F Rosa Rubicondior: Unintelligent Design - A Bat That Has Non-Penetrative Sex

Friday 24 November 2023

Unintelligent Design - A Bat That Has Non-Penetrative Sex

An 'intelligently designed' device for making holes in Swiss Cheese

Discovery of a new method of mating: a bat reveals its secret to us, size XXL - L · NEWS

It's almost as though creationism's putative designer took lessons from William Heath-Robinson, and then lost its sense of humour, the ludicrously complicated ways it designs to carry out simple tasks.

The evolutionary advantage of penetrative sex is that the male is able to deposit sperm close to the egg, using his penis, and the female is able to exercise a degree of selection in her choice of who is to father her babies. It is a considerable advantage over the more primitive forms of external fertilisation such as those used by amphibians where the sperm is shed onto the eggs as the female lays them, or by fish, where the sperm is deposited near the eggs and then swims towards them. The later method, especially, frequently allows opportunist males to sneak in and fertilise some of the eggs when another male has done all the work.

However, for reasons which are not entirely clear, most male birds have lost their penis and deposit their sperm into the female's reproductive opening by a 'cloacal kiss', a notable exception being the swans, geese and ducks which have retained a penis and sex is penetrative. This may be because a strategy used by male members of this order of birds is forcible penetration or, frankly, rape.

Of course, being unintelligently designed, birds lost their penis, not by simply losing the genes that grow one during embryonic development, but by have a gene that literally kills the growing penis soon after it starts to develop. Inhibit that gene in chickens and the male chick is born with a penis. Give it to a goose, and the male gosling is born without one.

William Heath-Robinson
And now, in what looks like another example of unintelligent design (by that I mean, of course, evolution) there is a species of bat in which the male's penis is too big to penetrate the female, so he uses it to transfer his sperm into the vagina by pressing the tip against her vulva and holding it there until the deed is done. which usually takes about 53 minutes but can take over 12 hours.

The bat is the common serotinus, Eptesicus serotinus. It is the only known example of non-penetrative sex in a mammal. Quite why it evolved is something of a mystery, but it could be something to do with needing to get round the female's tail membrane resulting in a penis that, when erect is 22% of the bat's body length. The tip is large and bulbous and almost seems designed to prevent penetration.

The study began when Nicolas Fasel, an evolutionary biologist at the University of Lausanne in Switzerland, and his colleagues noticed that the serotine bat has a rather large and unusual penis. When erect, it is 22% of the bat’s head–body length and has a bulbous, heart-shaped tip. “We were thinking it would be really difficult for it to enter anything,” he says.

It is described in a University of Lausanne (UNIL) news release and published Current Biology:
It is difficult to observe the behavior of nocturnal animals, and even more so of flying animals. Bat biology still holds many secrets. In particular, little is known about their modes of reproduction, which certainly vary greatly between the 1,400 species of bats known to date. Until now, it was thought that the copulatory mode of mammals always involved penetration of the penis into the vagina. A study reveals a major exception in bats, a group of mammals whose sexual habits are still very poorly documented.

This study, published in the journal Current Biology , was carried out by Nicolas J. Fasel , scientific collaborator in the group of Professor Philippe Christe in the Department of Ecology and Evolution of the Faculty of Biology and Medicine of UNIL, in collaboration with the Naturéum ( Vaud Cantonal Museum of Natural Sciences ) and researchers from Ukraine, the Netherlands, Poland and Germany. She focused on the description of the mating and morphology of the reproductive system of the common serotinus ( Eptesicus serotinus ), an insectivorous bat whose distribution area extends to Europe, the Middle East and in Central Asia. In this species, the size of the erect penis is disproportionately large – almost a quarter of the body size – compared to that of the vagina.

To understand how these bats mate, biologists observed their behavior in the attic of a church in the Netherlands, in temporary captivity in a rehabilitation center in Ukraine as well as in the mines of Baulmes in Switzerland.

Live observation of the reproductive behavior of around a hundred couples shows that males do not use their penis as an intromission organ for mating. After grabbing the female in a dorsoventral position, the male firmly presses his penis against his partner's vulva. The couple can stay in this position for several hours. These observations and the particular morphology of the common serotine penis constitute the first evidence of reproduction without intromission in a mammal.
A common serotinus, Eptesicus serotinus.
© Olivier Glaizot

Copulatory behaviours stand as cornerstones of sexual selection, yet they remain mysterious in many species. Because of their nocturnal and elusive lifestyle, the copulatory behaviours of bats have been mostly overlooked1. Several aspects of bat reproduction differ from other mammals (e.g. prolonged sperm storage2, delayed development3). Here, we show that in serotine bats (Eptesicus serotinus) the penis is used as a ‘copulatory arm’ rather than an intromittent organ, revealing a novel copulatory behaviour in mammals.
Figure 1 Mating behaviour of Eptesicus serotinus does not imply intromission and summer activity around subterranean sites does not coincide with the peak of copulations. (A) Ventral and (B) dorsal views of the erect penis. (C) Scaled digital microscopic photographs of E. serotinus female genital tract: (A) a formalin-fixed and (B) a HE-stained histology slide of a female genital tract. c = cervix, ov = ovary, r = rectum, ub = urinary bladder, ut = uterine horn, v = vagina. The female died on the 14th of May 2015 and was not pregnant. The scale in the lower right corner accounts for both images. [1] Length of the erect penis shaft (16.4 mm). [2] Width of the erect penis terminal swelling (7.5 mm). [3] Outer diameter of the cervix (0.7 mm) and [4] vagina (1.1 mm). (D) Copulation of an Eptesicus serotinus pair. The male, above on the drawing, uses its erect penis to pass by the uropatagium of the female, below on the drawing. The terminal swelling of the erect penis is firmly pressed against the vulva, without vaginal intromission. (E) Numbers of copulations merged by month. (F) Average number of bats captured at underground site per night. The numbers of capture events between 2001 and 2022 occurring during the respective months are indicated in brackets.
Mating behaviour of Eptesicus serotinus
Stichting De Laatvlieger.
From creationism's intelligent [sic] design perspective, we are expected to believe their putative designer designed these bats and equipped the females with a normal mammalian vagina, but to get around the fact that it had also given her a tail membrane to help her fly, it had given the male a large penis that was far too big to enter the female's vagina, so it had then had to redesign the male's penis to give it a large tip so it could hold it tightly against the female's vulva to deliver sperm into it, making it look more like something William Heath-Robinson would have designed.

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