THE DEVELOPMENT OF THE ELECTRORECEPTORS OF THE PLATYPUS (ORNITHORHYNCHUS-ANATINUS)

A series of developmental stages of the platypus were examined to obta in an anatomical description of the development of the periphery of th e electroreceptive system. Putative electroreceptors, composed of modi fied mucous glands, were observed to appear at 10 days post hatching ( p.h.). The typical striped arrangement of peripheral electroreceptors in the platypus was seen at 12 days p.h. The arrangement of the stripe s was modified during development with a range of additions and divisi ons of stripes occurring until the adult pattern is obtained, approxim ately 6 months p.h. After appearing at 10 days p.h., the number of ele ctroreceptors increases rapidly until sometime between 24 and 28 days p.h. when there is massive death of electroreceptors, the number prese nt at 28 days p.h. being 60% of the number present at 24 days p.h. Thi s massive death of receptors is coincident with the appearance of othe r sensory structures in the epidermis of the bill skin, the push-rod m echanoreceptors and the sensory serous glands. Histological examinatio n of a range of developmental stages demonstrated poorly differentiate d innervation at 28 days p.h., which became differentiated and reached the adult configuration between 11 weeks p.h. and 6 months p.h., the time at which nestling platypuses leave the burrow Lamination of the c ells lining the duct of the electroreceptors showed a similar developm ental profile. This study indicates that the electroreceptive system o f the developing platypus is not functional, in a similar manner to th e adult, until it is time for the platypus to leave the nesting burrow However, the system may be functional in the developing platypus, and may be used speculatively in the location of the mammary region for s uckling.