Armoured Frog

Litoria lorica is a medium-sized frog (females 32.9-37.3 mm, males 29.6-33.1 mm SVL). The head is rounded with a short, truncated snout. Nostrils almost at tip of snout and slightly lateral. Curved canthus rostralis; sloping loreal region. Prominent eyes. Small, indistinct tympanum, over which a glandular supratympanic fold runs. Vomerine teeth are present on two transverse ridges, just posterior to choanae. Tongue is broad and oval. Fingers are long, webbed only at the base, lack fringes, and are ordered 3>4>2>1. Finger discs are present, with those on fingers II, III and IV well-developed, more than 2x the finger-width; the disc on Finger I is reduced in size compared to the other fingers. Moderately-sized subarticular and palmar tubercles. All fingers have supernumerary metacarpal tubercles. Both males and females have a well-developed prepollex. Forearm is somewhat robust, more so in males than females. Hindlimbs are somewhat long. Toes have nearly full webbing, and are ordered 4>3>5>2>1, with prominent subarticular tubercles. Many small, supernumerary metatarsal tubercles. The inner metatarsal tubercle is small and oval; the outer metatarsal tubercle is lacking. A narrow tarsal ridge is present. The dorsum is finely tuberculate, particularly on the upper eyelids and tympanic region. On the ventral surfaces of the thorax, abdomen and thighs, the skin is granular, but smooth on other ventral surfaces. Males have a densely spinous nuptial pad, as well as more robust forearms and pectoral spines, and lack vocal sacs (Davies and McDonald 1979). During breeding season, males also develop further keratinized, conical spines along the ventral and lateral upper arms, and smaller spines on the head in the loreal and maxillary regions, and the underside of the mandible (Cunningham 2002; Davies and McDonald 1979).In life, this frog is gray or gray-brown dorsally and white ventrally, with tiny dark brown spots on the throat (Cogger 2000). It may be uniform or mottled dorsally (Cunningham 2002). The iris is silver to golden (Cunningham 2002).Litoria lorica is a member of the Litoria nannotis group. This frog can be distinguished from L. nannotis (Waterfall Frog), with which it is sympatric, by its smaller size (L. nannotis females measure 46.3-56.0 mm, L. nannotis males 40.1-53.2 mm), a truncate snout, and terminal nares; also, male L. lorica have fewer accessory spines on the head, forearm, and thighs, and less robust forearms than male L. nannotis. It can be distinguished from L. rheocola (Common Mistfrog) and L. nyakalensis (Mountain Mistfrog) by the indistinct tympanum and enlarged prepollex, and the male's pectoral spines (Davies and McDonald 1979).The specific epithet lorica is Latin for "breast plate", referring to the male's pectoral spines.

Litoria lorica was first located in 1976 and later described by Davies and McDonald (1979). It is known from five localities - four on the Thornton Massif: Alexandra Creek (the type locality; TR165); Hilda Creek (near Thornton Peak, Cape Tribulation NP); Roaring Meg Cascades (via Mt Sorrow TR165); and Bluff Creek (Mossman Gorge Daintree NP, N.E. Queensland); and the Carbine Tableland, in far north Queensland (Cunningham 2002; http://www.jcu.edu.au/top/JCUPRD_037882.html). The historical extent of occurrence of L. lorica was thought to be approximately 120 km2 (M. Cunningham pers. comm.). Litoria lorica is a rainforest specialist endemic to the Wet Tropics Bioregion (Williams and Hero 1998; 2001). As a stream dwelling/stream breeding species (Hero and Fickling 1994) it prefers fast flowing streams in upland rainforest between 640 and 1000 m altitude (McDonald 1992), although it may previously have been present at lower altitudes (M. Cunningham pers. comm.). It has been found on granite boulders in notophyll vine forest in the splash zone near turbulent fast flowing water (Davies and McDonald 1979).

Until the most recent sighting in July 2008, L. lorica had not been seen since December 1991 and was thought to possibly be extinct (Cunningham 2002). This frog is nocturnal; at night the frogs cluster in the splash zone of the cascade, and shelter by day in deep cracks beside the cascade (Hillis, Cunningham and Moritz, pers. obs., cited in Cunningham 2002). The ova are unpigmented (Davies and McDonald 1979), as are the eggs; one clutch with 163 eggs was found, presumably laid in water under rocks in the stream (Cunningham, unpublished). The tadpoles of the species have not been described but are thought to be torrent adapted (dorsoventrally flattened and suctorial) and similar to that of the sympatric species, Litoria nannotis (Davies and McDonald 1979). There is little information available on the species, (as it has only been observed a few times) but ecological similarity to L. nannotis would suggest similar movement patterns generally confined to the stream environment (M. Cunningham pers. comm.). No data are available on population structure or genetic variation of L. lorica (M. Cunningham pers. comm.). The newly discovered Carbine Tableland population is syntopic (shares habitat) with a population of Litoria nannotis.

The reason(s) for the decline of L. lorica are unknown. The habitat of the species in the Wet Tropics has been protected since 1988, therefore habitat destruction is no longer a threat (McDonald and Alford 1999). Feral pigs have been suggested as a potential cause of riparian habitat damage and adult frog mortality (Richards et al. 1993). However, feral pigs are unlikely to have a direct impact on L. lorica due to the close association of this species with rocky cascades in streams (M. Cunningham pers. comm.). Disease, such as a viral infection or chytrid fungus, may have contributed to the decline of this species (Berger et al. 1999). Amphibian chytrid fungus is thought to have been responsible for the extinctions of all known high elevation populations of seven Australian frog species in the Wet Tropics between the late 1980s and early 1990s (http://www.jcu.edu.au/top/JCUPRD_037882.html). The newly discovered Carbine Tableland population is infected with chytrid, but the population has been described as "healthy" and individuals are apparently persisting with the chytrid infection (http://www.jcu.edu.au/top/JCUPRD_037882.html). This suggests that either the infection is present at low levels which are not lethal, or that the variant of chytrid present at this site was not lethal, or that this population is resistant to chytrid, perhaps being descendants of frogs which survived an initial chytrid wipe-out.

The armoured frog (Ranoidea lorica), or armoured mist frog, is a species of tree frog in the torrent frog complex, a group restricted to north-eastern Queensland, Australia.