Ecological light pollution.

Therésa M Jones and Kathryn B McNamara introduce the ecological effects of artificial light at night.

Age, but not an immune challenge, triggers terminal investment in the Pacific field cricket, Teleogryllus oceanicus.

The terminal investment hypothesis proposes that, when individuals are faced with a threat to survival, they will increase investment in current reproduction. The level of the threat necessary to elicit terminal investment (the dynamic terminal investment threshold) may vary based on other factors that also influence future reproduction. Here, we tested whether there is an interactive effect of age and an immune challenge on the dynamic terminal investment threshold in the Pacific field cricket, Teleogryllus oceanicus. We measured the courtship call, mating attractiveness, ejaculate size, and offspring production of T. oceanicus males. We found only limited support for the dynamic terminal investment threshold: there was no consistent evidence of a positive interaction between male age and immune challenge intensity. However, we found evidence for age-related terminal investment: older males produced a larger spermatophore than younger males. Older males also had a slower calling rate compared to younger males, suggesting a potential trade-off between these two pre- and post-copulatory traits. As some, but not all, reproductive traits responded plastically to cues for terminal investment, our research highlights the importance of considering a broad range of pre-and post-copulatory traits when exploring the potential for terminal investment to occur.

Trans-generational immune priming is not mediated by the sex of the parent primed: a meta-analysis of invertebrate data.

Traditionally, only vertebrates were thought capable of acquired immune responses, such as the ability to transfer immunological experience vertically to their offspring (known as trans-generational immune priming, TGIP). Increasing evidence challenges this belief and it is now clear that invertebrates also have the ability to exhibit functionally equivalent TGIP. This has led to a surge in papers exploring invertebrate TGIP, with most focusing on the costs, benefits or factors that affect the evolution of this trait. Whilst many studies have found support for the phenomenon, not all studies do, and there is considerable variation in the strength of positive results. To address this, we conducted a meta-analysis to answer the question: what is the overall effect of TGIP in invertebrates? Then, to understand the specific factors that affect its presence and intensity, we conducted a moderator analysis. Our results corroborate that TGIP occurs in invertebrates (demonstrated by a large, positive effect size). The strength of the positive effect was related to if and how offspring were immune challenged (i.e. whether they were challenged with the same or different insult as their parents or not challenged at all). Interestingly, there was no effect of the ecology or life history of the species or the sex of the parent or the offspring primed, and responses were comparable across different immune elicitors. Our publication bias testing suggests that the literature may suffer from some level of positive-result bias. However, even after accounting for potential bias, our effect size remains positive. Publication bias testing can be influenced by diversity in the data set, which was considerable in our data, even after moderator analysis. It is therefore conceivable that differences among studies could be caused by other moderators that were unable to be included in our meta-analysis. Nonetheless, our results suggest that TGIP does occur in invertebrates, whilst providing some potential avenues to examine the factors that account for variation in effect sizes.

Experimental immune challenges reduce the quality of male antennae and female pheromone output.

Sexual signalling is a key feature of reproductive investment, yet the effects of immune system activation on investment into chemical signalling, and especially signal receiver traits such as antennae, are poorly understood. We explore how upregulation of juvenile immunity affects male antennal functional morphology and female pheromone attractiveness in the gumleaf skeletonizer moth, Uraba lugens. We injected final-instar larvae with a high or low dose of an immune elicitor or a control solution and measured male antennal morphological traits, gonad investment and female pheromone attractiveness. Immune activation affected male and female signalling investment: immune challenged males had a lower density of antennal sensilla, and the pheromone of immune-challenged females was less attractive to males than their unchallenged counterparts. Immune challenge affected female investment into ovary development but not in a linear, dose-dependent manner. While there was no effect of immune challenge on testes size, there was a trade-off between male pre- and post-copulatory investment: male antennal length was negatively correlated with testes size. Our study highlights the costs of elaborate antennae and pheromone production and demonstrates the capacity for honest signalling in species where the costs of pheromone production were presumed to be trivial.

Influenza-Like Illness Among Personnel Responding to U.S. Quarantine of Cruise Ship Passengers Exposed to SARS-CoV-2.

OBJECTIVES: Before community transmission of COVID-19 was recognized in the United States, cruise ship passengers with high risk for exposure to SARS-CoV-2 were repatriated and quarantined. We describe cases of influenza-like illness (ILI) among responders. METHODS: We reviewed situation reports and responder illness reports to characterize ill responders, including illness onset date, symptoms, fever, diagnostic tests, potential breaches in PPE use, and return to work status. RESULTS: Among 339 responders, nine (3%) reported ILI. No breaches in PPE were reported. Three responders with ILI were tested for both SARS-CoV-2 infection and influenza A; none tested positive for SARS-CoV-2 infection and two tested positive for influenza A. CONCLUSIONS: Despite an outbreak of ILI among responders, none were diagnosed with COVID-19, suggesting preventive measures in place might have been sufficient to prevent responders from SARS-CoV-2 exposure.

Quantifying variation in female internal genitalia: no evidence for plasticity in response to sexual conflict risk in a seed beetle.

Sexually antagonistic coevolution can drive the evolution of male traits that harm females, and female resistance to those traits. While males have been found to vary their harmfulness to females in response to social cues, plasticity in female resistance traits remains to be examined. Here, we ask whether female seed beetles Callosobruchus maculatus are capable of adjusting their resistance to male harm in response to the social environment. Among seed beetles, male genital spines harm females during copulation and females might resist male harm via thickening of the reproductive tract walls. We develop a novel micro computed tomography imaging technique to quantify female reproductive tract thickness in three-dimensional space, and compared the reproductive tracts of females from populations that had evolved under high and low levels of sexual conflict, and for females reared under a social environment that predicted either high or low levels of sexual conflict. We find little evidence to suggest that females can adjust the thickness of their reproductive tracts in response to the social environment. Neither did evolutionary history affect reproductive tract thickness. Nevertheless, our novel methodology was capable of quantifying fine-scale differences in the internal reproductive tracts of individual females, and will allow future investigations into the internal organs of insects and other animals.

Socially cued anticipatory adjustment of female signalling effort in a moth.

Juvenile population density has profound effects on subsequent adult development, morphology and reproductive investment. Yet, little is known about how the juvenile social environment affects adult investment into chemical sexual signalling. Male gumleaf skeletonizer moths, Uraba lugens, facultatively increase investment into antennae (pheromone receiving structures) when reared at low juvenile population densities, but whether there is comparable adjustment by females into pheromone investment is not known. We investigate how juvenile population density influences the 'calling' (pheromone-releasing) behaviour of females and the attractiveness of their pheromones. Female U. lugens adjust their calling behaviour in response to socio-sexual cues: adult females reared in high juvenile population densities called earlier and for longer than those from low juvenile densities. Juvenile density also affected female pheromonal attractiveness: Y-maze olfactometer assays revealed that males prefer pheromones produced by females reared at high juvenile densities. This strategic investment in calling behaviour by females, based on juvenile cues that anticipate the future socio-sexual environment, likely reflects a response to avoid mating failure through competition with neighbouring signallers.

Experimental evolution reveals divergence in female genital teeth morphology in response to sexual conflict intensity in a moth.

The rapid evolutionary divergence of male genital structures under sexual selection is well documented. However, variation in female genital traits and the potential for sexual conflict to drive the coevolution between male and female traits has only recently received attention. In many lepidopterans, females possess genital teeth (collectively, signa). Comparative studies suggest these teeth, involved in the deflation of spermatophores, may have coevolved with male spermatophore thickness via sexually antagonistic coevolution in a contest over the rate of deflation of spermatophores within the reproductive tract. We tested the hypothesis that sexual conflict should generate coevolution between genital teeth and spermatophore morphology by examining these traits under experimental manipulation of sexual conflict intensity. Using micro-CT scanning, we examined spermatophore and teeth morphology in populations of the Indian moth, Plodia interpunctella, which had been evolving for 110 generations under different adult sex-ratio biases. We found divergence in female signa morphology in response to sexual conflict: females from female-biased populations (reduced sexual conflict) developed wider signa. However, we found no evidence of coevolution between signa traits and spermatophore thickness as reported from comparative studies.

Forecasting Dose from Unobserved Times: Case Study of Transient Workers at a Nuclear Power Plant.

Objectives: To evaluate the likelihood of exceeding the occupational exposure limit (OEL) for annual ionizing radiation doses among transient workers at the Hope Creek Nuclear Generating Station, and to propose a method for forecasting exposures among transient workers in general. Methods: We obtained personal dosimeter data from the Hope Creek Nuclear Generating Station for the period of January-December 2014, comprising 1955 monthly dose measurements from 498 transient workers. The majority of the transient workers (96%) did not report 12 months of data. The missing months indicate that transient workers may receive ionizing radiation doses at other nuclear power plants throughout the year. We estimated the likelihood of a worker exceeding the Nuclear Regulatory Commission's annual OEL of 5000 mrem. To do so, we had to account both for left-censored data below the limit of detection (27% of all measurements) and make assumptions about doses received during months not employed at the facility. We used a maximum likelihood estimation method for non-detected measurements that accounted for repeated measurements on an individual. To account for missing months of measurements, we considered two extreme scenarios: the best case of workers who receive zero exposures outside of the Hope Creek, and the illustrative worst case of workers who receive multiple exposures at other nuclear power plants with similar exposure scenarios to Hope Creek. We employed a bootstrap procedure to forecast annual personal doses under both scenarios, while imputing non-detected measurements. Results: None of the workers' reported measurements exceeded the OEL. Bootstrapped annual exposure doses revealed similar patterns, with a very small likelihood of exceeding the OEL, but great potential for variability. Some workers under the best-case scenario may reach Hope Creek's 2000 mrem internal action limit if exposed at the 98th percentile of their projected annual dose. This scenario becomes more likely when assuming that a worker received doses at other nuclear power plants besides Hope Creek throughout the year. Conclusions: The Hope Creek Nuclear Generating Station appears to be typical of its industry peers in terms of annual ionizing radiation doses, which makes it a good test subject for predicting worker doses received elsewhere. Transient workers may receive doses at more than one nuclear power plant throughout the year, which makes them especially at risk for overexposure. The presence of internal plant monitoring systems and the use of tools such as bootstrapping to predict compliance are therefore important for health protection. An argument can also be made for better tracking of exposures in real time of transient workers across facilities. Our method applies to transient workers in any industry for whom exposure assessment is complicated by gaps in exposure histories and records.

Sexual conflict and correlated evolution between male persistence and female resistance traits in the seed beetle Callosobruchus maculatus.

Traumatic mating (or copulatory wounding) is an extreme form of sexual conflict whereby male genitalia physically harm females during mating. In such species females are expected to evolve counter-adaptations to reduce male-induced harm. Importantly, female counter-adaptations may include both genital and non-genital traits. In this study, we examine evolutionary associations between harmful male genital morphology and female reproductive tract morphology and immune function across 13 populations of the seed beetle Callosobruchus maculatus We detected positive correlated evolution between the injuriousness of male genitalia and putative female resistance adaptations across populations. Moreover, we found evidence for a negative relationship between female immunity and population productivity, which suggests that investment in female resistance may be costly due to the resource trade-offs that are predicted between immunity and reproduction. Finally, the degree of female tract scarring (harm to females) was greater in those populations with both longer aedeagal spines and a thinner female tract lining. Our results are thus consistent with a sexual arms race, which is only apparent when both male and female traits are taken into account. Importantly, our study provides rare evidence for sexually antagonistic coevolution of male and female traits at the within-species level.

Male-biased sex ratio does not promote increased sperm competitiveness in the seed beetle, Callosobruchus maculatus.

Sperm competition risk and intensity can select for adaptations that increase male fertilisation success. Evolutionary responses are examined typically by generating increased strength of sexual selection via direct manipulation of female mating rates (by enforcing monandry or polyandry) or by alteration of adult sex ratios. Despite being a model species for sexual selection research, the effect of sexual selection intensity via adult sex-ratio manipulation on male investment strategies has not been investigated in the seed beetle, Callosobruchus maculatus. We imposed 32 generations of experimental evolution on 10 populations of beetles by manipulating adult sex ratio. Contrary to predictions, males evolving in male-biased populations did not increase their testes and accessory gland size. This absence of divergence in ejaculate investment was also reflected in the fact that males from male-biased populations were not more successful in either preventing females from remating, or in competing directly for fertilisations. These populations already demonstrate divergence in mating behaviour and immunity, suggesting sufficient generations have passed to allow divergence in physiological and behavioural traits. We propose several explanations for the absence of divergence in sperm competitiveness among our populations and the pitfalls of using sex ratio manipulation to assess evolutionary responses to sexual selection intensity.

Rapid loss of behavioral plasticity and immunocompetence under intense sexual selection.

Phenotypic plasticity allows animals to maximize fitness by conditionally expressing the phenotype best adapted to their environment. Although evidence for such adjustment in reproductive tactics is common, little is known about how phenotypic plasticity evolves in response to sexual selection. We examined the effect of sexual selection intensity on phenotypic plasticity in mating behavior using the beetle Callosobruchus maculatus. Male genital spines harm females during mating and females exhibit copulatory kicking, an apparent resistance trait aimed to dislodge mating males. After exposing individuals from male- and female-biased experimental evolution lines to male- and female-biased sociosexual environments, we examined behavioral plasticity in matings with standard partners. While females from female-biased lines kicked sooner after exposure to male-biased sociosexual contexts, in male-biased lines this plasticity was lost. Ejaculate size did not diverge in response to selection history, but males from both treatments exhibited plasticity consistent with sperm competition intensity models, reducing size as the number of competitors increased. Analysis of immunocompetence revealed reduced immunity in both sexes in male-biased lines, pointing to increased reproductive costs under high sexual selection. These results highlight how male and female reproductive strategies are shaped by interactions between phenotypically plastic and genetic mechanisms of sexual trait expression.

Why do female Callosobruchus maculatus kick their mates?

Sexual conflict is now recognised as an important driver of sexual trait evolution. However, due to their variable outcomes and effects on other fitness components, the detection of sexual conflicts on individual traits can be complicated. This difficulty is exemplified in the beetle Callosobruchus maculatus, where longer matings increase the size of nutritious ejaculates but simultaneously reduce female future receptivity. While previous studies show that females gain direct benefits from extended mating duration, females show conspicuous copulatory kicking behaviour, apparently to dislodge mating males prematurely. We explore the potential for sexual conflict by comparing several fitness components and remating propensity in pairs of full sibling females where each female mated with a male from an unrelated pair of full sibling males. For one female, matings were terminated at the onset of kicking, whereas the other's matings remained uninterrupted. While fecundity (number of eggs) was similar between treatments, uninterrupted matings enhanced adult offspring numbers and fractionally also longevity. However, females whose matings were interrupted at the onset of kicking exhibited an increased propensity to remate. Since polyandry can benefit female fitness in this species, we argue that kicking, rather than being maladaptive, may indicate that females prefer remating over increased ejaculate size. It may thus be difficult to assess the presence of sexual conflict over contested traits such as mating duration when females face a trade off between direct benefits gained from one mating and indirect benefits from additional matings.

Promiscuous words.

Promiscuity is frequently used to describe animal mating behaviour, and especially to describe multiple mating by females. Yet this use of the term is incorrect, perhaps reflecting an erroneous adoption of common language to pique reader interest. We evaluated the patterns of use and misuse of the word 'promiscuity' in a representative journal of animal behaviour. This survey highlights how inappropriately the term is used, and how it can conceal critical features of animal mating strategies with intriguing evolutionary significance. Further analysis of the scientific impact of papers identified by the term promiscuous or polyandrous revealed that the former were cited less frequently. We argue that using promiscuity to describe animal mating strategies is anthropomorphic, inaccurate, and potentially misleading. Consistent with other biological disciplines, the word promiscuity should be used to describe indiscriminate mating behaviour only, and that polygyny and polyandry should be used to describe male and female mating frequency respectively.

Experimental evolution reveals trade-offs between mating and immunity.

Immune system maintenance and upregulation is costly. Sexual selection intensity, which increases male investment into reproductive traits, is expected to create trade-offs with immune function. We assayed phenoloxidase (PO) and lytic activity of individuals from populations of the Indian meal moth, Plodia interpunctella, which had been evolving under different intensities of sexual selection. We found significant divergence among populations, with males from female-biased populations having lower PO activity than males from balanced sex ratio or male-biased populations. There was no divergence in anti-bacterial lytic activity. Our data suggest that it is the increased male mating demands in female-biased populations that trades-off against immunity, and not the increased investment in sperm transfer per mating that characterizes male-biased populations.

Age-dependent trade-offs between immunity and male, but not female, reproduction.

Immune function is costly and must be traded off against other life-history traits, such as gamete production. Studies of immune trade-offs typically focus on adult individuals, yet the juvenile stage can be a highly protracted period when reproductive resources are acquired and immune challenges are ubiquitous. Trade-offs during development are likely to be important, yet no studies have considered changes in adult responses to immune challenges imposed at different stages of juvenile development. By manipulating the timing of a bacterial immune challenge to the larvae of the cotton bollworm moth, we examined potential trade-offs between investment into immunity at different stages of juvenile development (early or late) and subsequent adult reproductive investment into sperm or egg production. Our data reveal an age-dependent trade-off between juvenile immune function and adult male reproductive investment. Activation of the immune response during late development resulted in a reduced allocation of resources to eupyrene (fertilizing) sperm production. Immune activation from the injection procedure itself (irrespective of whether individuals were injected with an immune elicitor or a control solution) also caused reproductive trade-offs; males injected early in development produced fewer apyrene (nonfertilizing) sperm. Contrary to many other studies, our study demonstrates these immune trade-offs under ad libitum nutritional conditions. No trade-offs were observed between female immune activation and adult reproductive investment. We suggest the differences in trade-offs observed between male sperm types and the absence of reproductive trade-offs in females may be the result of ontogenetic differences in gamete production in this species. Our data reveal developmental windows when trade-offs between immune function and gametic investment are made, and highlight the importance of considering multiple developmental periods when making inferences regarding the fundamental trade-offs expected between immune function and reproduction.

Repeatedly reactivated memories become more resistant to hippocampal damage.

We examined whether repeated reactivations of a context memory would prevent the typical amnesic effects of post-training damage to the hippocampus (HPC). Rats were given a single contextual fear-conditioning session followed by 10 reactivations, involving a brief return to the conditioning context (no shock). Subsequently, the rats received sham or complete lesions of the HPC. When tested for retention, the HPC rats that experienced the reactivations froze significantly more than nonreactivation HPC rats and did not significantly differ from their respective control group. These findings suggest that memory reactivations contribute to long-term memories becoming independent of the HPC.