Copulatory adjustment in snakes, by Clifford H. Pope.

Abstract

The reproductive habits of snakes, though long neglected, are at last receiving considerable attention from a variety of angles. Sex recognition, courtship patterns, and viability of the sperm have been investigated recently with surprising results.The literature is, however, silent on one aspect of reproduction, namely, the actual position of the hemipenis in the cloaca during copulation. Just how is the seminal fluid conducted to the oviducts? The older literature, Boulenger's "Snakes of Europe" (1913), for

Mechanisms and Evidence of Genital Coevolution: The Roles of Natural Selection, Mate Choice, and Sexual Conflict

“…In at least some species, this close shape fit has been used to suggest a coevolutionary process that could result from female choice (Böhme and Ziegler 2009), sexual conflict (King et al 2009), or natural selection lockand-key mechanisms (Pope 1941). Our own observations in 12 species of snakes including natricine and non-natricines, and two lizards have also revealed shape correspondence (Fig.…”

“…Similar to the dung beetles, there seems to be correspondence between how spiny the hemipenes are, and the thickness of the vaginal wall in two species of Asiatic pit vipers (Pope 1941). This is likely a widespread phenomenon in squamates as many species have spiny hemipenes that leave imprints inside the female after copulation (Pope 1941).…”

“…Eversion of one hemipenis takes place into the female cloaca and vaginal tract. Not much work has been performed specifically on genital coevolution in this group, although shape correspondence indicative of coevolution seems widespread (Pope 1941;Edgren 1953;Pisani 1976;Böhme and Ziegler 2009;King et al 2009). …”

New Taxa and Cryptic Species of Neotropical Snakes (Xenodontinae), with Commentary on Hemipenes as Generic and Specific Characters

“…That simple declaration was derived from an important paper by Pope (1941). But, in that paper, Pope himself had commented: ''One unfamiliar with snake genitalia might conclude that [my] observation … virtually closes the problem of hemipenial adjustment, whereas actually the problem is barely opened.''…”

“…Ultimately such questions lead to the topic of sexual selection and ''sperm competition,'' with growing awareness that there are degrees of difference between snake and lizard hemipenes, both in anatomy and functional use (see the extended treatment by Olsson and Madsen, 1998; also referenced below under Conclusions and Brief Summation). Pope (1941) illustrated the hemipenis and the cloaca of two snakes (Liophis poecilogyrus) ''killed while copulating and preserved without dislodging the penis.'' His illustration is instructive and reproduced herein as figure 22.…”