Effects of ovarian fluid on sperm traits and its implications for cryptic female choice in zebrafish

In polyandrous mating systems, females maintain the opportunity to bias male fertilization success after mating in a process known as cryptic female choice. Mechanisms of cryptic female choice have been described both in internal and external fertilizers, and may affect fertilization processes at different stages before, during, and after fertilization. In internal fertilizers, females have substantial control over sperm storage and fertilization, whereas in external fertilizers, female control is limited. A key factor proposed to mediate cryptic female choice is the fluid surrounding the eggs, the ovarian fluid, as it may directly affect sperm performance. Here, we studied the role of ovarian fluid in post-mating sexual selection using the zebrafish, Danio rerio. Firstly, we assessed how ovarian fluid affects sperm swimming performance compared with freshwater. We focused on sperm motility, velocity, swimming trajectory, and longevity, all traits associated with competitive fertilization success in externally fertilizing fish. In a second step, we used a North Carolina II design to explore female, male, and female x male effects by testing sperm motility of 2 males in the ovarian fluid of 2 females in a total of 11 blocks. Our results indicate that the ovarian fluid affects sperm performance differently from freshwater. Specifically, sperm velocity, motility, and longevity were higher in the ovarian fluid than in freshwater, whereas sperm linearity and beat cross frequency showed the opposite pattern. Moreover, these effects varied according to male, female, and male x female identities, supporting the potential for cryptic female choice mediated by ovarian fluid in this species

Male Genital Morphology and Its Influence on Female Mating Preferences and Paternity Success in Guppies

In internally fertilizing species male genitalia often show a higher degree of elaboration than required for simply transferring sperm to females. Among the hypotheses proposed to explain such diversity, sexual selection has received the most empirical support, with studies revealing that genital morphology can be targeted by both pre-and postcopulatory sexual selection. Until now, most studies have focused on these two episodes of selection independently. Here, we take an alternative approach by considering both components simultaneously in the livebearing fish, Poecilia reticulata. We allowed females to mate successively (and cooperatively) with two males and determined whether male genital length influenced the female's propensity to mate with a male (precopulatory selection, via female choice) and whether male genital size and shape predicted the relative paternity share of subsequent broods (postcopulatory selection, via sperm competition/cryptic female choice). We found no evidence that either episode of sexual selection targets male genital size or shape. These findings, in conjunction with our recent work exposing a role of genital morphology in mediating unsolicited (forced) matings in guppies, further supports our prior speculation that sexual conflict may be an important broker of genital evolution in this species

Possible glimpses into early speciation: the effect of ovarian fluid on sperm velocity accords with post-copulatory isolation between two guppy populations.

Identifying mechanisms of reproductive isolation is key to understanding speciation. Among the putative mechanisms underlying reproductive isolation, sperm-female interactions (postmating-prezygotic barriers) are arguably the hardest to identify, not least because these are likely to operate at the cellular or molecular level. Yet sperm-female interactions offer great potential to prevent the transfer of genetic information between different populations at the initial stages of speciation. Here we provide a preliminary test for the presence of a putative postmating-prezygotic barrier operating between three populations of Trinidadian guppies (Poecilia reticulata), an internally fertilizing fish that inhabits streams with different levels of connectivity across Trinidad. We experimentally evaluate the effect of female ovarian fluid on sperm velocity (a predictor of competitive fertilization success) according to whether males and females were from the same (native) or different (foreign) populations. Our results reveal the potential for ovarian fluid to act as a postmating-prezygotic barrier between two populations from different drainages, but also that the strength of this barrier is different among populations. This result may explain the previous finding that, in some populations, sperm from native males have precedence over foreign sperm, which could eventually lead to reproductive isolation between these populations. This article is protected by copyright. All rights reserved

I.S.Mu.L.T. Achilles Tendon Ruptures Guidelines

This work provides easily accessible guidelines for the diagnosis, treatment and rehabilitation of Achilles tendon ruptures. These guidelines could be considered as recommendations for good clinical practice developed through a process of systematic review of the literature and expert opinion, to improve the quality of care for the individual patient and rationalize the use of resources. This work is divided into two sessions: 1) questions about hot topics; 2) answers to the questions following Evidence Based Medicine principles. Despite the frequency of the pathology andthe high level of satisfaction achieved in treatment of Achilles tendon ruptures, a global consensus is lacking. In fact, there is not a uniform treatment and rehabilitation protocol used for Achilles tendon ruptures

Postmating Female Control: 20 Years of Cryptic Female Choice

Cryptic female choice (CFC) represents postmating intersexual selection arising from female-driven mechanisms at or after mating that bias sperm use and impact male paternity share. Although biologists began to study CFC relatively late, largely spurred by Eberhard's book published 20 years ago, the field has grown rapidly since then. Here, we review empirical progress to show that numerous female processes offer potential for CFC, from mating through to fertilization, although seldom has CFC been clearly demonstrated. We then evaluate functional implications, and argue that, under some conditions, CFC might have repercussions for female fitness, sexual conflict, and intersexual coevolution, with ramifications for related evolutionary phenomena, such as speciation. We conclude by identifying directions for future research in this rapidly growing field

A systematic map of studies testing the relationship between temperature and animal reproduction

Funding: This work was funded by the European Society for Evolution (which funds a Special Topic Network on Evolutionary Ecology of Thermal Fertility Limits to CF, AB, RRS and TARP), the Natural Environment Research Council (NE/P002692/1 to TARP, AB and RRS, NE/X011550/1 to LRD and TARP), the Biotechnology and \Biological Sciences Research Council (BB/W016753/1 to AB, TARP and RRS) and a Heisenberg fellowship from the German Research Foundation (FR 2973/11-1 to CF).1. Exposure to extreme temperatures can negatively affect animal reproduction, by disrupting the ability of individuals to produce any offspring (fertility), or the number of offspring produced by fertile individuals (fecundity). This has important ecological consequences, because reproduction is the ultimate measure of population fitness: a reduction in reproductive output lowers the population growth rate and increases the extinction risk. Despite this importance, there have been no large‐scale summaries of the evidence for effect of temperature on reproduction. 2. We provide a systematic map of studies testing the relationship between temperature and animal reproduction. We systematically searched for published studies that statistically test for a direct link between temperature and animal reproduction, in terms of fertility, fecundity or indirect measures of reproductive potential (gamete and gonad traits). 3. Overall, we collated a large and rich evidence base, with 1654 papers that met our inclusion criteria, encompassing 1191 species. 4. The map revealed several important research gaps. Insects made up almost half of the dataset, but reptiles and amphibians were uncommon, as were non‐arthropod invertebrates. Fecundity was the most common reproductive trait examined, and relatively few studies measured fertility. It was uncommon for experimental studies to test exposure of different life stages, exposure to short‐term heat or cold shock, exposure to temperature fluctuations, or to independently assess male and female effects. Studies were most often published in journals focusing on entomology and pest control, ecology and evolution, aquaculture and fisheries science, and marine biology. Finally, while individuals were sampled from every continent, there was a strong sampling bias towards mid‐latitudes in the Northern Hemisphere, such that the tropics and polar regions are less well sampled. 5. This map reveals a rich literature of studies testing the relationship between temperature and animal reproduction, but also uncovers substantial missing treatment of taxa, traits, and thermal regimes. This database will provide a valuable resource for future quantitative meta‐analyses, and direct future studies aiming to fill identified gaps.Publisher PDFPeer reviewe

Sperm Swimming Velocity Predicts Competitive Fertilization Success in the Green Swordtail Xiphophorus helleri

Sperm competition is expected to favour the evolution of traits that influence the performance of sperm when they compete to fertilize a female's eggs. While there is considerable evidence that selection favours increases in sperm numbers, much less is known about how sperm quality contributes towards competitive fertilization success. Here, we determine whether variation in sperm quality influences competitive fertilization success in the green swordtail Xiphophorus helleri, a highly promiscuous livebearing fish. We use artificial insemination as a method of controlled sperm delivery and show that sperm swimming velocity is the primary determinant of fertilization success when ejaculates from two males compete to fertilize a female's eggs. By contrast, we found no evidence that sperm length had any effect on siring success. We also found no evidence that pre- and postcopulatory sexual traits were phenotypically integrated in this species, suggesting that the previous observation that reproductive skew favours males with high mating rates is unlikely to be due to any direct association between sperm quality and male sexual ornamentation

A systematic map of studies testing the relationship between temperature and animal reproduction

DATA AVAILABILITY STATEMENT ; All data are available on Figshare: https://doi.org/10.6084/m9.figshare.24182745.v1 (Dougherty et al., 2023).SUPPORTING INFORMATION : FIGURE S1: Phylogenetic tree showing the relationship between the 1191 species in the systematic map. Note that branch lengths are standardised because branch length information was not available.Exposure to extreme temperatures can negatively affect animal reproduction, by disrupting the ability of individuals to produce any offspring (fertility), or the number of offspring produced by fertile individuals (fecundity). This has important ecological consequences, because reproduction is the ultimate measure of population fitness: a reduction in reproductive output lowers the population growth rate and increases the extinction risk. Despite this importance, there have been no large-scale summaries of the evidence for effect of temperature on reproduction. We provide a systematic map of studies testing the relationship between temperature and animal reproduction. We systematically searched for published studies that statistically test for a direct link between temperature and animal reproduction, in terms of fertility, fecundity or indirect measures of reproductive potential (gamete and gonad traits). Overall, we collated a large and rich evidence base, with 1654 papers that met our inclusion criteria, encompassing 1191 species. The map revealed several important research gaps. Insects made up almost half of the dataset, but reptiles and amphibians were uncommon, as were non-arthropod invertebrates. Fecundity was the most common reproductive trait examined, and relatively few studies measured fertility. It was uncommon for experimental studies to test exposure of different life stages, exposure to short-term heat or cold shock, exposure to temperature fluctuations, or to independently assess male and female effects. Studies were most often published in journals focusing on entomology and pest control, ecology and evolution, aquaculture and fisheries science, and marine biology. Finally, while individuals were sampled from every continent, there was a strong sampling bias towards mid-latitudes in the Northern Hemisphere, such that the tropics and polar regions are less well sampled. This map reveals a rich literature of studies testing the relationship between temperature and animal reproduction, but also uncovers substantial missing treatment of taxa, traits, and thermal regimes. This database will provide a valuable resource for future quantitative meta-analyses, and direct future studies aiming to fill identified gaps.Deutsche Forschungsgemeinschaft; Natural Environment Research Council; European Society for Evolutionary Biology; Biotechnology and Biological Sciences Research Council.http://www.wileyonlinelibrary.com/journal/eso3hj2024Zoology and EntomologySDG-03:Good heatlh and well-bein

Sexual conflict in the guppy, Poecilia reticulata

Sexual conflict is a widespread phenomenon in nature and it occurs over a wide range of decisions involving female-male interactions. This conflict drives the evolution of sexually antagonistic traits. Under a sexual conflict scenario, a trait that is beneficial to one sex is detrimental to the other driving the evolution of counteradaptation in a sort of ‘arm race’. In this process every evolutionary change in one sex is followed by a change in the opposite sex in order to minimize costs associated to the former. Mating frequency is one of the aspects of reproduction that could especially fuel sexual conflict and consequently sexually antagonistic coevolution because generally males have an optimal mating rate higher than females. My PhD thesis is aimed to study different aspects of sexual conflict using a small livebearing fish, Poecilia reticulata, as a model system. This species is particularly suitable for this purpose since sexual conflict is evident over mating rate, as revealed doubtless from the presence of high level of sexual harassment. I divided my researches into two main trends. First, I investigated costs and benefits of sexual conflict. Second, I focused on sexually antagonistic coevolution. Costs and benefits of sexual conflict. Estimate costs and benefits of sexual conflict shed new light on the evolution of female resistance that is assumed to evolve to minimize the costs associated to superfluous matings. However, a recent hypothesis argues that female resistance evolves as a way to screen the more successful male and therefore operate via indirect benefits mechanism. Results from a study of the effects of sexual harassment on female’s lifetime fecundity and on offspring’s quality revealed that do not support this latter hypothesis. I demonstrated only costs of sexual harassment on offspring both in daughters and in sons. Moreover, study on heritability of males’ traits influencing reproductive success both at pre- and postcopulatory level revealed scarce sire heritability that instead is a fundamental assumption of the hypothesis. The low heritability for males’ traits may be explained by adaptive phenotypic plasticity that has been investigated for sperm velocity. This demonstrated an adjustment in sperm velocity by males according to mating opportunities. Sexually antagonistic coevolution. My study of sexually antagonistic coevolution focuses on genitalia (male gonopodium and female oviduct). Gonopodial shape and dimension result important factors in determining the outcome of both consensual and coercive mating. Gonopodial length and shape resulted to be under sexual selection by female premating choice, with females mate more quickly with males possessing longer gonopodia with an enlarged shape. Gonopodium tip shape is revealed to be important in sperm transfer both in consensual and in forced matings. Another experiment demonstrated that females from low conflict population have minor control over sperm transfer in forced copulations by high conflict population males than relative counterparts. This result highlights the importance of male-female antagonistic coevolution in a sexual conflict scenario. An intraspecific study at population level corroborates this conclusion by providing evidence for a coevolutionary pattern between male and female concerning genitalia morphology. For this reason, genitalia might be the result of an evolutionary arm race between males and females in the struggle for control over mating rate and insemination success.Il conflitto sessuale è un fenomeno ubiquitario in natura e interessa molte delle interazioni maschio-femmina portando alla evoluzione di caratteristiche sessuali antagonistiche. Per definizione, nel conflitto sessuale una caratteristica che avvantaggia un sesso comporta dei costi per l’altro sesso, per cui di conseguenza in quest’ultimo viene favorita la comparsa di controadattamenti in una sorta di ‘corsa agli armamenti’, in cui ogni cambiamento evoluzionistico che appare in un sesso è seguito da un cambiamento nell’altro sesso volto a minimizzarne i costi. La frequenza degli accoppiamenti è uno degli aspetti cruciali in cui il conflitto sessuale si manifesta e porta alla selezione sessuale antagonistica perché in generale i maschi hanno una frequenza ottimale di accoppiamenti che è maggiore di quella delle femmine. La mia tesi di dottorato ha avuto lo scopo di studiare alcuni aspetti del conflitto sessuale utilizzando Poecilia reticulata come modello di studio. Questa specie è particolarmente adatta per lo studio di queste tematiche, dal momento che è evidente la presenza del conflitto sessuale per quanto riguarda il numero di accoppiamenti, come si evince chiaramente dall’alto livello di sexual harassment (i continui tentativi di copula da parte dei maschi) subito dalle femmine. Le ricerche che ho effettuato per la mia tesi di dottorato si possono suddividere in due filoni. Primo: costi e benefici del conflitto sessuale. Secondo: coevoluzione sessuale antagonistica. Costi e benefici del conflitto sessuale. Studiare costi e benefici legati al conflitto sessuale è importante per capire l’evoluzione della resistenza femminile che si assume si sia evoluta con lo scopo di ridurre i costi legati agli accoppiamenti superflui. Di recente tuttavia si è avanzata l’ipotesi che la resistenza evolva attraverso il meccanismo dei benefici indiretti ottenuti selezionando i maschi più persistenti. Il primo lavoro ha riguardato lo studio degli effetti del sexual harassment sulla fecondità life-time delle femmine, ma anche degli effetti sulla prole. I risultati indicano che il costo del sexual harassment è visibile sulla prole, sia nei maschi che nelle femmine. Questi risultati non supportano perciò l’ipotesi che la resistenza femminile evolva attraverso l’acquisizione di benefici indiretti. Inoltre lo studio sull’ereditabilità di tratti maschili legati al successo riproduttivo ha dimostrato che tali caratteristiche sono poco ereditabili per via paterna, presupposto essenziale per questa ipotesi. La plasticità adattativa dei caratteri ne può spiegare la scarsa ereditabilità paterna riscontrata. Ho testato questa possibilità per un tratto legato al successo riproduttivo, la velocità spermatica, a seconda delle opportunità di accoppiamento percepite dal maschio. Si è dimostrato che i maschi sono in grado di modulare la velocità spermatica, confermando perciò la possibilità di un certo grado di plasticità che può spiegare i bassi valori di ereditabilità. Coevoluzione sessuale antagonistica. Lo studio della coevoluzione sessuale antagonistica si è concentrato sulla morfologia dei genitali, sia maschili che femminili. I risultati indicano che la morfologia dell’organo copulatore influenza il successo nel maschio sia negli accoppiamenti cooperativi che in quelli forzati. In particolare la dimensione e la forma generale dell’organo copulatore sono sessualmente selezionati attraverso la scelta femminile, e le femmine si accoppiano più velocemente con maschi dotati di gonopodi più lunghi e di forma allargata. Anche la forma della parte più distale del gonopodio risulta importante nel determinare il trasferimento degli spermi. La coevoluzione sessuale antagonistica prevede che quando una caratteristica modellata dal conflitto sessuale differisce tra popolazioni diverse, le femmine siano più resistenti ai maschi della propria popolazione, con cui si sono coevolute, rispetto a quelli di popolazioni diverse contro cui esse non hanno gli adattamenti necessari per resistere ad accoppiamenti non voluti. Questa previsione è stata confermata attraverso uno studio su maschi e femmine di popolazioni a diverso conflitto sessuale, in cui è stato dimostrato che femmine poste con maschi provenienti da una popolazione con un maggiore grado di conflitto sessuale hanno un minor controllo sul trasferimento degli spermi, rispetto a femmine che hanno avuto la possibilità di coevolvere con tali maschi. Infine uno studio comparativo fra popolazioni diverse indica l’esistenza di coevoluzione tra genitali maschili e femminili, che varia a seconda del grado di conflitto sessuale a cui le popolazioni sono soggette. Per cui l’evoluzione dei genitali sembra essere il risultato di una corsa agli armamenti tra maschi e femmine per il controllo della frequenza degli accoppiamenti e del successo di inseminazione

Experiment III

Experiment III (male coloration and aggressive behaviour