

Snout broadly rounded and greatly expanded; long and sloping in lateral profile.

Oral Disc

Oral disc forming a ventral sucker, approximately as wide as, or slightly wider than, maximum body width. Lower lip with a uniserial row of marginal papillae; upper lip margin devoid of free papillae, forming a bulged rim instead. Flat, rounded submarginal papillae present on the lower lip. Posterior (distal) row of submarginal papillae uninterrupted (15–16 papillae); a second, anterior row consists of 1–3 papillae per side at the far lateral portion of the lower lip, present or absent. Labial keratodonts (LTRF 2/3) with two rows on the upper lip and three on the lower. Upper keratodont rows reach the lateral level of the lower lip rows but do not curl inward beyond them. Upper beak divided into two short, widely spaced, serrated edges, with the gap 2.0–2.6× the length of a single edge. Lower beak very shallowly V-shaped, medially thin.

Body

In dorsal view, body contour pear-shaped, widest anterior to the eyes, approximately at the level of the nostrils. Body narrows only slightly posterior to the eyes. Body dorsoventrally depressed. Spiracle sinistral, attached to the body wall medially, positioned low on the flank in lateral view.

Eyes & Nostrils

Eyes dorsally positioned, clearly set away from the body contour in dorsal view. Nostrils small, situated much closer to the eyes than to the tip of the snout. Iris black, with a golden ring surrounding the pupil.

Tail

Relative tail length 64–69%. Tail fins originate posterior to the trunk-tail junction within the first third of the tail. Fins increase slightly in height over the proximal 50% of the tail. Dorsal and ventral fins low, with the ventral fin slightly higher than the dorsal. Fins taper gradually with mild convexity to an acuminate tip. Tail musculature strong, nearly as high as the trunk at the trunk-tail junction.

Similar Species

Tadpoles of Ansonia kanak were previously reported under the name A. platysoma (Haas et al. 2009) until reassessed by Matsui et al. (2020). Due to the presence of a ventral sucker and the absence of a gastric sucker (unlike Meristogenys and Huia) and their droplet-shaped body silhouette, these tadpoles can only be confused with other sucker-mouthed Ansonia species. In general body shape and coloration, they resemble A. hanitschi; however, A. hanitschi is larger and has conspicuously long, laterally curled keratodont rows on the upper lip. It remains unclear whether the light area at the head-trunk transition is a consistent species-specific character. Likely, further diversity exists within Ansonia, and the taxonomy of A. platysoma may be revised as new evidence emerges.

Literature

Details unknown.
Haas, A., Wolter, J., Hertwig, S.T., Das, I. (2009) Larval morphologies of three species of stream toads, genus Ansonia (Amphibia: Bufonidae) from East Malaysia (Borneo), with a key to known Bornean Ansonia tadpoles. Zootaxa 2302: 1–18.

Matsui, M., Nishikawa, K., Eto, K., Hossman, M.Y. (2020) Two new Ansonia from mountains of Borneo (Anura, Bufonidae). Zoological Science 37: 1–12.