Bioacoustics of Xenopus itombwensis

Diagnosis: Xenopus itombwensis is a member of the vestitus-wittei subgroup of clawed frogs ( Kobel et al. 1996 ) and can be distinguished from other members of this group by (1) unique but variable morphological coloration and smaller size (Table 1, Fig. 2 ), by (2) numerous temporal and spectral characteristics of the male advertisement call (Table 2, Fig. 3 ), and by (3) divergent mitochondrial and autosomal genes ( Fig. 4 ). Xenopus wittei and X. vestitus are both medium sized clawed frogs, with female snout-vent length (SVL) typically 46 and 47 mm , respectively, and a maximum SVL of 61 and 55 mm , respectively ( Kobel et al. 1996 ; Tinsley et al. 1979 ). Based on a small sample size of two females, X. itombwensis appears smaller, averaging approximately 35 mm (Table 1). Dorsal coloration of X. wittei is a uniform dark brown to chocolate with no spots and of X. vestitus is a marbeling of light silver-golden to bronze chromatophores over a brown background ( Kobel et al. 1996 ). In contrast, some X. itombwensis individuals have a mottled pattern of brown spots that are slightly darker than the brown background ( Fig. 2 B,C). The male advertisement call of X. itombwensis differs from the male advertisement calls of X. wittei and X. vestitus in that the call of the new species is much shorter (~600 milliseconds), and consists of two distinct components including a “fast trill” and a “slow trill” (Table 2, Fig. 3 ; Kobel et al. 1996 ; Vigny 1979 ). The dominant frequency of the fast trill component is similar to that of X. wittei but other acoustic characteristics of this part of the vocalization are different, and all parameters we measured from the slow trill component are distinct (Table 2). The most obvious difference between these vocalizations is the slow trill that follows vocalizations of the new species but not X. wittei . Other aspects of the slow trill are distinct from call parameters of X. wittei including the lower dominant frequencies, longer interclick interval, and lower number of clicks (Table 2). The fast portion of the call of the new species is also unique in that the interclick interval is shorter than that of X. wittei and there are fewer clicks per call.