In Spiders And Insects
Spiders are often confused with insects, but they are not insects; instead, they are arachnids. Spiders have separate male and female sexes. Before mating and copulation, the male spider spins a small web and ejaculates on to it. He then stores the sperm in reservoirs on his large pedipalps, from which he transfers sperm to the female’s genitals. The females can store sperm indefinitely.
For primitive insects, the male deposits spermatozoa on the substrate, sometimes stored within a special structure; courtship involves inducing the female to take up the sperm package into her genital opening, but there is no actual copulation. In groups that have reproduction similar to spiders, such as dragonflies, males extrude sperm into secondary copulatory structures removed from their genital opening, which are then used to inseminate the female. In dragonflies, it is a set of modified sternites on the second abdominal segment. In advanced groups of insects, the male uses its aedeagus, a structure formed from the terminal segments of the abdomen, to deposit sperm directly into the female’s reproductive tract.
Factors Affecting The Occurrence Of Delaying
Among traits that make delaying beneficial for a male are a low risk of losing copulations and the strong tendency of females to copy each other. Especially the capercaillie shows some ecological aspects that allow these conditions to be fulfilled: 1) the capercaillie holds large display territories which may minimise the risk of sneak copulations; 2) the annual death-rate of adult capercaillies is the lowest among grouse and, thus, the probability that a capercaillie male or his females will die during delaying is probably low as well; 3) the female-biased sex ratio of capercaillie may even increase the possible benefits for a delaying male .
Large display territories within forests may also promote female copying. Limited visibility and audibility make simultaneous comparison of capercaillie males difficult for females, which may hinder and prolong their selection of a male. If the choice is difficult, earlier experience will be valuable, and without it , copying other females may be the best coping mechanism .
Resistance And Tolerance As Separate Defense Strategies
Different outcomes of evolutionary conflicts occur depending on whether the offended party responds by resistance or tolerance . The same seems true for sexual conflict and CW research and we explicitly recommend making this distinction . Resistance is a defense strategy that causes costs to the offending party and therefore represents a selection pressure that induces coevolution. Tolerance does not impose costs on the offending party and may instead, perhaps more strongly, select for evolutionary novelties. As an example, consider the female response to piercing of the vaginal tissue. Females may respond by thickening the connective tissue, which may give males a reduced anchorage and so may reduce their fitness. Alternatively, females may instead accelerate resource allocation to rapid wound healing. Female wound healing does not impose costs on males and so may not represent resistance.
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Frequency And Timing Of Cloacal Kissing
Copulation frequency varies greatly among species. For example, European magpies only copulate about 3 times per clutch while goshawks copulate up to 600 times . In Japanese quail , multiple copulations appear necessary to ensure fertilisation, as a single copulation is usually not sufficient to fertilise a complete clutch . However, several hundred copulations seem overly excessive to ensure fertilisation in species such as the goshawk, and instead, high rates of copulation appear related to the risk of sperm competition, with species with a greater risk of promiscuity exhibiting higher rates of copulation. When risk of sperm competition is high, more frequent copulations may allow the male to dilute or displace the sperm of rival males and thus increase his own reproductive success .
Copulations by cloacal kissing show distinctive diurnal and seasonal patterns. In aquatic warblers, copulations were most frequent in morning or late evening . A similar diurnal pattern was observed in Smiths longspurs , with 57 copulations/h during the morning but almost 0 copulations/h during the afternoon, before increasing to about 3 copulations/hour in the evening . This diurnal pattern is typical of most birds . As ovulation occurs in the morning in most birds, copulations early in the day may be timed to coincide with the short window after ovulation in which an egg can be fertilised.
Patricia A. Gowaty, in, 2019
Nonconsensual Sex Forced Sex And Rape
In cases of rape and nonconsensual sex, injuries to the victim are common . Nonconsensual sex was found to result in much, moderately, or not significantly more female genital injuries compared with consensual sex . However, the lack of a classification scheme of female genital injuries until recently and the occurrence of genital wounds after consensual sex made a recent review conclude that the presence or absence of genital injury should not be used to render an opinion regarding consent to sexual intercourse . We do not discuss this topic in more detail as such cases usually represent situations in which human males use sex as a weapon . Although sperm transfer is involved in a large number of rape cases we, unlike some investigators, consider such cases as generically, rather than reproductively, aggressive male behavior . The limited relevance to applying sexual conflict theory is, among others, apparent from the fact that many victims are outside reproductive age .
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Outlook And Future Research In Cw
The study of CW has gained momentum, especially in sexual conflict research. Below, we propose that CW is probably still grossly underreported. Getting a more complete picture of the taxonomic distribution and abundance of CW is an important task for future research. However, we also wish to emphasize that some of the existing data already indicate that the study of CW may provide exceptional contributions to some areas of evolutionary biology.
Which Sex Causes Cw
Because of the different fitness optima for mating traits , males and females experience different selection pressures and it will often be important to identify which sex inflicts the copulatory trauma. Although it is usually males that have specific wounding organs , it may be worth pointing out a number of circumstances under which it is difficult to predict which sex inflicts the wound.
Consider a male whose copulatory organ does not inflict a genital wound in most female phenotypes, but does so in females that show unusual movement during copulation. Here, the mismatch causing CW arose from a behavioral deviation in the female. The term wound inflictor can therefore be ambiguous. In species in which CW is rare, such ambiguity can be circumvented by classifying whether it is the male or female that departs from the sex-specific morphological or behavioral population mean . However, even this approach is not free from anthropomorphic judgment because it may be the male that induces the behavioral deviation in the female. In species in which CW occurs routinely, the ancestral state of male and female morphology or behavior may be predicted from related species.
The same considerations apply to cases in which the male intromittent organ is injured during copulation. This situation may be self-inflicted, but may also arise from female resistance behavior or morphology and, hence, not be self-inflicted.
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Sexual Conflict And The Evolution Of Traumatic Mating
The physiological demands and their life-history consequences induced by CW will carry fitness costs and affect evolutionary change if CW varies among wound inflictors and recipients, and if characters affecting CW are heritable . Similar to the success of any new mutation in a population, the initial occurrence of CW may be beneficial, neutral, or deleterious to either wound inflictor or recipient, and so will persist or disappear. Details of the costs and benefits of CW have extensively been discussed elsewhere . Here, we only briefly consider scenarios that occur under sexual conflict, that is, when only one sex, but not the other, incurs fitness costs. This includes a new hypothesis on facilitated transfer of STDs.
Flow diagram highlighting CW as a signature of sexual conflict. Several outcomes of sexual conflict are possible, including male and female genital exaggeration, male and genital female simplification, and, across populations, male and female genital diversity. The complete disappearance of CW is also possible. As not all genital characters under selection may respond in the same way, CW may also contribute to the evolution of genital complexity.
Selection for Traumatic Penetration from Accidental CW
Selection for TI and TST from Accidental Transfer of Sperm and Seminal Fluids
Selection for the Transfer of STDs in the Wound Inflictor
Sex Organs In Male And Female:
The role of the reproductive system of the male is to
1. Produce sperms
2. Deliver these sperms in the vagina that is the reproductive tract of the female
The important organs of the male reproductive system are the prostate, penis, scrotum, testes, epididymis, seminal vesicles, and vas deferens. The penis and the urethra are also a part of the urinary system in males.
The production of the sperms is known as spermatogenesis. Sperms are produced in the testes. The testis comprises of the seminiferous tubules where the process of spermatogenesis takes place. They get divided by the process of mitosis & produce more spermatogonia. This spermatogonium is differentiated into spermatocytes. In the next step, each spermatocyte forms four spermatids that are haploids by the virtue of meiosis. This process require three weeks to complete. The spermatids are differentiated into sperm. They lack most of their cytoplasm.
The sperm cells have nuclei in the flagellum. This helps them to be motile & travel to the vagina & then to the uterus. Each sperm comprises a head, a midpiece, and a tail.
1. The head of the sperm has
An acrosome at its end. An acrosome is a degenerative enzyme that dissolves the zona pellucida of the ovum to integrate with the haploid sperm.
A haploid set of chromosomes is present in an inactive and compact state.
2. A midpiece with mitochondria and a single centriole
3. A tail that is a flagellum that allows motility to the sperm
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Reproductive System Of Earthworm
Earthworms are known as farmers friends. They have a cylindrical shape metamerically segmented body. They are reddish-brown in colour. Dorsal side is characterized by a dark line of blood vessels and the ventral side is characterized by the genital openings. The body consists of S-shaped setae, which help in locomotion.
Defensive Adaptations And Variation In Cw
Wound inflictors and recipients coevolve like other parties in evolutionary conflicts . This causes costs and benefits of CW, TI, and TST to vary over evolutionary time, and generates several predictions.
Low Costs of CW over Most of Evolutionary Time
Females will often carry large costs of CW and are expected to adapt very rapidly. As a consequence, the observable costs of CW may be low over much of evolutionary time and, hence, in many study systems . Therefore, the costs of mating in species with TM may not, generally, be expected to be higher than in species without TM or other forms of CW . This can be tested by comparing female fitness in response to mating rates in species with CW and other species . Following the approach by , we measured the response rate of two fitness proxies to elevated mating rates for both species groups. Response ratios >1 indicate benefits, response ratios <1 indicate costs.
Distribution of response ratios illustrating positive or negative effects of enhanced mating frequencies on female egg production. All species refers to all species listed by . They are compared with species showing CW . Original data for the CW species and definitions of the three experimental types are given in .
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Rearing Of Flies For Experiments
To generate a range of phenotypic body sizes, we provided stock cultures of each population pots with different amounts of cow dung and allowed for oviposition overnight. We transferred these pots into another container and reared them under the above-mentioned standard conditions. After approximately 2;weeks of juvenile development, we sexed emerging flies individually under a microscope within 24;h of eclosion and subsequently housed virgin males and females in separate containers.
The Nature Of The Physiological Costs
Once the copulatory trauma is inflicted, one or several immediate effects can occur in the wounded individual: blood loss, the entry of microbes, and the entry of other nonself particles. These effects and subsequent defensive responses have been discussed earlier and are only briefly considered here.
Preventing Blood Loss
The activation of repair cascades, the transport of cells to a wound, and wound closure are ubiquitous among vertebrates and common among invertebrates . Although the process of wound healing after CW is almost unstudied, we, here, assume it is similar to general wound healing.
Preventing Microbial Infection
After CW, external male or female surface-dwelling or sexually transmitted microbes may enter the wound . This elicits a series of responses. For example, in insects, blood clots are formed and prevent systemic infection . After clotting, the next line of defense is the activation of local and systemic immune cascades . It is important to note that genital infections, at least in males, cause systemic responses and sepsis much more often than infection through other tissues .
Responses toward other Non-Self Particles
Other non-self objects, such as blood and sperm cells, seminal fluid molecules, or particles from the environment, may also elicit clotting or immune responses. Immune responses toward male ejaculate proteins occur widely and seem particularly energy intense .
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How Sexual Selection Came To Be Recognized
Charles Darwin proposed that all living species were derived from common ancestors. The primary mechanism he proposed to explain this fact was natural selection: that is, that organisms better adapted to their environment would benefit from higher rates of survival than those less well equipped to do so. However he noted that there were many examples of elaborate, and apparently non-adaptive, sexual traits that would clearly not aid in the survival of their bearers. He suggested that such traits might evolve if they are sexually selected, that is if they increase the individual’s reproductive success, even at the expense of their survival . Darwin noted that sexual selection depends on the struggle between males to access females. He recognized two mechanisms of sexual selection: intrasexual selection, or competition between members of the same sex for access to mates, and intersexual selection, where members of one sex choose members of the opposite sex. The idea of cumbersome traits evolving to aid males in competition during aggressive encounters was readily accepted by scientists shortly after Darwin’s publication. However, the idea of female mate choice was received with ridicule, and was not seriously reconsidered until nearly 80 years later . In the 40 years since, there has been much progress in our understanding of how sexual selection operates.
References And Recommended Reading
Bateman, A. J. Inter-sexual selection inDrosophila. Heredity2, 349-368 .
Birkhead, T. R. & Moller, A. P. Sperm Competition and Sexual Selection. San Diego, CA: Academic Press, 1998.
Calhim, S. & Birkhead, T. R. Testessize in birds: quality versus quantity assumptions, errors and estimates. Behavioral Ecology18, 271-275 .
Chapman, T., Arnqvist, G. et al. Sexual conflict. Trends in Ecology and Evolution3, 41-47 .
Clutton-Brock, T. H. & Parker, G. A.Sexual coercion in animal societies. AnimalBehavior49, 1345-1365 .
Cronin, H. The Ant and the Peacock. Cambridge, UK: Cambridge UniversityPress, 1991.
Darwin, C. TheDescent of Man, and Selection in Relation to Sex. London,UK: Murray, 1871.
Eberhard, W. Female Control: Sexual Selection by Cryptic Female Choice. Princeton, NJ: Princeton UniversityPress, 1996.
Emlen, D. J. The Evolution ofAnimal Weapons. Annual Review of Ecology, Systematics,and Evolution39, 387-413.
Fisher, R. A. The Genetical Theory of Natural Selection. Oxford, UK:Clarendon Press, 1930.
Hamilton, W. D. & Zuk, M. Heritabletrue fitness and bright birds: a role for parasites? Science218, 384-387.
Keller, L. & Reeve, H. K. Why do femalesmate with multiple males? The sexually selected sperm hypothesis. Advanced Studies in Behavior, 24, 291-315 .
Kirkpatrick, M. Sexual selection and theevolution of female choice. Evolution82, 1-12 .
Lande, R. Models of speciation by sexualselection on polygenic traits. Proceedingsof the National Academy of Sciences, USA78, 3721-3725 .
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Occurrence Of Delayed Copulation In Capercaillie And Other Species
Ignoring soliciting females seems to be quite common also in other capercaillie leks . Some mornings no mating takes place at all, even though numerous, frequently squatting females gather around a male . Apparently, the same willing females seem to return to the same male the next morning . It is unclear how long this kind of behaviour may last, but females have been observed to offer themselves for up to four hours during one morning without result . After delaying, the male may eventually mate with either a few of the squatting females or with all of them successively .
The capercaillie is not the only species where males have been observed to ignore soliciting females. The same kind of behaviour has been observed in lekking sage grouse and great bustards, Otis tarda . The reason for this behaviour, however, is unknown.
Cw And Reproductive Isolation
CW as a Barrier against Hybridization between Species
Almost universally, genitalia differ between species. Therefore, in cross-species mating attempts, mismatches between male and female morphology and copulatory behavior will be larger in inter- than in intraspecific pairings, and fitness costs will likely be higher. In this case, CW would represent a barrier against hybridization. Empirical examples have confirmed such barrier function. In ground beetles and Drosophila , interspecific matings resulted in more severe CW than intraspecific mating crosses, but in both cases, asymmetrically in only one direction. Remarkably, the risk of foreign, bacteria-sized particles to invade the copulatory wound was increased in both interspecific pairings . This points toward the possibility that infection, in addition to CW itself, may generate a hybridization barrier. For traumatically inseminating plant bugs, speculated that the interspecific morphological genitalia variation also has evolved by selection against hybridization .
CW as an Isolating Factor in Reproductive Isolation
Consistent interpopulation differences in CW may also drive evolutionary variation in wound healing, but no data exist on healing differences between populations.
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