Phrynobatrachus acridoides (Cope, 1867)
Original Published Description:
East African Puddle Frog (English), Zanzibar Puddle Frog (English), Mababe Toad-frog (English), Cope's Toad-frog (English), Small Puddle Frog (English), Zanzibar River Frog (English), Eastern Puddle Frog (English)
Phrynobatrachus acridoides is medium-sized species (SVL < 30 mm) of puddle frog endemic to East Africa. Members of this genus are identified by the presence of a midtarsal tubercle, elongate inner metatarsal tubercle, and outer metatarsal tubercle. Phrynobatrachus acridoides is characterized by a tympanum that is most often visible, moderate webbing, and a number of different color morphs. Males exhibit shaded throats, and females often exhibit speckled throats, so this characteristic may not be used to identify the sexes.
This species ranges from southern Somalia and Kenya, south to eastern Zimbabwe, Mozambique and northern KwaZulu-Natal Province in South Africa. It occurs on Mafia, Zanzibar and Pemba islands in Tanzania. It is likely to occur in Zambia, but there do not appear to be any confirmed records. Records from Budongo Forest in western Uganda, from Lokichokio in northwestern Kenya and from Ngatana in northeastern Kenya require confirmation (Pickersgill et al., 2004).
This species appears to be named after another frog species, Acris gryllus of North America; the author reports that this species and Phrynobatrachus acrioides are similar in size and proportions. 'Acris' is derived from the Greek 'acr' meaning sharp or cricket and '-oides' meaning like.
Phrynobatrachus acridoides is a medium-sized species (SVL < 30 mm) characterized by a tympanum that is most often visible, moderate webbing, and a number of different color morphs. Males exhibit light gray or black throats, and females often exhibit mottled throats, so this characteristic may not be used to identify the sexes. The ventral surface is smooth and pale, usually with a yellowish tinge near the vent.
The holotype measured 27.56 mm (13 lines; Cope, 1867). According to Pickersgill (2007) males measure 18.5-27 mm, while females measure 21-25 mm; Channing (2001) and Harper and Vonesh (2003) report that the species is slightly larger with males reaching 28 mm and females 30 mm in length.
The profile from the front is convex. Canthus rostralis is obtuse, straight. Snout is narrowed, rounded, and lightly prominent. The head width, femur, tibia, and foot are 33-37%, 43-53%, 47-56%, and 43-53% of the snout-vent length, respectively. The diameter of the orbit is equal to the distance from the eye to the snout tip. The tympanum is round and equal to 40-50% of the orbit, although sometimes it may be indistinct (Cope, 1867, Pickersgill, 2007). According to Cope (1867) pedal webbing is moderate with three phalanges of toe IV are free of webbing; Pickersgill (2007) reports that webbing can be more substantial with 2-3 phalanges free on toe IV, and toes III and V are webbing to the last phalanx. Digital tips are swollen or exhibit small discs. A midtarsal tubercle, elongate inner metatarsal tubercle and small outer metatarsal tubercle are present. The tibiotarsal articulation of the adpressed hind limb reaches the middle of the orbit to beyond the tip of the snout (Cope, 1867; Pickersgill, 2007). Skin with weak or flattened tubercles on dorsum, although fairly smooth. Two dorsal glands convergent from orbits to scapular region and diverge. Males exhibit asperities on the throat, and a single or multiple lateral folds are present on each side of the gular region, visible when the vocal sac is deflated; females exhibit asperities only in proximity to the vent (Pickersgill, 2007).
Dorsum is greyish-olive or greyish-brown, often with a narrow pale or green vertebral band. According to Pickersgill (2007), 70% of specimens exhibit the plain morph with dorsal glands often outlined in black and a "W" shaped mark behind the head, while the dorsal stripe occurs in 15%. A dark supratympanic streak is present, curving towards the axilla. A dark band is present on the side, front and hind faces of the femur; a pale band is present above the latter. According to Cope (1867), the lip exhibits three broad blackish bars: one from the canthus rostralis and orbit and two below the orbit; Pickersgill (2007) reports that the upper lip is uniformly grey with weak dark and light barring and Channing (2001) describes the upper jaw as having light speckling. Limbs are barred. The venter is white with a yellowish hue near the groin, and a pale stripe occurs no the back of the thigh (Channing, 2001; Harper and Vonesh, 2003). The throat and breast are white with punctuations of brown or generally darkened in both sexes, and therefore can not be used to distinguish the sexes (Cope, 1867).
Phrynobatrachus pakenhami is morphologically most similar to P. acridoides. According to Loveridge (1941), the latter can be distinguished by the barring (brown and white) present on the lower jaws, and the smaller body size (23-27 mm). However, he used these characters to distinguish P. pakenhami from what he believed was P. acridoides on Pemba Island, and this species is not believed to be found on the island. Pickersgill (2008) reported that apart from the advertisement call and slightly smaller size, there is little to distinguish P. acridoides from P. pakenhami.
Habitat and Ecology
It is a low-altitude species found below 700 m that inhabits dry and humid savannahs, shrubland, grassland and coastal habitats, and it is adaptable to alteration of its habitats (Pickersgill et al., 2004; Harper et al., 2010).
It is generally a common, sometimes abundant, species. It is important to note that there have been no recent records from South Africa, which is on the edge of its range (Pickersgill et al., 2004).
Populations of this species are stable (Pickersgill et al., 2004).
Loveridge (1936) reports that the stomach contents of one frog included a beetle, four larvae of a tineid moth, and four undigested catepillars.
This species breeds in both temporary and permanent, waterbodies, including puddles, pools, swamps, vleis, roadside ditches, and flooded grassy depressions; eggs are generally laid in clumps within aquatic vegetation below the surface of the water (Pickersgill, 2008; Harper et al., 2010). Eggs are small, dark and 0.8 mm in diameter (Channing, 2001).
Pickersgill (2008) described the call as "a coase, rasping croak." Harper et al. (2010) describes the call as a continual harsh creaking snore or “cricket-like”. Antiphonal chorusing occurs in this species with a distinctive twp-tone "five-four, five-four" sound. Males were recorded with frequencies ranging between 1.1-3.6, with dominating frequencies between approximately 1.1-2.9 kHz. Calls lasted 0.37-0.48 seconds for two recorded males with 23-30 pulses per call and 53-66 pps. (Pickersgill, 2008). Intervals between calls last approximately 0.34-0.36 seconds with calls of different males overlapping by approximately 0.04-0.08 seconds. Channing (2001) also reported that the call is a "harsh creak" with males calling from vegetation in shallow waters; calls lasted 0.9 second with a dominant frequency of 2 kHz and 50 pps.
Metamorphosing froglets measure 7-7.5 mm in length (Pickersgill, 2008).
Tadpoles are small and fat with oval bodies and eyes situation close together on the dorsum on the head. The nostrils are closer to the snout tip than the eyes. The eye diameter is less than the interorbital space. The spiracle is barely visible on the flank, only slightly protruding, with its opening directed postero-laterally. The tail is 150% of the trunk length, and the caudal muscle, excluding the fins, is 50% of the trunk depth. The tail tip is sharply pointed. The oral disc is not visible from above. The upper lip is only weakly developed and is slightly convex. Rostrodonts are narrow and finely pigmented. A single row of keratodonts are present supra-angularly, and the proximal rows are drawn into a 'V' shape. Either row may be interrupted medially. A single row of weak papillae is present laterally and double on either side of the outermost row of keratodonts. Ventrally there is a row of long, filamentous papillae (Pickersgill, 2008).
Activity and Special Behaviors
This frog has been recorded as the food of the sand snake Psammophis sibilans and the vine snake Thelotornis capensis (Channing, 2001).
Evolution and Systematics
Mitochodrial sequence data from 12S rRNA, valine-tRNA, and 16S rRNA fragment, as well as combined sequence data from mitochondrial and nuclear (RAG-1) genes indicate that P. acridoides and P. pakenhami are sister species (Zimkus et al., 2010). These two species are in turn sister taxa to P. francisci and P. bullans.
IUCN Red List Category and Justification of Conservation Status
The IUCN Red List (2010) categorizes this species as Least Concern in view of its wide distribution, its tolerance of a broad range of habitats, its presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category (Pickersgill et al., 2004).
It is a very adaptable species that is not facing any significant threats, although it does seem to have declined in the edge of its range in South Africa for reasons that are unclear (Pickersgill et al., 2004).
Conservation Actions and Management
It occurs in many protected areas (Pickersgill et al., 2004).
- Staurois acridoides Cope, 1867 (synonym)
- Phrynobatrachus acridoides — Boulenger, 1882 (synonym)
- Phrynobatrachus boulengeri De Witte, 1918 (synonym)
- Hylarthroleptis boulengeri — Ahl, 1925 "1923" (synonym)
- Hylarthroleptis medilineatus Ahl, 1925 "1923" (synonym)
- Hylarthroleptis janenschi Ahl, 1925 "1923" (synonym)
- Arthroleptis boulengeri — Barbour and Loveridge, 1928 (synonym)
- Phrynobatrachus acridoides — Parker, 1931 "1930" (synonym)
- Phrynobatrachus janenschi — Deckert, 1938 (synonym)
- Phrynobatrachus medilineatus — Deckert, 1938 (synonym)
- Phrynobatrachus (Phrynobatrachus) acridoides — Laurent, 1941 (synonym)