Osgood’s Ethiopian Toad
There are two palmar tubercles present on the slender hands, with the inner palmar tubercle being small and oval, while the outer is larger, round, or squarish. The fingers of A. osgoodi have singular subarticular tubercles that are barely raised, and quite smooth. The first finger is slightly shorter than the second. In breeding males, cornfield nuptial asperities appear on the first three fingers and axillae. The length of the tibia is more than ⅓ of the snout-vent length. The feet are slender. The toes of A. osgoodi are slender, tapering, and devoid of webbing on all but the fifth toe, which has a thick fleshy rudiment on the basal half of the proximal phalanx. On the toes, the subarticular tubercles are singular, except for the basal tubercles, which are slightly elevated and barely discernible. The tubercles on the soles of the feet are smaller than the basal ones, and are indistinct and smooth (Grandison 1978).
The dorsal skin of A. osgoodi is smooth, with the exception of a few small flattened warts mostly confined to the lumbar region, and the backs of the thighs. The flanks and ventral surfaces are uniformly granular. The forearm has an extensive, broadly oval development of glandular tissue covering the entire upper and posterior surfaces. There is a small patch of glandular tissue on the upper portion of the upper arm. A small band of skin over the wrist lacks glands, but immediately distally and over the back of the hand there is further glandular development. On the leg, a small oval patch overlies the distal ⅔ of the cruralis and is narrowly separated from a thick and conspicuous tibial gland that cover the entire surface from the knee to the heel (Grandison 1978).
Some individuals of A. osgoodi were found in the larval stage, and were estimated to be approximately 44 days old. At Gosner stage 35, the total length averaged 19.4 mm, average body length was 6.2 mm, and average tail length was 13.2 mm. At Gosner stage 34, the average total length was 18.2 mm, average body length was 5.6 mm, and average tail length was 12.6 mm. At Gosner stage 33, the average total length was 17.6 mm, average body length was 5.5 mm, and average tail length was 12.1 mm. At Gosner stage 31, the total length averaged 15.6 mm, average body length was 5.0 mm, and average tail length was 10.6 mm. The tadpole is overall slender, with a moderately elongated body. It is round in cross-section and almost as high as it is wide. The nares are large, and with an ovoid aperture that is approximately ½ of an eye diameter. They have a well-defined, rounded rim, and are positioned equidistant between the eyes and tip of the snout. The eyes are dorsally positioned, and are about one eye diameter away from the body outline when viewed dorsally. The spiracle is sinistral, and the aperture is an inconspicuous and simple slitlike opening. It is located well below the lateral midline, and is closer to the body-tail junction than the snout tip. The vent is medium-sized, and the gut is coiled. The tail is about twice as long as the body, and has a rounded tip at its end. The tail fins are low, and the dorsal and ventral fins have equal heights in the distal portion but the ventral fin is deeper than the dorsal fin on the proximal portion (Grandison 1978, Müller 2019).
As of 2020, there are only two individuals that belong to the Altiphrynoides genus: A. osgoodi and A. malcolmi. Altiphrynoides osgoodi is distinctly larger than A. malcolmi, and is also less plump than A. malcolmi. Both A. osgoodi and A. malcolmi have parotid glands, although the gland of A. osgoodi extends to the temporal region, whereas A. malcolmi’s parotid gland does not extend. The hands and feet of A. osgoodi are slender, whereas the hands and feet of A. malcolmi are thick and fleshy. Also, there is significant reduction in the phalangeal length of A. malcolmi, but no reduction in A. osgoodi. The length of the tibia in A. osgoodi is more than ⅓ of the snout-vent length, while the tibial length of A. malcolmi is less than ⅓ of the snout-vent length. There are cornfield nuptial asperities on the first three fingers and axillae of A. osgoodi, but only on the first two fingers of A. malcolmi. The toe webbing on A. osgoodi is present only on the 4th and 5th toes, but is present on all by the first toe in A. malcolmi. The coloration also varies among these two species. In A. osgoodi, there is a dark inverted Y-shaped mark over the occiput and shoulders that is absent in A. malcolmi. There is also variation between the reproductive methods between the two species. In A. osgoodi, amplexus is axillary, while in A. malcolmi, amplexus is inguinal. Finally, A. malcolmi has terrestrial larvae, while A. osgoodi has aquatic larvae (Grandison 1978).
Tadpoles of A. osgoodi have a typical bufonid tadpole body shape and keratodont formula, but they are significantly darker in coloration than other Bufo members. Altiphrynoides osgoodi differs further from other bufonids in having a fairly large, inconspicuous, and more slit-like spiracular aperture (Müller 2019).
In life, the coloration of A. osgoodi ranges from greyish-green or brownish-yellow, to very dark brown. There is an inverted, Y-shaped mark on the head and shoulders. Generally, this mark is bounded in the front by a dark interorbital bar, an inverted triangle, or a wide open V-shape. On the posterior dorsum, a pair of dark blotches may be present, and may join medially to form a chevron. In juvenile individuals, these marks are distinct, but in mature individuals, become more indistinct. The most consistent markings are a light bar passing obliquely from below the eye to the rictus, and a dark line or stripe going from the snout tip, along the canthal loreal border, to the temporal region. This dark band then broadens out and forms a prominent lateral dark band that extends backwards to the flanks. At the flanks, the line becomes paler and fragmented. The dorsolateral band, fine vertebral line, flanks, limbs, and warts on the posterior face of the thigh are paler than the ground color, and are sometimes bright yellow or tinged with orange. The dorsal cruciform pattern, broad lateral band, and lumbar chevrons are dark blackish brown, and edged with pale cream or yellowish coloration. The oblique suborbital bar is pale white or cream. The ventral surfaces ranges from cream or yellowish to dirty greyish white, often becoming bright yellow on the under-surfaces of the hind limbs. Ventral surfaces sometimes have grey or brown spots or blotches. The upper surfaces of the feet can be immaculate or spotted with pale grey or heavily blotched with grey brown or dark purplish brown spots (Grandison 1978).
In preservative, the body of larval A. osgoodi is uniformly light brown, both dorsally and laterally. A dark thin vertebral line is present and pronounced on the anterior half of the body. It begins from a patch of dark pigmentation anterior to the nostrils, and becomes indistinct slightly behind the eyes, towards the base of the tail. The raised nostril rim is unpigmented, but is surrounded by a thin dark ring. Ventrally behind the oral disc is a dark pigmented area in the shape of a Y, a V, or a crescent. Other than that area, the ventral side of the body is mainly unpigmented. The tail is densely pigmented anterodorsally near the body-tail junction. The pigmentation is more concentrated on the dorsal side, and extends to the tail for ⅔ of its length. The posterior third, and the dorsal and ventral tail fins are all relatively unpigmented, with the exception of a few scattered melanophores on the anterior half of the dorsal fin (Müller 2019).
Besides, variation in color (see above) between individuals, there appears to be some sexual dimorphism in A. osgoodi. Although the dorsal skin is usually smooth with occasional flattened warts, in sexually mature males, the skin is strikingly spiny. Rictal glands in adult males are more elevated and consist of three longitudinally elongated warts. In sexually mature males, these warts are beset with horn-tipped spinules. Also, some females and juvenile individuals have a finely granular dorsal surface, which is composed of dense tiny spinules. Limb glands are equally well-developed in both sexes, but are more obvious in mature individuals (Grandison 1978).
There is little variation among larval A. osgoodi. However, most of the variation is seen in the shape of the gulag pigmented patch. It is most strongly pigmented in younger individuals, and becomes increasingly lighter as age increases (Müller 2019).
Distribution and Habitat
Life History, Abundance, Activity, and Special Behaviors
Despite lacking a middle ear, at night, many single males expressed mating calls. The mating call is a low creak, audible at no farther than 6 - 8 m away, and resembles the clucking of a hen (Grandison 1978).
A pair was found depositing a long, thin, double string of eggs in a small pool in the morning. The eggs, which were half black and half grayish-white, became uniformly black three days later. Altiphrynoides osgoodi larvae are aquatic (Grandison 1978).
Trends and Threats
The area which A. osgoodi inhabits is currently threatened by environmental degradation due to human settlement and subsistence exploitation. Additionally, the pathogenic chytrid fungus, Batrachochytrium dendrobatidis, is prevalent among frog species in highland Ethiopia, although the specific impacts on A. osgoodi are unknown (IUCN 2020).
There is a long-running conservation program in the Bale Mountains National Park, where A. osgoodi inhabits. However, there is a severe lack of amphibian-specific conservation activities (IUCN 2020).
Possible reasons for amphibian decline
General habitat alteration and loss
As of 2020, no molecular analysis has been done on A. osgoodi and its congeners. Existing cladograms have been created with morphometric analysis. The most recent morphometric analysis results in A. osgoodi and A. malcolmi forming a clade that is sister to the Werneria, Wolterstorffina, Nectophryne, Laurentophryne, Didynamipus, and Nymbaphrynoides genera. The clade formed by the aforementioned genera is sister to Nectophrynoides cryptus, and the tree then extends to the rest of the Nectophrynoides genus (Graybeal and Cannatella 1995).
Altiphrynoides osgoodi, like many Ethiopian anurans, have a complicated naming history. In 1987, Dubois reclassified two members of the Nectophrynoides genus as Altiphrynoides malcolmi and Spinophrynoides osgoodi, based on the assumption that they were monophyletic species because of their differing reproductive methods; A. malcolmi has terrestrial larvae, while A. osgoodi has aquatic larvae. However, he then reclassified S. osgoodi as a member of the Altiphrynoides genus in order to make for more informative taxonomy (Frost et al. 2006).
Frost, D. R., Grant, T., Faivovich, J., Bain, R. H., Haas, A., Haddad, C. F. B., de Sá, R. O., Channing, A., Wilkinson, M., Donnellan, S. C., Raxworthy, C. J., Campbell, J. A., Blotto, B. L., Moler, P., Drewes, R. C., Nussbaum, R. A., Lynch, J. D., Green D. M., Wheeler, W. C. (2006). "The amphibian tree of life." Bulletin of the American Museum of Natural History, 297, 1-370. [link]
Grandison, A. G. C. (1978). ''The occurrence of Nectophrynoides (Anura: Bufonidae) in Ethiopia. A new concept of the genus with a description of a new species.'' Monitore Zoologico Italiano, N.S. Supplemento, 11(6), 119-172.
Graybeal, A., Cannatella, D.C. (1995). ''A new taxon of Bufonidae from Peru, with descriptions of two new species and a review of the phylogenetic status of supraspecific bufonid taxa.'' Herpetologica, 51(2), 105-131.
IUCN SSC Amphibian Specialist Group. 2020. Altiphrynoides osgoodi (amended version of 2014 assessment). The IUCN Red List of Threatened Species 2020: e.T54886A175788627. Downloaded on 12 November 2020.
Müller, H. (2019). ''Description of the tadpole of the critically endangered Ethiopian toad Altiphrynoides osgoodi (Amphibia: Anura: Bufonidae).'' Journal of Herpetology, 53(3), 218-223.
Originally submitted by: Alice Drozd (first posted 2020-11-11)
Edited by: Ann T. Chang (2020-11-12)
Species Account Citation: AmphibiaWeb 2020 Altiphrynoides osgoodi: Osgood’s Ethiopian Toad <https://amphibiaweb.org/species/423> University of California, Berkeley, CA, USA. Accessed May 23, 2022.
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Citation: AmphibiaWeb. 2022. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 23 May 2022.
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