Typical body shape of a pipid frog; tentacle below the eye that is 0.5 times the length of the eye diameter; foot with four horny claws.
A small clawed frog with small protruding eyes located almost on the top of the head. Body flattened. SVL of mature specimens 28-40 mm. A small tentacle below the eye barely reaches 0.3 to 0.5 times the lenght of the eye diameter. No visible tympanum. The skin is finely granular. Starting at the posterior border of the eye, a double line of elongate, vaguely alternating and unpigmented dermal tubercles
stretch along the flanks,that are though to be lateral line sense organs; sensual tubercles according to Vigny (1977).
The outer line comprises 18 - 20 tubercles arranged at right angles to the body axis, whereas the 15-16 inner tubercles run parallel to this. 3-4 additional tubercles are situated in the neck region, and the inferior border of the lower jaw also bears 9-11 tubercles. Numerous unpigmented wart-like dermal elevations are scattered across the jaw and the dorsum. They are also present on the digits which are not broadened at all, so that the skin appears scaly. On breeding males, the outer parts of the fingers are blackish. The dermal lobes situated above the vent are better developed in females. The hind limbs are fully webbed. They have 3-5 toes with black horny claws. The inner metatarsal tubercle has been transformed into a fourth claw.
The SVL is 45 mm according to Arnold & Lamotte (1968),
Fischberg et al. (1982)
indicate 32-39 mm for adult males (x = 36 mm) and 48-55 mm for adult females (x = 50 mm). According to the latter authors, 3-7 (x= 4.5) sensory tubercles are arranged around the eyes.
report on a 56 mm long specimen, but his specimens were composite, including X. fraseri.
Frétey & Dewynter (1998) cite a 42mm specimen from Gabon (but compare "range").
Dorsal parts of body and limbs light to dark brown with numerous fine gray and black spots which never form larger spots. The iris is yellowish. Venter whitish to yellowish, vaguely mottled with black. Some specimens have scattered black dots on the white belly, which become more numerous on the hind limbs. Arnoult & Lamotte (1968)
report on beige ventral surfaces bearing brown spots, and
figures a specimen whose belly is vaguely spotted.
mentions frogs from Cameroon bearing yellow vertebral stripes on their neck regions. However, it is rather doubtful whether these animals are really X. tropicalis.
reports on a cream-pink female whose belly showed irregular mottling. Coloration in alcohol corresponds largely to live coloration. In most cases, neither the black dots of the dorsum nor the mottled pattern of the venter remain visible in alcohol, and animals generally become beige-gray to brown, the belly and the ventral parts of the limbs become white. One female turned totally black, and the black claws of another specimen turned white.
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Benin, Burkina Faso, Cote d'Ivoire, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Nigeria, Senegal, Sierra Leone, Togo
So far, this species has been found mainly in rainforest regions, a fact which explains its presence in the gallery forests of the Comoé National Park. These habitats are immediately connected with the proper coastal rainforest belt by the river Comoé. According to Lamotte (1966),
it is restricted to the West African rainforest belt, but
Böhme et al. (1996)
report on a population in Burkina Faso, i.e. in arid continental West Africa. According to Frost (1985),
X. tropicalis inhabits the forest regions of West Africa, i.e. an area stretching from Senegal to Cameroon and eastern Zaire.
However, Loumont (1983)
maintains that the range of this species just includes the western part of the above-mentioned region (from Senegal to western Cameroon), the southern and eastern sector being occupied by X. epitropicalis. The river Sanaga separates the ranges of the species. The frogs occurring on the islands of Fernando Póo, Principe, Sao Tomé and Annobón represent the species Xenopus andrei
(Loumont 1983). According to
Gorham (1966) and
the range of X. tropicalis also includes Angola. In particular, this species has been recorded from the following countries: Senegal, Gambia, Guinea Bissau, Sierra Leone, Liberia, Guinea, Burkina Faso, Ivory Coast, Ghana, Togo, Benin, Nigeria, Cameroon, Gabon, Congo, R.D. Congo, Angola; reported in the following references:
Peters (1875) ,
Müller (1885b) ,
Johnston (1906) ,
Nieden (1908) ,
Noble (1924) ,
Barbour & Loveridge (1930a) ,
Witte (1934) ,
Parker (1936a) ,
Sanderson (1936) ,
Mertens (1938b) ,
Loveridge (1941) ,
Laurent (1952e) ,
Romer (1953) ,
Guibé & Lamotte (1958a) ,
Taylor & Weyer (1958) ,
Schiøtz (1963) ,
Euzet et al. (1966) ,
Gorham (1966) ,
Perret (1966) ,
Knoepffler (1967) ,
Lamotte (1967b) ,
Arnoult & Lamotte (1968) ,
Walker (1968) ,
Maeder (1969) ,
Vigny (1977b) ,
Joger (1981) ,
Loumont (1983) ,
Böhme 1987, (1994c) ,
Hughes (1988) ,
Gruschwitz et al. (1991a) ,
Böhme et al. (1996) ,
Bourgat et al. (1996) ,
Pauwels & Meirte (1996) ,
Rödel (1996) ,
Frétey & Dewynter (1998) .
At Comoé National Park, this species is mainly restricted to pools in the gallery forests. However, some populations are found in savanna ponds not too far away from those forests. This species is generally considered a forest-dweller, as cited in: Loveridge (1955a),
Arnoult & Lamotte (1968),
In this habitat, it occupies still and slow-running waters.
Noble (1924) cites shallow brooks that drain the rain forest. The presence of this species in the savanna has also been reported by
and Joger (1981).
even found it, alhough rather rarely, in temporary ponds of the northern Guinea and Sudan savannas.
Life History, Abundance, Activity, and Special Behaviors
Voice: In the Comoé National Park, no calls have been registered so far. According to Vigny (1979),
the call of other specimens from Ivory Coast can be characterized as a rather low, vibrating thrill lasting about 1-10.5 sec whose dominant frequency is around 1 kHz, and which vaguely sounds like "rooa" or "roa ooa".
Eggs: No eggs have been found so far in the national park. According to Arnoult & Lamotte (1968),
single eggs are attached to the stems and leaves of aquatic plants.
reports on couples turning over in the water while spawning, similar to Pipa pipa. He wrote that the eggs remain at the water surface.
Tadpoles: A typical pipid tadpole with a broad mouth, quite similar to that of a catfish. No jaws or keradonts (denticles). Long thin tentacles arise on the upper lip on both sides of the mouth, reaching the dorsal inset of the tail fin when held against the body. The ventral fin is considerably broader than the dorsal one. The fin is only slightly convex between body and vent. Tadpoles found in clear-water forest pools are generally orange to flesh-colored with almost transparent tail fins whose lower margins are often black. In rather somber habitats, the fin is blackish. One paired spiracle on the venter. Measured and weighed specimens showing no trace of limbs brought the following results (TL in mm, weight in g): 23/0.12; 27/0.18; 31/0.22. The forelimbs emerge at a BL of approx. 17 mm (TL:42-46 mm). Metamorphosis begins when the tadpoles measure less than 5 cm (TL).
Young larvae are found throughout the rainy season. In 1992, we found the first tadpoles in early May. Two weeks later, all the animals had developed hind limbs, and their forelimbs were beginning to emerge. When the latter were present, their BL was 12.2-15.5 mm (TL: 44 mm). The last frogs had metamorphosed within one month, showing then a SVL of 11.5 to 15.5 mm.
Arnoult & Lamotte (1968) ,
tadpoles measuring 6 mm still bear external gills but do not bear any tentacles. When the forelimbs had emerged, their TL was 49-52 mm (BL: 31-44 mm). However, these data sharply contradict the size at which the tadpoles are said to metamorphose (SVL: 14.4 mm).
Altig & Johnston (1986)
refer to this description. In the analysis of diverse pipid larvae, Sokol (1977) also examined X. tropicalis tadpoles.
During the dry season, X. tropicalis migrates from its breeding sites to the riverbanks where it spends the day under flat stones, in holes in the banks or under roots. At night, this species is occasionally found in small rock-pools. Other authors also report that this species spends all of the year in its water habitats, as referred to in
Guibé & Lamotte (1958a) ,
Perret (1966) ,
Lamotte (1967b) .
If this proves to be impossible, the frogs will burrow into the mud
(Arnoult & Lamotte 1968)
or seek refuge in humid litter
As soon as the rainy season sets in, the frogs migrate to the forests. Looking for appropriate spawning sites, they even colonize tiny water bodies, e.g. the buckets filled with washing water we usually put in front of our huts. At night, during periods of heavy rainfall, X. tropicalis occasionally covers considerable distances beyond its preferred habitat. On these excursions, it sometimes succeeds in colonizing savanna ponds in close vicinity to the gallery forest.
Tadpoles are found exclusively in large forest pools most of which harbor abundant vegetation of floating plants and clear water during the rainy season. Yet X. tropicalis equally inhabits rather muddy ponds that lack any vegetation. At Tai National Park I regularly recorded X. tropicalis tadpoles in water filled holes of the dwarf crocodile (Osteolaemus tetraspis). During the day the adult frogs hide under dead trunks in shallow water. At night they forage for food all over the water. Their diet comprises any animal prey they are able to overwhelm. Prey landing on the surface of the pools is also devoured
New observations on X. laevis showed that platannas are able to feed terrestrially, from the pond bank, as well as underwater
(Measey 1998) .
Earthworms, insect larvae and tadpoles are reported to form the bulk of their diet
as seen in Loveridge (1955a) ,
Guibé & Lamotte (1958a) , and
Arnoult & Lamotte (1968) .
wrote that prey mostly consists of arthropods but recorded tadpoles in the stomach of adult X. tropicalis, as well. Their prey is sucked into the broad mouth and crammed in by means of the forelimbs.
According to other authors, X. tropicalis is a purely aquatic species inhabiting permanent waters floating regularly at the surface and retiring if necessary into the dense vegetation
(Johnston 1906) .
Gruschwitz et al. (1991a)
found this species throughout the year in small ponds near the riverside. Other habitats mentioned in the literature comprise small muddy ponds within and beyond the forest belt as seen in Guibé & Lamotte (1958a) ,
and stagnant waters in secondary and tertiary forests
(Sanderson 1936) .
Arnoult and Lamotte (1968)
expressly exclude running waters as potential habitats. However,
found this species in fast-running spring brooks in Senegal. Amplexus is inguinal. They attach their eggs to aquatic plants. Tadpoles are found at Comoé National Park throughout the rainy season. According to
Böhme (1994c) ,
in certain residuary rainforests of Guinea the frogs collected in July are exclusively freshly metamorphosed young, whereas those caught in October are generally adult ones. According to
Guibé & Lamotte (1958a)
and Arnoult & Lamotte (1968) ,
the frogs spawn from July to August. At Mt. Nimba, metamorphosis is reported to take place in November (an observation which contradicts the observations made by Böhme). In the vicinity of Lamto, Ivory Coast, froglets were found in May, December and January, whereas tadpoles are reported to occur throughout the year
(Lamotte 1967b) ,
here, most tadpoles were found in ponds in the gallery forests.
At Comoé National Park, the tadpoles are often restricted to certain sections of the ponds, and they always form huge swarms in open water, whenever possible in sunlit sectors of the ponds. Almost parallel to each other, the tadpoles either swim on the spot, filtering the water with their heads pointing downward, or they will move forward rather slowly, regulating their positions by rotating movements of the tips of their tails. According to my experiments, these swarms are formed even if no predators are present. A phenomenon which contrasts with that shown by the tadpoles of Phrynomantis microps
Rödel & Linsenmair (1997).
As all tadpoles in a swarm are of similar size, one might assume that they are close relatives.
Relation to Humans
Like Xenopus laevis, X. tropicalis was formerly used in pregnancy tests (Bergerard & Lamotte 1949).
The genome of X. tropicalis has been sequenced (Hellsten et al. 2010). This is the first amphibian genome to be sequenced, enabling new insights into vertebrate evolution and the last common ancestor of tetrapods. Despite amphibians having diverged about 360 mya from mammals, birds, and reptiles, Hellsten et al. (2010) report that there is considerable sequence and gene order conservation. However, mammalian genomes have undergone far more chromosomal rearrangements. Many aspects of the vertebrate immune system are conserved, but unique to the amphibian genome are genes that code for antimicrobial peptides.
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Written by M.O. Roedel (roedel AT biozentrum.uri-wuerzburg.de), Biozentrum der Universitaet, Lehrstuhl fuer Tieroekologie und Tropenbiologie, Wuerzburg
First submitted 2001-02-21
Edited by Vance Vredenburg, M. J. Mahoney, Tate Tunstall, Kellie Whittaker (2010-05-01)
Species Account Citation: AmphibiaWeb 2010 Xenopus tropicalis: Tropical Clawed Frogs <http://amphibiaweb.org/species/5246> University of California, Berkeley, CA, USA. Accessed Oct 20, 2017.
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Citation: AmphibiaWeb. 2017. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 20 Oct 2017.
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