Description
Astylosternus diadematus is a stocky-bodied, West African frog that have males that range from 44.2 - 51.0 mm in snout–vent length with an average of 47.8 mm, and females that are generally larger. This species has a square head with a short snout and a small, distinct canthus rostralis. The tympanum to eye ratio is 54%. The dorsal integument is smooth with small wrinkles or lines of granulations visible on the back, flanks and side of the head. The hind feet have a small extent of webbing at the base, and the toe tips are undilated (Amiet 1977). The last phalanx of toes II–V is recurved and can protrude through the ventral skin of the toe, likely used to defend the frog by scratching potential predators (Blackburn et al. 2008). Males, during breeding season, have a single nuptial pad and no gular spines (Amiet 1977).

The dorsal coloration of adults ranges from chocolate brown to beige, gray, or yellow with round markings, outlined in black, dotting the back and flanks. The thighs are marked with typically 3 to 4 (but ranging from 0 to 5) darker transverse bars. The transition from dorsal to ventral coloration is marked by large dark spots on the flanks, and a high contrast black and yellow marbling on the groin. The ventral coloration is yellow with a darkly speckled throat area. The ventral side of the legs is either light yellow or yellow covered with dark speckling (Amiet 1977).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Cameroon, Nigeria

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (9 records).

This species is found in the southwestern region of the Cameroon Volcanic Line, i.e. southwestern Cameroon and southeastern Nigeria (Amiet 1977, Channing and Rödel 2019), where it is associated with streams in lowland to submontane forests from 250 - 1100 meters. Its presence has been confirmed through surveys in the following areas in Cameroon: Nkongsomba, Mamfé, Loum-Tombel, northern Mt. Cameroon, Kumba (Amiet 1975, 1977, 1978), Mt Nlonako (Hofer et al. 1999, Plath et al. 2004, Herrmann et al. 2005), and Mt. Oku (Doherty-Bone and Gvoždík 2017); and in Nigeria: Obudu Plateau (Lea et al. 2005), Ngel Nyaki Forest Reserve, and Mambilla Plateau (Arroyo Lambaer 2015), and Cross River National Park (Onadeko et al. 2010).

Life History, Abundance, Activity, and Special Behaviors
The adults are nocturnal (Channing and Rödel 2019, Plath et al. 2004).

During the breeding season in April to May and sometime November, males are found in swampy areas or streams at the edges of torrents. Males call from hiding spots in leaf litter or rocks near the water. Amiet describes the males’ call as "hou" or "rrroua" with one note every 1.5 seconds (Amiet 1977).

On Mt. Nlonako, Astylosternus diadematus has been found at the same sites as A. fallax, A. perreti, and A. montanus. Astylosternus perreti and A. montanus are typically found at higher elevations and overlap with A. diadematus only at the upper end of its elevational limit (Hofer et al. 1999, Plath et al. 2004, Herrmann et al. 2005).

Larva
Tadpoles have a total length of 72 mm with a body length of 23 mm. The body length to total length ratio is between 31.3 - 36.7% . The keratodont formula is 1:2+2/2+2:1. The anterior lip papillae are positioned laterally, and the posterior lip papillae are in 2 rows of 20 papillae. The central papillae are long and narrow, with the papillae becoming smaller towards the angles of the mouth. The rostral gaps are large and the jaw sheaths are massive and serrated. The upper jaw has a medial fang, and the lower jaw is U-shaped with a medial notch (Griesbaum et al. 2019).

Tadpole coloration varies from brown to dark brown, with the dorsal surfaces being darker. The ventral coloration is paler and more grayish, and the flanks are densely marked with diffuse and small brown spots. The jaw sheaths are black (Griesbaum et al. 2019).

Trends and Threats
This species has a decreasing population trend caused by habitat loss due to farming and logging, as well as human consumption in some areas (IUCN 2021).

Relation to Humans
This species is consumed in both its larval and adult stages on Mt. Manengouba in Cameroon and on the Obudu Plateau in Nigeria (Gonwouo and Rödel 2008, IUCN 2021).

Comments

Phylogenetic relationships

Astylosternus diadematus is the only species in the genus that has been karyotyped and was found to be tetraploid with 2n of 54 (Bogart and Tandy 1981, Evans et al. 2012).

References

Amiet, J.-L. (1977). ''Les Astylosternus du Cameroun (Amphibia Anura, Astylosterninae).'' Annales de la Faculté des Sciences de Yaoundé, 23/24, 99-227.

Amiet, J.-L. (1978). ''A propos d'Hyperolius platyceps Boulenger, H. kuligae Mertens et H. adametzi Ahl (Amphibiens Anoures).'' Annales de la Faculté des Sciences du Cameroun, 25, 221-256.

Amiet, J.L. (1975). ''Ecologie et distribution des amphibiens anoures de la région de Nkongsamba (Cameroun).'' Annales de la Faculté des Sciences de Yaoundé, 20, 33-107.

Arroyo-Lambaer, D. (2015). "Conserving amphibian diversity: a species inventory and gene flow studies in fragmented montane forest, Mambilla Plateau, Nigeria." Doctoral Dissertation. University of Canterbury. School of Biological Sciences.

Blackburn, D. C., Hanken, J., Jenkins Jr, F. A. (2008). "Concealed weapons: erectile claws in African frogs." Biology Letters 4, 355–357. [link]

Bogart, J. P. and Tandy, M. (1981). ''Chromosome lineages in African frogs.'' Monitore Zoologico Italiano, N.S. Supplemento, 15(5), 55-91.

Channing, A., Rödel, M.-O. (2019). Field Guide to the Frogs and Other Amphibians of Africa. Penguin Random House South Africa, Cape Town, South Africa.

Doherty-Bone, T. M., Gvoždík, V. (2017). "The amphibians of Mount Oku, Cameroon: an updated species inventory and conservation review." ZooKeys, 643, 109–139. [link]

Evans, B. J., Pyron, R. A., Wiens, J. J. (2012). "Polyploidization and sex chromosome evolution in amphibians." Polyploidy and genome evolution. Soltis, P. S., Soltis, D. E., eds., Springer, Berlin, Heidelberg.

Griesbaum, F., Hirschfeld, M., Barej, M. F., Schmitz, A., Rohrmoser, M., Dahmen, M., Mühlberer, F., Liedtke, H.C. Gonwouo, N.L., Doumbia, J., Rödel, M. O. (2019). "Tadpoles of three western African frog genera: Astylosternus Werner, 1898, Nyctibates Boulenger, 1904, and Scotobleps Boulenger, 1900 (Amphibia, Anura, Arthroleptidae)." Zoosystematics and Evolution, 95, 133–160. [link]

Herrmann, H.-W., Böhme, W., Herrmann, P.A., Plath, M., Schmitz, A., Solbach, M. (2005). ''African biodiversity hotspots: the amphibians of Mt. Nlonako, Cameroon.'' Salamandra, 41(1/2), 61–81.

Hofer U, Bersier L-F, Borcard D (1999). ''Spatial organization of a herpetofauna on an elevational gradient revealed by null model tests.'' Ecology, 80(3), 976–988. [link]

IUCN SSC Amphibian Specialist Group. (2017). "Astylosternus diadematus." The IUCN Red List of Threatened Species 2017: e.T54416A95838823. https://dx.doi.org/10.2305/IUCN.UK.2017-2.RLTS.T54416A95838823.en. Accessed on 11 January 2022.

Lea, J. M., Luiselli, L., Politano, E. (2005). "Are there shifts in amphibian faunal composition in Nigerian landscapes undergoing long-term degradation? A case study from a montane environment." Revue d'écologie, 60, 65–76. [link]

Onadeko, A. B., Rodel, M. O., Egonmwan, R. I., Saliu, J. K. (2010). "Herpetological surveys of south-western and south-eastern regions of Nigeria." Zoologist, 8, 34–43. [link]

Plath M, Solbach M, Herrmann H-W (2004). ''Anuran habitat selection and temporal partitioning in a montane and submontane rainforest in southwestern Cameroon – first results.'' Salamandra (Frankf), 40, 239-260. [link]

Portik DM, Bell RC, Blackburn DC, Bauer AM, Barratt CD, Branch WR, Burger M, Channing A, Colston TJ, Conradie W, Dehlin JM, Drewes RC, Ernst R, Greenbaum E, Gvozdík V, Harvey J, Hillers A, Hirschfeld M, Jongsma GFM, Kielgast J, Kouete MT, Lawson LP, Leaché AD, Loader SP, Lötters S, van der Meijden A, Menegon M, Müller S, Nagy ZT, Ofori-Boateng C, Ohler A, Papenfuss TJ, Rößler D, SinschU, Rödel MO, Veith M, Vindum J, Zassi-Boulou AG, McGuire JA (2019). ''Sexual dichromatism drives diversification within a major radiation of African amphibians.'' Systematic Biology , 68(6), 859-875. [link]

Species Account Citation: AmphibiaWeb 2023 Astylosternus diadematus: Crowned Night Frog <https://amphibiaweb.org/species/1481> University of California, Berkeley, CA, USA. Accessed Nov 26, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 Nov 2024.

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