Species Description: Richards, SJ, Hoskin CJ, Cunningham MJ, McDonald K, Donnellan SC. 2010. Taxonomic re-assessment of the Australian and New Guinean green-eyed treefrogs Litoria eucnemis, L. genimaculata and L. serrata (Anura: Hylidae). Zootaxa 2391:33-46.
© 2010 Eric Vanderduys (1 of 7)
The dorsal texture of the species varies from smooth to granular, occasionally punctuated by larger tubercles (Hoskin and Hero 2008). Ventrally, the skin is granular.
There is a prominent and well-developed serrated fold or fringe along the edge of each limb. The inner metatarsal has an oval tubercle, and the outer metatarsal has a smaller tubercle (Hoskin and Hero 2008). The fingers are partially webbed, the toes are almost completely webbed, and the discs on both the fingers and toes are relatively large (Hoskin and Hero 2008, Vanderduy 2012). There is also a small and pointed tubercle on the heel.
At stage 40, tadpoles have a total length up to 15 mm. The eyes are positioned dorsolaterally. The oral disc is surrounded by marginal and submarginal papillae. The anterior gap is wider than the width of the jaw. The labial tooth row formula is 2 (2)/3 (1). The spiracle is sinistral and the vent tube is dextral. The tail musculature has a discontinuous line of dorsal granules (Hoskin and Hero 2008).
Originally described from six specimens by Andersson in 1916, L. serrata was later considered a junior subjective synonym of L. genimaculata (Richards et al. 1993) or errantly synonymized with L. eucnemis (eg., Frost 2001). Based on molecular and morphological data, L. serrata was recently resurrected as a species containing most of the Australian populations of treefrogs formerly considered to be L. genimaculata, leaving only the New Guinea population as L. genimaculata (Richards et al. 2010). Isolated populations in Australia were previously described as a new species, L. myola, based on reproductive isolation, call differences, and morphological discrepancies from the L. genimaculata lineage that was later recognized as L. serrata (Hoskin 2007). Litoria serrata can be distinguished from L. genimaculata and the closely related L. papua and L. exophthalmia by its larger size (the males of the other species do not exceed snout-vent lengths of 38.6 mm) as well a well-developed fold on the outer margin of the limbs (versus an absent or highly reduced fold in L. genimaculata, L. papua, and L. exophthalmia). It is differentiated from L. eucnemis by the presence of a small tubercle or spike on the heel as opposed to a triangular lappet, as well as a distinct male advertisement call comprised of a series of quiet ticking notes instead of the raucous growl of L. eucnemis. Litoria serrata differs from the sympatric and genetically and morphologically very similar species L. myola by the smaller size (male snout-vent ranges of 32.8 - 38.6 mm, average 36.3 mm; female snout-vent average of 53.5 mm) and shorter, faster, and higher-pitched call of L. myola. A paucity of molecular data and reporting of call data had previously confounded species limits within this complex, as many of the taxa are morphologically similar in both size, pattern, and coloration (Richards et al. 2010).
A cryptic species, coloration and patterning are highly variable in live adult L. serrata. Dorsal coloration ranges from brown, grey, tan, or orange and mottled with irregular green, brown, orange, or white patches that resemble moss or lichen. There is often a darker colored patch between the eyes, and a lighter patch on the forehead. Ventrally, coloration is cream-white, occasionally with brown flecks on the throat. The hind limbs often have irregular brown or green cross bands. The flank, under the limbs, and in the thigh and groin are finely mottled. There is a distinct green colored crescent across the upper portion of the iris, but the rest of the eye is a silver-grey color (Hoskin and Hero 2008).
In preservative, adult dorsal coloration is grey in larger specimens and is dark olive, brown, or grey in smaller specimens. Dorsal mottling is black in color. The ventral surface is light grey (Andersson 1916).
In life, tadpoles are light brown or grey in color. The dorsal fin and tail musculature have scattered pigment, and the posterior part of the body is overall a darker shade, and the ventral surface is pale (Hoskin and Hero 2008).
There is considerable variation in the dorsal coloration (see above) of adult L. serrata, and the species is sexually dimorphic by size (Hoskin and Hero, 2008). The northern and southern L. serrata are similar morphologically, but can be differentiated by their slightly different calls (Hoskin 2007, Hoskin and Hero 2008, Richards et al. 2010).
Distribution and Habitat
Life History, Abundance, Activity, and Special Behaviors
Litoria serrata breeds in streams during the wet summer months of September-March (Hoskin and Hero 2008). Males have a soft, slow to medium-paced call, resembling a series of quiet ticking or tocking notes (Hero 1995). The call tap rates are just over 1 tap per second, but can accelerate (Vanderduys 2012). However, like other species in the L. eucnemis species-group, L. serrata lacks a vocal sac.
Eggs are small and pigmented. The clutch size is large and is laid in a single gelatinous clump in slow-moving or still parts of a stream, and tadpoles undergo indirect development (Hoskin and Hero 2008).
Litoria serrata is often parasitized by a Batrachomyia fly; the maggot can often be seen as a lump beneath the skin. It appears to have little effect on the frog’s overall health (Hoskin and Hero 2008).
This treefrog and some of its relatives have unique anti-microbial peptide defenses that have been found to effectively defend them from the fungus Batrachochytrium dendrobatidis (Bd) that causes chytridiomycosis infection, particularly in lowland populations (Woodhams et al. 2012). Due to higher variability in peptide expression, higher-elevation populations tend to be less stoutly defended against chytrid infections. The peptide defense profile of L. serrata is distinct from L. eucnemis (Jackway et al. 2011, Richards and Alford 2005). Additionally, anti-Bd bacterial symbionts prevalent in cooler conditions are found in the epidermis of L. serrata and other rainforest Litoria, and have been associated with Bd declines (Daskin et al. 2014).
Trends and Threats
Relation to Humans
Possible reasons for amphibian decline
General habitat alteration and loss
Litoria serrata is a part of the L. eucnemis species group, which includes L. eucnemis, L. genimaculata, L. serrata, L. exophthalmia, L. papua, and L. myola. The species group is found in Australia and New Guinea. A recent phylogenetic analysis inferred L. serrata and L. eucnemis as sister taxa (but did not include L. myola), and that clade as sister to a clade containing L. genimaculata, L. exophthalmia, and allied species in New Guinea (Richards et al. 2010).
There are two distinct genetic lineages of L. serrata, a northern one and a southern one. The species L. myola evolved within a highly isolated zone in the hybridization contact area between the two lineages of L. serrata, an example of speciation by reinforcing natural selection (Richards et al. 2010).
The species epithet, “serrata” refers to the presence of serrated-looking and well-developed dermal folds on the limbs (Andersson 1916).
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Hoskin, C.J. (2007). ''Description, biology and conservation of a new species of Australian tree frog (Amphibia: Anura: Hylidae: Litoria) and an assessment of the remaining populations of Litoria genimaculata Horst, 1883: systematic and conservation implications of an unusual speciation event.'' Biological Journal of the Linnean Society, 91(4), 549-563.
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Richards, S. J., Hoskin, C. J., Cunningham, M. J. (2010). ''Taxonomic re-assessment of the Australian and New Guinean green-eyed treefrogs Litoria eucnemis, L. genimaculata and L. serrata (Anura: Hylidae.'' Zootaxa, 46, 33-46. [link]
Richards, S. J., McDonald, K. R., Ingram, G. J. (1993). ''Recognition of Litoria eucnemis (Lönnberg) (Anura: Hylidae) in Australia.'' Memoirs of the Queensland Museum, 34, 94.
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Vanderduys, E. (2012). Field Guide to the Frogs of Queensland. CSIRO Publishing, Clayton, Victoria, Australia.
Woodhams, D. C., Bell, S. C., Kenyon, N., Alford, R. A., Rollins-Smith, L. A. (2012). ''Immune evasion or avoidance: Fungal skin infection linked to reduced defense peptides in Australian green-eyed treefrogs, Litoria serrata.'' Fungal Biology, 116(12), 1203-1211. [link]
Written by Simon Scarpetta (scas100 AT utexas.edu), Jackson School of Geosciences, University of Texas at Austin
First submitted 2019-10-24
Edited by Ann T. Chang (2019-10-28)
Species Account Citation: AmphibiaWeb 2019 Litoria serrata: Green-eyed treefrog <http://amphibiaweb.org/species/7469> University of California, Berkeley, CA, USA. Accessed Jul 5, 2020.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 5 Jul 2020.
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