The penis of an echidna has 4 heads however only two become erect at any one time. Now, Australian researchers have uncovered why.
Scientists found the marsupial has uncommon reproductive anatomy that causes male echidnas to ejaculate from only two of their 4 penile heads at one time.
The analysis, printed within the peer-reviewed journal Sexual Development, discovered that echidna penises have related options to these of different mammals, together with platypuses, but additionally similarities to reptiles.
The scientists studied the inner anatomy of a number of echidnas that had been introduced into the Currumbin Wildlife Sanctuary in Queensland with extreme accidents and needed to be euthanised.
Male echidnas haven’t any scrotum and retailer their penis internally when not utilizing it. Every of the 4 suggestions of the echidna penis has a department of their urethra however only semen passes by way of.
The researchers discovered that in echidnas, the most important blood vessel of the penis splits into two primary branches, which every provide two of the penile heads.
Jane Fenelon of the College of Melbourne, the research’s lead writer, stated beforehand it was suspected that male echidnas alternated between two of their 4 penile heads by way of a valve mechanism on the urethra, however that they didn’t discover any proof of this.
As a substitute, they discovered the spongy tissue of the penis, which turns into erect when full of blood, was separated by a septum – that means the echidna penis has two distinct halves. By directing blood movement down one of the principle artery branches, the echidna is ready to management which half – and which two heads – turns into erect.
“Their penis is definitely appearing like two separate penises that simply occur to be merged collectively,” stated Fenelon.
“It’s the primary time we’ve seen this in mammals. We all know that in different species with actually elaborate penises, it usually occurs as a result of of male–male competitors for females.” In that case, a multi-headed penis would possibly lower the time wanted between mating periods, however the evolutionary motive for the behaviour in echidnas has not been confirmed definitively.
Fenelon stated the analysis was motivated by the behaviour of an echidna at the wildlife sanctuary, who had been noticed alternating the use of his penile heads as much as 10 instances in a row.
Fenelon famous similarities between echidnas and platypuses which have a two-headed penis coated with spines.
“Internally, we predict it’s fairly much like an echidna, however no one’s ever seen an erect platypus penis, so we’re undecided in the event that they only use one of their two heads at one time,” she stated.
Echidnas and platypuses are the only two residing monotremes – marsupials that lay eggs as a substitute of giving delivery to dwell younger.
Two-pronged penises are widespread in lots of different marsupial species, together with kangaroos, koalas, bilbies and wombats.
There have been additionally anatomical similarities between the male echidna’s reproductive tracts and people of crocodiles and turtles, notably in how the sperm enters the penis.
Feminine echidnas have a cloaca – a single opening that they use to urinate, defaecate, and mate. Internally, the cloaca branches into totally different methods, together with a two-branched reproductive tract.
“We expect when the penis is erect that it’s lengthy sufficient to achieve the place the uterus branches off,” stated Fenelon. Males additionally use their cloaca to urinate and defaecate.
Unusually, earlier research have proven that echidna sperm cells work cooperatively, swimming in related bundles of as much as 100 sperm to achieve the egg.