Taxonomy

(Barker et al.,1995; Hutchison and Maxon, Steinborner, 1994; Tyler and Davies, 1978; Tyler, 1982; Wabnitz, 1999)

The name 'rubella' translates as 'little red' . Litoria rubella belongs to a species-group known as the Litoria rubella Group. Members include the Australian species Litoria dentata and L. electrica ; and New Guinea species. L. capitula ; L. congenita;
L. pygmaea; and L. wisselensis. The closest species to L. rubella is the North-western QLD species L. electrica which has a higher pitched buzz-like call from whence it achieves its name. L. rubella is not close to any other native Litoria treefrog spp. outside its own group (based on immunilogical distances). Phylogennically this places the group (in Australia) on its own separate lineage for a long period of time.

The peptide content of the glandular secretions of L. rubella specimens have been examined from areas in Western Australia and the Northern Territory and show such a marked content difference between areas that it may be that L. rubella warrants further investigation as to whether further species or sub-species could be isolated from the present species.

Description

(Barker et al., 1995; Cameron and Cogger 1992; Cogger,1988 ; McDonald, 2000.)

L. rubella is a small rather "pear" shaped, short legged arboreal frog with large finger and toe discs and a roughish texture to its dorsal surface. Variable in colour, it ranges from pale grey to brown or fawn above. It can have a broad darker vertabral band, bounded on either side by a lighter brown zone. On the lateral surface of the head area runs a blackish stripe that continues behind the eye, over the base of the forelimb and along the lateral surface of the body. Its ventral surface is granular and whitish but may be brown flecked as is the throat, excepting in breeding males where it may be very dark grey-brown. The groin area may be yellow and there may be two darker patches on the lower back area. It has vomerine teeth situated almost entirely behind the choanae. Its pectoral fold is prominent. The eye is gold flecked and high set and the obvious tympanum is bridged above by a prominent skin fold. When the legs are adpressed (at elbow and knee) they do not meet. The fingers are slightly webbed and the toes are half webbed. Two phlanges and the disc on the forth toe are unwebbed. A moderate inner metatarsal tubercle is present and elongated, whereas the outer one is small and rounded.

Size (snout-vent). Recorded average for species is 35mm. Females range between 34 -43mm and apx with males smaller, from 28 to 37 mm. apx.

        Adult male

Call

(Baker, 1999; Barker et al., 1995; Cameron and Cogger, 1992; Clyne, 1969; McDonald, 2000; Swan, 2001)
The call is described as a "high pitched, repeated Kreeee". It is lengthy, tremulous and rises in pitch at the end and a large group may be almost deafening to humans. Individuals will repeat call more than once with intervals. Males have been heard to call in the daytime after rain. As with all frog calls, becoming familiar with this call by listening, however is an easier way to learn to identify it.

Geographic range

(Baker, 1999; Barker et al., 1995; Cameron and Cogger, 1992; Cogger,1988; Clyne, 1969; McDonald, 2000; Tyler and Davies, 1978; Tyler et al., 1994)

An Australopapuan species it is one of Australia's most widespread species found from Northern NSW in an arc through the northeast corner of SA then arcing again to mid WA near Pt Headland.(see map).There may be some gap areas in this distribution as they have only been found (south) to just north of Ayres Rock in the N.T. It is found throughout the entirety of QLD and north to southern New Guinea.

Biology/physiology

(Davies and Withers, 1991; Steinborner, 1996; Tyler and Davies, 1978; Warburg, 1964; Young et al., 2005)

Evaporative water loss has been measured in this species in the wet and dry seasons and there is thought to be little seasonal difference not even relating to mass or environment. They have been measured with a body temperature of up to 39.2° C. At 40°, in laboratory conditions, they can live for 8+ days without water or food uptake, before dying.

The diploid chromosome number of this species is 26 which it shares with two other members of its species-group, L. congenita, L. pygmaea. L. rubella has cartilaginous or ossified intercalary structures and its
hyoid plate lacks alary processes.

The skin of the Litoria rubella, has yielded up 17 different peptides from specimens collected from 15 locations throughout Australia. They include members of two different "families" of peptides , the tryptophyllins and two types of Rubellidins,the first of which has, so far ,only been found in L. rubella.

Typical breeding habitat for this species on Magnetic Islandµ

Habitat, Ecology and Behaviour

( Barker et al., 1995; Cameron and Cogger, 1994; Clyne, 1969; Cogger, 1988; Friend and Cellier, 1990; Frith, 1987/1992, Swan, 2001, Tyler, 1982; Tyler et al,1994, Withers, 1997; Tyler, 1994; Warburg, 1964; Williams et al, 2000)

Litoria rubella has a wide habitat tolerance, both coastal and inland, and can be found in open or closed forest, eucalypt woodland,paperbark woodland, gallery forest, grassland, sedgeland as well as urban areas and regenerated areas. It is one of the few tree frogs to be found in arid areas. In poorly treed granite areas (such as exist on Magnetic Island and in W.A.) it can be found sheltering in rock crevices. In other areas it is often found diurnally sheltering under tree bark. In Kakadu surveys found them to have a preference for treed areas in both the wet and dry seasons. In some areas they will utilise human structures for shelter.

The diet of Litoria rubella, analysed in the N.T. showed a predominance of ants (70%) with beetles, flies, other insects and spiders making up the balance. Diet composition, of course, will often vary with local conditions.

Laboratory tests for anti-predator mechanisms has shown this species to emit a grass-like smell when threatened and to crouch down and partially inflate its body. The conjecture from this behaviour is that changing shape may 'fool' potential predators.

Water loss in individuals can be halved when they engage in 'congregation' behaviour. As the title suggests numbers of Litoria rubella have been found aggregated together, diurnally, under bark with their lateral surfaces pressed together in addition to utilising their normal 'water holding' positions. They also exist in very arid areas by positioning themselves within damper microhabitat areas ie: under rocks in creek beds..

Reproduction

(Anstis, 2002; Cameron and Cogger 1992; Barker et al., 1995; Cogger, 1988; Crossland, 1998; Dziminski and Alford, 2005; Lee and Jamieson, 1993; McDonald, 2000; Tyler, 1994; Tyler et al, 1994,Tyler and Davies, 1991)

Calling begins with the first summer rains in November/December, this species appears to call throughout the rainy season (pers. Obs). Breeding male Litoria rubella will group in large numbers around permanent water, if available, and more temporary, if not, calling from tree limbs near or overhanging the waters as well as from ground level. This species is widely distributed so the breeding season will vary geographically and climatically. Litoria rubella is only one of two species (among many) tested where the yolk volume in relationship to female mass shows a positive correlation. Spermatozoon body size is apx. 14µm.

From apx. 40-300 eggs, with a capsule size of between 1.9-2.3mm are spawned on the water surface forming a small brown-gold mass which may change to a film. They will usually hatch within 3 days.

Tadpoles have a medium body size and a cylindrical shape. They fit the known tadpole class that is described as "deep bodied, with moderately high tail fins and moderately developed tail musculature". Their eyes have a gold iris, they have small nares and a slightly raised dorsal fin on the tail. Depth and width of the body are about equal, with width being slightly more if there is difference. There are 2 upper and 3 lower labial tooth rows in the larval mouth. Tadpole max. length is up to apx 35mm with a body size of about 17mm apx. Tadpoles seem to prefer the upper to mid water layers. The tooth formula is 1,1,1,/1,2,1.

Tests done on offered food preferences to large tadpoles showed that they will eat some varieties of other frog spawn if it is available but are no danger to hatchlings. The highest temperature recorded for tadpoles of this species is from W.A. where they were measured at 39.6°C in flooded grasslands.

The time to metamorphosis will vary depending on the duration of the water and its temperature and it is known to be as little as 14 days. A more usual length would be 38 days apx. at 30°C with permanent water. Small metamorphs have been known to sun bask on grasses or leaves beside water and on Magnetic Island, at least are active diurnally (pers obs).

Metamorph

References

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

Baker, S.,(1999) Litoria rubella, James Cook University, http://www.jcu.edu.au/school/tbiol/zoology/herp/nqherp.shtml

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.

Crossland, M.R., (1998) A comparison of cane toad and native tadpoles as predators of native anuran eggs, hatchlings and larvae,Wildlife Research, 25: 373–381

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

Dziminski, M.A. and Alford, Ross A.(2005), Patterns and fitness consequences of intraclutch variation in egg provisioning in tropical Australian frogs, Oecologia 146: 98–109

Friend, G.R. and Cellier,K.M. (1990) Wetland Herpetofauna of Kakadu National Park, Australia: Seasonal Richness Trends, Habitat Preferences and the Effects of Feral Ungulates, Journal of Tropical Ecology, 6(2):131-152

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.

Lee, M.S.Y.and Jamieson ,B. G. M.,(1993), The ultrastructure of the spermatozoa of bufonid and hylid frogs (Anura, Amphibia): implications for phylogeny and
fertilization biology, Zoologica Scripta, 22;3, :309-323.

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

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.and Davies, M. (1986), Frogs of the Northern Territory, For the Conservation Commision of the Northern Territory by the University of Adelaide.

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

Tyler, M.J., Smith, L.H. and Johnstone, R.E. (1994), Frogs of Western Australia, W.A. Museum, Perth.

Steinborner, S.,Wabnitz, P.,Waugh, R.,Blumenthal, T., Bowie, J., Gao, C., Tyler, M. and Wallace, J., (1996) The Structures of New Peptides from the Australian Red Tree Frog 'Litoria rubella '.The Skin Peptide Profile as a Probe for the Study of Evolutionary Trends of Amphibians; Aust. J. Chem.,49, 955-963

Steinborner, S., Gao, C.,Raftery, M., Waugh, R., Bowie, J., Wallace, J. and Tyler, M. (1994) The Structures of Four Tryptophyllin and Three Rubellidin Peptides from the Australian Red Tree Frog Litoria rubella) Australian Journal of Chemistry:47;2099-2108, C.S.I.R.O

Wabnitz, P., Bowie, J., Wallace, J. and Tyler, M. (1999) Peptides from the Skin Glands of the Australian Buzzing Tree Frog Litoria electrica. Comparison with the Skin Peptides of the Red Tree Frog Litoria rubella; Aust. J. Chem.; 52, 639-645.

Warburg, 1965,Studies on the Water Economy of some Australian Frogs, Aust. J. Zool., ; 13: 317-30

Williams, C.,Brodie, Jr., J., Tyler, M., ; Walker., S., (2000) Antipredator Mechanisms of Australian Frogs; Journal of Herpetology, 34, (3) 431-443.

Withers,P C & Edward D H., (1997) Terrestrial fauna of granite outcrops in Western Australia: Journal of of the Royal Society of Western Australia, 80:159-166.,

Young, J.E., Christian, K.A., Donnellan, S., Tracey, C.R.and Parry, D. Comparative analysis of Cutaneous Evaporative Water Loss in Frogs :Physiological and Biochemical Zoology 78(5):847-856 2005 University of Chicago

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