The development of extremely large male genitalia under spatial limitation.

Extensive research in evolutionary biology has focused on the exaggeration of sexual traits; however, the developmental basis of exaggerated sexual traits has only been determined in a few cases. The evolution of exaggerated sexual traits may involve the relaxation of constraints or developmental processes mitigating constraints. Ground beetles in the subgenus Ohomopterus (genus Carabus) have species-specific genitalia that show coevolutionary divergence between the sexes. Here, we examined the morphogenesis of the remarkably enlarged male and female genitalia of Carabus uenoi by X-ray microcomputed tomography. The morphogenetic processes generating the male and female genitalia at the pupal stage were qualitatively similar to those in closely related species with standard genital sizes. Higher growth rates contributed to the exaggeration of both the male and female genital parts of C. uenoi, possibly related to a gene network commonly upregulated in both sexes. Additionally, the length of the copulatory piece (CP), the enlarged male genital part stored in the aedeagus (AD), reached close to that of the AD at the later developmental stages and thereafter decelerated to grow in parallel with the AD, suggesting a structural constraint on the CP by the outer AD. Then, unlike related species, the lengths of the CP and AD increased at eclosion, suggesting a mechanism leading to further elongation of the male genitalia. These observations suggest that a developmental process allows continuous growth of the male genitalia even under the spatial limitation. These results revealed the spatio-temporal dynamics of the development of exaggerated genital structures under structural constraints.

Rapid divergent evolution of internal female genitalia and the coevolution of male genital morphology revealed by micro-computed tomography.

Animal genitalia are thought to evolve rapidly and divergently in response to sexual selection. Studies of genital evolution have focused largely on male genitalia. The paucity of work on female genital morphology is probably due to problems faced in quantifying shape variation, due to their composition and accessibility. Here we use a combination of micro-computed tomography, landmark free shape quantification and phylogenetic analysis to quantify the rate of female genital shape evolution among 29 species of Antichiropus millipedes, and their coevolution with male genitalia. We found significant variation in female and male genital shape among species. Male genital shape showed a stronger phylogenetic signal than female genital shape, although the phylogenetic signal effect sizes did not differ significantly. Male genital shape was found to be evolving 1.2 times faster than female genital shape. Female and male genital shape exhibited strong correlated evolution, indicating that genital shape changes in one sex are associated with corresponding changes in the genital shape of the other sex. This study adds novel insight into our growing understanding of how female genitalia can evolve rapidly and divergently, and highlights the advantages of three-dimensional techniques and multivariate analyses in studies of female genital evolution.

Personal genital satisfaction is associated with differences in perception of male and female sexual anatomy and function.

BACKGROUND: Prior studies primarily of men correlated low personal genital satisfaction (PGS) with decreased sexual activity; however, the association between PGS and genital anatomy perceptions is unknown, and there is a paucity of studies examining women. AIM: We assessed the relationship between genital satisfaction, survey respondent sexual activity, and perceptions of anatomy and function. METHODS: A 54-item REDCap survey was distributed to any-gendered volunteers ≥18 years of age through ResearchMatch from January to March 2023. Responses were split into (1) high PGS and (2) low PGS. Analysis was performed using chi-square tests on survey responses and a Mann Whitney U test on median satisfaction level. OUTCOMES: Outcomes were genital anatomy perceptions, sexual activity, and respondents' PGS. RESULTS: Of the 649 respondents who started the survey, 560 (86.3%) completed it. Median PGS was 7 of 10, forming subgroups of high (≥7 of 10) satisfaction (n = 317 of 560 [56.6%]) and low (<7 of 10) satisfaction (n = 243 of 560 [43.4%]). The mean age was 45.8 ± 16.8 years, and demographics were notable for 72.1% women (n = 404 of 560), 83.2% White (n = 466 of 560), 47.9% married (n = 268 of 560), and 75.5% bachelor's degree holders (n = 423 of 560). Comparing high- and low-PGS groups, more low-PGS respondents felt normal flaccid penis length to be <2 inches (11.1% vs 5.1%; P = .008). High-PGS respondents more often responded that it is normal for women to have orgasms over half the time (20.8% vs 13.2%; P = .0002) or to identify as being sexually active (81.1% vs 71.6%; P = .008). Women were more likely than men to report larger normal testicle sizes as 60.1 to 90 mL (24.5% vs 10.3%; P < .0001), whereas more men felt that normal testicle size was 7 to 15 mL (26.3% vs 11.4%; P < .0001). Orgasm length perceptions also differed: more women felt female orgasm length was 2.6 to 5 seconds (36.6% vs 16.7%; P < .0001), and more men believed female orgasms to be longer, at 7.6 to 10 seconds (29.5% vs 17.3%; P = .002), 10.1 to 12.5 seconds (11.5% vs 5.2%; P = .0008), and >12.5 seconds (12.2% vs 5.7%; P = .009). Respondents' views on their genitalia differed by gender, with women more likely to feel that their genitals are normal compared with men (89.4% vs 75.0%; P < .0001). CLINICAL IMPLICATIONS: PGS may be a useful screening tool given its association with sexual activity. STRENGTHS AND LIMITATIONS: Our large-scale survey assesses public perceptions of genital anatomy and function. Limitations include a lack of gender nonbinary perceptions. CONCLUSION: Gender and PGS interact with perceptions of male anatomy and female sexual activity, and the frequency of sexual activity was higher among high-PGS respondents; however, the direction of these interactions remains unclear and requires future causal analysis.

Discovery of a novel ejaculation mechanism in danceflies (Diptera: Empididae), with implications for genital elongation.

Genitalia are known to evolve rapidly and are among the most variable structures in insect morphology, making them a target of active research. However, function and evolutionary significance of internal genital structures remain less well understood. Here, we report the morphology and mechanism of a novel ejaculatory system that has evolved in the dancefly genus Rhamphomyia (Insecta: Diptera: Empididae). Using synchrotron µCT technology, we examined the male genitalia of five dancefly species and identified an ejaculatory system resembling a leverage hydraulic jack, which is thought to have derived from a plunger-like pumping system. This jacking system amplifies the applied muscle power by up to 4.2 times, allowing the system to produce the same pumping power with much smaller muscles. However, the volume of the pumping muscle in the jacking system is comparable to that of the plunger system, indicating a significant increase in ejaculation power in this genus. We hypothesize that the greater pumping power evolved through sexual selection favoring strong ejaculation to rapidly pass semen through a thin and elongated phallus and spermathecal duct.

Resolving between novelty and homology in the rapidly evolving phallus of Drosophila.

The genitalia present some of the most rapidly evolving anatomical structures in the animal kingdom, possessing a variety of parts that can distinguish recently diverged species. In the Drosophila melanogaster group, the phallus is adorned with several processes, pointed outgrowths, that are similar in size and shape between species. However, the complex three-dimensional nature of the phallus can obscure the exact connection points of each process. Previous descriptions based upon adult morphology have primarily assigned phallic processes by their approximate positions in the phallus and have remained largely agnostic regarding their homology relationships. In the absence of clearly identified homology, it can be challenging to model when each structure first evolved. Here, we employ a comparative developmental analysis of these processes in eight members of the melanogaster species group to precisely identify the tissue from which each process forms. Our results indicate that adult phallic processes arise from three pupal primordia in all species. We found that in some cases the same primordia generate homologous structures whereas in other cases, different primordia produce phenotypically similar but remarkably non-homologous structures. This suggests that the same gene regulatory network may have been redeployed to different primordia to induce phenotypically similar traits. Our results highlight how traits diversify and can be redeployed, even at short evolutionary scales.

Morphology of the Female and Male Reproductive Tracts and More Data on the Spermatostyle in the Brazilian Gyretes sp. (Coleoptera, Adephaga, Gyrinidae).

We investigated the male and female reproductive tracts of Gyretes sp. with light and transmission electron microscopies. The male has a pair of testes with a single coiled follicle, followed by short efferent ducts, which have a similar shape and diameter to the testes. Long ducts (epididymides) with differential epithelium open in a pair of long vasa deferentia that lead to the accessory glands. Glycoprotein secretions from the vas deferens epithelium constitute the spermatostyle for spermatozoa aggregation. The female has numerous ovarioles per ovary, a coiled fertilization duct, an accessory gland, and an elongated vagina. Spermatozoa are stored as unaggregated cells in the fertilization duct. In Gyrinidae, the testes and accessory glands show diverse shapes, and the female sperm storage organs vary in shape, size, and type and may play a role in the interaction with sperm aggregates. Testes with a single follicle and vasa deferentia opening in the accessory glands of Gyretes sp. are features shared with other Gyrinidae and other Adephaga. We proposed adding this latter trait to characterize this suborder of beetles. The morphology of the reproductive organs in both sexes contributes to comparative analyses and knowledge of the reproductive biology of Gyretes and may provide additional features for systematics.

Unraveling the Genetic Basis for the Rapid Diversification of Male Genitalia between Drosophila Species.

In the last 240,000 years, males of the Drosophila simulans species clade have evolved striking differences in the morphology of their epandrial posterior lobes and claspers (surstyli). These appendages are used for grasping the female during mating and so their divergence is most likely driven by sexual selection. Mapping studies indicate a highly polygenic and generally additive genetic basis for these morphological differences. However, we have limited understanding of the gene regulatory networks that control the development of genital structures and how they evolved to result in this rapid phenotypic diversification. Here, we used new D. simulans/D. mauritiana introgression lines on chromosome arm 3L to generate higher resolution maps of posterior lobe and clasper differences between these species. We then carried out RNA-seq on the developing genitalia of both species to identify the expressed genes and those that are differentially expressed between the two species. This allowed us to test the function of expressed positional candidates during genital development in D. melanogaster. We identified several new genes involved in the development and possibly the evolution of these genital structures, including the transcription factors Hairy and Grunge. Furthermore, we discovered that during clasper development Hairy negatively regulates tartan (trn), a gene known to contribute to divergence in clasper morphology. Taken together, our results provide new insights into the regulation of genital development and how this has evolved between species.

tartan underlies the evolution of Drosophila male genital morphology.

Male genital structures are among the most rapidly evolving morphological traits and are often the only features that can distinguish closely related species. This process is thought to be driven by sexual selection and may reinforce species separation. However, while the genetic bases of many phenotypic differences have been identified, we still lack knowledge about the genes underlying evolutionary differences in male genital organs and organ size more generally. The claspers (surstyli) are periphallic structures that play an important role in copulation in insects. Here, we show that divergence in clasper size and bristle number between Drosophila mauritiana and Drosophila simulans is caused by evolutionary changes in tartan (trn), which encodes a transmembrane leucine-rich repeat domain protein that mediates cell-cell interactions and affinity. There are no fixed amino acid differences in trn between D. mauritiana and D. simulans, but differences in the expression of this gene in developing genitalia suggest that cis-regulatory changes in trn underlie the evolution of clasper morphology in these species. Finally, analyses of reciprocal hemizygotes that are genetically identical, except for the species from which the functional allele of trn originates, determined that the trn allele of D. mauritiana specifies larger claspers with more bristles than the allele of D. simulans Therefore, we have identified a gene underlying evolutionary change in the size of a male genital organ, which will help to better understand not only the rapid diversification of these structures, but also the regulation and evolution of organ size more broadly.

Evolution of sexual dimorphism and polychromatism in a lineage of tiger moths (Lepidoptera: Erebidae): advancing knowledge of a taxonomically chaotic group.

Pericopina is divided into 36 genera, with the greatest diversity recorded in the Neotropics. Studies on the taxonomy and systematics of pericopines are scarce, and one of the few phylogenetic hypotheses available in the literature places some Afro-Indo-Malayan lineages among the Neotropical representatives. Through a survey of adult morphological characters, we analyzed the phylogenetic relationships in Pericopina including Nyctemera and other Afro-Indo-Malayan genera as putative members of this subtribe. Additionally, we tested the monophyly of Dysschema, a key genus to understanding the evolutionary patterns of the extreme sexual dimorphism and polychromatism in Pericopina. Our cladistic analysis, based on 162 morphological characters, suggests that Pericopina is a polyphyletic group. Xenosoma is the only genus among the Neotropical pericopines related to the Afro-Indo-Malayan species; Scearctia is closely related to Lithosiini, and Pteroodes shows morphological similarities with Phaegopterina. Additionally, Seileria is a new junior subjective synonym of Thyrgis. The monophyly of Dysschema is supported only if the monotypic genera Myserla and Are are included. These are herein designated new synonyms of Dysschema. Our findings suggest that intersexual polychromatism and intersexual polymorphism for wing characters have arisen multiple times in the evolutionary history of Pericopina. Intersexual polychromatism is also widely distributed within Dysschema, perhaps representing a derived feature with multiple origins in the genus.

Phylogenetic analysis of the family Megalopodidae (Coleoptera: Chrysomeloidea): better taxon-sampling facilitates detection of new relationships and new taxa.

The systematics of Megalopodidae is not adequately known, in spite of it being a relatively small group of phytophagous beetles. The first phylogenetic analysis of Megalopodidae with a comprehensive generic representation (25 genera of 30 described, 10 subgenera and 77 species) is undertaken. A parsimony analysis under equal and implied weights was carried out based on 147 adult and larval morphological characters. Subfamilies Palophaginae and Zeugophorinae were recovered as monophyletic, by contrast with Megalopodinae, which proved to be paraphyletic. Atelederinae are proposed as a new subfamily. Also, three tribes and three subtribes within Megalopodinae are proposed: Leucasteini trib.n., Sphondyliini trib.n. and Megalopodini, the latter including Macrolophina subtrib.n., Temnaspidina subtrib.n. and Megalopodina. The genera Macrolopha, Kuilua, Poecilomorpha, Temnaspis, Antonaria, Agathomerus, Megalopus and Bothromegalopus were recovered as non-monophyletic. New delimitations of the polyphyletic genera Poecilomorpha and Macrolopha are proposed, Clythraxeloma is resurrected, and the subgenera of Agathomerus are suppressed. The following new combinations are proposed: Kuilua apicata (Fairmaire), K. nyassae (Jacoby), Poecilomorpha cribricollis (Pic), P. minuta (Pic), Clythraxeloma assamensis (Jacoby), C. bipartita (Lacordaeri), C. discolineata (Pic), C. downesii (Baly), C. gerstaeckeri (Westwood), C. laosensis (Pic), C. maculata (Pic), C. mouhoti (Baly), C. nigrocyanea (Motschulsky), C. pretiosa (Reineck), Temnaspis tricoloripes (Pic) and Barticaria faciatus (Dalman). Clythraxeloma cyanipennis Kraatz is a restored combination. Distribution patterns of Megalopodidae largely conform to the breakup of Gondwanaland, with its main clades having particular distributions: Andean-Australian (Palophaginae), Ethiopian (Leucasteini, Sphondyliini, and Macrolophina), Neotropical (Ateledrinae and Megalopodina) and Ethiopian-Oriental-Palaearctic (Temnaspidina the result of a secondary expansion. Zeugophorinae present a worldwide distribution, except for the Neotropical and Andean regions, which may be the result of geodispersal. The findings of the present study also shed light on groups with taxonomic issues, where phylogenetic analyses are strongly needed.

Rapid and efficient mating in mayflies (Ephemeroptera): morphological and reproductive strategies in primitive winged insects.

Mayflies (order Ephemeroptera) are primitive winged insects with a life cycle of aquatic nymphal development until emergence as adults that briefly fly seeking mates. Mayflies have reproductive morphology and strategies promoting efficient copulation and oviposition during the ephemeral terrestrial phase. The anatomy of the reproductive tract in males and females of Thraulodes latinus (Leptophlebiidae) is described in relation to the reproductive behavior of Ephemeroptera. Males have a pair of testes that are degenerate in the preadult life stage (subimago) and a pair of deferent ducts that open directly into the gonopores, without ejaculatory duct and accessory glands that are common in other insects. Adult females have a pair of pectinate ovaries with many mature oocytes, a pair of lateral oviducts, and a common oviduct, but lack spermatheca for storage of sperm and associated glands as in most insects. During mating, the paired deferent ducts of males inject sperm directly into females' lateral oviducts, where mass fertilization occurs. Contraction of the intrinsic muscles of the male's deferent ducts directs and rapidly propels the flow of spermatozoa. Reproductive strategies, such as facultative parthenogenesis in mayflies and associated selective pressures involved in the morphology and reproductive behavior of these insects, are discussed.

Two New Species of the Genus Eucorydia (Blattodea: Corydiidae) from the Nansei Islands in Southwest Japan.

Two new species of the cockroach genus Eucorydia Hebard, 1929 from the Nansei Islands in Southwest Japan were compared to two closely related congeners, Eucorydia yasumatsui Asahina, 1971 and Eucorydia dasytoides (Walker, 1868). Eucorydia donanensis Yanagisawa, Sakamaki, and Shimano sp. nov. from Yonaguni-jima Island was characterized by an overall length of 12.5-14.5 mm in males. The dorsal side of the male abdomen was entirely dark purple and there was an obscure orange band running down the middle of the tegmen. Eucorydia tokaraensis Yanagisawa, Sakamaki, and Shimano sp. nov. was characterized by an overall length of 12.0-13.0 mm in males and a distinct orange band running down the middle of the tegmen. Eucorydia yasumatsui, E. donanensis, E. tokaraensis and the zonata population of E. dasytoides were divided into four lineages in a maximum-likelihood tree generated from a dataset concatenated from five (two nuclear, 28S rRNA, histone H3, and three mitochondrial, COII, 12S rRNA, 16S rRNA) genes. We recognized the three Japanese lineages E. yasumatsui, E. donanensis, and E. tokaraensis as distinct species, which were also supported by the pairwise genetic distances (5.4-7.8%, K2P) of the COI sequences. Morphometric analysis was performed on the genitalia. A principal component analysis plot revealed that the sizes of the genitalia in the three Japanese species were similar to each other and smaller than that of the zonata population of E. dasytoides. The analysis also revealed that the three Japanese species were distinguished from each other by combinations of the sizes of L3 and L7 sclerites and the shape of R2 sclerite, with some overlapping exceptions.

Transgenerational Effects of Di(2-Ethylhexyl) Phthalate on Anogenital Distance, Sperm Functions and DNA Methylation in Rat Offspring.

Di(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer in the manufacture of polyvinylchloride plastics and has been associated with concerns regarding male reproductive toxicity. In this study, we hypothesized that maternal exposure to DEHP induces transgenerational inheritance of adult-onset adverse reproductive outcomes through the male germline in the F1, F2, and F3 generations of male offspring. Pregnant rats were treated with 5 or 500 mg of DEHP/kg/day through gavage from gestation day 0 to birth. The offspring body weight, anogenital distance (AGD), anogenital index (AGI), sperm count, motility, and DNA fragmentation index (DFI) were measured for all generations. Methyl-CpG binding domain sequencing was performed to analyze sperm DNA methylation status in the F3. DEHP exposure at 500 mg/kg affected AGD, AGI, sperm count, mean DFI, and %DFI in the F1; AGD, sperm count, and mean DFI in the F2; and AGD, AGI, mean DFI, and %DFI in the F3. DEHP exposure at 5 mg/kg affected AGD, AGI, sperm count, and %DFI in the F1; sperm count in the F2; and AGD and AGI in F3. Compared with the control group, 15 and 45 differentially hypermethylated genes were identified in the groups administered 5 mg/kg and 500 mg/kg DEHP, respectively. Moreover, 130 and 6 differentially hypomethylated genes were observed in the groups administered 5 mg/kg and 500 mg/kg DEHP. Overall, these results demonstrated that prenatal exposure to DEHP caused transgenerational epigenetic effects, which may explain the observed phenotypic changes in the male reproductive system.

Individual and synergistic effects of male external genital traits in sexual selection.

Male genital traits exhibit extraordinary interspecific phenotypic variation. This remarkable and general evolutionary trend is widely considered to be the result of sexual selection. However, we still do not have a good understanding of whether or how individual genital traits function in different competitive arenas (episodes of sexual selection), or how different genital traits may interact to influence competitive outcomes. Here, we use an experimental approach based on high-precision laser phenotypic engineering to address these outstanding questions, focusing on three distinct sets of micron-scale external (nonintromittent) genital spines in male Drosophila kikkawai Burla (Diptera: Drosophilidae). Elimination of the large pair of spines on the male secondary claspers sharply reduced male ability to copulate, yet elimination of the other sets of spines on the primary and secondary claspers had no significant effects on copulation probability. Intriguingly, both the large spines on the secondary claspers and the cluster of spines on the primary claspers were found to independently promote male competitive fertilization success. Moreover, when large and small secondary clasper spines were simultaneously shortened in individual males, these males suffered greater reductions in fertilization success relative to males whose traits were altered individually, providing evidence for synergistic effects of external genital traits on fertilization success. Overall, the results are significant in demonstrating that a given genital trait (the large spines on the secondary claspers) can function in different episodes of sexual selection, and distinct genital traits may interact in sexual selection. The results offer an important contribution to evolutionary biology by demonstrating an understudied selective mechanism, operating via subtle trait interactions in a post-insemination context, by which genital traits may be co-evolving.

Material heterogeneity of male genitalia reduces genital damage in a bushcricket during sperm removal behaviour.

Sperm removal behaviour (SRB) is known in many animals, and male genital structures are often involved in the SRB, e.g. rubbing female genitalia vigorously. However, it remains unclear how those male genital structures function properly without severe genital damage during SRB. In the present study, we focused on the bushcricket Metaplastes ornatus and examined the biomechanics of male and female genital structures, involved in their SRB as a model case. During an initial phase of mating, males of this species thrust their subgenital plate with hook-like spurs and many microscopic spines into the female genital chamber. By moving the subgenital plate back-and-forth, males stimulate females, and this stimulation induces the ejection of sperm previously stored in females. We aimed to uncover the mechanics of the interaction between the subgenital plate and genital chamber during SRB. The genital morphology and its material composition were investigated using modern imaging and microscopy techniques. The obtained results showed a pronounced material heterogeneity in the subgenital plate and the genital chamber. The material heterogeneity was completely absent in that of a second bushcricket species, Poecilimon veluchianus, which does not exhibit SRB. Finite element simulations showed that the specific material heterogeneity can redistribute the stress in the subgenital plate of M. ornatus and, thereby, reduces stress concentration during SRB. This may explain why only a few examined males had a broken spur. We suggest that the observed structural features and material heterogeneity in M. ornatus are adaptations to their SRB.

The evolution of the placenta drives a shift in sexual selection in livebearing fish.

The evolution of the placenta from a non-placental ancestor causes a shift of maternal investment from pre- to post-fertilization, creating a venue for parent-offspring conflicts during pregnancy. Theory predicts that the rise of these conflicts should drive a shift from a reliance on pre-copulatory female mate choice to polyandry in conjunction with post-zygotic mechanisms of sexual selection. This hypothesis has not yet been empirically tested. Here we apply comparative methods to test a key prediction of this hypothesis, which is that the evolution of placentation is associated with reduced pre-copulatory female mate choice. We exploit a unique quality of the livebearing fish family Poeciliidae: placentas have repeatedly evolved or been lost, creating diversity among closely related lineages in the presence or absence of placentation. We show that post-zygotic maternal provisioning by means of a placenta is associated with the absence of bright coloration, courtship behaviour and exaggerated ornamental display traits in males. Furthermore, we found that males of placental species have smaller bodies and longer genitalia, which facilitate sneak or coercive mating and, hence, circumvents female choice. Moreover, we demonstrate that post-zygotic maternal provisioning correlates with superfetation, a female reproductive adaptation that may result in polyandry through the formation of temporally overlapping, mixed-paternity litters. Our results suggest that the emergence of prenatal conflict during the evolution of the placenta correlates with a suite of phenotypic and behavioural male traits that is associated with a reduced reliance on pre-copulatory female mate choice.

Anogenital distance as a measure of male competitive ability in Rwenzori Angolan colobus.

Anogenital distance (AGD) is positively correlated to fetal androgen exposure and developmental masculinization in mammals. Independent of overall body size, AGD shows a strong positive correlation with male fertility and in rodents, AGD is a good indicator of male competitive ability and is associated with female choice. We hypothesized that AGD will also predict male competitive ability in non-human primates. To test this, we measured AGD noninvasively with a parallel laser in a wild population of Angolan colobus monkeys (Colobus angolensis ruwenzorii) in Uganda and correlated to it to their social structure. C. angolensis ruwenzorii form a multilevel society with both one-male/multifemale units (OMUs) and multimale/multifemale units (MMUs). We compared AGD in males from five OMUs and six MMUs and related it to their fecal androgen metabolite concentrations, dominance rank and body size, and to the number of females in their unit. Males in OMUs had greater access to females, so were predicted to have longer AGDs, but this was not found. AGD also did not correlate overall with mean fecal androgen metabolites in MMUs. However, AGD was correlated with dominance rank in MMUs, demonstrating that higher-ranking males in these multimale units had longer AGDs. Body size did not show the same relationship with dominance rank, suggesting that male rank was not just a reflection of absolute male size. Our findings indicate that AGD predicts male competitive ability in this species and that it may be a useful correlate throughout the non-human primates. These results also support the idea that prenatal androgen exposure increases the likelihood of the expression of behaviors that maintain high dominance rank.

Examination of jackass (Equus asinus) accessory sex glands by B-mode ultrasound and of testicular artery blood flow by colour pulsed-wave Doppler ultrasound: Correlations with semen production.

The accessory sex glands play a major role in the production of seminal plasma, and testicular artery blood flow seems to strongly influence testicular function. However, very little ultrasound imaging of these organs has been undertaken in donkeys. The present work reports the results of such examinations in five jackasses along the year. The accessory glands were inspected by B-mode ultrasound while the testicular artery blood flow was assessed by colour pulsed-wave Doppler ultrasound. The testicular artery was examined at pampiniform plexus (PPT), supratesticular area (ST) and capsular artery (CA). Values were recorded for the total arterial blood flow (TABF), peak systolic velocity (PSV), end-diastolic velocity (EDV), resistive index (RI), pulsatility index (PI) and time average maximum velocity (TAMV). Semen was obtained and assessed for sperm concentration, viability, abnormalities and motility using a CASA system. The bulbourethral glands, prostate and ductus deferens ampullae were relatively larger than in the stallion. Bulbourethral glands and ampullae sizes were inversely correlated with sperm motility. An reduction in blood flow between the level the PPP and the CA was observed, helping to reduce testis temperature and oxygen pressure. Blood flow at the CA showed the strongest correlation with semen production. PI and RI were positively correlated with the CASA motility variable STR (p = .02, p = .06) and sperm viability (p = .01), while sperm concentration (p = .05) correlated inversely with PSV, EDV, TAMV and TABF. EDV also correlated negatively with the CASA variables VSL, LIN, STR and VAP (p ≤ .05). PI and RI were also negatively correlated with testis length (p = .0093, p = -.0438).

Repeated evolution of asymmetric genitalia and right-sided mating behavior in the Drosophila nannoptera species group.

BACKGROUND: Male genitals have repeatedly evolved left-right asymmetries, and the causes of such evolution remain unclear. The Drosophila nannoptera group contains four species, among which three exhibit left-right asymmetries of distinct genital organs. In the most studied species, Drosophila pachea, males display asymmetric genital lobes and they mate right-sided on top of the female. Copulation position of the other species is unknown. RESULTS: To assess whether the evolution of genital asymmetry could be linked to the evolution of one-sided mating, we examined phallus morphology and copulation position in D. pachea and closely related species. The phallus was found to be symmetric in all investigated species except D. pachea, which displays an asymmetric phallus with a right-sided gonopore, and D. acanthoptera, which harbors an asymmetrically bent phallus. In all examined species, males were found to position themselves symmetrically on top of the female, except in D. pachea and D. nannoptera, where males mated right-sided, in distinctive, species-specific positions. In addition, the copulation duration was found to be increased in the nannoptera group species compared to closely related outgroup species. CONCLUSION: Our study shows that gains, and possibly losses, of asymmetry in genital morphology and mating position have evolved repeatedly in the nannoptera group. Current data does not allow us to conclude whether genital asymmetry has evolved in response to changes in mating position, or vice versa.

Weak premating isolation between Clitarchus stick insect species despite divergent male and female genital morphology.

Documenting natural hybrid systems builds our understanding of mate choice, reproductive isolation and speciation. The stick insect species Clitarchus hookeri and C. tepaki differ in their genital morphology and hybridize along a narrow peninsula in northern New Zealand. We utilize three lines of evidence to understand the role of premating isolation and species boundaries: (a) genetic differentiation using microsatellites and mitochondrial DNA; (b) variation in 3D surface topology of male claspers and 2D morphometrics of female opercular organs; and (c) behavioural reproductive isolation among parental and hybrid populations through mating crosses. The genetic data show introgression between the parental species and formation of a genetically variable hybrid swarm. Similarly, the male and female morphometric data show genital divergence between the parental species as well as increased variation within the hybrid populations. This genital divergence has not resulted in reproductive isolation between species, instead weak perimating isolation has enabled the formation of a hybrid swarm. Behavioural analysis demonstrates that the entire mating process influences the degree of reproductive isolation between species undergoing secondary contact. Mechanical isolation may appear strong, whereas perimating isolation is weak.