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In this review, we analyze erectile dysfunction (ED) in the context of sexual selection. We highlight that ED is a specific human male characteristic linked to the loss of the baculum or penile bone and results from a range of physical and psychological factors. We discuss evolutionary interpretations that consider dysfunctional penile erection as an honest signal of a low-quality male. We further emphasize the importance of considering psychosocial context and early attachment dynamics for understanding the etiology of some types of ED. Finally, we suggest that the integration of developmental factors for understanding the emergence of this sexual disorder is instrumental for the calibration of more effective therapies. [ABSTRACT FROM AUTHOR]

The present study was based on the bacula of 39 male (17 juvenile, 22 adult) stone marten (Martes foina) samples obtained from all geographical regions of Turkey between 1995 and 2016. Morphological variability in 11 characteristics of bacula was investigated. The purpose of this study was to measure numerical characters of the baculum, to identify relationships between measurements, and to evaluate variabilities in its morphology. Weight, total length, base length, base height, base width, apex height, apex width, median width, and median height were significantly greater in the bacula of adults compared to the bacula of juveniles. The most variable characteristic in adults was base width (18.96%). There was a significant relationship between some characteristics of the bacula measured. The strongest positive relationships were observed between median height and baculum weight (r = 0.771), weight and base length (r = 0.755), and median width and weight (r = 0.750) characteristics. Statistical analysis (PCA) also revealed a strong relationship between some characteristics. In particular, positive correlations between width and height sizes in the base (proximal), median, and distal of the baculum, as well as axis-apex height and apex width, suggest relationships that protect the urethra and baculum from fissures and fractures during copulation. [ABSTRACT FROM AUTHOR]

The baculum (os penis) is a mineralized bone within the glans of the mammalian penis and is one of the most morphologically diverse structures in the mammal skeleton. Recent experimental work provides compelling evidence for sexual selection shaping the baculum, yet the functional mechanism by which this occurs remains unknown. Previous studies have tested biomechanical hypotheses for the role of the baculum based on simple metrics such as length and diameter, ignoring the wealth of additional shape complexity present. For the first time, to our knowledge, we apply a computational simulation approach (finite-element analysis; FEA) to quantify the three-dimensional biomechanical performance of carnivoran bacula (n = 74) based upon high-resolution micro-computed tomography scans. We find a marginally significant positive correlation between sexual size dimorphism and baculum stress under compressive loading, counter to the 'vaginal friction' hypothesis of bacula becoming more robust to overcome resistance during initial intromission. However, a highly significant negative relationship exists between intromission duration and baculum stress under dorsoventral bending. Furthermore, additional FEA simulations confirm that the presence of a ventral groove would reduce deformation of the urethra. We take this as evidence in support of the 'prolonged intromission' hypothesis, suggesting the carnivoran baculum has evolved in response to pressures on the duration of copulation and protection of the urethra. [ABSTRACT FROM AUTHOR]

During a two year survey extending from 2014 through 2016, specimens (n = 3) of Hodgson's bat Myotis formosus were captured from Bajaur Agency, FATA in Pakistan using mist and hand nets. External body, cranial and bacular features of the captured specimens were recorded and compared with available literature. Mean head and body length of the captured specimens was 42.06±4.01 mm, forearm length was 47.16±0.93 mm, greatest length of skull (n = 2) was 17.38±0.17 mm while total baculum length (n = 1) was 8.1 mm. The species is the first record from the study area. [ABSTRACT FROM AUTHOR]

The penis is the reproductive organ that ensures efficient copulation and success of internal fertilization in all species of mammals, with special challenges for bats, where copulation can occur during flight. Comparative anatomical analyses of different species of bats can contribute to a better understanding of morphological diversity of this organ, concerning organization and function. In this study, we describe the external morphology and histomorphology of the penis and baculum in eleven species of molossid bats. The present study showed that penile organization in these species displayed the basic vascular mammalian pattern and had a similar pattern concerning the presence of the tissues constituting the penis, exhibiting three types of erectile tissue (the corpus cavernosum, accessory cavernous tissue, and corpus spongiosum) around the urethra. However, certain features varied among the species, demonstrating that most species are distinguishable by glans and baculum morphology and glans histological organization. Major variations in glans morphology were genus-specific, and the greatest similarities were shared by Eumops species and N. laticaudatus . The greatest interspecific similarities occurred between M. molossus and M. rufus and between Eumops species. Save for M. molossus and M. rufus , morphology of the baculum was species-specific; and in E. perotis , it did not occur in all specimens, indicating that it is probably under selection. In the histological organization, the most evident differences were number of septa and localization of the corpora cavernosa. In species with a baculum ( Molossus, Eumops and Nyctinomops species), the corpora cavernosa predominantly occupied the dorsal region of the penile glans and is associated with the proximal (basal) portion of the baculum. In species that do not have a baculum ( Cynomops , Molossops and Neoplatymops species), the corpora cavernosa predominantly occupied the ventro-lateral region of the glans. [ABSTRACT FROM AUTHOR]

In this study we investigated allometry and variation in the baculum of the stoat Mustela erminea and compared it with head-and-body length not involved in reproduction. The stoat is a species with pre-copulatory selection (manifested by the high degree of malebiased sexual size dimorphism) therefore we predicted that baculum allometry may be isometric or exhibited negative allometry. We also test the hypothesis that the baculum size is positively correlated with adult body size and may be used as a reliable indicator of male good condition. Results presented in this study were different according to which regression model type was used. While the OLS slope for baculum length in M. erminea indicated negative allometry, the RMA model showed positive allometry. The results obtained for M. erminea weren't in agreement with mentioned hypothesis that if baculum allometry is affected by the degree of pre-copulatory selection relative to post-copulatory selection, then we predict isometry or negative allometry of the baculum. Nevertheless, we suggest, that to confirm the above statements further analysis of more numerous material of M. erminea coupled with comparative analysis of testicular growth studies are needed to fully understand the importance and function of the baculum relative to the mating system. [ABSTRACT FROM AUTHOR]

Copyright of Therya is the property of Asociacion Mexicana de Mastozoologia, A. C. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We present information on the morphological structure and measurements of the os penis for eight families and 28 species of bats occurring on Madagascar, most being endemic to the island. For one of these families, Miniopteridae, no bacular structure was found and for a second family, Emballonuridae, the structure was absent in one species ( Taphozous mauritianus). For the majority of taxa, the descriptions and measurements given herein of their respective bacula are presented for the first time in the published literature. In cases when samples are sufficient for certain species, we examine intra-specific variation in bacular morphology. For species the subject of previous published phylogeographical studies and which showed clade structure associated with elevational or latitudinal clines, we investigate if intra-specific differences in bacular structure are correlated with clade associations. We examine possible correlates associated with os penis measurements and, in general, across all species or within certain families, there was not a clear correlation between body size, as measured by forearm length, and different bacular measurements. [ABSTRACT FROM AUTHOR]

The extreme morphological variability of the baculum across mammals is thought to be the result of sexual selection (particularly, high levels of postcopulatory selection). However, the evolutionary trajectory of the mammalian baculumis little studied and evidence for the adaptive function of the baculum has so far been elusive. Here, we use Markov chain Monte Carlo methods implemented in a Bayesian phylogenetic framework to reconstruct baculum evolution across the mammalian class and investigate the rate of baculum length evolution within the primate order. We then test the effects of testes mass (postcopulatory sexual selection), polygamy, seasonal breeding and intromission duration on the baculum in primates and carnivores. The ancestral mammal did not have a baculum, but both ancestral primates and carnivores did. No relationship was found between testes mass and baculum length in either primates or carnivores. Intromission duration correlated with baculum presence over the course of primate evolution, and prolonged intromission predicts significantly longer bacula in extant primates and carnivores. Both polygamous and seasonal breeding systems predict significantly longer bacula in primates. These results suggest the baculum plays an important role in facilitating reproductive strategies in populations with high levels of postcopulatory sexual selection. [ABSTRACT FROM AUTHOR]

Mammalian penises are morphologically diverse, including a highly variable and taxonomically informative baculum (os penis), and variable penile spines, both of which are possessed by many--but not all--species. To understand the evolution of genital morphologies, as well as the potential role of both the baculum, and penile spines that directly interact with female reproductive tract, we undertook a comparative study of male penile spines and their relationship with the baculum across all mammalian orders. Specifically, we investigated several factors that may explain the presence or absence of penile spines in mammals, including mating system, risk of sperm competition, female reproductive physiology, presence and width of the baculum, and phylogenetic history. We observed that the presence of both the baculum and penile spines is correlated with residual testes size, suggesting a potential role in sexual selection for these traits. We found no association between the presence of spines and mating system, or with the presence/width of the baculum, although relative testes mass was marginally associated with baculum width. We found no relationship between baculum presence or width and mating system. We also noted that spines presence or absence have an orderlevel distribution, and clear phylogenetic patterns of distribution across mammals. It is likely that spine morphology and distribution, not just presence, play an important role in genital evolution in mammals, but these features are poorly described in most groups. Quantitative data collection in most mammalian taxa would be useful to further elucidate the evolution of the complex genital morphology of this group. [ABSTRACT FROM AUTHOR]

The rapid evolution of male genitalia is a nearly ubiquitous pattern across sexually reproducing organisms, likely driven by the evolutionary pressures of male-male competition, male-female interactions, and perhaps pleiotropic effects of selection. The penis of many mammalian species contains a baculum, a bone that displays astonishing morphological diversity. The evolution of baculum size and shape does not consistently correlate with any aspects of mating system, hindering our understanding of the evolutionary processes affecting it. One potential explanation for the lack of consistent comparative results is that the baculum is not actually a homologous structure. If the baculum of different groups evolved independently, then the assumption of homology inherent in comparative studies is violated. Here, we specifically test this hypothesis by modeling the presence/absence of bacula of 954 mammalian species across a wellestablished phylogeny and show that the baculum evolved a minimum of nine times, and was lost a minimum of ten times. Three different forms of bootstrapping show our results are robust to species sampling. Furthermore, groups with a baculum show evidence of higher rates of diversification. Our study offers an explanation for the inconsistent results in the literature, and provides insight into the evolution of this remarkable structure. [ABSTRACT FROM AUTHOR]

In this study we investigated the allometry and variation in the baculum of the weasel Mustela nivalis and compared it with head-and-body length, which is not involved in reproduction. The females of many mammalian species select mates in part during intromission and evaluate attributes of the penis that are informative in regard to a male’s size or other characteristics. If females benefit by mating with large males by estimation of the size of the male's penis, then positive allometry between penile size relative to body size is realized. Small residuals in the allometric regression may evolve. In species with pre-copulatory selection (manifested as male-biased sexual size dimorphism) baculum allometry may be isometric or exhibit negative allometry. Weasels exhibit a sexual-size dimorphism, with males being larger, and as a result we predicted that baculum size would exhibit negative allometry or isometry. We also tested the hypothesis that baculum size is positively correlated with adult body size and may be used as a reliable indicator of good genes for female mates during breeding. Negative allometry and a relative weak relationship between baculum size and head-and-body length suggest that the baculum is under stabilizing selection for optimal baculum size. We assumed that penile width as related to bacular thickness could be a reliable indicator of quality during copulation. [ABSTRACT FROM AUTHOR]

Morphological characteristics of the bacula of 62 Gray Wolves (Canis lupus) harvested in Wisconsin were related to age estimates generated from cementum annuli analyses. Baculum analysis suggested that 47 of 62 wolves (75.8%) were correctly classified as the appropriate age category (pup, yearling, adult) assessed by cementum analyses; however, this success was limited for yearlings (53.5%) and adults (38.5%). Results could not corroborate future use of this approach for rapid aging of dead wolves. There remains a need for a wolf-aging technique that can be broadly implemented in a timely and cost-effective manner, while also preserving the inherent trophy value of an intact skull. [ABSTRACT FROM AUTHOR]

The rapid divergence of male genitalia is a preeminent evolutionary pattern. This rapid divergence is especially striking in the baculum, a bone that occurs in the penis of many mammalian species. Closely related species often display diverse baculum morphology where no other morphological differences can be discerned. While this fundamental pattern of evolution has been appreciated at the level of gross morphology, nearly nothing is known about the genetic basis of size and shape divergence. Quantifying the genetic basis of baculum size and shape variation has been difficult because these structures generally lack obvious landmarks, so comparing them in three dimensions is not straightforward. Here, we develop a novel morphometric approach to quantify size and shape variation from three-dimensional micro-CT scans taken from 369 bacula, representing 75 distinct strains of the BXD family of mice. We identify two quantitative trait loci (QTL) that explain ~50% of the variance in baculum size, and a third QTL that explains more than 20% of the variance in shape. Together, our study demonstrates that baculum morphology may diverge relatively easily, with mutations at a few loci of large effect that independently modulate size and shape. Based on a combination of bioinformatic investigations and new data on RNA expression, we prioritized these QTL to 16 candidate genes, which have hypothesized roles in bone morphogenesis and may enable future genetic manipulation of baculum morphology. [ABSTRACT FROM AUTHOR]

In this study we investigated variation in the baculum of the stone marten, Martes foina from the Czech part of Silesia (north-eastern Czech Republic). The aim of this study was to assess quantitative characteristics of the baculum size, relationships between measurements and description of the variability in baculum morphology. The study presents the morphological variation in six dimensional traits of the baculum based on an analysis of 15 specimens collected in the vicinity of Opava and deposited at the Šariš Museum Bardejov (Slovakia). The descriptive statistics revealed size variation of the bacula, while the statictic analysis (PCA) showed a strong positive correlation between morphological traits of the body and baculum. [ABSTRACT FROM AUTHOR]

The article presents a study on genetic diversity in Rhinolophus luctus (Chiroptera: Rhinolophidae) from Peninsular Malaysia. Topics include the description of the new species Rhinolophus luctus morio based on genetic and morphological characters and morphological examination showing differences in size of the baculum and length of the lower toothrow.

The baculum (os penis) has been extensively studied as a taxon-specific character in bats and other mammals but its mechanical function is still unclear. There is a wide consensus in the literature that the baculum is probably a sexually selected character. Using a novel approach combining postmortem manipulation and three-dimensional (3D) imaging, we tested two functional hypotheses in the common noctule bat Nyctalus noctula, the common pipistrelle Pipistrellus pipistrellus, and Nathusius' pipistrelle Pipistrellus nathusii: (i) whether the baculum can protect the distal urethra and urethral opening from compression during erection and copulation; and (ii) whether the baculum and corpora cavernosa form a functional unit to support both the penile shaft and the more distal glans tip. In freshly dead or frozen and thawed bats, we compared flaccid penises with artificially 'erect' penises that were inflated with 10% formalin. Penises were stained with alcoholic iodine and imaged with a lab-based high-resolution x-ray microtomography system. Analysis of the 3D images enabled us to compare the changes in relative positions of the baculum, corpora cavernosa, urethra, and corpus spongiosum with one another between flaccid and 'erect' penises. Our results support both functional hypotheses, indicating that the baculum probably performs two different roles during erection. Our approach should prove valuable for comparing and testing the functions of different baculum morphologies in bats and other mammals. Moreover, we have validated an essential component of the groundwork necessary to extend this approach with finite element analysis for quantitative 3D biomechanical modeling of penis function. [ABSTRACT FROM AUTHOR]

The article presented a study to test the reliability of morphometric baculum differences for discriminating the cryptic species, Pipistrellus pipistrellus and P. pygmaeus. The study used high-resolution microcomputed tomography (microCT) of the bacula of museum specimens of the two species and of Pipistrellus hanaki. It showed that quantitative details of morphology like simple baculum measurements, can be used to distinguish cryptic species and understand their phylogeographic distributions.

We discovered hard structures that resembled bone in the penis of 20 specimens of male American pikas ( Ochotona princeps) from the Rocky Mountains of southwestern Alberta, Canada. Histological sections of these structures showed features consistent with cortical bone and osteocytes, and scanning electron microscopy analyses indicated peaks in calcium and phosphorous. The anatomical positioning, internal texture, and elemental composition indicate that the structures are bacula. The presence of a baculum in O. princeps demonstrates that there is a greater phylogenetic distribution of this feature among Mammalia than commonly recognized, and it indicates that the absence of a baculum is not a derived character state for Lagomorpha. [ABSTRACT FROM AUTHOR]

The morphological variability of the baculum (os penis) of 147 adult specimens of species in the genus Nannospalax from 58 localities in Turkey was examined using morphological and numerical taxonomic methods. Significant differences among all of the Turkish species in the genus were determined by morphological and biometrical comparison of the bacula, and the results of this study showed that N. nehringi and N. xanthodon are separate species and that the names are not synonyms. Additionally, because the central Anatolian mole rat populations that were classified by previous studies as members of N. nehringi or N. xanthodon had highly different baculum morphologies, these populations were classified as a different species (N. labaumei) in this study. When compared to the other populations, the central Anatolian populations, which have greater diploid chromosomal sets (2n = 56, 58, 60), had very different baculum morphologies. Whereas individuals of the species N. labaumei had the smallest bacula, the largest baculum occurred in a representative of the species N. leucodon. From this study, the results indicate that 5 different blind mole rat species (N. ehrenbergi, N. leucodon, N. nehringi, N. xanthodon, and N. labaumei) live in Turkey, and in addition to these species, some of the chromosomal races (2n = 36, 40, 52) should be treated as distinct species. [ABSTRACT FROM AUTHOR]

Scotophilus kuhlii Leach, 1821 has only been reported from Chaklala and Chakri in Punjab, Pakistan. We captured five specimens from Lahore in a 2-year survey from June 2009 to May 2011. This is the first report of this species from Punjab province and the first from Lahore (31°29.223 N, 074°24.632 E) since the 1920s. The external body, cranial and bacular measurements of the captured specimens were compared with the available literature. The forearm length (n=5) was 49.40±3.03 mm, the greatest length of the skull (n=4) was 18.98±0.61 mm and C-M³ (n=4) was 6.27±0.49 mm. The echolocation call parameters of 25 pulses from five calls of the species were also analyzed. The mean frequency of maximum energy was 56.9±3.6 kHz, the mean start and end call frequencies were 103.5±12.3 kHz and 50.6±1.0 kHz, respectively. [ABSTRACT FROM AUTHOR]

Male genitalia exhibit a taxonomically widespread pattern of rapid and divergent evolution. Sexual selection is generally believed to be responsible for these patterns of evolutionary divergence, although empirical support for the sexual selection hypothesis comes mainly from studies of insects. Here we show that sexual selection is responsible for an evolutionary divergence in baculum morphology among populations of house mice Mus domesticus. We sourced mice from three isolated populations known to be subject to differing strengths of postcopulatory sexual selection and bred them under common-garden conditions. Mice from populations with strong postcopulatory sexual selection had bacula that were relatively thicker compared with mice from populations with weak selection. We used experimental evolution to determine whether these patterns of divergence could be ascribed to postcopulatory sexual selection. After 27 generations of experimental evolution, populations of mice subjected to postcopulatory sexual selection evolved bacula that were relatively thicker than populations subjected to enforced monogamy. Our data thereby provide evidence that postcopulatory sexual selection underlies an evolutionary divergence in the mammalian baculum and supports the hypothesis that sexual selection plays a general role in the evolution of male genital morphology across evolutionary diverse taxonomic groups. [ABSTRACT FROM AUTHOR]

The fossil bacula, or os penis, constitutes a rare subject of study due to its scarcity in the fossil record. In the present paper we describe five bacula attributed to the bear Indarctos arctoides Depéret, 1895 from the Batallones-3 site (Madrid Basin, Spain). Both the length and morphology of this fossil bacula enabled us to make interpretative approaches to a series of ecological and ethological characters of this bear. Thus, we suggest that I. arctoides could have had prolonged periods of intromission and/or maintenance of intromission during the post-ejaculatory intervals, a multi-male mating system and large home range sizes and/or lower population density. Its size might also have helped females to choose from among the available males. [ABSTRACT FROM AUTHOR]

Background: Diversity in penile morphology is characterised by extraordinary variation in the size and shape of the baculum (penis bone) found in many mammals. Although functionally enigmatic, diversity in baculum form is hypothesised to result from sexual selection. According to this hypothesis, the baculum should influence the outcome of reproductive competition among males within promiscuous mating systems. However, a test of this key prediction is currently lacking. Results: Here we show that baculum size explains significant variation in the reproductive success of male house mice under competitive conditions. After controlling for body size and other reproductive traits, the width (but not length) of the house mouse baculum predicts both the mean number of offspring sired per litter and total number of offspring sired. Conclusions: By providing the first evidence linking baculum morphology to male reproductive success, our results support the hypothesis that evolutionary diversity in baculum form is driven by sexual selection. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Callus cultures of Berberis lycium were initiated from leaves, internodes and hypocotyl explants of mature plant. Murashige and Skoog agar medium sustained growth of callus. A four fold increase in weight occurred during 4 week culture period at 25±2°C. The optimal hormonal concentration for initiation and growth of callus were 1 mg/l 2,4- dichlorophenoxy acetic acid and 0.2 mg/l Kn. Release of diverse chemicals in the nutrient media by callus resulted in failure to produce shoots, which on TLC and HPLC analysis shared berberine as an active constituent. This alkaloid is synthesized from plant parts. This was the main finding in the present study. [ABSTRACT FROM AUTHOR]

Genitalia are among the most variable of morphological traits, and recent research suggests that this variability may be the result of sexual selection. For example, large bacula may undergo post-copulatory selection by females as a signal of male size and age. This should lead to positive allometry in baculum size. In addition to hyperallometry, sexually selected traits that undergo strong directional selection should exhibit high phenotypic variation. Nonetheless, in species in which pre-copulatory selection predominates over post-copulatory selection (such as those with male-biased sexual size dimorphism), baculum allometry may be isometric or exhibit negative allometry. We tested this hypothesis using data collected from two highly dimorphic species of the Mustelidae, the American marten ( Martes americana) and the fisher ( Martes pennanti). Allometric relationships were weak, with only 4.5-10.1% of the variation in baculum length explained by body length. Because of this weak relationship, there was a large discrepancy in slope estimates derived from ordinary least squares and reduced major axis regression models. We conclude that stabilizing selection rather than sexual selection is the evolutionary force shaping variation in baculum length because allometric slopes were less than one (using the ordinary least squares regression model), a very low proportion of variance in baculum length was explained by body length, and there was low phenotypic variability in baculum length relative to other traits. We hypothesize that this pattern occurs because post-copulatory selection plays a smaller role than pre-copulatory selection (manifested as male-biased sexual size dimorphism). We suggest a broader analysis of baculum allometry and sexual size dimorphism in the Mustelidae, and other taxonomic groups, coupled with a comparative analysis and with phylogenetic contrasts to test our hypothesis. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 955-963. [ABSTRACT FROM AUTHOR]

The article discusses a study aimed at analyzing relationships between baculum size and body measurements and investigates whether the size of the baculum was correlated with body condition. The polecat bones used in the study came from the collection of the Department of Natural History, Sarisské Museum, Bardejob in Slovakia. It refers to Mustelidae as a group where a multi-male mating system happens in many species and which is one of the drivers of sperm competition. It indicates that holders of exaggerated features are preferred by females as breeding partners and the risk of losses like fracture of the baculum is outweighed by the benefits of increased reproduction caused by a greater attractiveness to the opposite sex.

Abstract: The baculum is an extraskeletal bone located in the penis of a few species in several orders of mammals such as carnivores, insectivores, rodents, bats and primates. This study aims to describe the structure, architecture and mechanical properties of the canine baculum. To this end canine bacula from castrated and uncastrated dogs were collected and examined by light microscopy, micro-computed tomography (microCT) scanning, histological staining, and mechanical testing. Their mineral density and mechanical properties were compared with those of a typical skeletal bone (the radius) in the same dog. Furthermore, a numerical model of a representative baculum was created and its mechanical performance analyzed using the finite element method, in order to try to elucidate its function. Examination of light microscopy images of transverse sections shows that the baculum consists of a typical sandwich structure, with two cortical plates separated, and joined, by loose cancellous bone. MicroCT scans reveal that the mineral density is lower in the baculum than in the radius, both in castrated as well as in uncastrated dogs, resulting in much lower stiffness. Castration was found to decrease the mineral density in both the baculum and the radius. The most likely function of the baculum of the dog is to stiffen the penis to assist intromission, and its much lower mineral density compared to that of the radius may be a mechanism designed to decrease the stiffness somewhat, and thus reduce the risk of fracture during copulation. [Copyright &y& Elsevier]

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 (≥ 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. [ABSTRACT FROM AUTHOR]

Abstract: The three-dimensional structure of channels and bacula cavities in the wall of hazel pollen grains was investigated by automated electron tomography in order to explore their role in the release of allergen proteins from the pollen grains. 3D reconstructions of 100–150nm thick resin-embedded sections, stabilized by thin platinum–carbon coating, revealed that the channels aimed directly towards the surface of the grain and that the bacula cavities were randomly sized and merged into larger ensembles. The number and the dimensions of the ensembles were quantitatively determined by neighboring voxel analysis on thresholded reconstructed volumes. To simulate the allergen release, allergen proteins were approximated by a hard sphere model of a diameter corresponding to the largest dimension of the known 3D structure of the major birch allergen, Bet v 1, whose amino acid sequence is highly similar to the amino acid sequence of the major hazel allergen, Cor a 1. The analysis of positions where the hard sphere fits into the resolved channels and bacula cavity structures revealed that unbound allergens could freely traverse through the channels and that the bacula cavities support the path of the allergens towards the surface of the grain. [Copyright &y& Elsevier]

In 2000, 2002, and 2006 we captured small mammals in the Liangshan Mountains, Mabian Dafengding National Nature Reserve and Meigu Dafengding National Nature Reserve, Sichuan Province, China. Among the collected specimens we identified a new species of the genus Proedromys. Its identifying characteristics are its relatively long tail, broad upper incisors without grooves, comparatively short lower incisors, and features of the molar teeth. The glans penis of the new species also is distinctive, the proximal and distal bacula are bony, whereas the lateral bacula are only slightly ossified. The proximal baculum is flask-shaped, the distal baculum is cap-shaped, and the lateral bacula are stick-shaped. This species is associated with high-elevation spruce-fir forest habitat, an unusual setting for Proedromys across its geographic range. [ABSTRACT FROM AUTHOR]

Structure and growth of the baculum (os penis) in arctoid carnivores have been well described for many species. This study presents the first extensive analysis of bacular growth and variation for bears (Ursidae), based on 871 bacula of polar bears Ursus maritimus (858 of known age) that were shot in the Canadian Arctic from 1994 to 1997. Bacular length, maximal diameter and mass increased from 109 mm, 5.93 mm and 2.68 g respectively in 1-year-old bears (n = 34) to 190 (maximum 222) mm, 18.7 (24.4) mm, and 20.4 (31.9) g respectively in bears≥10 years of age (n>200). Bacular length is ~8% of body length in adults. Bacula were moderately variable in size: coefficient of variation for length, diameter, and mass1/3 were 5.2, 10.0 and 5.4% respectively (16.3% for mass). No geographic variation in size was apparent. Bacula reached asymptotic size at 8–9 years of age. At physiological sexual maturity (~6 years of age), bacula were at 89, 73 and 62% of asymptotic length, diameter and mass respectively (compared with body length at ~95%). Interpretation of these findings must await behavioural and physiological information on courtship and copulation in the polar bear, and comparative data on other ursids. [ABSTRACT FROM AUTHOR]

Animals adapted to high latitude environments typically live at relatively low densities and require large areas to acquire the requisites for successful reproduction. Also, the unpredictable distribution of energy across time and space, such as environmental seasonality, constrains the timing of mating and parturition and imposes limitations to reproductive strategies. For example, limited mobility due to snow accumulation may reduce mate encounters, and this selective pressure may have resulted in morphological adaptations to assess mate quality during serial encounters. We tested whether mammalian carnivores living in high latitude environments displayed greater use of copulatory competition via length of the penis bone or baculum, and whether females in such settings enhance competition among males via multi-male matings. We then examined how baculum length may correlate with other reproductive adaptations in high latitude environments such as delayed implantation and induced ovulation. Statistical methods that account for phylogeny revealed that longer bacula occur in carnivores living in high latitude environments with greater snow accumulation, and that larger bacula is also associated with delayed implantation and multi-male mating systems. In contrast, the smallest bacula were observed in polygynous species. Our results provide an example of the effects of ecology on the evolution of a secondary sexual character due to sexual selection. Selection pressures imposed by seasonality of resources and environmental conditions affecting locomotion may have led to sexual selection via mating systems for females, and counter morphological adaptations of long penis bones in males. [ABSTRACT FROM AUTHOR]

ABSTRACT The function of the mammalian baculum is a puzzling enigma in mammalian morphology. Three hypotheses for the evolution and persistence of the mammalian baculum have been proposed: the vaginal friction hypothesis; the prolonged intromission hypothesis; and the induced ovulation hypothesis. We tested these three hypotheses using phylogenetically corrected methods and data on North American carnivores. Baculum length was independent of sexual dimorphism and duration of copulation, thus refuting the vaginal friction and prolonged intromission hypotheses, respectively. Also, baculum length did not differ between induced ovulators and simultaneous ovulators, thus also refuting the induced ovulation hypothesis. We suggest that other aspects of carnivore life history, such as mating systems, may help explain the evolution of the mammalian baculum. [ABSTRACT FROM AUTHOR]

The length of the baculum (os penis) was measured in 74 adult males representing 46 primate species. These data, and a review of previously published measurements, indicate that variation in baculum length among primates is related to taxonomic and behavioral differences. Thus, many New World monkeys have shorter bacula, relative to body weight, than Old World monkeys. The baculum is shorter in colobine monkeys than in cercopithecines. Among the great apes, reduction of the baculum is more pronounced in Pan and Gorilla than in Pongo. Very long bacula are found in some nocturnal prosimians (eg, Lorisidae) and also in Macaca arctoides. A comparison of baculum length relative to body weight was made in 34 species for which detailed information on copulatory behavior was available. The presence of an elongated baculum was shown to correlate with copulatory patterns involving prolonged intromission and/or the maintenance of intromission during the postejaculatory interval (eg, Galago crassicaudatus, Loris tardigradus, M. arctoides). The evolutionary significance of these observations is discussed and it is suggested that similar copulatory patterns may occur in species with elongated bacula (eg, Daubentonia, Perodicticus) for which behavioral data are lacking at present. The same hypothesis also applies to an extinct adapid primate which possessed a very large baculum. [ABSTRACT FROM AUTHOR]