Legler and Cann, 1980
Fitzroy River turtle
Recognition
This is a medium-sized (26.2 cm) short-necked chelid turtle with a white ring around its iris and huge cloacal bursae. The adult carapace is elliptical and has a smooth marginal border; that of juveniles (to 9.5 cm) is nearly round and extremely serrated at the edges. Juveniles bear a distinct keel, but adults are only slightly peaked or middorsally flattened. Neurals are absent, and the rib tips of costals 2-4 articulate with the centers of peripherals 4-6. Carapacial scutes are thin and translucent allowing the underlying intercostal sutures to be seen; their surfaces contain a series of sharp parallel ridges. A cervical scute is usually present. The interpleural seams touch the posterior parts of marginals 6 and 8. The adult carapace is medium to dark brown with some olive coloration present in pale individuals, and a few black spots may be present. Females tend to become slightly paler with age. Hatchlings are tan to pale brown with dark flecks, and a series of black dots occurs along their dorsal and lateral keels. The yellowish to brown plastron is narrow and tapered to a blunt point anteriorly and notched posteriorly. It is slightly concave in both sexes and lacks a hinge. The plastral formula is: fem > an > abd > pect > hum > intergul > gul. The bridge is broad and may be slightly darker than the plastron. The head is narrow and high with a short snout. The orbits are small in diameter, and there is no splenial bone. The triturating surface of the upper jaw is narrow and bears no ridge. The head is uniformly brown or olive dorsally, but yellow to orange ventrally; the male head becomes more brightly colored with age. The iris is ivory white in adults, but silver in juveniles. The neck is covered with large tubercles and rounded warts, and the chin bears one pair of barbels. Other skin is olive gray. The toes are heavily webbed.
Bull and Legler (1980) found the diploid number of chromosomes to be 50, with all macrochromosomes biarmed.
Males have longer, thicker tails with the vent beyond the edge of the carapace. The female's tail is short with the vent beneath the carapace.
Distribution
This turtle is known only from the Fitzroy River and its tributaries, eastern Queensland, Australia.
Habitat
Rheodytes leukops is a riffle dweller, preferring waters with some current. The bottom may be of sand or gravel, and if submerged logs are present, the turtles often hide about them. Apparently, the Fitzroy River turtle seldom comes to the surface to either bask or breathe. It seems to extract enough oxygen from the water by a form of cloacal breathing. The cloacal vent is held continuously open (Rheodytes leukops 3) while the huge cloacal bursae pulsate, drawing water in and then squirting it out the vent after the exchange of gases takes place. This is an excellent adaptation for living in the oxygen-rich waters of riffles.
Natural History
Observations by Legler and Cann (1980) indicate nesting occurs in September and October. Up to five clutches and 46-59 eggs may be laid each season. The small eggs are elongated, ranging from 23.2 to 33.1 mm in length and 19.0 to 23.8 mm in width (Legler, 1985). Two nests found by Legler and Cann were on a flat sand and gravel bar approximately 9 m from the water, but less than a meter above the water level. One was a slanting cavity 17 cm deep. The incubation period at 30°C ranged from 44 to 50 days. Small juveniles are quite secretive and spend most of their time hiding; adults are quite placid when caught (Cann, 1978).
Stomach contents examined by Legler and Cann (1980) consisted of insects and a few fragments of freshwater sponges. Food is apparently found by probing the substrate with the snout, which involves both olfactory and visual cues. A female observed by Cann (1978) used her beak to scrape aquatic life from rocks in her aquarium.
IUCN Red List Status (1996)
Vulnerable (A1c+2c, D2).