Sao Tome Giant Treefrog
© 2003 Robert C. Drewes (1 of 2)
Multilocus molecular data indicate that H. thomensis is in the genus Hyperolius and is part of the H. cinnamomeoventris species complex, which includes six described species: H. cinnamomeoventris, H. olivaceus, and H. veithi from continental Africa, H. molleri and H. thomensis endemic to São Tomé Island, and H. drewesi endemic to Príncipe Island in the Gulf of Guinea archipelago (Schick et al. 2010; Bell et al. 2015 J. Bio., Bell 2016, Bell et al. 2017). Hyperolius thomensis is sexually monochromatic and color polymorphic (males and females vary in color from uniform brown, to green, to blue-green) and differs in color from H. cinnamomeoventris and H. olivaceus, which are sexually dichromatic (females are green and males are tan with bright yellow dorsolateral lines), and from H. veithi, which is sexually monochromatic (both sexes are tan with bright yellow dorsolateral lines). Hyperolius thomensis differs from H. molleri and H. drewesi in male body size (the snout-vent lengths of H. molleri is 23 – 32 mm, H. drewesi is 25 –31 mm, and H. thomensis is 36 – 41 mm), in the distal portion of the terminal phalanx (H. molleri and H. drewesi are disc shaped while H. thomensis is oval/wider in horizontal plane), and in ventral coloration (H. molleri is red/orange/white, H. drewesi is white, H. thomensis is marbled black/orange; Bell 2016).
In life, the dorsum, dorsal surface of forelimb and hindlimb are brown, green, or blue-green. The dorsal asperities are black. The dorsal surface of thigh is marbled black and orange with a thin green medial band that has a thick black contour extending from dorsum to lower limb. The side of head brown, green, or blue-green. The dorsal surface of fingers and toes are orange. The ventral surfaces are orange with large black blotches. The chest is white with an orange wash and black blotches. The iris is gold (Bell 2016).
In preservative, the dorsum, side of head, and dorsal surface of forelimb and hindlimb are brownish grey. The dorsal asperities are dark. The dorsal surface of the thigh is cream with black blotches and a thin brown medial band that has a thick black contour extending from dorsum to lower limb. The ventral surfaces are cream with black blotches (Bell 2016).
There is some sexual dimorphism. Males have a round gular gland that occupies less than half of gular area, vocal sac, and dorsal asperities. Females are larger than males (Bell 2016).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Sao Tome and Principe
Life History, Abundance, Activity, and Special Behaviors
The dominant frequency range of the advertisement call for H. thomensis is 2338 – 2654 Hz with an average of 2513 Hz (Gilbert and Bell 2018).
Hyperolius thomensis breed in phytotelmata, including decaying logs and bamboo (Drewes and Stoelting, 2004). Females deposit eggs on the surface of leaves overhanging water or directly on the surface of the phytotelmata structure.
Trends and Threats
Possible reasons for amphibian decline
General habitat alteration and loss
Analysis of 16S and cytb mtDNA indicate that H. thomensis sister to the clade formed by H. drewesi and H. molleri. Together they from a clade of Hyperolius island endemics. The next most closely related species is Hyperolius olivaceus (Bell et al. 2017).
Hyperolius thomensis is an island giant; it is one of the largest member of the genus Hyperolius (Robert C. Drewes per. comm).
Bell R.C., Drewes, R.C., Zamudio K.R. (2015). ''Reed frog diversification in the Gulf of Guinea: overseas dispersal, the progression rule, and in situ speciation.'' Evolution , 69(4), 904–915. [link]
Bell RC, Drewes, RC, Channing A, Gvozdik V, Kielgast J, Lötters S, Stuart BL, Zamudio KR (2015). ''Overseas dispersal of Hyperolius reed frogs from Central Africa to the oceanic islands of Sao Tome and Principe.'' Journal of Biogeography, 42(1), 65-75. [link]
Bell RC, Parra JL, Badjedjea G, Barej MF, Blackburn DC, Burger M, Channing A, Dehling JM, Greenbaum E, Gvozdík V, Kielgast J, Kusamba C, Lötters S, McLaughlin PJ, Nagy ZT, Rödel M-O, Portik DM, Stuart BL, VanDerWal J, Zassi-Boulu, A-G, Zamudio KR (2017). ''Idiosyncratic responses to climate-driven forest fragmentation and marine incursions in reed frogs from Central Africa and the Gulf of Guinea Islands.'' Molecular Ecology, 26(19), 5223-5244. [link]
Bell, R.C. (2016). ''A new species of Hyperolius (Amphibia: Hyperoliidae) from Príncipe Island, Democratic Republic of São Tomé and Príncipe.'' Herpetologica , 72(4), 343-351. [link]
Drewes, R. and Wilkinson, J. (2004). ''The California Academy of Sciences Gulf of Guinea expedition I: The taxonomic status of the genus Nesionixalus with comments on the genus Hyperolius.'' Proceedings of the California Academy of Sciences, 55(20), 395-407.
Drewes, R., Schiøtz, A. (2004). ''Hyperolius thomensis''. The IUCN Red List of Threatened Species 2004: e.T56289A11442549. https://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T56289A11442549.en. Downloaded on 23 August 2020.
Drewes, R., and Stoelting, R. E. (2004). ''The California Academy of Sciences Gulf of Guinea expedition (2001) II. Additions and corrections to our knowledge of the endemic amphibians of São Tomé́ and Príncipe.'' Proceedings of the California Academy of Sciences, 55, 573-587.
Gilbert C.M., Bell R.C. (2018). ''Evolution of advertisement calls in an island radiation of African reed frogs.'' Biological Journal of the Linnean Society, 123(1), 1–11. [link]
Schick S, Kielgast J, Rödder D, Muchai V, Burger M, Lötters S. (2010). ''New species of reed frog from the Congo basin with discussion of paraphyly in Cinnamon-belly reed frogs.'' Zootaxa, 2501(1), 23-36. [link]
Written by Rayna C. Bell (rbell AT calacademy.org), California Academy of Sciences
First submitted 2001-02-12
Edited by Ann T. Chang (2020-08-24)
Species Account Citation: AmphibiaWeb 2020 Hyperolius thomensis: Sao Tome Giant Treefrog <http://amphibiaweb.org/species/611> University of California, Berkeley, CA, USA. Accessed Sep 19, 2020.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 19 Sep 2020.
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