Crinia riparia ( Littlejohn & Martin 1965 )

Donnellan, S., Anstis, M., Price, L. & Wheaton, L., 2012, A new species of Crinia (Anura: Myobatrachidae) from the Flinders Ranges, South Australia, Zootaxa 3499, pp. 1-26 : 14-17

Crinia riparia ( Littlejohn & Martin 1965)

Southern Flinders Ranges froglet

Figures 6, 9–10.

Holotype. Mature male No. 950163 in the Zoology Department Collection, University of Melbourne collected at Alligator Gorge , 8.5 miles SSW of Wilmington, Flinders Ranges , South Australia between 9 September 1962 and 29 October 1963.

Material examined. See Appendix 1.

Description. Although Littlejohn and Martin (1965) included specimens from within the geographic range of C. flindersensis sp. nov. in their paper, their description of C. riparia is based only on the type series (n=14), which were all collected from Alligator Gorge. Consequently we do not redescribe C. riparia sensu stricto herein.

Colour. Using the back pattern polymorphism nomenclature characteristic of some species of the C. signifera complex ( Main 1957, 1961) the dorsal pattern ranges from ‘lyrate’ to ‘intermediate’ to ‘smooth’ [i.e. unpatterned] ( Fig. 9). In a sample of 36 preserved individuals from across the species range, the proportion of individuals with a ‘lyrate’ pattern was 39%, with an ‘intermediate’ pattern 17% and with the ‘smooth’ pattern 17% (27% of specimens were too faded to determine the back pattern). Ventral patterns vary considerably ( Fig. 10). In specimens from the southern end of the range, the abdomen has a white background with large highly contrasting black marks and patches, while in the rest of the range the background tends to be cream and the darker marks are smaller, greyer and more numerous.

Mating call structure. Mating calls of a series of males from Alligator Gorge are presented in Littlejohn and Martin (1965).

Larval morphology. Littlejohn and Martin (1965) described the larvae of C. riparia from Alligator Gorge but did not have material available beyond stage 28. The larvae we examined from Alligator Gorge showed very little variation in pigment or in the oral disc and matched the description of the type material in pigment and features of the oral disc. Larvae from a creek at Horrock’s Pass were lighter golden-brown in colour (with a few diffuse darker patches on one) after anaesthetisation in warmer water prior to photography. These would likely turn darker in the cold, clear water of the creek.

Larvae from Alligator Gorge (n=18) and Horrock’s Pass (n=3) are described. Maximum length was 38 mm, with a minimum body length of 12.9 mm (stage 36, Horrock’s Pass). The tail is slightly more than twice body length ( Table 3). Body small, streamlined, often broadest across gill region and abdomen slightly wider than deep. Snout broadly rounded in dorsal view, elongate and narrowly rounded in profile. Eyes dorsolateral with a dorsal tilt. Iris mostly golden with a gold ring around pupil and a V-shaped projection (umbraculum) in centre of dorsal edge. Nares small, moderately spaced, closer to eyes than tip of snout and open mainly dorsally with a small raised flap on inside rim. Spiracle visible from above, tapers slightly to dorsoposterior opening below horizontal body axis and posterior to midpoint. Vent tube dextral, broad, opens midway up ventral fin and mostly unattached to fin behind.

Dorsum and sides of body (Alligator Gorge) mostly uniform dark brown or black with a diffuse layer of fine copper iridophores (denser laterally) over all but a small darker patch over base of body. Three larvae photographed from Horrock’s Pass were lighter golden-brown, one with small, diffuse darker patches over dorsum and tail muscle ( Figure 6A, D). Body wall around sides of head and body transparent in earlier stages, increasingly pigmented with melanophores as larva grows. By stage 41, hind limbs are banded and diffuse darker markings of adult are visible. Small dorsal tubercles present in some. Venter dark over abdomen, clearer anteriorly with fine specks of iridophores increasing during larval growth, but never dense (Alligator Gorge). Larvae from Horrock’s Pass had a more uniform layer of copper sheen over abdomen.

Larvae are known to metamorphose in the field in spring (late October to November), but depending on weather conditions, some may do so in December. Metamorphs are miniatures of adults with variable dorsal patterns. The undersurface is translucent dark grey with finely scattered whitish granulation. Mean SVL of eight metamorphs from Alligator Gorge is 10.4 mm (9.7–11.4).

Habitat. Odendaal and Bull (1982) describe the habitat of C. riparia in detail. The range of C. riparia abuts the range of C. signifera along a north-south axis of the southern Flinders Ranges with a narrow zone of overlap on the eastern slopes of the ranges or through the middle of the ranges before the creeks flow down the western slopes. Creeks occupied by C. riparia tend to have much steeper slopes, swifter water flow and less vegetation than creeks occupied by C. signifera in the southern Flinders Ranges.

Larvae are lotic and benthic, hiding among rocks and leaf litter on the substrate where they graze on sediments in gravel and algae on rocks. They often lie on rocks in stream pools or in shallow water at the sides among smaller stones and can swim rapidly undercover if disturbed. With their broad, more elongate and depressed body, wide adherent oral disc and shallow fins, larvae are stream-adapted.

Distribution. The Southern Flinders Ranges from Mt Brown Conservation Park 15 km S of Quorn (32° 27' 27"S, 138° 00' 21"E) in the north to Napperby Gorge (33° 09' 11"S, 138° 08' 08"E) in the south.

Remarks. The species identity of a collection (SAMA R13609A-G) from 1.5km south-east Bagalowie Homestead, north-east of Carrieton (32° 19’ 12”S, 138° 52’ 59”E) collected in May 1973 requires some comment (see Fig. 1). This location is 88km further east than any record of the C. riparia complex in the main Flinders Ranges and from an area where either member of the C. riparia complex could be present. From an inspection of dorsal and ventral patterns and body size, the specimens clearly do not conform with C. signifera , the taxon to which they would intuitively most likely belong. The locality would seem unlikely habitat for a member of the C. riparia complex as it is in relatively low relief ranges. We do note however a record of C. flindersensis sp. nov. (SAMA R64562) about 30km east of the Flinders Ranges on the flood plain of the Big John Creek (30° 41’ 08”S, 139° 31’ 01”E). In the absence of molecular genetic data or information on larval morphology we are not able ascertain the species identity of the Bagalowie Homestead series.