Litoria gracilenta (Peters 1869); Graceful Tree Frog, Dainty Tree Frog, Slender Tree Frog, Banana Frog

C.Lane 2007

 

 

Taxonomy

( Barker et al., 1995; Barker et al., 1995; Hutchison and Maxon, 1987; McLean et al., 2006; Menzies and Tyler, 2004; Tyler and Davies, 1978)

Litoria gracilenta was said (by Tyler and Davies) to belong to the Aruensis Species Group which contained L. aruensis, L. gracilenta, L. chloris, L. graminea and L. multiplica. This was mostly morphology based on such common group features as a large frontoparietal fontanelle and no distal flange on the third metatarsal, for example. More recent Immunilogical studies, however, assert that serum albumen comparisons on many litoria species include L.chloris but not L.gracilenta except as having little immunilogical distance from L. chloris. Then L.chloris is placed very close to L. caerulea with the possibility of them sharing a common ancestor, just between the two. The implication is that the same would be true for L. gracilenta. The same study then combines the Caerulea and Aruensis Groups based on this comparison of L. chloris. Another study has the skin peptides of L.gracilenta as most closely resembling a member of the Caerulea Group.

Even more recently, based on morphological and vocal characteristics, Menzies and Tyler now say that the formerly called Aruensis group should have been called the Gracilenta group as L.gracilenta was discovered before L. aruensis. They have done further work on the PNG members and now say that L. gracilenta is not present in New Guinea but what was formerly thought to be this frog is actually three more recently split species that belong to this Gracilenta Group . They have removed all the previous members from the Gracilenta Group and are now calling it the Chloris Group. To this student this seems a little at odds with the immunological work previously mentioned so perhaps further developments in this evolutionary tree should be awaited.

This frog looks like Litoria chloris, from which it differs in size and skin granulation as well as call.

 

 

Description

( Barker et al., 1995; Cameron and Cogger, 1992; Cogger, 1988; Frith, 1987; McDonald, 2000; Swan, 2001; Tyler, 1976; Tyler and Davies, 1978)

An arboreal and terrestrial frog with most reference sources alluding to its aesthetic qualities. It has large developed discs and moderately long legs. Its dorsal surface is grained and may contain a few small tubercles on the side areas.
L. gracilenta is bright leafy green above with the lower sides and ventral area yellow and heavily grained. There may be a yellowish-green stripe that runs along the side of the snout and over the eye. There is a distinct granular tympanum. The iris is gold to reddish often appearing orange. The labial area is edged with yellow and prominent vomerine teeth are mostly positioned between the choanae. The hind arm, fingers and toes are bright lemony yellow whilst the forearm is green on the outside and yellow on the inner surface. When the legs and arms are closed in a water-retaining position this frog appears entirely green. The posterior of the thigh area may range from a rich maroon to purple brown and can have an iridescent bluish sheen. Cape York specimens have been reported to have blue inner thighs. The dorsal area of the thigh is pale yellow. The fingers are 3/4 webbed and the toes fully webbed, with the second finger longer than the first. Metatarsal tubercles are absent, as is a pectoral fold.

Size (snout-vent). Recorded average for species is 45 mm. Females range between 32mm and 45mm apx. with males smaller, from 31-42mm apx.

 

Adult Male Calling

 

 

Call

(Barker et al., 1995,Frith, 1995; McDonald, 2000)


The call is described as a 'long, drawn out waaaaa' or alternatively a 'growl-like aaarrrc' that is only emitted in wet weather. As with all frog calls, becoming familiar with this call by listening, however is an easier way to learn to identify it.

Geographic range.

(Anstis, 2002; Barker et al., 1995; Cameron and Cogger, 1992: Cogger,1988; Frith, 1987; McDonald, 2000; Menzies and Tyler, 2004)

This species ranges from the coast and near-coastal areas of eastern Australia from just above Sydney to the top of Cape York. Recent work has split the south-western P.N.G. populations into different species.

 

 

 

Biology/physiology etc.

(Davies and Withers, 1991; McLean et al, 2006; Tyler and Davies 1978)

Sixteen different peptides have been isolated from the skin secretions of Litoria gracilenta. All have been named caerins eight of which are new and two have been found to have strong antibiotic properties. Many of these moisture rich substances have multifaceted active properties which may protect the frog from such annoyances as fungus and microbes. The peptide profile most closely resembles that of Litoria splendida (from the Caerulea Species Group) of the frogs profiled.

Litoria gracilenta has a resistance of 118 sec/cm to water loss. An open water surface in the same conditions will be subject to evaporation at a much higher rate.

Both L. gracilenta and it species group member L. chloris have a diploid chromosome number of 26.

The hyoid in this species is without alary processes.

 

Calling Male Nelly Bay

C.Lane

 

Typical breeding habitat for this species on Magnetic Island

Habitat, Ecology and Behaviour

( Barker et al., 1995; Cameron and Cogger,1994; Clyne, 1969; Cogger, 1988; Frith, 1987,1995; McLean et al, 2006; Swan, 2001, Tyler, 1976)

Litoria gracilenta can be found in habitats that range from paperbark woodlands, other forested areas as well as grassland, open forest and suburban areas. Sightings of L. gracilenta on bitumen roads, during and after heavy rain has fallen, have often been reported. It has been said that this species prefers lower vegetation, especially beside creeks but they have been found in the top of very tall trees in dry areas. In Cape York Litoria gracilenta often spends the day on floating foliage and vegetation. In their water holding position they are well camouflaged and not easy to spot and it may be that this position serves both purposes. This frog has the common name of Banana Frog in Northern NSW as it is regularly found on these trees and within their bunches during the harvest

All the peptides isolated from L. gracilenta are considered to be related in some way to its defensive capabilities. It contains the neuropeptide caerulean in its skin secretions which is known to effect predators who attempt to ingest it. The secretions also have a regulatory protein that activates certain enzymes that disrupt cellular function in a potential predator and cause it discomfort.

 

Reproduction.

(Anstis, 2002; Barker et al., 1995; Cameron and Cogger 1992; Tyler, 1994; Tyler and Davies, 1976; Tyler and Davies, 1991)

Male Litoria gracilenta come down from the canopy to call from such places as low tree branches overlooking water. Breeding season starts with the onset of the wet season, in tropical areas, and further south, in late spring and early summer. Litoria gracilenta prefers still water for amplexis.

Although often termed as a "swamp breeding type", Litoria gracilenta on Magnetic Island, at least, seems to prefer creeks or creek waterholes to breed in (pers. obs.)

The vegetal pole of the eggs is off-white and the animal pole is dark brown. Experiments conducted to see if yolk mass was significantly correlated to female body size revealed a negative correlation in the case of L. gracilenta .The same researchers found that the difference between size of the eggs in a clutch get smaller as the size of the clutch itself decreased.

Spawn forms a surface cluster or layer which may or may not be attached to adjacent vegetation or water reeds. The size of the fertilised eggs may range from 1.31 - 1.39mm apx. Three to four days after fertilisation hatching will begin.

The tadpoles average size is apx. 52mm, with a 1,1,1,/1,2,1 tooth formula. The body shape of tadpoles is a rough oval .Tadpole eyes are situated on the sides of the head area close to the snout. The pigmentation of the iris is copperish-gold in colour. Tadpoles are brown with a yellowish tinge and some patches that are clear and translucent. The ventral colouring is is mixed yellowish brown with some silver or gold sheening. The arch of the tail fin is slight to medium and tapering to a roundish tail tip. They are predominantly bottom-feeding and in regularly disturbed areas they are very quick to hide, whilst in isolated creeks they are not. (pers. obs)

Metamorphs may emerge in 112 days if the water temperature is around 20°C. Two months is the said to be average time to metamorphose. The apx. size of the rather translucent metamorphs is 13-15mm.

Spawn

 

 

References

Anstis, M (2003) Tadpoles of South-eastern Australia, Reed New Holland, Sydney, NSW

Barker, J,Grigg, G. and Tyler, M.(1995) A Field Guide to Australian Frogs: Surrey, Beatty and Sons, NSW. Cogger, H. G., 1988. "Reptiles and Amphibians of Australia ". Reed Books, N.S.W.

Cameron, E.E. and Cogger, H.G.,(1992) The Herpetofauna of the Weipa
Region, Cape York Peninsula;Technical Report Number 7, Australian Museum.

Clyne, D., (1969) Australian Frogs, Lansdowne Press, Melbourne.

Cogger, H. G., 1988. "Reptiles and Amphibians of Australia ". Reed Books, N.S.W.

Davies, M & Withers, P.C. Morphology and Physiology of the Anura - Fauna of Australia Series - Australian Government Publication, C.S.I.R.O., Australia

Frith, D. and Frith C., (1987), Australian Tropical Reptiles and Frogs, Tropical Australia Graphics, Paluma.

Frith, D. and Frith C., (1995), Cape York Peninsula - A Natural History, Reed Books, NSW.

Hutchinson, M.N. and Maxon, L.R. (1987),Phylogenetic Relationships among Australian
Tree Frogs (Anura : Hylidae : Pelodryadinae): an Immunological Approach,Aust. J. Zool.,35; 61-74.

Menzies, J.I. and Tyler, M.J.(2004) Litoria gracilenta (Anura: Hylidae) and related species in New Guinea.,Aust. Journal of Zoology,52::191-214.

McDonald, K., 2000, in "Wildlife of Tropical North Queensland" Eds. Ryan, M. & Burwood,.C.Pp.170-195 :Queensland Museum.


Maclean, M.J., Brinkworth, C.S., Bilusich, D., Bowie, J.H., Doyle, J.R., Llewellyn, L.E., Tyler, M.J. (2006), New caerin antibiotic peptides from the skin secretion of the Dainty Green Tree Frog Litoria gracilenta. Identification using positive and negative ion electrospray mass spectrometry,Toxicon. ;47:6:664-75.

Swan, G.,(2001) Frogs of Australia,New Holland Publishers, Melbourne

Tyler, M.J., (1982) Frogs, Reed Books, Chatsworth, NSW.

Tyler M.J., (1994), Australian Frogs - A Natural History,Reed Books, Chatsworth, NSW.


Tyler M.J.and Davies, M. (1978)Species-groups within the Australopapuan Hylid Frog
Genus Eitovia Tschudi: Australian Journal of Zoology Supplementary Series No. 63 C.S.I.R.O

Tyler, M.J. & Davies, M. (1992) Family Hylidae, Fauna of Australia Series - Australian Government Publication, C.S.I.R.O., Australia

 

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Amplexis

 

        

 

Tadpole

L. Corbett/C.Lane

 

 

 




 


 

Photo Credits

All photos and audio by author unless otherwise captioned.

Corbett, L. Magnetic Island, unpublished

Updated last: 30/0109