Morphometric Variation and Function in the Baculum, with Comments on Correlation of Parts

Long, Charles A.; Frank, T.

doi:10.2307/1377725

Cited by 61 publications

(59 citation statements)

References 15 publications

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“…High intraspecific variation in bacular size is common among mammals (Kinahan et al 2007;Miller and Burton 2001;Scheffer and Kenyon 1963;Tasikas et al 2009) and consistent with the hypothesis that the baculum is subject to sexual selection (Long and Frank 1968). In adult ringed seals variation in bacular length was higher than in mandibular length.…”

Section: Discussionsupporting

confidence: 65%

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Bacular and testicular growth and allometry in the ringed seal (Pusa hispida): evidence of polygyny?

2011

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We determined ringed seal (Pusa hispida) bacular and testicular growth relationships and made interspecific comparisons to species with better-known mating systems to elaborate on current hypotheses about the mating system of the ringed seal. We measured 161 bacula, 251 pairs of testes, and 55 mandibles collected from ringed seals of known age from Inuit subsistence harvests in Arviat and Sanikiluaq, Nunavut, Canada, from 2003 to 2006. Ringed seal bacular and testicular sizes were positively allometric relative to mandibular size for immature males (,7 years of age) but increased isometrically in mature males (7 years of age), similar to relationships between bacular size and body length for known polygynous pinnipeds. Adult isometric growth contrasted with harp seals (Pagophilus groenlandicus), a promiscuous species, in which bacular size likely is sexually selected. Our results, combined with previously reported ecological and behavioral ringed seal characteristics, suggest that ringed seals display a polygynous mating system.

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Section: Discussionsupporting

confidence: 65%

“…(Long and Frank 1968;Mohr 1963). In addition, the ringed seal baculum is a relatively simple structure with a slight curvature, typical of phocid bacula (Miller 2009;Scheffer 1950).…”

Section: Discussionmentioning

confidence: 99%

Bacular and testicular growth and allometry in the ringed seal (Pusa hispida): evidence of polygyny?

2011

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“…For instance, in some primates, keratinized penile spines purportedly serve a mechanical function by gripping the walls of the female's reproductive opening during copulation (Dixson 1987). Moreover, the complex shape at the distal end of the baculum might assist males of many species to gain entry and/or support prolonged intromission (Long & Frank 1968;Patterson & Thaeler 1982;Dixson 1987). Although copulation in spotted hyenas involves multiple, prolonged intromissions, undoubtedly placing significant pressure on the penis, members of Hyaenidae do not possess a baculum (Drea et al 1999).…”

Section: Discussionmentioning

confidence: 99%

Exposure to naturally circulating androgens during foetal life incurs direct reproductive costs in female spotted hyenas, but is prerequisite for male mating

Drea¹,

Place²,

Weldele³

et al. 2002

Proc. R. Soc. Lond. B

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Among all extant mammals, only the female spotted hyena (Crocuta crocuta) mates and gives birth through the tip of a peniform clitoris. Clitoral morphology is modulated by foetal exposure to endogenous, maternal androgens. First births through this organ are prolonged and remarkably difficult, often causing death in neonates. Additionally, mating poses a mechanical challenge for males, as they must reach an anterior position on the female's abdomen and then achieve entry at the site of the retracted clitoris. Here, we report that interfering with the actions of androgens prenatally permanently modifies hyena urogenital anatomy, facilitating subsequent parturition in nulliparous females who, thereby, produce live cubs. By contrast, comparable, permanent anatomical changes in males probably preclude reproduction, as exposure to prenatal anti-androgens produces a penis that is too short and has the wrong shape necessary for insertion during copulation. These data demonstrate that the reproductive costs of clitoral delivery result from exposure of the female foetus to naturally circulating androgens. Moreover, the same androgens that render an extremely unusual and laborious process even more reproductively costly in the female are apparently essential to the male's physical ability to reproduce with a normally masculinized female.

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“…The baculum's bony nature has led some authors to suggest that it provides additional support to the ancestral hydrostatic skeletons in the penis by bracing the corpus spongiosum and urethral tissue in the glans (Romer, 1970;Dixson, 1987Dixson, , 1995. It has also been suggested that the baculum facilitates penetration, acting as a wedge to open the female's vaginal tract (Ruth, 1934;Long and Frank, 1968), or that it stimulates the female during copulation, eliciting a neuroendocrine response that could either enhance sperm transport, induce ovulation, or prepare the uterus for implantation (Patterson and Thaeler, 1982;Eberhard, 1985Eberhard, , 1996. None of these hypotheses has been biomechanically tested, and the baculum's true function could be any one or a combination of those proposed.…”

mentioning

confidence: 99%

Anatomy of the baculum–corpus cavernosum interface in the Norway rat (Rattus norvegicus), and implications for force transfer during copulation

Kelly

2000

Journal of Morphology

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Morphometric Variation and Function in the Baculum, with Comments on Correlation of Parts

Cited by 61 publications

References 15 publications

Bacular and testicular growth and allometry in the ringed seal (Pusa hispida): evidence of polygyny?

Bacular and testicular growth and allometry in the ringed seal (Pusa hispida): evidence of polygyny?

Exposure to naturally circulating androgens during foetal life incurs direct reproductive costs in female spotted hyenas, but is prerequisite for male mating

Anatomy of the baculum–corpus cavernosum interface in the Norway rat (Rattus norvegicus), and implications for force transfer during copulation

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