AMPHIBIAWEB
Conraua derooi
family: Conrauidae

© 2012 Daniel Portik (1 of 9)
Conservation Status (definitions)
IUCN (Red List) Status Critically Endangered (CR)
CITES
Other International Status None
National Status None
Regional Status None

Country distribution from AmphibiaWeb's database: Ghana, Togo

 

View distribution map using BerkeleyMapper.

   

From the Encyclopedia of Life account:

Etymology

The specific epithet derooi is a tribute to the ornithologist Antoon De Roo, a member of the expedition that discovered this species (Hulselmans 1972).


Author: Dietterich, Lee
License: http://creativecommons.org/licenses/by-nc/3.0/

Taxonomic Notes

This species includes all records of Conraua alleni from eastern Ghana and Togo (Rödel and Schiøtz 2004).


Author: Dietterich, Lee
License: http://creativecommons.org/licenses/by-nc/3.0/

Summary

Conraua derooi is a completely aquatic frog restricted to forest streams in Ghana and Togo. This species is most easily identified by its large size, blackish dorsal coloration, externally hidden tympanum, widely indented tongue, well-developed toe disks, and extensive swelling of the postoccipital and suprascapulary regions. Males have well defined white warts on the snout and jaws, and they have prominent, non-chitinous nuptial pads. The IUCN Red List (2004) categorizes this species as Critically Endangered, in light of serious threats posed to its populations by the loss of its already limited habitat, stream sedimentation, and hunting for consumption by local people.


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

Distribution

Conraua derooi was originally described from the Misahohé forest in western Togo, and includes all records of Conraua alleni from eastern Ghana and Togo. This species was thought to be endemic to the Togo-Volta Highlands of eastern Ghana and western Togo (Rödel and Schiøtz 2004) until Kouamé et al. (2007) found what are likely the largest remaining populations of this species in the Atewa Range Forest Reserve, extending its western range limit into central Ghana (Kouamé et al. 2007).


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

Osteology

Clarke (1981) provides an extensive treatment of the osteology of Conraua in relation to other “ranine” genera and species. However, while he discusses C. alleni, C. beccarii, C. crassipes, and C. goliath as well as members of several other genera, (Clarke 1981), his analysis does not include material from C. derooi, potentially limiting the extent to which his conclusions for Conraua apply to this species.


Author: Dietterich, Lee
License: http://creativecommons.org/licenses/by-nc/3.0/

Morphology

The head is as wide (35.6 mm) as it is long (35.4 mm), and the horizontal diameter of the orbit (10.1 mm) is barely greater than the length of the snout (9.6 mm). The nostrils are closer to the tip of the snout than to the eye, and the distance between the nostrils (5.9 mm) is slightly less than the interorbital distance (6.9 mm). The tongue is widely indented, and the vomerine teeth are present but poorly developed. The loreal region is rather oblique, the canthus rostralis is rounded, the tympanum is invisible externally, and the postoccipital and suprascapulary regions are significantly swollen. A dermal fold extends from the eye to the shoulder, where it is continued by a few fine warts. The front legs bear very fine granular folds. Finger 1 is almost 1.5 phalanges shorter than finger 2, which is in turn 1.5 phalanges shorter than finger 3. Finger 3 is the longest, and has a distinct external dermal fringe. Finally, finger 4 is one phalanx shorter than finger 3. All of the fingers have a large subarticular tubercle except for finger 4, which has two. The internal metacarpal tubercle is rather large but not very prominent. The external metacarpal tubercle is narrower, and the elbow lacks a dermal fold (Hulselmans 1972).

The hindlimbs are very long and robust. The dorsal surfaces of the femur, tibia, and tarsus bear fine, granular longitudinal folds. The toes end in very distinct disks, although the disk on toe 5 is slightly less developed than the others. On toe 1, an internal cutaneous fold extends from the disk to the internal metatarsal tubercle. Toe 5 bears an external cutaneous fold. The internal metatarsal tubercle is very large and quite prominent, and the tarsal fold covers two-thirds of the internal side of the tarsus. The subarticular tubercles are prominent and elongated. The skin is fairly smooth dorsally and granular laterally (Hulselmans 1972).

In alcohol-preserved specimens, the dorsal and lateral surfaces are dark brown, marbled with small, irregular darker spots. The ventral surfaces are a dirty white color, except for the throat and chest which are a smoky, dirty brown color. The dorsal surfaces of the femur and tibia have faint transversal bars, and the undersides of the arms and legs are largely colored dirty brown. In terms of sexual dimorphism, males are larger than females. The male’s nuptial pads are not chitinous, and they cover the entire dorsal surface of the thumb except the terminal phalanx. Compared to the female, the male also has well-developed white verrucae on the snout and jaws; this same verrucosity is present to a much lesser degree on all of the dorsal surfaces. The male of this species lacks a vocal sac and there is no buccal opening (Hulselmans 1972).


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

Size

Adult males of this species reach 76-84 mm in snout-vent length (SVL), and adult females reach 74-82 mm in SVL (Hulselmans 1972).


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

Diagnostic Description

Conraua derooi is a relatively large frog with long and robust limbs that dwells exclusively in or near forest streams. Its tympanum is not visible externally, its post-occipital and suprascapulary regions are rather swollen, and its tongue is widely indented. Its toes bear very distinct adhesive disks, with webbing that extends until midway through the disks (Hulselmans 1972).


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

Comparisons

Conraua derooi resembles C. robusta rather closely, in its highly developed toe disks, the swelling in the postoccipital and suprascapulary region, the coloration, and the fine dermal folds on the dorsal surface of the limbs. However, C. derooi differs from C. robusta by its smaller size, its more indented tongue, its shorter tibia, its finer tarsal fold, and its non-chitinous nuptial pads. The digit lengths of C. derooi also vary less per individual than in C. robusta (Hulselmans 1972).

Conraua derooi differs more visibly from C. crassipes: C. derooi is slightly larger, with darker coloration, no well-defined dorsal spots, and no dermal fold near the elbow. Additionally, C. derooi has better developed toe disks, a relatively longer first toe, and a better developed internal metatarsal tubercle than C. crassipes. Furthermore, the tympanum of C. derooi is not visible externally, and the placement of the supratympanic fold differs between the two species (Hulselmans 1972).

Conraua derooi differs from C. alleni by its much larger size, its much darker coloration, its more widely smoky-brown ventral surface, the absence of well-defined dorsal spots, and its well-defined toe disks. Thus, these two species are easily differentiated even though they share several characters, including the pattern of subtle lateral warts and the position of the supratympanic fold (Hulselmans 1972).


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

Habitat and Ecology

Conraua derooi is a permanently aquatic species confined to flowing water in rainforest habitats. Adults prefer slightly rocky streams (Hillers 2008, Hillers et al. 2009), and tadpoles of this species have also been found in streams (Rödel and Schiøtz 2004).


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

Population Biology

Conraua derooi may once have been abundant, but a survey in Ghana in the early 2000s failed to find it, suggesting a stark decline (Rödel and Schiøtz 2004). Since its original description in 1972, C. derooi had been recorded only twice, both times during the late 1970s, until its rediscovery in 2005 and 2007 in Ghana and Togo, respectively (Hillers et al. 2009). Fast-flowing streams in the Atewa Range Forest Reserve in southeastern Ghana appear to hold large and viable populations of C. derooi; these are likely to be this species’ largest remaining populations (Kouamé et al 2007). Overall, reliable demographic information for this species does not yet exist, especially in the Togo-Volta highlands where it may be limited to small, isolated patches of forest. More thorough population monitoring is urgently necessary in order to better understand this species’ population biology (Hillers et al. 2009).


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

Phylogenetics

Preliminary analysis shows that the Conraua derooi populations in the Atewa Range Forest Reserve in central Ghana are genetically differentiated from those in the Volta region further north in eastern Ghana and western Togo, underlining the need to protect populations of this species in both regions (Rödel et al. unpubl. data, cited in Hillers et al. 2009).


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

IUCN Red List Category and Justification of Conservation Status

The IUCN Red List (2004) categorizes this species as Critically Endangered because its Area of Occupancy is probably less than 10 square kilometers, it occurs in a single sub-population, and the extent of its habitat at Misahohé, the forest in Togo from which it was originally described, is probably declining (Rödel and Schiøtz 2004). Despite the recent rediscoveries of this species subsequent to this assessment (Kouamé et al. 2007, Hillers et al. 2009), the future of Conraua derooi remains very tenuous.


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

Trends

Populations of this species are decreasing (Rödel and Schiøtz 2004).


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

Threats

One of the two known localities of Conraua derooi, the Togo-Volta Highlands, has been subject to heavy deforestation as a result of agricultural expansion, logging, and human settlement, which likely constitutes a serious threat to this species. Furthermore, C. derooi may be threatened by hunting for human consumption in both Ghana and Togo, as well as stream sedimentation which is thought to potentially affect its breeding (Rödel and Schiøtz 2004, Hillers et al. 2009).


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

Conservation Actions and Management

According to the IUCN Red List (2004), “there are some small protected areas within the range of the species, including Kiabobo National Park in Ghana, but it has not been confirmed from any of these. Improved protection and maintenance of the remaining habitat in the range of the species is recommended. Surveys are urgently needed to determine whether or not this species survives. Captive breeding might need to be considered” (Rödel and Schiøtz 2004).


Author: Goldsmith, Willy
License: http://creativecommons.org/licenses/by-nc/3.0/

Uses

Conraua derooi is hunted for human consumption where it occurs in both Ghana and Togo (Hillers et al. 2009).


Author: Dietterich, Lee
License: http://creativecommons.org/licenses/by-nc/3.0/