Tracking the Echidna’s Sex Life: Studying Echidna’s Life Cycle To Improve Breeding Programs

Researchers at the University of Adelaide, South Australia, and Adelaide zoos are halfway through a two-year study into the reproductive cycle of the echidna in order to understand its biology and ecology better, which could improve captive breeding programs of these iconic monotremes.

Dr Frank Grützner from the University’s School of Molecular and Biomedical Science, Dr Peggy Rismiller from Anatomical Science, Dr Greg Johnston from the Royal Zoological Society of South Australia and Professor Steve Donnellan from the South Australian Museum are observing wild echidnas within the 1000 ha area of South Australia’s Monarto Zoo.

Dr Grützner said the scientists have “a unique combination of expertise. We all work together to learn more about the biology of this weird animal.”

“In many aspects of reproduction, monotremes are truly unique,” he said.

“Although they are the most distant mammalian relative to humans, they also bear similarities to birds. They lay eggs, their sperm are elongated like chicken sperm, they have nine or 10 sex chromosomes that are very similar to sex chromosomes in chicken.”

Australia Leads in Monotreme Genetics

Australia leads the world in monotreme reproductive research, mainly because monotremes – platypus and echidnas – live only in mainland Australia, Tasmania and New Guinea.

Dr Grützner, who moved to Australia from Berlin eight years ago, has done extensive research into platypus genetics.

Four years ago he led the international team that discovered that platypus has an incredibly complex sex chromosome system consisting of 10 sex chromosomes (Grutzner et al., Nature).

Echidna Life Cycle Still Holds Mysteries

He explained that many aspects of the echidna life cycle “are still quite mysterious”.

The monotremes have successfully populated most areas in Australia, from the Snowy Mountains to dry areas of central Australia and rain forests in Queensland, so they are capable of adapting to different environments.

Echidnas vary markedly in size and coat colour from one area to another, as well between different parts of the country.

“Still, it seems that they do not reproduce fast. In addition, in cold climates, they go into a hibernation-like state where they decrease their body temperature, but they do not have brown fat like other mammals that hibernate,” he said. (See Snow Echidnas Show Endothermy)

“We are integrating state-of-the-art animal tracking and molecular genetic techniques that we established in studying the platypus. We are growing cell lines from individual echidnas so we can develop genetic fingerprints.”

Paternity Testing Echidnas

A major project is to determine how echidnas breed successfully. During the breeding seasons, the animals form ‘echidna trains’ where a female is followed by several males.

“We want to find out which of the males is successful – the biggest, smallest, the first or last?” Dr Grützner said. “Basically we will do paternity testing to determine the male that has been breeding successfully. Never before has this been done in echidna.

“We do sex echidnas, which can be challenging in the field and impossible in younger animals,” he said, “and do genetic testing of the animals to determine paternity.”

From tissue and hair samples, he and his team are establishing fibroblast cell lines for DNA and chromosome preparation and isolation of mitochondrial DNA.

Link to Human Genetics

“We expect that new sex determination genes that we discover in echidna will also be relevant in humans and mice,” he said.

“Many important genes have been discovered and analysed in species other than humans, and understanding the evolution these genes will help understanding the function of these genes in humans and other mammals.”