Evolution Of Sperm Morphology Research Articles

Evolution of sperm morphology in a crustacean genus with fertilization inside an open brood pouch

Evolution of sperm morphology in a crustacean genus with fertilization inside an open brood pouch

Evolution of sperm morphology in Daphnia within a phyologenetic context

A recommendation of: Duneau, David; Moest, Markus; Ebert, Dieter Evolution of sperm morphology in a crustacean genus with fertilization inside an open brood pouch. https://doi.org/10.1101/2020.01.31.929414

Sperm morphology and the evolution of intracellular sperm-egg interactions.

Sperm morphology is incredibly diverse, even among closely related species, yet the coevolution between males and females of fertilization recognition systems is necessary for successful karyogamy (male and female pronuclear fusion). In most species, the entire sperm enters the egg during fertilization so sperm morphological diversity may impact the intracellular sperm–egg interactions necessary for karyogamy. We quantified morphological variation of sperm inside eggs prior to and following karyogamy in several species of Drosophila to understand whether evolution of sperm morphology could influence intracellular sperm–egg interactions (ISEIs). We measured seven parameters that describe ISEIs among species to determine whether these parameters varied both within a species across development and across species at the same developmental stage. We used heterospecific crosses to test the relative role of male origin, female origin, and interaction between the male and female in determining ISEIs. We found that sperm shape changed within a species as development proceeded and, at particular development stages, species varied in some ISEIs. Parental origin had an effect on some ISEIs, with a general trend for a stronger female effect. Overall, our findings identify conserved and variable ISEIs among species and demonstrate the potential to contribute understanding to gamete evolution and development.

Differences in sperm morphology in foam‐nesting leptodactyline frogs (Anura, Leptodactylidae)

AbstractSperm morphology is diverse among vertebrates and is influenced by the reproductive strategies adopted by species. In anurans, sperm morphology is associated with reproductive modes and mating systems. Here, we describe the sperm morphology of 11 frog species in the genus Leptodactylus and that of Lithodytes lineatus and discuss the relationship between sperm morphology and species' mating systems. We observed two distinct sperm morphotypes among the leptodactyline species, which differed mostly in head morphology. Type I sperm had triangular head, discrete acrosome vesicle with posterior margin not clearly visible; type II sperm had elongated head, clear acrosomal vesicle with posterior margin clearly visible. These sperm types do not seem to be associated with phylogeny; instead, type II sperm was observed in all polyandrous species analysed and in species with evidences of polyandry. Moreover, sperm of all species presented tail with undulating membrane connected to the axial fibre. We suggest that differences in sperm morphology might be associated with sperm competition to what polyandrous species are subjected. However, natural history observations on polyandrous mating in some species presenting type II sperm and phylogenetic comparative studies are need to elucidate the role of mating systems in the evolution of sperm morphology in leptodactylines.

Evolution of sperm morphology in anurans: insights into the roles of mating system and spawning location.

BackgroundThe degree of postcopulatory sexual selection, comprising variable degrees of sperm competition and cryptic female choice, is an important evolutionary force to influence sperm form and function. Here we investigated the effects of mating system and spawning location on the evolution of sperm morphology in 67 species of Chinese anurans. We also examined how relative testes size as an indicator of the level of sperm competition affected variation in sperm morphology across a subset of 29 species.ResultsWe found a significant association of mating system and spawning location with sperm morphology. However, when removing the effects of body mass or absolute testes mass for species for which such data were available, this effect became non-significant. Consistent with predictions from sperm competition theory, we found a positive correlation between sperm morphology and relative testes size after taking phylogeny into account.ConclusionsOur findings suggest that sexual selection in Chinese anurans favors longer sperm when the level of sperm competition is high. Pre-copulatory male-male competition and spawning location, on the other hand, do not affect the evolution of sperm morphology after taking body mass and absolute testes mass into account.

No Evidence for Pre-Copulatory Sexual Selection on Sperm Length in a Passerine Bird

There is growing evidence that post-copulatory sexual selection, mediated by sperm competition, influences the evolution of sperm phenotypes. Evidence for pre-copulatory sexual selection effects on sperm traits, on the other hand, is rather scarce. A recent paper on the pied flycatcher, Ficedula hypoleuca, reported phenotypic associations between sperm length and two sexually selected male traits, i.e. plumage colour and arrival date, thus invoking pre-copulatory sexual selection for longer sperm. We were unable to replicate these associations with a larger data set from the same and two additional study populations; sperm length was not significantly related to either male plumage colour or arrival date. Furthermore, there was no significant difference in sperm length between populations despite marked differences in male plumage colour. We also found some evidence against the previously held assumption of longer sperm being qualitatively superior; longer sperm swam at the same speed as shorter sperm, but were less able to maintain speed over time. We argue that both empirical evidence and theoretical considerations suggest that the evolution of sperm morphology is not primarily associated with pre-copulatory sexual selection on male secondary sexual traits in this or other passerine bird species. The relatively large between-male variation in sperm length in this species is probably due to relaxed post-copulatory sexual selection.

Quantitative genetic correlation between trait and preference supports a sexually selected sperm process.

Sperm show patterns of rapid and divergent evolution that are characteristic of sexual selection. Sperm competition has been proposed as an important selective agent in the evolution of sperm morphology. However, several comparative analyses have revealed evolutionary associations between sperm length and female reproductive tract morphology that suggest patterns of male-female coevolution. In the dung beetle Onthophagus taurus, males with short sperm have a fertilization advantage that depends on the size of the female's sperm storage organ, the spermatheca; large spermathecae select for short sperm. Sperm length is heritable and is genetically correlated with male condition. Here we report significant additive genetic variation and heritability for spermatheca size and genetic covariance between spermatheca size and sperm length predicted by both the "good-sperm" and "sexy-sperm" models of postcopulatory female preference. Our data thus provide quantitative genetic support for the role of a sexually selected sperm process in the evolutionary divergence of sperm morphology, in much the same manner as precopulatory female preferences drive the evolutionary divergence of male secondary sexual traits.

Male and female effects on sperm precedence in the giant sperm species Drosophila bifurca

Sperm competition is expected to be a driving force in sexual selection. In internally fertilized organisms, it occurs when ejaculates from more than one male are present simultaneously within the female's reproductive tract. It has been suggested that greater sperm size may improve the competitive ability of sperm, but studies provide contradictory results depending on the species. More recently, the role of females in the evolution of sperm morphology has been pointed out. We investigate here the male and female effects that influence sperm precedence in the giant sperm species, Drosophila bifurca Patterson & Wheeler. Females were mated with two successive males, and the paternity outcomes for both males were analyzed after determining sperm transfer and storage. We found very high values of last male sperm precedence, suggesting a strong interaction between rival sperm. However, the data also indicate high frequencies of removal of the sperm of the first male from the female reproductive tract prior to any interaction with the second male. This implies that successful paternity depends mainly on successful sperm storage. Knowing what happens to the sperm within females appears to be a prerequisite for disentangling post-copulatory sexual interactions between males and females.

Variation in paternity in the field cricket Teleogryllus oceanicus: no detectable influence of sperm numbers or sperm length

Recent attention has focused on the role that sperm competition may play in the evolution of sperm morphology. Theoretical analyses predict increased sperm size, decreased sperm size, and no change in sperm size in response to sperm competition, depending on the assumptions made concerning the life history and function of sperm. However, although there is good evidence that sperm morphology varies widely within and between species, the adaptive significance of this variation has not been examined. Here we document significant intraspecific variation in sperm length in the field cricket, Teleogryllus oceanicus. Sperm length did not influence the rate of migration of sperm from the spermatophore to the female's spermatheca. We performed sperm competition trials in which we varied the numbers of sperm transferred by each of two males that differed in the length of sperm they produced. Neither sperm length nor the number of sperm transferred influenced paternity. The same results were obtained using two different methods for assigning paternity. The distribution of paternity across a female's mates was highly variable, with frequently one, or more in the case of females mated to four males, principal sire. There were no mating order effects on paternity. These data show that sperm do not mix randomly in the female's spermatheca. We discuss several alternative explanations for the patterns of paternity observed. Copyright 2003.