Friday, April 17, 2020

[Herpetology • 2020] Raorchestes rezakhani • A New Species of Cryptic Bush Frog (Anura, Rhacophoridae, Raorchestes) from northeastern Bangladesh

Raorchestes rezakhani 
Al-Razi, Maria & Muzaffar, 2020

Raorchestes is a speciose genus of bush frogs with high diversity occurring in the Western Ghats of India. Relatively fewer species have been recorded across India, through Bangladesh, southern China, into Vietnam and Peninsular Malaysia. Many bush frogs are morphologically cryptic and therefore remain undescribed. Here, a new species, Raorchestes rezakhani sp. nov., is described from northeastern Bangladesh based on morphological characters, genetics, and bioacoustics. The 16S rRNA gene distinguished this species from 48 known species of this genus. Bayesian Inference and Maximum Likelihood analyses indicated that the new species was most similar to R. tuberohumerus, a species found in the Western Ghats, and to R. gryllus, a species found in Vietnam. Bioacoustics indicated that their calls were similar in pattern to most Raorchestes species, although number of pulses, duration of pulses, pulse intervals and amplitude differentiated it from a few other species. It is suggested that northeastern India, Bangladesh, northern Myanmar, and southern China represent important, relatively unexplored areas that could yield additional species of Raorchestes. Since many remaining habitat patches in Bangladesh are under severe threat from deforestation, efforts should be made to protect these last patches from further degradation.

Keywords: Amphibian, bush frog, DNA, herpetofauna, Raorchestes rezakhani sp. nov.

Figure 4. Color variation in Raorchestes rezakhani sp. nov. A holotype, showing single transparent vocal sac during advertisement call (B holotype with brown dorsum and “)-(“ mark; C dorsolateral view of paratype (JnUZool- A0519) D ventral view of paratype (JnUZool- A0519), showing small dark brown spots.

Raorchestes rezakhani sp. nov.
 Suggested English name: Reza Khan’s bush frog

Etymology: We take great pleasure in naming the new species as a patronym for one of the pioneers in the field of wildlife research in Bangladesh, Dr. Mohammad Ali Reza Khan.

Diagnosis: A species of Raorchestes having the following unique combination of characters: (1) relatively small size (adult males = 18.85–20.90 mm SVL); (2) head wider than long (HW/HL 1.55; range 1.53–1.56, N = 4); (3) dark brown, granular dorsum bearing small, horny spicules; (4) vomerine teeth absent; (5) single transparent vocal sac while calling; (6) snout projecting, sub-elliptical in ventral aspect, and subequal to or smaller than horizontal diameter of eye; (7) tympanum indistinct; (8) supratympanic fold weakly distinct; (9) finger and toe discs well developed and rounded; (FD IV 0.50–0.60, TD IV 0.56–0.65 mm); (10) both inner and outer metacarpal and metatarsal tubercles absent; (11) nostril is closer to tip of snout than to eye (NS 0.63–0.90, EN 1.10–1.25 mm); (12) Tongue without papilla (13) venter pale white, with minute dark gray flecks present in the vocal sac region. Details of these measurements are provided in Table 3.
Figure 5. Holotype of Raorchestes rezakhani sp. nov. A dorsal view B ventral view C ventral view of right hand D ventral view of right foot E web pattern in foot.

Figure 1. Map showing the type location of Raorchestes rezakhani sp. nov. in northeastern Bangladesh as well as adjoining areas.

Distribution and natural history: Raorchestes rezakhani sp. nov. was recorded from the semi-evergreen forests of northeastern Bangladesh. They were active with the onset of the rainy season in the month of April. We did not hear calls of this species after August. Frogs were found inside the primary and secondary forest mainly on the edge of streams and near man-made trails. They often use the hilly slopes during calling. Individuals perch on leaves and branches of small trees and on bamboo trunks (with diameters of 1.5–4 cm). Vocalizing individuals were perched 1–1.5 m above the forest floor. We usually heard the calls immediately after the sunset (ca. 1815 h in April) although calling activity started a little earlier when it was raining.

 Hassan Al-Razi, Marjan Maria and Sabir Bin Muzaffar. 2020. A New Species of Cryptic Bush Frog (Anura, Rhacophoridae, Raorchestes) from northeastern Bangladesh. ZooKeys. 927: 127-151. DOI: 10.3897/zookeys.927.48733