Description

Phrynobatrachus ambanguluensis is a pointy-headed frog with a male snout-vent length range of 20.0 - 45.3 mm and a female range of 21.1 - 39.6 mm. The characteristics of its head and associated features are as follows: head pointed with a tapered snout. The canthus rostralis is obliquely directed and flat. The snout distinctly overhangs the lower jaw. The nostrils are at the end of the blunt snout, near the edge of the canthus rostralis, and positioned closer to the apex of the snout (1/3 of the total distance of the eye to the snout end) than the eye. The tongue present with medial conical papilla. The choanae is visible and is anterior to the roof of the mouth. The eyes represent about 1.5x the size of the tympanum, the latter being distinct and circular. The interorbital distance is twice as large as the upper-eyelid distance. Unpaired vocal sacs are positioned in subgular region, but not easy to decipher. Other noticeable characteristics comprise the absence of glandular mass under the armpits. The palm shows both an inner and outer metatarsal tubercule with the former being long and thin and is directed along the inner edge of the thick nuptial pad on the thumb while the latter is rounded and relatively large. The fingers moderately long and do not show any webbing with distal and slightly expanded toe tips. The first finger is shorter than both the second and third while the second is longer than the third. The tibio-tarsal articulation reaches the snout with the knee joint adjacent to the anterior margin of the tympanum. The legs are long with muscular thighs. The tarsal tubercle clearly visible and the toes are relatively long and thin, with extensive webbing (1e(0), 2i(1), 2e(0), 3i(0.5), 3e(0), 4i(1.5), 4e(0), 5i(0)). The tips of toes slightly swollen and expanded. Tubercles are present on the inner toe, long and thin, directed along the inner edge of the first toe. A small-rounded tubercle is present on the outer/mid-portion of the anterior margin of the foot and spines can be found on the toes between the tubercles (Greenwood et al. 2020).

There are number of features that distinguish P. ambanguluensis from its sister species P. krefftii and perhaps the most notable of all is the shape of the snout, in the latter, the upper and lower jaw more or less extends to the same point in lateral view, whereas in the former the snout visibly extends beyond the lower jaw in both ventral and lateral view. Similarly, the snout is rounded in dorsal view in the latter, whereas the former’s is more pointed arrow-like shape. Similarly, the color of P. ambanguluensis is much darker, as opposed to that of P. krefftii, which is typically lighter with more distinct patterning. In addition, the cartilage cushion differs between the two sister species, with a lighter brown than the tympanic membrane in P. ambanguluensis and darker in P. krefftii (Greenwood et al. 2020).

COLORATION:

In life, brown colouration is dominant in P. ambanguluensis though it slightly darkens or lightens here and there. The species dorsal view shows a brown mottling, with a darker thin brown interorbital band that is light brown edged on the anterior side at the mid-line of the eyes. The snout is light brown as well. So are the legs, except that they show a slightly darker brown banding on their length. Small white spines are found regularly distributed along with all toes between tubercles. The ventral view shows that the lower jaw is edged with brown overlaying a cream-yellow colouration. The gular flap is lighter brown coloured, with a darker cream/brown ventral region, mottled with light brown along edges of the legs. In preservation, the yellow colorations fade, but otherwise coloration is similar to that in life (Greenwood et al. 2020).

VARIATION:

Phrynobatrachus ambanguluensis is sexually dimorphic both in size and aspects of throat coloration. Mature males exhibit a bright yellow throat with an unpaired subgular vocal sac whereas females lack the vocal sac and their throat is brown and slightly speckled. Males are also larger with a maximum snout-vent length of 45 mm versus 40 mm in females (Greenwood et al. 2020).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Tanzania, United Republic of

View distribution map in BerkeleyMapper.

This species is known from the submontane and montane forest of West Usambara Mountains, Tanzania where the altitude range is 1450 - 1850 m (Greenwood et al. 2020).

Life History, Abundance, Activity, and Special Behaviors
This species is diurnal and endemic to the West Usambara Mountains. It is associated with streams in forested habitat. It breeds in damp and moist areas alongside streams where it lays eggs that can be found in mass attached to rocks or vegetation above water. Adults have been observed in close proximity of eggs suggesting that they probably engage in parental care (Greenwood et al. 2020).

Male P. ambanguluensis have been observed calling either sitting in shallow water or on the edge. Calls are described as a soft trill of 7 – 11 pulsed notes (mean 9.4), emitted at a rate ranging between 17.2 – 19.6 s ^-1 (mean 18.0), with a dominant frequency that varies from 2153 – 2928 Hz (mean 2820) (Channing 2020).

Visual signaling in which males do not call but instead flash their yellow vocal sac has been observed in this species. Similar non-vocal communication has also been documented in its sister species P. krefftii in which flashing throat has a role in male-male confrontations (Channing 2020).

Larva
The anatomy of the tadpoles of this species primarily relies on Channing (2020). This account points out that tappoles greatly vary in length. Total length of stage 28 measures between 13.1 - 18.9 mm. The tadpole body is slightly broader than high. In the dorsal view, the body is elongated, and the sides are parallel. The shape of the snout is bluntly rounded, and the oral disc is not visible. However, the oral disc is 0.55 of the head width at the level of the disc. The labial tooth row formula varies with the size of the specimen and is 2(1)/4, with the smallest specimen 2(1)/3. The anterior and posterior jaw sheaths are deeply pigmented along their margins, which are finely serrated. There is a single row of posterior marginal papillae, with additional rows in the angle of the mouth. There is a broad anterior gap in the marginal papillae. The rounded nostrils are small, emarginate, dorsally positioned and are close together, and appear nearer to the snout tip than to the eyes. A pineal spot not visible. The extraocular proportion (the position of the eyes across the head) is calculated as the width of the head minus the distance between the lateral limits of the eyes/distance between lateral limits of eyes is 0.44 (0.33 - 0.62). The spiracle opening is rounded with an opening at the level of the eyes, situated 0.55 posteriorly along the body. The vent tube is posteriorly directed, confluent with the dextral ventral tail fin margin. The vent ratio (vent tube length/vent width) is 1.0. In ventral view, gut coils are visible through the body wall, filled with sand and detritus. The tail is 0.63 of total length and the tail fin is slightly higher than the body. The dorsal fin is highest at the anterior third of the tail length. The dorsal fin reaches the body as a low ridge. The ventral fin is subuniform in height along its length. The tail is sharply rounded (Channing 2020).

In preservative the colouration is not uniform. In dorsal view, the pigmentation is dark brown, solid over body, but absent below the eyes and nostrils. Pigment is present medial to nostrils. The tail muscle and dorsal fin speckled while the ventral fin is clear. The ventral surfaces are unpigmented with the gut visible through transparent body wall (Channing 2020).

Trends and Threats
The narrow distribution of P. ambanguluensis can be found in West Usambaras Lushoto Mountain Reserve, but the species is still of of high conservation concern as this area is greatly affected by anthropogenic change. The species has not been found in deforested areas, but has been found in habitats with modified waterways, such as dams and artificial waterbodies (Greenwood et al. 2020).

Comments

Maximum Likelihood and Bayesian analyses on 16S rRNA found that P. ambanguluensis is sister to P. krefftii, which it was previously mistaken to be (Greenwood et al. 2020).

Phrynobatrachus ambanguluensis was assigned to the genus Phrynobatrachus because it shares many of the features common to members of this taxonomic group. Notably, the absence of webbing between fingers, presence of elongated mid-tarsal tubercules and elongated inner and small round outer metatarsal tubercules (Greenwood et al. 2020).

References
Greenwood, L. Loader, S. P., Lawson, L., Greenbaum, E., Zimkus, B. M. (2020). A new species of Phrynobatrachus (Amphibia: Anura: Phrynobatrachidae) from the Northern Mountains of Tanzania. Journal of Natural History, 54, 63 – 85. [link]

Channing, A. (2020). The advertisement call and tadpole of the Ambangulu Puddle Frog (Phrynobatrachus ambanguluensis) (Anura: Phrynobatrachidae) from Tanzania. Journal of Natural History, 54, 2889 – 2896. [link]

Species Account Citation: AmphibiaWeb 2023 Phrynobatrachus ambanguluensis: Ambangulu Puddle Frog <https://amphibiaweb.org/species/9200> University of California, Berkeley, CA, USA. Accessed Feb 5, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 5 Feb 2025.

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