![]() ![]() The secret lives of farmed fishįurthermore, we found that the major blood vessel of the penis also splits into four branches following the branching of the urethra. In the echidna, the corpora cavernosoa merge into one structure and the corpora spongiosa remains as two separate structures. In most other mammals, both the corpus cavernosum and the corpus spongiosum start off as two separate tissues at the base of the penis but then the corpora spongiosa merge into one. The corpus spongiosum also fills up with blood, but its main role is to ensure that the urethral tube remains open at erection so that semen can pass through. The main role of the corpus cavernosum is to fill up with blood and maintain an erection. Picture: Jane FenelonĪll mammalian penises consist of two erectile tissues, the corpus cavernosum and the corpus spongiosum. Instead, we found that the erectile tissues that make up the echidna’s penis are a very unusual. Initially, we thought we’d find some sort of valve mechanism on the urethra when it first started branching to control the one-sided action seen in our tame echidna. The echidna urethra starts as a single tube, but toward the end of the penis it splits into two and each of these then splits again – resulting in each of the four branches ending up at one of the four glans. ![]() Most mammals have a single urethral tube which carries the semen to the penis tip. This meant we could create a 3D model of the whole echidna penis and its important internal structures in order to see how it operates. A normal CT scan, which uses computer technology to make 3D images from X-rays, only picks up mineralised (hard) tissue, but by staining the penis with iodine we could pick up the soft tissue details. To understand the mechanisms at work we used microCT (Computer Tomography) scanning in combination with microscopy techniques. Male fertility 'precariously close' to climate change extinction limits It’s these animals we used for the study, but we were also able to observe a tame echidna. Unfortunately, many of these echidnas are hurt beyond recovery and have to be euthanised. Our research is a collaborative project involving scientists from the University of Melbourne, University of Queensland and Monash University, but most crucial to the work has been the Currumbin Wildlife Sanctuary on the Gold Coast, which has established a small breeding colony of echidnas.Īround 50 injured echidnas are brought to the wildlife hospital at Currumbin every year, the majority from road accidents. The echidnas penis is stored internally when not in use. But for the first time we have untangled what is going on anatomically, with the results now published in the journal Sexual Development. Only two of these four glans ever become functional during erection and which glans are functional appears to alternate between subsequent erections.Įxactly how echidnas do this has always been a mystery. Unlike other mammals, the monotreme penis is used only for mating and never carries urine.Īmong echidna females, in addition to laying an egg, the pouch where they nurse their young is only a temporary structure and develops by the thickening of the lateral margins around the abdominal region that surrounds the mammary glands.īut perhaps what is most bizarre about the echidna penis is that it has four heads, which are actually rosette-like glans at the end. Delving into the DNA of our iconic platypus and echidna In most other species, sperm swim individually and it’s every sperm for themselves. Monotremes are the only egg-laying mammals, but they also have a number of other unique reproductive characteristics.įor the males, their testes never descend, they have no scrotum, when not in use, their penis is stored internally and their ejaculate contains bundles of up to 100 sperm that swim cooperatively until they reach the egg. Picture: Getty ImagesĮven today, they remain the least understood group of living mammals. The platypus and the four species of echidna make up living monotremes. Eventually, a new group of mammals had to be created to account for the platypus and its fellow monotremes – the four different species of echidnas. When British scientists in the 18th Century first saw a platypus they dismissed it as a hoax. Monotremes are among the world’s strangest animals, mixing mammalian and reptilian characteristics in the one creature. ![]()
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