(Gray, 1831b)
Murray River turtle
Recognition
The broad, oblong, olive to brown carapace (to 31 cm) is broadest behind the center, and may have either a smooth or a slightly serrated posterior rim. The posterior marginals are flared and those along the sides may be upturned. A cervical scute is present. Juveniles and males may have a medial keel, which becomes lower with age; a medial groove may develop in larger individuals, especially females. No neurals are present. Vertebrals 1, 4, and 5 are broader than long; the 1st may be expanded anteriorly and the 5th is flared posteriorly. Vertebrals 2 and 3 may be as long as or longer than broad. The surface of the carapacial scutes is roughened with numerous longitudinal striations. The plastron is long and narrow, leaving much of the carapacial opening uncovered. Its forelobe is rounded in front and only slightly broader than the hindlobe, which gradually tapers toward the rear and has an anal notch. The intergular scute is longer than broad and totally separates the gulars. The plastral formula is: fem > pect > abd > intergul >< an > gul > hum. Plastron, bridge, and undersides of the marginals are cream to yellow. The moderate-sized head has a slightly projecting snout and an unnotched upper jaw. The diameter of the mandibular symphysis is broader than the greatest diameter of the orbit. Two chin barbels are present. Dorsally, the head is covered with smooth skin, and the small neck tubercles are blunt and rounded. Head, neck, and limbs are grayish to olive brown. A yellow to cream-colored stripe runs backward from the corner of the mouth to the neck, and a yellow spot occurs on each side of the chin.
The karyotype is 2n = 50; 26 macrochromosomes (16 metacentric, 6 submetacentric, 4 acrocentric) and 24 microchromosomes (Killebrew, 1976; Bull and Legler, 1980).
Females are larger than males, and have higher domed carapaces and shorter tails.
Distribution
Emydura macquarrii lives in southeastern Australia from south-central Queensland southward to northern Victoria and extreme southeastern South Australia.
Habitat
This turtle inhabits large rivers, lagoons, and waterholes. It hibernates during the winter.
Natural History
During courtship the male approaches the female with a series of head bobs, touches her cloacal vent with his snout, swims to the front and faces her, and then attempts to align his chin barbels with hers; finally he strokes her barbels and snout with his foreclaws (Murphy and Lamoreaux, 1978). Copulation soon follows.
The eggs are laid from late October through December in nests dug in the stream banks, usually after a rainstorm. The eggs are elongated (33 x 23 mm) with brittle shells; a single clutch may contain 6 to 24 eggs, but usually about 15. When laid the egg shells are translucent, but within a day a small opaque patch forms on the top of the shell above the embryo. The white patch grows to form a collar around the equator of the egg. At least one end of the egg also becomes opaque before the egg hatches. The opaque patch forms by partial drying of the shell and shell membranes adjacent to the underlying extra-embryonic membranes. Water is lost through the egg shell, thus facilitating exchange of respiratory gases. This increase in conductance enables the shell to supply the increasing demand for oxygen to the developing embryo during incubation (Thompson, 1985). Natural incubation takes about 75 (66-85) days. Hatchlings have carapaces about 30 mm in length with a high medial keel and a serrated posterior rim.
Foods taken from the stomach of this turtle include fish, various aquatic worms, crustaceans, insects, bivalves, snails, algae, and parts of aquatic plants, indicating it is omnivorous (Chessman, 1986). Emydura macquarrii is fond of basking on river banks.
Remark
Georges and Adams (1996) proposed Emydura krefftii and E. signata should be synonymized with E. macquarrii.
IUCN Red List Status (1996)
Not listed.