Female sperm use and storage between fertilization events drive sperm competition and male ejaculate allocation

Sperm competition theory has traditionally focused on how male allocation responds to female promiscuity, when males compete to fertilize a single clutch of eggs. Here, we develop a model to ask how female sperm use and storage across consecutive reproductive events affect male ejaculate allocation and patterns of mating and paternity. In our model, sperm use (a single parameter under female control) is the main determinant of sperm competition, which alters the effect of female promiscuity on male success and, ultimately, male reproductive allocation. Our theory reproduces the general pattern predicted by existing theory that increased sperm competition favors increased allocation to ejaculates. However, our model predicts a negative correlation between male ejaculate allocation and female promiscuity, challenging the generality of a prevailing expectation of sperm competition theory. Early models assumed that the energetic costs of precopulatory competition and the level of sperm competition are both determined by female promiscuity, which leads to an assumed covariation between these two processes. By modeling precopulatory costs and sperm competition independently, our theoretical framework allows us to examine how male allocation should respond independently to variation in sperm competition and energetic trade‐offs in mating systems that have been overlooked in the past.     

Postthaw survival of rhesus macaque sperm: variation in the response of individual males to different freezing protocols

This study was designed to assess the effects of various cryopreservation protocols on the postthaw survival of rhesus macaque sperm. Multiple ejaculates of five mature males were collected and frozen by each of four different methods. Cryopreservation significantly reduced motility in all samples, regardless of the method, and the response of different ejaculates of the same male to each method proved to be consistent. The freezing method was a significant factor in determining the immediate postthaw motility, although this effect disappeared after 4 hr. Moreover, there was a significant interaction between individual males and freezing method suggesting that developing a single freezing protocol that is universally suitable may be difficult.     

Corazonin reduces the spinning rate in the silkworm,Bombyx mori

The insect neuropeptide, [Arg⁷]-corazonin was injected into larvae of the silkworm, Bombyx mori to investigate its influence on development and behavior. A single injection of 50 pmol of corazonin into the fourth and fifth instar larvae induced prolongation of the spinning period in all experimental groups except for those injected on day 10 of the fifth instar. The injection also caused a prolongation of the pupal period in some experimental groups, while it had no effect on the timing of larval ecdysis and the length of feeding period of the fifth instar. The spinning period was significantly prolonged even at a low dose of 1 pmol. Both the spinning rate and the rate of increase in hemolymph ecdysteroid level during the spinning stage were reduced by injection of corazonin. However, corazonin injection during days 5-7 of the fifth instar reduced the spinning rate without influencing the ecdysteroid level until the end of day 8, thereafter the rate of increase in hemolymph ecdysteroid level was slower in the corazonin-injected larvae than in the control larvae. Therefore, the suppressed ecdysteroid level observed in the corazonin-injected larvae appears to be a result rather than a cause of the reduced spinning rate. This study is the first published report for the corazonin effect on the behavior in insects.     

Reproductive and Developmental Toxicity of Orally Administered Botanical Composition,UP446‐Part III: Effects on Fertility and Early Embryonic Development to Implantation in Sprague Dawley Rats

In recent years, high prevalence of adverse effects associated to the use of traditional medicines during pregnancy is becoming alarming due to the self‐medication of oral supplements by expecting mothers without supervision. Many expectant mothers use alternative and complementary medicines as a supplement to conventional pregnancy management with an inherent belief of considering herbal remedies as harmless. To the contrary, herbal remedies could incur a potential teratogenic risk both to the child bearing mother and the developing fetuses when consumed before or at the time of gestation. Here, we describe the potential adverse effects of orally administered UP446, a standardized bioflavonoid composition from the roots of Scutellaria baicalensis and the heartwoods of Acacia catechu, on fertility and early embryonic development to implantation in Sprague Dawley rats at doses of 250, 500, and 1000 mg/kg. Besides body weight and food consumption, reproductive functions, sperm motility and morphology, estrus cycle, and fertility rate were monitored. There were no statistically significant differences in reproductive function in all UP446 treated groups in both genders. Test substance impacts on reproductive parameters were very minimal. Neither sperm motility nor morphology was affected as a result of oral UP446 administrations in males. There were no treatment‐related effects on estrus cycle stages in females. No significant changes in necropsy or histopathology were observed for all the groups. Therefore, the no observed adverse effect level (NOAEL) of UP446 was considered to be 1000 mg/kg, the highest dose tested, in both genders     

High yield expression of non-phosphorylated protein tyrosine kinases in insect cells

The key role of kinases in signal transduction and cell growth regulation has been a long standing interest among academics and the pharmaceutical industry. Recombinant enzymes have been used to understand the mechanism of action as well as to screen for chemical inhibitors. The baculo-insect system has been the primary method used to obtain soluble and active kinases, usually producing a mixture of the kinase in various phosphorylation states in different conformations. To obtain a homogenous preparation of non-phosphorylated kinases is critical for biochemical, biophysical and kinetic studies aimed at understanding the mechanism of kinase activation. Taking advantage of the eukaryotic expression property of insect cells, we were able to obtain high yield expression of non-phosphorylated protein tyrosine kinases BTK, JAK3 and Eph2A through coexpression with the tyrosine phosphatase YopH, which suggests that this method can be applied to protein tyrosine kinases in general. We have demonstrated that the fully non-phosphorylated BTK obtained with this method is suitable for various biochemical and kinetic studies.     

Plant organ abscission and the green island effect caused by gallmidges (Cecidomyiidae) on tropical trees

Plants exhibit a wide array of inert and induced responses in defense against herbivore attack. Among these the abscission of organs has been argued to be a highly effective mechanism, depending, however, on the herbivore’s feeding mode. While consisting of plant tissues, insect induced galls are seen as the extended phenotype of the gall inducer which might circumvent many or most of the plant defenses. There is very little information whether and how far beyond the gall tissue gall inducers might affect plant tissues. A localized impact is likely to leave the abscission of galled organs as a viable defense although at a cost. Here, we report on an instance where the host plant, Neea madeirana (Nyctaginaceae) abscises leaves galled by two species of Bruggmannia (Diptera: Cecidomyiidae), more frequently than ungalled leaves in a rain forest in Amazonia, Brazil. Once on the forest floor the leaves decay quickly, while both gall types show signs of localized maintenance of healthy tissues for a while (the green island effect). However, on the forest floor galls are exposed to a new set of potential natural enemies. Both gall types show a minimum of a five-fold increase in mortality due to pathogens (fungi and bacteria) compared to galls that were retained on the host tree. We discuss the adaptive nature of plant organ abscission as a plant defense against gallers and as a gall inducer adaptive trait. Handling editor: Graham Stone.     

A preliminary study of oscillating electromagnetic field effects on human spermatozoon motility

Some effects of extremely low frequency electromagnetic fields (ELF-EMFs) on human spermatozoa are reported. Significant increases in the values of the motility and of the other kinematic parameters have been observed when spermatozoa were exposed to an ELF-EMF with a square waveform of 5 mT amplitude and frequency of 50 Hz. By contrast, a 5 mT sine wave (50 Hz) and a 2.5 mT square wave (50 Hz) exposure did not produce any significant effect on sperm motility. The effects induced by ELF-EMF (50 Hz; 5 mT) during the first 3 h of exposure persisted for 21 h after the end of the treatment. These results indicate that ELF-EMF exposure can improve spermatozoa motility and that this effect depends on the field characteristics.     

Anatomical and functional characterisation of the stomatogastric nervous system of blowfly (Calliphora vicina) larvae

The anatomy and functionality of the stomatogastric nervous system (SNS) of third-instar larvae of Calliphora vicina was characterised. As in other insects, the Calliphora SNS consists of several peripheral ganglia involved in foregut movement regulation. The frontal ganglion gives rise to the frontal nerve and is connected to the brain via the frontal connectives and antennal nerves (ANs). The recurrent nerve connects the frontal- to the hypocerebral ganglion from which the proventricular nerve runs to the proventricular ganglion. Foregut movements include rhythmic contractions of the cibarial dilator muscles (CDM), wavelike movements of crop and oesophagus and contractions of the proventriculus. Transections of SNS nerves indicate mostly myogenic crop and oesophagus movements and suggest modulatory function of the associated nerves. Neural activity in the ANs, correlating with postsynaptic potentials on the CDM, demonstrates a motor pathway from the brain to CDM. Crop volume is monitored by putative stretch receptors. The respective sensory pathway includes the recurrent nerve and the proventricular nerve. The dorsal organs (DOs) are directly connected to the SNS. Mechanical stimulation of the DOs evokes sensory activity in the AN. This suggests the DOs can provide sensory input for temporal coordination of feeding behaviour.     

Long term oviposition preference and larval performance of Schizomyia macrocapillata (Diptera: Cecidomyiidae) on larger shoots of its host plant Bauhinia brevipes (Fabaceae)

The Plant Vigor Hypothesis (PVH) proposes that natural selection on female oviposition choice results from higher fitness of larvae on more vigorous and larger plant modules. For six consecutive years we tested the PVH predictions by investigating the effect of shoot size of Bauhinia brevipes (Fabaceae) on the oviposition preference and offspring survival of the gall-midge Schizomyia macrocapillata (Diptera: Cecidomyiidae). Additionally, we analyzed the effects of bottom-up and top-down mortality forces on the system. The hypersensitive reaction (bottom-up effect) accounted for more than 90% larval mortality of S. macrocapillata, making available few galls to be found and killed by natural enemies (top-down effect). Smaller shoots were always more abundant while longer shoots were rare. Nevertheless, the percent number of galls induced by S. macrocapillata was up to 10-fold greater on the largest shoots, corroborating the preference prediction of the PVH. Schizomyia macrocapillata should use over-exploit larger shoots to maximize the preference for, and consequently increase the performance on these shoots. Our results partially support the performance prediction of the PVH: (1) the observed survival was higher than expected on longer shoots, and (2) the ratio of survival per shoot was positively related with shoot length only in 2 years. Thus, we found a link between female preference and larval performance on large-sized shoots, at least in some years. The gall-midge attack pattern in this study might be an evolved response to maximize the female preference and increased larval performance on longer shoots of the host plant.     

Ejaculate traits in relation to male body size in the eastern mosquitofish Gambusia holbrooki

In the present study, the correlation between sperm number, sperm quality (speed, viability, longevity and length), sperm bundles quality (size and dissolving rate) and male body size has been tested in the eastern mosquitofish Gambusia holbrooki a poecilid species characterized by coercive mating tactics where males do not possess obvious ornaments, and the body size is the key determinant of pre‐copulatory male mating success. The results do not tally with theoretical predictions. Indeed, no correlation between male body size and either sperm or sperm‐bundle traits has been found, evidencing the lack of the theoretically expected trade‐off between the investment in characters involved in mate acquisition and the investment in ejaculate quality. An explanation for the observed pattern comes from the extremely dynamic mating system of G. holbrooki, characterized by variable size‐related male mating success and strong post‐copulatory selective pressure, with all males facing a similar high level of sperm competition. In this situation, a higher investment in growth and maintenance at the expense of ejaculate quality is not expected. These results underscore the necessity to comprehend detailed information on species’ reproductive biology and reproductive environment to understand both the evolution of ejaculate characteristics and possible deviations from theoretical predictions.