Description
Astylosternus occidentalis is an oval bodied West African frog where males range from 44.5 - 61.8 mm in snout–vent length with an average of 52.0 mm. The snout–vent length of females ranges from 47.5 - 65.3 mm with an average of 55.9 mm. This species has a square head with a rounded snout and a rounded, slightly bulging canthus rostralis. The tympanum is large, distinct and vertically elliptical with a tympanum to eye ratio of 66%. The dorsal integument is mostly smooth to slightly granular with small spines only visible at higher magnifications. The skin on the vocal sac and the outer parts of the thighs is granular. The inner metatarsal tubercle almost as long as the shortest toe and the outer metatarsal tubercle is absent. The front feet have no digital webbing, but there is rudimentary webbing on the feet. The subarticular tubercles are very prominent. Toe tips are slightly expanded. Males, during breeding season, have a single large nuptial pad on the thumb and conical spines on the lower mandible arranged in 2 - 3 rows parallel to the lower lip. Scattered small spines are also present along lateral edges of the fingers, beneath the tympanum, and on the belly (Rödel et al. 2012).

Tadpoles have a total length of 77.4 - 95.9 mm, with a body length to total length ratio of 31.1+/- 2.8%. The ventral-fin-height to dorsal-fin-height ratio is 71.6 ± 13.7%. The keratodont formula is 1:2+2/2+2:1. The anterior lip papillae consist only of a few lateral papillae. The posterior lip papillae are in two or three rows of about 30 short and triangular papillae, the inner rows are smaller than those of the marginal rows. The rostral gaps are large and the jaw sheaths are massive and serrated. The upper jaw is broadly arched with a small medial projection, and the lower jaw is narrowly U-shaped (Griesbaum et al. 2019).

Dorsal coloration in adults varies from gray to yellow, orange or light brown. The back is covered with small, roundish, dark brown spots. The tip of the snout is darker, and there is a pale intraocular bar that is posteriorly bordered by black. Ventral coloration is yellowish white. The thighs have indistinct brown transverse, partly interrupted bars and the soles of the feet are dark (Rödel et al. 2012).

Tadpole coloration is more or less uniformly dark brown on the back, while the ventrum is more pale, slightly grayish. The tail fin margins are missing dark pigmentation and the last third of the tail are almost black. The jaw sheaths are black (Griesbaum et al. 2019).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Cote d'Ivoire, Guinea, Liberia, Sierra Leone

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (2 records).

Astylosternus occidentalis is distributed in the western part of the Upper Guinean forest (Channing and Rödel 2019; Rödel et al. 2012). It is typically found near small streams in dense primary, secondary, or gallery forests at elevations from 130 - 1300 m (Rödel et al. 2012). Its presence has been confirmed through surveys in a number of areas throughout its widespread distribution in Sierra Leone (Parker 1931; Schiøtz 1964a); Liberia (Parker 1936; Hillers and Rödel 2007); Guinea (Guibé and Lamotte 1958; Böhme 1994; Rödel and Bangoura 2004; Rödel et al. 2004; Hillers et al. 2006, 2008-Salamandra); and Ivory Coast (Rödel and Branch 2002; Rödel 2003; Ernst and Rödel 2006; Ernst et al. 2006; Hillers et al. 2008-Conservation).

Life History, Abundance, Activity, and Special Behaviors
Astylosternus occidentalis adults are nocturnal (Amiet 1977; Channing and Rödel 2019).

During courtship, males call from dense vegetation or cracks and stream edges close to but not in the water (Amiet 1977; Channing and Rödel 2019). The calls are described as a deep rattling note followed by a buzzing note, or a buzzing note alone (Channing and Rödel 2019).

Tadpoles have been observed at night on the bottom of slow or almost stagnant pools of forest creeks and rivers (Rödel et al. 2012).

Rödel et al. (2012) noted that, in contrast to Central African Astylosternus, A. occidentalis and A. laticephalus have never been observed using the terminal phalanges of their hind feet in defense (as in Blackburn et al. 2008), despite the phalanges of the two groups being anatomically indistinguishable (Barej et al. 2010).

Astylosternus occidentalis is known to eat spiders, orthopterans, and isopterans, and consumes more snails than syntopic species of Odontobatrachus and Conraua alleni (Schäfer et al. 2022).

Trends and Threats
Ongoing deforestation for wood, agriculture and human settlement are known threats to this species (IUCN 2021).

Comments
Preliminary genetic studies have found two clades in the genus, a West African clade and a Central African clade (Portik et al. 2019). Astylosternus occidentalis and its sister species A. laticephalus are the only species found in the West African clade (Rödel et al. 2012; Portik et al. 2019).

References

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

Barej, M.F., Böhme, W., Perry, S.F., Wagner, P., Schmitz, A. (2010). "The hairy frog, a curly fighter? – A novel hypothesis on the function of hairs and claw-like terminal phalanges, including their biological and systematic significance (Anura: Arthroleptidae: Trichobatrachus)." Revue Suisse de Zoologie, 117, 243–263. [link]

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

Böhme, W. (1994). "Frösche und Skinke aus dem Regenwaldgebiet Südost–Guineas, Westafrika. I. Einleitung; Pipidae, Arthroleptidae, Bufonidae." Herpetofauna, 16, 11–19.

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.

Ernst, R., Linsenmair, K.E., Rödel, M.-O. (2006). "Diversity erosion beyond the species level: Dramatic loss of functional diversity after selective logging in two tropical amphibian communities." Biological Conservation, 133(2), 143–155. [link]

Ernst, R., Rödel, M.-O. (2006). "Community assembly and structure of tropical leaf-litter anurans." Ecotropica, 12, 113–129. [link]

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]

Guibé, J., Lamotte, M. (1958). "La réserve naturelle intégrale du Mont Nimba. XII. Batraciens (sauf Arthroleptis, Phrynobatrachus et Hyperolius)." Mémoires de l’Institut fondamental d’Afrique noire, 53, 241–273.

Hillers, A., Bangoura, M.A., Loua, N.S., Rödel, M.-O. (2006). "Inventaire rapide des amphibians et des reptiles dans la région de Boké dans le nord-ouest de la Guinée." Une inventaire biologique rapide de la préfecture de Boké dans le nord-ouest de la Guinée. RAP Bulletin of Biological Assessment Wright, H.E., McCullough, J., Diallo, M.S., eds., RAP Bulletin of Biological Assessment, Conservation International, Washington D.C., 59–64, 131–136, 178–181.

Hillers, A., Loua, N.-S., Rödel, M.-O. (2008). "A preliminary assessment of the amphibians of the Fouta Djallon, Guinea, West Africa." Salamandra, 44, 113–122. [link]

Hillers, A., Rödel, M.-O. (2007). "The amphibians of three national forests in Liberia, West Africa." Salamandra, 43, 1–10. [link]

Hillers, A.,Veith, M., Rödel, M.-O. (2008). "Effects of forest fragmentation and habitat degradation on West African leaf-litter frogs." Conservation Biology, 22, 762–772. [link]

IUCN SSC Amphibian Specialist Group. (2013). "Astylosternus occidentalis." The IUCN Red List of Threatened Species 2013: e.T54421A18390613. https://dx.doi.org/10.2305/IUCN.UK.2013-2.RLTS.T54421A18390613.en. Accessed on 11 January 2022.

Parker, H.W. (1931). "XLV.—Some new and rare frogs from West Africa." Annals and Magazine of Natural History, series 10, 7, 492-498.

Parker, H.W. (1936). ''Amphibians from Liberia and the Gold Coast.'' Zoologische Mededelingen (Leiden), 19, 87-102.

Rödel, M.-O. (2003). "The amphibians of Mont Sangbé National Park, Ivory Coast." Salamandra, 39, 91–110 [link]

Rödel, M.-O., Bangoura, M.A. (2004). "A conservation assessment of amphibians in the Forêt Classée du Pic de Fon, Simandou Range, southeastern Republic of Guinea, with the description of a new Amnirana species (Amphibia Anura Ranidae)." Tropical Zoology, 17, 201–232. [link]

Rödel, M.-O., Bangoura, M.A., Böhme, W. (2004). "The amphibians of south-eastern Republic of Guinea (Amphibia: Gymnophiona, Anura)." Herpetozoa, 17, 99–118. [link]

Rödel, M.-O., Branch, W.R. (2002). "Herpetological survey of the Haute Dodo and Cavally forests, western Ivory Coast, Part I: Amphibians." Salamandra, 38, 245–268. [link]

Rödel, M.-O., Barej, M. F., Hillers, A., Leaché, A. D., Kouamé, N.G., Ofori-Boateng, C., Assemian, N. E., Tohé, B., Penner, J., Hirschfeld, M., Doumbia, J., Gonwouo L.N., Nopper, J., Brede, C., Diaz, R., Fujita, M.K., Gil, M., Segniagbeto, G.H., Ernest, R., Sandberger, L. (2012). "The genus Astylosternus in the Upper Guinea rainforests, West Africa, with the description of a new species (Amphibia: Anura: Arthroleptidae)." Zootaxa, 3245, 1–29. [link]

Schiøtz, A. (1964). ''A preliminary list of amphibians collected in Sierra Leone.'' Vedenskabelige Meddelelser fra Dansk Naturhistorisk Forening, 127, 19-33.

Schäfer, M., Neira-Salamea, K., Sandberger-Loua, L., Doumbia, J., Rödel, M.-O. (2022). "Genus-specific and habitat-dependent plant ingestion in West African sabre-toothed frogs (Anura, Odontobatrachidae: Odontobatrachus)." Herpetological Monographs, 36(1), 49-79. [link]

Species Account Citation: AmphibiaWeb 2022 Astylosternus occidentalis <https://amphibiaweb.org/species/1486> 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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