REPRODUCTIVE SYSTEM
Breeding season
The platypus breeding season varies widely depending on location. Mating usually occurs from July to October in mainland Australia.
Both sexes have a structure called a cloaca - a single external opening into which the reproductive, excretory and digestive systems open.
In the female platypus only the left ovary is functional. The male testicles are inside the abdomen, rather than in an external scrotum.
Sex determination:
Platypuses have multiple sex chromosomes.
Males have 5 X and 5 Y chromosomes, which form a chain at meiosis and segregate into 5 X and 5 Y sperm.
Females produce 1-3 eggs annually, usually 2
After fertilization the first shell layer is laid down and the egg passes down the oviduct into the uterus where second and third layers of the shell, secreted by glands in the walls of the uterus, are added.
The uterus also supplies nutrients to the egg, facilitating a size increase to about 14mm in diameter and 17mm in length by the time it is laid.
Breeding season
The platypus breeding season varies widely depending on location. Mating usually occurs from July to October in mainland Australia.
Both sexes have a structure called a cloaca - a single external opening into which the reproductive, excretory and digestive systems open.
In the female platypus only the left ovary is functional. The male testicles are inside the abdomen, rather than in an external scrotum.
Sex determination:
Platypuses have multiple sex chromosomes.
Males have 5 X and 5 Y chromosomes, which form a chain at meiosis and segregate into 5 X and 5 Y sperm.
Females produce 1-3 eggs annually, usually 2
After fertilization the first shell layer is laid down and the egg passes down the oviduct into the uterus where second and third layers of the shell, secreted by glands in the walls of the uterus, are added.
The uterus also supplies nutrients to the egg, facilitating a size increase to about 14mm in diameter and 17mm in length by the time it is laid.