Coevolution between eggs and sperm of insects.

Sexual selection is known to play a major role in the evolution of insect sperm size, whereas natural selection is thought to be a major driver of insect egg size. Despite these differing forms of selection operating, it is possible coevolution between male and female gametes can occur owing to their vital interactions during fertilization. We tested egg-sperm coevolution in insects and found that longer sperm correlated to longer and wider eggs. Moreover, the size of the entry point of sperm into insect eggs (micropyles), was positively related to the diameter of sperm, on average being approximately three times the diameter of the sperm. This suggests a function in reducing and channelling sperm entry, but potentially still leaving space for movement. Our work suggests that greater attention needs to be paid to egg-sperm interactions prior to the point of fertilization as they may influence the evolution of gametes.

Systematic approaches to assessing high-temperature limits to fertility in animals.

Critical thermal limits (CTLs) gauge the physiological impact of temperature on survival or critical biological function, aiding predictions of species range shifts and climatic resilience. Two recent Drosophila species studies, using similar approaches to determine temperatures that induce sterility (thermal fertility limits [TFLs]), reveal that TFLs are often lower than CTLs and that TFLs better predict both current species distributions and extinction probability. Moreover, many studies show fertility is more sensitive at less extreme temperatures than survival (thermal sensitivity of fertility [TSF]). These results present a more pessimistic outlook on the consequences of climate change. However, unlike CTLs, TFL data are limited to Drosophila, and variability in TSF methods poses challenges in predicting species responses to increasing temperature. To address these data and methodological gaps, we propose 3 standardized approaches for assessing thermal impacts on fertility. We focus on adult obligate sexual terrestrial invertebrates but also provide modifications for other animal groups and life-history stages. We first outline a "gold-standard" protocol for determining TFLs, focussing on the effects of short-term heat shocks and simulating more frequent extreme heat events predicted by climate models. As this approach may be difficult to apply to some organisms, we then provide a standardized TSF protocol. Finally, we provide a framework to quantify fertility loss in response to extreme heat events in nature, given the limitations in laboratory approaches. Applying these standardized approaches across many taxa, similar to CTLs, will allow robust tests of the impact of fertility loss on species responses to increasing temperatures.

National action plans on antimicrobial resistance in Latin America: an analysis via a governance framework.

In 2015, the World Health Assembly adopted a global action plan (GAP) on antimicrobial resistance (AMR). Member states were encouraged to develop their own national action plans (NAPs) in alignment with the GAP. To-date, in systematic assessments of NAPs, the Latin American specific context has not been previously analysed. Here we examined 11 Latin American NAPs published between 2015 and 2021 using content analysis. We focused on two approaches: (1) alignment between the strategic objectives and actions defined in the GAP, and those outlined in the NAPs via a content indicator; and (2) assessment of the NAPs via a governance framework covering 'policy design', 'implementation tools' and 'monitoring and evaluation' areas. We observed a high alignment with the strategic objectives of the GAP; however, the opposite was observed for the corresponding actions. Our results showed that the governance aspects contained within coordination and participation domains were addressed by every Latin American NAP, whereas monitoring and assessment areas, as well as incorporating the environment, would need more attention in subsequent NAPs. Given that AMR is a global health threat and collective efforts across regions are necessary to combat it, our findings can benefit member states by highlighting how to strengthen the AMR strategies in Latin America, while also supporting global policy formulation.

Temperature-induced developmental plasticity in Plodia interpunctella: Reproductive behaviour and sperm length.

In both plants and animals, male gametogenesis is particularly sensitive to heat stress, to the extent that a single hot or cold day can compromise crop productivity or population persistence. In animals, heat stress during development can impact a male's ability to secure copulations and/or his post-copulatory fertility. Despite such observations, relatively few studies have examined the consequences of developmental temperature on the reproductive behaviour and physiology of individuals. Here, we report for the first time the effects of developmental temperature on the phenotypic expression of both apyrene and eupyrene sperm and the copulatory behaviour of the Indian meal moth, Plodia interpunctella. We show that the length of both apyrene and eupyrene sperm decreases with increasing developmental temperature and that males are less likely to engage in copulation when reared at the highest and lowest temperatures. Where copulation occurred, the duration of copula decreased as male developmental temperature increased. We argue that identification of the mechanisms and consequences of reproductive failure in animals facing heat stress will help understand how wild and domesticated populations will respond to global climate change. We also contend that such studies will help elucidate long-standing evolutionary questions around the maintenance of genetic variation in traits highly relevant to fitness and the role of phenotypic plasticity in driving the evolution of novel traits.

Sex-Specific Differences in Thermal Fertility Limits.

Critical thermal limits (CTLs) are established viability thresholds when studying the impact of climate change on natural populations. Novel thermal fertility limits (TFLs) of species have been proposed alongside CTLs, to better assess the sublethal effects of rising temperatures on species persistence. However, sex-specific sensitivity of fertility to temperature also needs consideration.

Micropyle number is associated with elevated female promiscuity in Lepidoptera.

In the majority of insects, sperm fertilize the egg via a narrow canal through the outer chorion called the micropyle. Despite having this one primary function, there is considerable unexplained variation in the location, arrangement and number of micropyles within and between species. Here, we examined the relationship between micropyle number and female mating pattern through a comparative analysis across Lepidoptera. Three functional hypotheses could explain profound micropylar variation: (i) increasing micropyle number reduces the risk of infertility through sperm limitation in species that mate infrequently; (ii) decreasing micropyle number reduces the risk of pathological polyspermy in species that mate more frequently; and (iii) increasing micropyle number allows females to exert greater control over fertilization within the context of post-copulatory sexual selection, which will be more intense in promiscuous species. Micropyle number was positively related to the degree of female promiscuity as measured by spermatophore count, regardless of phylogenetic signal, supporting the hypothesis that micropyle number is shaped by post-copulatory sexual selection. We discuss this finding in the context of cryptic female choice, sperm limitation and physiological polyspermy.

Temporal genetic variation of the red fox, Vulpes vulpes, across western Europe and the British Isles.

Quaternary climatic fluctuations have had profound effects on the phylogeographic structure of many species. Classically, species were thought to have become isolated in peninsular refugia, but there is limited evidence that large, non-polar species survived outside traditional refugial areas. We examined the phylogeographic structure of the red fox (Vulpes vulpes), a species that shows high ecological adaptability in the western Palaearctic region. We compared mitochondrial DNA sequences (cytochrome b and control region) from 399 modern and 31 ancient individuals from across Europe. Our objective was to test whether red foxes colonised the British Isles from mainland Europe in the late Pleistocene, or whether there is evidence that they persisted in the region through the Last Glacial Maximum. We found red foxes to show a high degree of phylogeographic structuring across Europe and, consistent with palaeontological and ancient DNA evidence, confirmed via phylogenetic indicators that red foxes were persistent in areas outside peninsular refugia during the last ice age. Bayesian analyses and tests of neutrality indicated population expansion. We conclude that there is evidence that red foxes from the British Isles derived from central European populations that became isolated after the closure of the landbridge with Europe.

The welfare and suitability of primates kept as pets.

Amid growing concern about keeping exotic species as companion animals, nonhuman primates have been highlighted as inappropriate for private ownership. However, there has been no comprehensive review of the suitability of primates as pets, using a framework such as Schuppli and Fraser's (2000). Schuppli and Fraser incorporate welfare of the individual, of others, and of the environment. This article (a) examines the numbers, origins, ages, and ownership trends of primates kept as pets in the United Kingdom and (b) identifies a number of welfare, health, and environmental concerns. Overall, strong evidence supports the argument that primates are not suitable pets; it is unlikely that the welfare of pet primates can be adequately addressed in normal households. Finally, using unpublished data on complaints and inquiries received by the Royal Society for the Prevention of Cruelty to Animals, the study assesses the degree of public concern about the welfare of primates kept as pets in England and Wales. The article identifies a wide range of concerns about keeping pet primates and concludes that this practice should end.

Environmental variation at the onset of independent foraging affects full-grown body mass in the red fox.

The period following the withdrawal of parental care has been highlighted as a key developmental period for juveniles. One reason for this is that juveniles cannot forage as competently as adults, potentially placing them at greater risk from environmentally-induced changes in food availability. However, no study has examined this topic. Using a long-term dataset on red foxes (Vulpes vulpes), we examined (i) dietary changes that occurred in the one-month period following the attainment of nutritional independence, (ii) diet composition in relation to climatic variation, and (iii) the effect of climatic variation on subsequent full-grown mass. Diet at nutritional independence contained increased quantities of easy-to-catch food items (earthworms and insects) when compared with pre-independence. Interannual variation in the volume of rainfall at nutritional independence was positively correlated to the proportion of earthworms in cub diet. Pre-independence cub mass and rainfall immediately following nutritional independence explained a significant proportion of variance in full-grown mass, with environmental variation affecting full-grown mass of the entire cohorts. Thus, weather-mediated availability of easy-to-catch food items at a key developmental stage has lifelong implications for the development of juvenile foxes by affecting full-grown mass, which in turn appears to be an important component of individual reproductive potential.