Description
Boophis ankarafensis is a small, delicate-looking frog. Adult males have a snout-vent range of 22.9 - 24.0 mm and one female had a snout-vent length of 28.5 mm. The slender body is much narrower than the head. The snout is rounded in the dorsal view but appears truncated in the lateral view. The laterally facing nostrils are slightly closer to end of the snout than to the eyes. The canthus rostralis and loreal region are both somewhat concave. The eyes are large in proportion to head, round with widely elliptical, horizontal pupils. The distinct tympanum is less than half the diameter of the eye. The supratympanic fold is indistinguishable (Penny et al. 2014).

Boophis ankarafensis has slender arms. No metacarpal tubercles are recognizable. The relative finger lengths are 1 < 2 < 4 < 3, with finger 2 being noticeably shorter than finger 4. The fingers are slightly webbed with a webbing formula of 1(1), 2i(1.75), 2e(0.75), 3i(2.5), 3e(1.75), 4(1). The fingers have single, round subarticular tubercles and end in moderately large finger discs. Nuptial pads are present on the inner side of finger 1 (Penny et al. 2014).

Boophis ankarafensis has slender hind limbs. When adpressed to the body, the tibotarsal articulation is level with the nostrils. The inner metatarsal tubercle is distinct but there is no outer metatarsal tubercle. The relative toe lengths are 1 < 2 < 5 = 3 < 4 and there is slight webbing between the toes with a formula of 1(0), 2i(0.75), 2e(0), 3i(0.75), 3e(0), 4i(1), 4e(1.5), 5(0.25). The toes end with slightly enlarged discs (Penny et al. 2014).

The skin on the dorsum and throat are smooth. The skin on the belly and in the cloacal region is glandular (Penny et al. 2014).

Boophis ankarafensis is assigned to the genus Boophis based on general similarity in appearance to other species in the genus such as the absence of femoral glands in males, presence of intercalary cartilage proximal to the terminal phalanges, and presence of nuptial pads on the hands in males. Boophis ankarafensis is assigned to the subgroup of Boophis rappiodes due to small size absence of lateral fringes along lower arm and tarsus, and greenish, translucent skin with translucent venter (organs are visible through the skin in live specimens). It can be distinguished from other species based morphology and coloration. Boophis ankarafensis is distinguished from B. erythrodactylus because B. ankarafensis lacks red coloration on fingertips. Boophis ankarafensis is distinguished from B. erythrodactylus and B. tasymena because B. ankarafensis’ red dorsal spots have an irregular pattern. Boophis ankarafensis is distinguished from B. viridis because B. ankarafensis is smaller in size, possesses a beige colored iris with a bluish border, and has faintly yellow dorsolateral stripes. Boophis ankarafensis is distinguished from B. rappiodes because B. ankarafensis has a more reddish-brown spots that becomes dark brown in preservative whereas B. rappiodes’ coloration remains bright red in preservation before fading. The morphology of B. ankarafensis cannot be distinguished from that of B. bottae, but the two are distinguishable by advertisement call and molecular evidence. Both species have two types of calls, composed of either trill or click notes. In B. ankarafensis, the broadband pulse rate of the trill note is faster and the number of pulses in the click note is rarely three, but in B. bottae the click note is typically three. Additionally, the spectral frequencies of the calls are slightly different, both the broadband peak of the trill note and the click note being lower in B. ankarafensis (4.10 – 4.24 kHz at 25.2 °C vs. 4.30 – 4.64 kHz at 23 °C, and 3.75 – 3.84 kHz at 22.9 °C vs. 4.23 – 4.42 kHz at 23 °C, respectively)(Penny et al. 2014).

In life, B. ankarafensis has pale green skin with irregularly patterned reddish brown spots on the dorsum, arms, and legs. Red spots interspersed with yellow speckling congregate on the area between and above the eyes, forming a band connecting the eyes, which may have a line of red dots extending posteriorly from the middle of the band. Lines of red also extend behind the eyes and from the anterior side of eyes to tip of nose, forming a triangle when viewed from the dorsal view. Yellow, irregularly patterned spots may also be present on the dorsum, as well as faintly yellow dorsolateral stripes that run from behind the eyes along the forelimbs and fade at the mid-dorsum. The fingers and toes and their webbing and discs are yellowish green. The nuptial pads are unpigmented. The venter is a translucent white, with the organs visible, and the throat is bluish. During the day, coloration fades—the dorsal green becoming paler and the red markings becoming a pale, brownish red. The eyes have horizontal pupils and a beige iris with brown patches and reticulations, and a bluish border (Penny et al. 2014).

In preservative, reddish brown coloration becomes darker brown and can cover the dorsum. Coloration, after 4 months in preservative, remains vivid. After 18 months, the green of the dorsum fades from green to whitish-yellow except for the upper eyelids and a bar between the eyes. The eyes become blackish with whitish pupils (Penny et al. 2014).

Patterns of the various pigments can vary in distribution of spots and in intensity of color. Some paratypes showed fine, regularly spaced black spots on the dorsum and limbs, which may have been melanophores and have been observed in B. bottae too (Penny et al. 2014).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Madagascar

View distribution map in BerkeleyMapper.

Boophis ankarafensis is endemic to Madagascar and, as of 2020, has only been recorded in Ankarafa Forest, Sahamalaza Peninsula, Northwest Madagascar. Specimens were collected from 130 to 140 m above sea level. The species is an arboreal frog that lives in forest habitat along the banks of streams, which may become fast-flowing after heavy rains (Penny et al. 2014).

Life History, Abundance, Activity, and Special Behaviors

All individuals observed were found near a stream with vegetation. Calling males were in vegetation at a height of about 0.5 - 2 m and were positioned closely to one another along stream banks (Penny et al. 2014).

Calling and breeding activity was most frequent just after dusk during the first months of wet season from October to December and disappeared by January to February. Males typically call singerly, but will also call in a chorus. Two types of call types exist: a trill with multiple pulses and a click with 1 - 3 pulses. Trill notes were recorded at air temperatures between 25.2 and 30.3 °C and had a duration between 1.614 – 8.091 s. The call alternated between broad- and narrow band pulses. The broadband pulses had pulse rates of 11.7 – 17.3 pulses/s, a peak frequency of 3.69 – 4.48 kHz, and a duration of 2.50 – 5.06 ms. The narrowband pulses ranged from 4.00 – 4.31 kHz. At a -10 dB threshold, bandwidths for broadband pulses were 0.120 - 0.780 kHz and for narrowband pulses they were 0.129 – 0.280 kHz (Penny et al. 2014).

Click notes tended to be composed of two pulses. At air temperatures between 22.9 and 29.7 °C, the total duration lasted from 40.0 – 68.7 ms, the interpulse interval was 20.0 – 50.7 ms, and the peak frequency was 3.57 - 4.30 kHz. At a – 10 dB threshold, the bandwidth ranged from 0.120 - 0.143 kHz (Penny et al. 2014).

Mating pairs were seen on leaves that overhang the bank of stream or on rocks in axillary amplexus. Females were rarely found alone, but one was observed in a tree, ~3 m high and 30 m from a stream (Penny et al. 2014).

Trends and Threats
The species is rare, with an average occurrence of three individuals for every 200 m of stream. Despite being found in a protected area, B. ankarafensis meets the criteria for a “Critically Endangered” IUCN Red List status. The extent of occurrence is 5 km², based on suitable habitat (intact forest) being all areas of the Ankarafa Forest, which is the largest area of remaining forest on the Sahamalaza Peninsula. The area of occupancy is 4 km². Even though the species lives in Sahamalaza Îles Radama National Park, habitat destruction by slash and burn agriculture, small-scale logging, and uncontrolled burns of nearby grasslands are still threats. As the two known subpopulations are separated by the grassland and within 2 km of each other, an uncontrolled burn could have negative effects on the whole population. Gene flow may also be restricted by the grassland that separates the two subpopulations and may affect the long-term viability of the species. Lastly, the species was not found in the immediate areas surrounding its small range or in other protected areas in the region (Penny et al. 2014).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Habitat fragmentation
Climate change, increased UVB or increased sensitivity to it, etc.

Comments
The species authority is: Penny, S. G., Andreone, F., Crottini, A., Holderied, M. W., Rakotozafy, L. S., Schwitzer, C., Rosa, G. M. (2014). “A new species of the Boophis rappiodes group (Anura, Mantellidae) from the Sahamalaza Peninsula, northwest Madagascar, with acoustic monitoring of its nocturnal calling activity.” ZooKeys, (435), 111–132.

BLAST analysis of 16S rRNA mtDNA indicate that most closely related species to B. ankarafensis in the B. rappiodes group was B. bottae and the species most distantly related was B. erythrodactylus (Penny et al. 2014).

Further analysis with Bayesian Inference and Maximum Likelihood of five mitochondrial and five nuclear markers support the finding that B. ankarafensis is sister to B. bottae. The next most closely related species is B. rappiodes, followed by the clade composed of B. erythrodactylus and B. tasymena, and finally B. virdris to complete the B. rappiodes species complex. The next most closely related species complexes are the clade composed of the B. microtympanum group and the B. majori group (Hutter et al. 2018).

Specific epithet, “ankarafensis”, is a reference to the forest in which B. ankarafensis was discovered, the Ankarafa Forest (Penny et al. 2014).

At the time of its description, B. ankarafensis was the only member of the B. rappiodes group that could be found entirely in Western Madagascar and the only member found in transitional forests. One population of B. erythrodactylus can also be found on the western slopes of Madagascar’s central plateau in the Mahajeby Forest (Penny et al. 2014).

References

Hutter, C.R., Lambert, S.M., Andriampenomanana, Z.F., Glaw, F., Vences, M. (2018). ''Molecular phylogeny and diversification of Malagasy bright-eyed tree frogs (Mantellidae: Boophis).'' Molecular Phylogenetics and Evolution, 127, 568-578. [link]

Penny, S. G., Andreone, F., Crottini, A., Holderied, M. W., Rakotozafy, L. S., Schwitzer, C., Rosa, G. M. (2014). ''A new species of the Boophis rappiodes group (Anura, Mantellidae) from the Sahamalaza Peninsula, northwest Madagascar, with acoustic monitoring of its nocturnal calling activity.'' ZooKeys, 435, 111–132. [link]

Species Account Citation: AmphibiaWeb 2020 Boophis ankarafensis <https://amphibiaweb.org/species/8285> University of California, Berkeley, CA, USA. Accessed Nov 5, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 5 Nov 2024.

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