First record of a bicephalic chondrichthyan found in Australian waters; the southern fiddler ray, Trygonorrhina dumerilii (Chondrichthyes: Rhinobatidae)

Abstract

We report the first documented case of bicephaly in a chondrichthyan, the southern fiddler ray, Trygonorrhina dumerilii, in Australian waters. Females in the latter stages of pregnancy, as confirmed by ultrasound, were captured by hand in Swan Bay, Victoria (38.252°S, 144.616°E) in February 2013 and transported to aquaria. Up to 10 females gave birth in aquaria in early April 2013 to 11 neonates, one of which was a still-born, bicephalic neonate. Magnetic resonance imagery of the bicephalic neonate displayed the presence of two parallel vertebral columns running the entire length of the animal, diverging into two well formed heads. Morphological measurements were also made, comparing the bicephalic neonate to normal neonates. The cause of bicephaly is unknown, although congenital and environmental stressors during development may cause this condition.