Male Echidna 4 Heads: Why Only 2 of Spiny Anteaters' 4-Headed Penis Function During Erection?

Male echidnas have bizarre and interesting anatomy. The quill-covered monotremes laying mammals have four-headed penis, which isn't usual in mammals.

Male Echidna 4 Heads

Echidnas are spiky creatures with long tongues attached to the insects they eat, a beak, and no teeth. Even though they are mammals, the females lay eggs. But that is still nothing compared to what men are capable of.

The penis of a male echidna has four heads. It is unknown why male echidnas developed a peculiar penis with four leaders only used for mating and not urination. Biologist Jane Fenelon of the University of Melbourne in Australia has her theories about how the odd penis might have developed in her study.

She said it's hard to describe why they changed that way. Evolution is rife with experiments that test out various possibilities. Likewise, we only see positive examples. They most likely acquired the capacity to exclusively utilize their penis for mating initially, which provided them far more latitude to alter their anatomy.

The echidna is reportedly similar to the amphibious humanoid creature from "The Shape of Water" in that it stores its penis inside when unused. The four-headed monster only emerges during mating season, and echidnas urinate from a cloaca. Other animals' penises had to adapt to accommodate mating and urinating; the echidna, however, has an advantage in this department.

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Male Echidnas' Anatomy Explained

The four heads on an echidna penis are rosette-shaped glans at the tip. During an erection, only two of these four glans ever become active, and the active glans appear to change between succeeding erections.

Researchers combined microscopy methods with micro CT (Computer Tomography) scanning to understand the mechanisms at play better. The semen is transported to the penis tip by a single urethral tube in most mammals.

The echidna urethra begins as a single tube but splits into two toward the end of the penis, and each of these splits again, resulting in four branches, each of which ends up at one of the four glans.

The corpus cavernosum and corpus spongiosum, two erectile tissues, make up every mammalian penis. The corpus cavernosum's primary function is to swell with blood and sustain an erection. Blood also accumulates in the corpus spongiosum, but its primary function is to keep the urethral canal open during an erection so that semen can pass through. The corpus cavernosum and corpus spongiosum begin as two distinct tissues at the base of the penis in most other mammals, but they eventually combine to form the corpora spongiosa.

In the echidna, the corpora spongiosa persist as two distinct structures, while the corpora cavernosoa combine into one. In addition, the researchers discovered that the primary blood supply of the penis likewise divides into four branches after the urethra branches.

This effectively means that the echidna penis functions as two distinct glans penises. To control which branch of the urethra remains open and which part of the corpus spongiosum grows erect, blood flow can be directed down either side of the structure.

It remains unclear why they only ever use two glans at once. It likely has to do with men vying for female attention. With this strategy, the tame echidna can ejaculate ten times without noticeable pauses by switching between using either side, enabling him to out-mate less effective males.