Mosquito Host-Seeking Diel Rhythm and Chemosensory Gene Expression is Affected by Age and Plasmodium Stages

Malaria parasites can affect vector-related behaviours, increasing transmission success. Using Anopheles gambiae and Plasmodium falciparum, we consider the effect of interaction between infection stage and vector age on diel locomotion in response to human odour and the expression of antennal chemosensory genes. We demonstrate age-dependent behavioural diel compartmentalisation by uninfected females. Infection disrupts overall and diel activity patterns compared with age-matched controls. Mosquitoes carrying transmissible sporozoites are more active, shifting activity periods to coincide with human host availability, in response to human odour. Older, uninfected females reduce activity during their peak host-seeking period in response to human odour. Age- and infection stage-specific changes in odour-mediated locomotion coincide with altered transcript abundance of select chemosensory genes providing a possible molecular mechanism regulating the behaviour. Our results support the hypothesis that vector-related behaviours of female mosquitoes are altered by infection stage and further modulated by the age of the vector, and have important implications for malaria transmission and disease dynamics.

Diel Activity Patterns of Two Distinct Populations of Aedes Aegypti in Miami, FL and Brownsville, TX

The diel biting activity of Aedes (Stegomyia) aegypti (L) populations was extensively investigated in the early 1900s to gain more information on the biology of Ae. aegypti, and this information was used to devise effective approaches to controlling populations of this species and protect the human population from widespread arbovirus outbreaks. However, few contemporary studies are available regarding the diel activity patterns of Ae. aegypti. To assess the diel activity patterns of Ae. aegypti in southern Florida and Texas, we conducted 96-hour uninterrupted mosquito collections once each month from May through November 2019 in Miami, Florida, and Brownsville, Texas, using BG-Sentinel 2 Traps. The overall diel activity pattern in both cities was bimodal with morning and evening peak activity between 7:00 and 8:00 and between 19:00 and 20:00. There were significant daily, monthly, seasonal, and site-specific differences in activity patterns, but these differences did not affect the overall peak activity times. These differences suggest daily, monthly, seasonal, and site-specific variations in human exposure to Ae. aegypti. Our observations can be used in planning and executing Ae. aegypti vector control activities in southern Florida and Texas, especially those targeting the adult mosquito populations.

A closer look at pupil diversity and evolution in frogs and toads

The eyes of frogs and toads (Anura) are among their most fascinating features. Although several pupil shapes have been described, the diversity, evolution, and functional role of the pupil in anurans have received little attention. Studying photographs of more than 3200 species, we surveyed pupil diversity, described their morphological variation, tested correlation with adult habits and diel activity, and discuss major evolutionary patterns considering iris anatomy and visual ecology. Our results indicate that the pupil in anurans is a highly plastic structure, with seven main pupil shapes that evolved at least 116 times during the history of the group. We found no significant correlation between pupil shape, adult habits, and diel activity, with the exception of the circular pupil and aquatic habits. The vertical pupil arose at least in the most-recent common ancestor of Anura + Caudata, and this morphology is present in most early-diverging anuran clades. Subsequently, a horizontal pupil, a very uncommon shape in vertebrates, evolved in most neobatrachian frogs. This shape evolved into most other known pupil shapes, but it persisted in a large number of species with diverse life histories, habits, and diel activity patterns, demonstrating a remarkable functional and ecological versatility.

Seasonal and diel activity patterns of the endangered taiga bean goose (Anser fabalis fabalis) during the breeding season, monitored with camera traps

Taiga bean goose (Anser fabalis fabalis) is an endangered subspecies that breeds sporadically in remote habitats in the arctic and boreal zones. Due to its elusive behaviour, there is a paucity of knowledge on the behaviour of taiga bean goose during the breeding season, and survey methods for monitoring numbers in the breeding areas are lacking. Camera traps are a useful tool for wildlife monitoring, particularly when there is a need for non-invasive methods due to the shy nature of the species. In this study, we tested the use of camera traps to investigate seasonal and diel activity patterns of taiga bean goose in Finland over two successive breeding seasons, 2018 and 2019. We did this by modelling counts of geese from images with generalized linear and additive mixed models. The camera type (cameras placed by experts specialized in bean goose ecology vs randomly placed cameras) did not influence the count of taiga bean goose (p = 0.386). However, the activity varied significantly by region, Julian day, time of day and temperature, with the study site (individual peatland) and year adding substantial random variation and uncertainty in the counts. Altogether, the best fitting model explained nearly 70% of the variation in taiga bean goose activity. The peak in activity occurred about a month later in the southernmost region compared to the more northern regions, which may indicate behaviours related to migration rather than breeding and moulting. Our results show that long-term monitoring with game camera traps provide a potential unobtrusive approach for studying the behavioural patterns of taiga bean goose and can increase our ecological knowledge of this little-known subspecies. The results can be applied to planning of the annual censuses and finding the optimal time frame for their execution.

Predation risk increases intraspecific heterogeneity in white-tailed deer diel activity patterns

Prey species often mitigate predation risk through alteration of spatiotemporal diel activity patterns whereby prey access high-quality resources in risky areas during predator downtimes. However, dominance hierarchies exist in some prey species, and temporal partitioning is a mechanism thought to reduce aggressive intraspecific interactions. How demographic-specific responses to predation risk influence intraspecific temporal partitioning in prey are largely unknown and could be key to understanding the effects of predators on intraspecific interactions in prey. To assess the effects of predation risk on intraspecific interactions in white-tailed deer (Odocoileus virginianus), we monitored deer diel activity during the fawning season in four pairs of predator exclusion and control plots (~40 ha) from 2015 to 2018 using 16 camera traps. We examined the effect of predation risk on diel activity of males, females, and nursery groups by comparing the within-group coefficient of activity overlap (d̂) across predator exclusion and control plots. We then examined within-treatment activity overlap between groups in the predator exclosure and control plots. All groups maintained different diel activity patterns in safe and risky areas. Unconstrained by predation risk, all groups behaved more similarly, and interspecific group overlap was greater in the predator exclusion plots than control plots. Male-nursery group overlap exhibited the strongest treatment effect, increasing 24% in predator exclusion plots (d̂ = 0.91, confidence interval [CI]: 0.87–0.95) relative to control plots (d̂ = 0.67, CI: 0.57–0.76). Our results suggest predators increase heterogeneity in prey behavior and may be important drivers of behavioral processes, such as temporal partitioning, that minimize antagonistic intraspecific interactions of prey.