Species-Specificity in Thermopreference and CO2-Gated Heat-Seeking in Culex Mosquitoes

Combining thermopreference (Tp) and CO2-gated heat-seeking assays, we studied the thermal preferendum and response to thermal cues in three Culex mosquito species exhibiting differences in native habitat and host preference (e.g., biting cold and/or warm-blooded animals). Results show that these species differ in both Tp and heat-seeking behavior. In particular, we found that Culex territans, which feed primarily on cold-blood hosts, did not respond to heat during heat-seeking assays, regardless of the CO2 concentration, but exhibited an intermediate Tp during resting. In contrast, Cx. quinquefasciatus, which feeds on warm blooded hosts, sought the coolest locations on a thermal gradient and responded only moderately to thermal stimuli when paired with CO2 at higher concentrations. The third species, Cx. tarsalis, which has been shown to feed on a wide range of hosts, responded to heat when paired with high CO2 levels and exhibited a high Tp. This study provides the first insights into the role of heat and CO2 in the host seeking behavior of three disease vectors in the Culex genus and highlights differences in preferred resting temperatures.

Biological parameters and host preference of Tyrophagus putrescentiae (Schrank) on different Pleurotus ostreatus cultivars

Tyrophagus putrescentiae (Acari: Acaridae) is a destructive pest of edible fungi. Different species of edible fungi have variable effects on the growth, development and fecundity of T. putrescentiae, but it is unclear whether these effects exist in the same species. We used nine cultivars of the oyster mushroom (Pleurotus ostreatus) to evaluate the development and reproduction parameters of T. putrescentiae at 26 ± 1°C and 80 ± 5% humidity. Different P. ostreatus cultivars had significant effects on the immature stages, female fertility, and reproductive lifespan. Total egg-to-adult development time ranged from 10.0 ± 1.2 d (on Po389 cultivar) to 12.5 ± 1.0 d (on Po62 cultivar). Mite mortality ranged from 54.3 ± 4.2% (on Po86 cultivar) to 100.0 ± 0.0% (on Po62 cultivar). The number of eggs laid per female ranged from 3.2 ± 0.4 (on Po45 cultivar) to 9.1 ± 1.1 (on Po86 cultivar). The average lifespan of females ranged from 3.0 ± 0.5 d (on Po45 cultivar) to 16.3 ± 1.7 d (on Po86 cultivar). Host preference of the mite was significantly different among the nine cultivars with a preference for cultivars Po65, Po80, Po389, and Po86. These results indicate that P. ostreatus cultivars significantly affect the biology of T. putrescentiae and the relationship between mite damage and mushroom yield.

Species composition and host preference of fleas (Insecta: Siphonaptera) on rodent and domestic animals in Tamil Nadu, India

The species composition and host preference of medically important fleas monitored in urban, semi-urban, and rural revealed 412(65%) and 222(35%) fleas. From urban and rural habitats 90 and 345 fleas were collected respectively. There was a significant difference between urban and rural habitats in flea abundance. From rodents and domestic animals 209 (33%) Xenopsylla cheopis, 203 (32%) X. astia and 222 (35%) Ctenocephalides felis fleas were recorded. Fleas were predominantly found on Rattus rattus 45(83.3%) and Canis familiaris 31(83.8%). Among the habitats, there was no significant difference in rodent flea positivity and dog/cat flea positivity.

Behavioral Responses of a Generalist Pest, Spilosoma Obliqua Walker, Towards the Leaf Surface Wax Chemicals of Three Types of Jute Crop and Implications in Pest Management

Behavioral responses of a generalist pest, Spilosoma obliqua Walker (Lepidoptera: Arctiidae), towards the leaf surface wax chemicals of three types of jute crops (white jute, Corchorus capsularis, tossa jute, C. olitorious,, and mesta jute or kenaf, Hibiscus cannabinus [Malvaceae]) and their implications in pest management was studied under laboratory conditions. The GC-MS and GC-FID analyses of the jute leaf epicuticular waxes indicated the presence of 27 n-alkanes, having chain lengths from n-C14 to n-C36 and 14 free fatty acids (FFAs) having chain lengths from C12:0 to C22:0. Among the identified n-alkanes and FFAs of selected jute cultivars n-C34 (144.397±6.971 µg leaf−1) and C16:1 (37.034±0.848 µg leaf−1) of tossa jute leaves were most abundant. The host preference (white jute> tossa jute > mesta jute) of S. obliqua was evaluated simultaneously by olfactory, visual, and tactile recognition, as valid for other lepidopteran species. For olfaction [females], oviposition [gravid females], and feeding [larvae]) in S. obliqua, the most stimulating combined-synthetic-mixture of epicuticular wax components was represented by 4 n-alkanes (n-C16, n-C18, n-C20, n-C22) and 5 FFAs (C16:1, C16:0, C18:0, C20:0, C22:0) in mixture at leaf equivalent (µg leaf−1) amounts (195.209±2.950 µg, 119.777±1.857 µg, and 50.567±3.508 µg, respectively) in white jute, tossa jute, and mesta jute, respectively. Thus, the present study suggests that the synthetic blends of 4 n-alkanes and 5 FFAs of respective jute crops can be used as lures to develop baited trap as a part of integrated pest management (IPM) of S. obliqua for sustainable jute cultivation.

Evolution of parasitoid host preference and performance in response to an invasive host acting as evolutionary trap

The invasion of a novel host species can create a mismatch in host choice and offspring survival (performance) when native parasitoids attempt to exploit the invasive host without being able to circumvent its resistance mechanisms. Invasive hosts can therefore act as evolutionary trap reducing parasitoids’ fitness and this may eventually lead to their extinction. Yet, escape from the trap can occur when parasitoids evolve behavioural avoidance or a physiological strategy compatible with the trap host, resulting in either host-range expansion or a complete host-shift. We developed an individual based model to investigate which conditions promote parasitoids to evolve behavioural preference that matches their performance, including host-trap avoidance, and which conditions lead to adaptations to the unsuitable hosts. One important aspect of these conditions was reduced host survival during incompatible interaction, where a failed attempt by a parasitoid resulted in host killing. This non-reproductive host mortality had a strong influence on the likelihood of establishment of novel host-parasitoid relationship. Killing unsuitable hosts can constrain adaptation under conditions which in fact promoted adaptation when parasitoids would leave the trap host unharmed and survive parasitoid attack. Moreover, our model revealed that host-search efficiency and genetic variation in host-preference play a key role in the likelihood that parasitoids will include the suboptimal host in their host range, or will evolve behavioural avoidance resulting in specialization and host-range conservation, respectively. Hence, invasive species might change the evolutionarily trajectory of native parasitoid species, which is important for predicting biocontrol ability of native parasitoids towards novel hosts.

The economical lifestyle of CPR bacteria in groundwater allows little preference for environmental drivers

Background The highly diverse Cand. Patescibacteria are predicted to have minimal biosynthetic and metabolic pathways, which hinders understanding of how their populations differentiate in response to environmental drivers or host organisms. Their mechanisms employed to cope with oxidative stress are largely unknown. Here, we utilized genome-resolved metagenomics to investigate the adaptive genome repertoire of Patescibacteria in oxic and anoxic groundwaters, and to infer putative host ranges. Results Within six groundwater wells, Cand. Patescibacteria was the most dominant (up to 79%) super-phylum across 32 metagenomes sequenced from DNA retained on 0.2 and 0.1 µm filters after sequential filtration. Of the reconstructed 1275 metagenome-assembled genomes (MAGs), 291 high-quality MAGs were classified as Cand. Patescibacteria. Cand. Paceibacteria and Cand. Microgenomates were enriched exclusively in the 0.1 µm fractions, whereas candidate division ABY1 and Cand. Gracilibacteria were enriched in the 0.2 µm fractions. On average, Patescibacteria enriched in the smaller 0.1 µm filter fractions had 22% smaller genomes, 13.4% lower replication measures, higher proportion of rod-shape determining proteins, and of genomic features suggesting type IV pili mediated cell–cell attachments. Near-surface wells harbored Patescibacteria with higher replication rates than anoxic downstream wells characterized by longer water residence time. Except prevalence of superoxide dismutase genes in Patescibacteria MAGs enriched in oxic groundwaters (83%), no major metabolic or phylogenetic differences were observed. The most abundant Patescibacteria MAG in oxic groundwater encoded a nitrate transporter, nitrite reductase, and F-type ATPase, suggesting an alternative energy conservation mechanism. Patescibacteria consistently co-occurred with one another or with members of phyla Nanoarchaeota, Bacteroidota, Nitrospirota, and Omnitrophota. Among the MAGs enriched in 0.2 µm fractions,, only 8% Patescibacteria showed highly significant one-to-one correlation, mostly with Omnitrophota. Motility and transport related genes in certain Patescibacteria were highly similar to genes from other phyla (Omnitrophota, Proteobacteria and Nanoarchaeota). Conclusion Other than genes to cope with oxidative stress, we found little genomic evidence for niche adaptation of Patescibacteria to oxic or anoxic groundwaters. Given that we could detect specific host preference only for a few MAGs, we speculate that the majority of Patescibacteria is able to attach multiple hosts just long enough to loot or exchange supplies.

Biological Characterization and Evolutionary Dynamics of Pigeon Paramyxovirus Type 1 in China

Pigeon paramyxovirus type 1 (PPMV-1) is considered as an antigenic variant of Newcastle disease virus (NDV) which has an obvious host preference for pigeons and has caused significant economic losses to the global poultry industry. The evolutionary dynamics of PPMV-1 in China, however, are poorly understood. In this study, we characterized seven PPMV-1 isolates from diseased pigeons collected in Jiangsu, Anhui, and Henan provinces during 2020. Phylogenetic analysis revealed that seven isolates belonged to sub-genotype VI.2.1.1.2.2. Biological characterization indicated that seven isolates were mesogenic based on the mean death time (69.6–91.2 h) and intracerebral pathogenicity index (1.19–1.40) and had similar growth kinetics in chicken embryos and CEFs. Furthermore, the four representative viruses (AH/01/20/Pi, JS/06/20/Pi, HN/01/20/Pi, and HN/02/20/Pi) could result in marked cytopathic effects (CPE) in CEFs and induced syncytium formation in Vero cells. Our Bayesian phylogenetic analysis showed that PPMV-1 might first emerge in East China in 1974 and East China had the highest genotypic diversity of PPMV-1. Besides, phylogeographic analysis indicated that East China and South China were probably the major epicenters of dissemination of PPMV-1 in China. Selection pressure analysis and amino acid substitutions analysis revealed that the viral replication complex (NP, P, and L proteins) was likely related with the host preference of PPMV-1. Collectively, this study uncovered the epidemiology and evolutionary dynamics of PPMV-1 circulating in China, emphasizing the importance of strengthening the monitoring of PPMV-1 in East China and South China and providing significant clues for further studies on the molecular mechanism underlying host preference of PPMV-1.