Penny A. Cook

Butterflies tailor their ejaculate in response to sperm competition risk and intensity

Males of many insects eclose with their entire lifetime sperm supply and have to allocate their ejaculates at mating prudently. In polyandrous species, ejaculates of rival males overlap, creating sperm competition. Recent models suggest that males should increase their ejaculate expenditure when experiencing a high risk of sperm competition. Ejaculate expenditure is also predicted to vary in relation to sperm competition intensity. During high intensity, where several ejaculates compete for fertilization of the females eggs, ejaculate expenditure is expected to be reduced. This is because there are diminishing returns of providing more sperm. Additionally, sperm numbers will depend on males ability to assess female mating status. We investigate ejaculate allocation in the polyandrous small white butterfly Pieris rapae (Lepidoptera). Males have previously been found to ejaculate more sperm on their second mating when experiencing increased risk of sperm competition. Here we show that males also adjust the number of sperm ejaculated in relation to direct sperm competition. Mated males provide more sperm to females previously mated with mated males (i.e. when competing with many sperm) than to females previously mated to virgin males (competing with few sperm). Virgin males, on the other hand, do not adjust their ejaculate in relation to female mating history, but provide heavier females with more sperm. Although virgin males induce longer non–receptive periods in females than mated males, heavier females remate sooner. Virgin males may be responding to the higher risk of sperm competition by providing more sperm to heavier females. It is clear from this study that males are sensitive to factors affecting sperm competition risk, tailoring their ejaculates as predicted by recent theoretical models.

Non-fertile sperm delay female remating

Sperm competition is thought to be responsible for the tremendous inter- and intraspecific variation in sperm number and size. But why several animals produce a range of sperm types,, some of which are incapable of fertilizing the females eggs, has remained unexplained for nearly 100 years. We have found that non-fertile sperm protect a males reproductive investment by delaying female remating in the polyandrous green-veined white butterfly, Pieris napi (Pieridae).

Effects of risks of sperm competition on the numbers of eupyrene and apyrene sperm ejaculated by the moth Plodia interpunctella (Lepidoptera: Pyralidae)

This study examines the effects of different risks of sperm competition upon ejaculate characteristics in the moth Plodia interpunctella. In this short-lived species, females will remate and thus generate sperm competition, while males have a limited sperm supply. We therefore predict males to have evolved prudence in ejaculate allocation and investigate the effects of (1) rival male presence, (2) female mating history and (3) female age, upon the ejaculation of eupyrene (fertilizing) and apyrene (non-fertile) sperm numbers. We found no effect of the presence of rival males upon ejaculate characteristics, and conclude, due to the mating system of P. interpunctella, that rival males do not represent a proximate risk of sperm competition. We controlled female mating history by allowing females to receive different and predictable numbers of sperm which they then store for at least 7 days. In subsequent matings (7 days later) we found that new males ejaculated significantly more eupyrene sperm to females that had previously received larger numbers of sperm. We conclude that males increase numbers of eupyrene sperm to maintain success in sperm competition with rival sperm already in storage in the female. We found no effect of female mating history upon the ejaculation of apyrene sperm. Female age, however, had a significant negative effect upon both sperm types. We discuss these results in relation to sperm competition theory and apyrene sperm function.

Ejaculate Dynamics in Butterflies: A Strategy for Maximizing Fertilization Success?

The butterfly spermatophore is a complex structure containing both sperm and accessory substances. Most of the sperm are anucleated ‘apyrene’ sperm, which do not fertilize the eggs. The fertilizing ‘eupyrene’ sperm comprise only 10-15 % of the total sperm number transferred to the female at mating. In addition to sperm, some butterfly species also provide the female with nutrients that are used for egg production and/or somatic maintenance. Many butterflies eclose with most resources available for reproduction already present. Consequently, resources have to be allocated to the different spermatophore components over consecutive matings. This study is the first to quantify eupyrene and apyrene sperm numbers in relation to spermatophore mass, mating history and larval diet. Spermatophore mass was significantly reduced on the male’s second mating. However, both eupyrene and apyrene sperm numbers were dramatically increased, as was the proportion of eupyrene sperm. Theory predicts that sperm numbers should increase under sperm competition. On males’ second matings, the probability of encountering virgin females is reduced. Males may therefore maximise fertilization success by providing these females with large numbers of sperm. Simultaneously, it may be advantageous for males to reduce their nutrient donation because of their lower paternity assurance. Larval diet affected mass of the first spermatophore but had no effect on sperm number. This suggests that males maintain sperm numbers when resources are limited, prioritising fertilization success over investment in offspring.

Teenage drinking, alcohol availability and pricing: a cross-sectional study of risk and protective factors for alcohol-related harms in school children

BackgroundThere is a lack of empirical analyses examining how alcohol consumption patterns in children relate to harms. Such intelligence is required to inform parents, children and policy relating to the provision and use of alcohol during childhood. Here, we examine drinking habits and associated harms in 15-16 year olds and explore how this can inform public health advice on child drinking.MethodsAn opportunistic survey of 15-16 year olds (n = 9,833) in North West England was undertaken to determine alcohol consumption patterns, drink types consumed, drinking locations, methods of access and harms encountered. Cost per unit of alcohol was estimated based on a second survey of 29 retail outlets. Associations between demographics, drinking behaviours, alcohol pricing and negative outcomes (public drinking, forgetting things after drinking, violence when drunk and alcohol-related regretted sex) were examined.ResultsProportions of drinkers having experienced violence when drunk (28.8%), alcohol-related regretted sex (12.5%) and forgetting things (45.3%), or reporting drinking in public places (35.8%), increased with drinking frequency, binge frequency and units consumed per week. At similar levels of consumption, experiencing any negative alcohol-related outcome was lower in those whose parents provided alcohol. Drunken violence was disproportionately associated with being male and greater deprivation while regretted sex and forgetting things after drinking were associated with being female. Independent of drinking behaviours, consuming cheaper alcohol was related to experiencing violence when drunk, forgetting things after drinking and drinking in public places.ConclusionThere is no safe level of alcohol consumption for 15-16 year olds. However, while abstinence removes risk of harms from personal alcohol consumption, its promotion may also push children into accessing drink outside family environments and contribute to higher risks of harm. Strategies to reduce alcohol-related harms in children should ensure bingeing is avoided entirely, address the excessively low cost of many alcohol products, and tackle the ease with which it can be accessed, especially outside of supervised environments.

Determinants of paternity in a butterfly

Success in sperm competition is of fundamental importance to males, yet little is known about what factors determine paternity. Theory predicts that males producing high sperm numbers have an advantage in sperm competition. Large spermatophore size (the sperm containing package) also correlates with paternity in some species, but the relative importance of spermatophore size and sperm numbers has remained unexplored. Males of the small white butterfly, Pieris rapae (Lepidoptera: Pieridae), produce large nutritious spermatophores on their first mating. On their second mating, spermatophores are only about half the size of the first, but with almost twice the sperm number. We manipulated male mating history to examine the effect of spermatophore size and sperm numbers on male fertilization success. Overall, paternity shows either first male or, more frequently, second male sperm precedence. Previously mated males have significantly higher fertilization success in competition with males mating for the first time, strongly suggesting that high sperm number is advantageous in sperm competition. Male size also affects paternity with relatively larger males having higher fertilization success. This may indicate that spermatophore size influences paternity, because in virgin males spermatophore size correlates with male size. The paternity of an individual male is also inversely correlated with the mass of his spermatophore remains dissected out of the female. This suggests that females may influence paternity by affecting the rate of spermatophore drainage. Although the possibility of female postcopulatory choice remains to be explored, these results clearly show that males maximize their fertilization success by increasing the number of sperm in their second mating.

Sperm Numbers and Female Fertility in the Moth Plodia interpunctella (Hübner) (Lepidoptera; Pyralidae)

I investigated two possible reasons for remating in female Plodia interpunctella: i) females remate to obtain sufficient sperm to maintain fertility; and ii) male investment in non-sperm components increases female fecundity and longevity. The number of sperm and the mass of the spermatophore transferred by males decreases on successive matings. Sperm numbers and potential male investment were varied by allowing females to mate either once or twice with males either on their first or second mating. Females receiving a single small spermatophore containing few sperm (from a male on his second mating) had sufficient sperm to fertilize all their eggs. Females did not show increased fecundity or longevity as a result of obtaining more spermatophore material. I discuss why females remate when they already have sufficient sperm to fertilize all their eggs.

Under-reporting of foetal alcohol spectrum disorders: an analysis of hospital episode statistics

BackgroundInternationally, 0.97 per 1,000 live births are affected by foetal alcohol syndrome (FAS). However, prevalence intelligence has been limited in the UK, hindering the development of appropriate services. This analysis compares hospital admissions over time, between regions and with alcohol-related admissions for adult females to assess whether established patterns (such as the North experiencing elevated harms) can be identified.MethodsA retrospective analysis of hospital admissions data (April 2002 to March 2008) for foetal alcohol spectrum disorder (FASD)-related conditions: foetal alcohol syndrome (dysmorphic) (n = 457); foetus and newborn affected by maternal use of alcohol (n = 157); maternal care for (suspected) damage to foetus from alcohol (n = 285); and 322,161 women admitted due to alcohol-related conditions.ResultsWhilst the rate of admission for alcohol-related conditions in women aged 15-44 years increased significantly by 41% between 2002/03 and 2007/08 (p < 0.0001), significant increases were only seen in the numbers of FAS. Established regional rates of admission for alcohol-related conditions in women aged 15-44 years old were not associated with admission for FASD-related conditions.ConclusionsIt would be expected that the North West and North East regions, known to have higher levels of alcohol harm would have higher levels of FASD-related conditions. However, this was not reflected in the incidence of such conditions, suggesting under-reporting. With incomplete datasets, intelligence systems are severely limited, hampering efforts to develop targeted interventions. Improvements to intelligence systems, practitioner awareness and screening are essential in tackling this.

Re-emerging syphilis: a detrended correspondence analysis of the behaviour of HIV positive and negative gay men

BackgroundRecent syphilis outbreaks in the UK have raised serious concerns about the sexual health of the population. Moreover, syphilis appears more likely to facilitate HIV transmission than any other sexually transmitted infection (STI).MethodsThe sexual and other risk behaviour of a sample of HIV positive and negative gay men with and without syphilis was subjected to a detrended correspondence analysis (DCA).ResultsA DCA plot was used to illustrate similarity of individuals in terms of their behaviours, regardless of their infection status. The majority of those with syphilis (78%; 18/23) fell into a high-risk group with more partners, and use of anonymous sex venues and drugs during sex. However, 16% of uninfected controls (8/49) and 62% of HIV positive individuals without syphilis (8/13) also fell into this high-risk group.ConclusionsUsing a statistical technique that is novel for this type of investigation, we demonstrate behavioural overlaps between syphilis-infected individuals in an ongoing UK outbreak and uninfected HIV positive and negative controls. Given the high-risk behaviour of a significant proportion of uninfected individuals, ongoing transmission of syphilis and HIV in this population seems likely.

EFFECT OF GAMMA RADIATION AND SEX-LINKED RECESSIVE LETHAL MUTATIONS ON SPERM TRANSFER IN EPHESTIA KUEHNIELLA (LEPIDOPTERA: PYRALIDAE)

Sperm quality and sperm competition play important roles in determining the efficiency of genetic methods for suppression of lepidopteran populations. Herein we have examined competitiveness of mutant and irradiated males of Ephestia kuehniella by counting eupyrene (fertile) and apyrene (non-fertile) sperm transferred to the female during copulation. Mutant BL-2 males, trans-heterozygous for two sex-linked recessive lethal mutations sl-2 and sl-15, produced 50% fewer of both types of sperm as compared to with WT-C (wild-type) males. However, the ratio of apyrene to eupyrene sperm remained the same in both male types (9.5:1). Irradiation of mature male pupae, heterozygous for either sl-2 or sl-15 mutations, with doses between 150 and 350 Gy showed dose-dependent effects on the amount of sperm transferred and on the total length of mating times. As the treatment dose increased the volume of sperm transferred by the male decreased and the mating times got longer. In the F1 descendants of the treated males, males were found to transfer either a relatively normal or a very small volume of sperm, which could reflect changes in gamete segregation and in chromosomal aberrations that are inherited. The dose of 175 Gy is suggested as optimal for irradiation of Ephestia kuehniella.