Chemosensory responses of Aporcelaimellus nivalis (Nematoda: Dorylaimida) towards kairomones emitted by prey nematodes belonging to different trophic groups

Abstract

Observations were made on the attraction of Aporcelaimellus nivalis towards kairomones/attractants emitted by prey nematodes belonging to different trophic categories, viz., saprophagous, epidermal, migratory semi-endodermal, predatory nematodes, virus vectors and cortical feeders. Aporcelaimellus nivalis responded positively and significantly to prey kairomones, but showed variation in their individual behaviour. Predators are most attracted towards epidermal feeders and least attracted to virus vectors. The differential responses of A. nivalis towards different prey were attributed to the inert behaviour of predators, their preference for a particular species of prey, chemical composition, concentration, quality, quantity of prey attractant, formation of minimum perceptible attraction gradient of prey and minimum response threshold of predators. Various factors such as prey density, period of prey incubation, starvation of predators, temperature, agar concentration, agar thickness and distance of predators from the source of attraction (prey) govern chemosensory responses of predator. Aporcelaimellus nivalis maximum response was towards Hirschmanniella oryzae, when tested as 10 day starved predators in agar plates containing 2 mm thick layer of 1% water-agar with 200 prey individuals previously incubated for 16 h at 30°C. Prey kairomones were most attractive when A. nivalis were tested from a distance of 2 and 3 cm.     

Schistosoma mansoni: Assessment of effects of oleic acid,cercarial age and water temperature on parasite-host attraction

Although the lifecycle of Schistosoma spp. and pathophysiology of schistosomiasis have been established, the mechanism by which cercariae find their host is not well understood. Speculatively, host infection by random and accidental host contact is not as biologically plausible as a biochemical mechanism of mammalian attraction. A few studies have indicated that biochemical cues and temperature gradients may play a role in host identification, attraction and attachment triggers. This study aimed to elucidate these mechanisms more specifically through evaluation of biochemical, age and temperature influences leading to Schistosoma mansoni cercariae attraction and attachment behaviors. Oleic acid, a common unsaturated free fatty acid in the outer layer of human skin, was tested for cercariae attraction across biologically relevant concentrations. Influence of media type (beeswax, nail varnish and agar), age-dependent behavior variability and environmentally appropriate temperatures (22 and 30 °C) were also evaluated. Results indicated that oleic acid at concentrations of 0.3, 0.9 and 1.8 g/mL in beeswax significantly increased median attachment to media (median attachment of 7.50%, 4.20% and 3.71%, respectively, P < 0.001), compared with plain beeswax, with maximal attachment of 30.30% at 0.3 g/mL of oleic acid. In media containing 0.3 g/mL of oleic acid, cercarial attachment was highest for freshly emerged cercariae to 5 h post-emergence, with a significant decrease in attachment behavior at 10 h post-emergence (P < 0.01). Aquatic temperature at which cercariae were exposed to media did not yield significant results (P value >0.05). Biochemical, age and environmental factors influencing cercarial host attraction and attachment behavior have been elucidated by this study. This information will inform further development of devices for environmental surveillance and potentially improve cercarial exposure prevention strategies.     

Niche construction initiates the evolution of mutualistic interactions

Niche construction theory explains how organisms' niche modifications may feed back to affect their evolutionary trajectories. In theory, the evolution of other species accessing the same modified niche may also be affected. We propose that this niche construction may be a general mechanism driving the evolution of mutualisms. Drosophilid flies benefit from accessing yeast‐infested fruits, but the consequences of this interaction for yeasts are unknown. We reveal high levels of variation among strains of Saccharomyces cerevisiae in their ability to modify fruits and attract Drosophila simulans. More attractive yeasts are dispersed more frequently, both in the lab and in the field, and flies associated with more attractive yeasts have higher fecundity. Although there may be multiple natural yeast and fly species interactions, our controlled assays in the lab and field provide evidence of a mutualistic interaction, facilitated by the yeast's niche modification.     

Synergism and redundancy in a plant volatile blend attracting grapevine moth females

A flight tunnel study was done to decipher the behavioral effect of grape odor in grapevine moth Lobesia botrana. A blend of 10 volatile compounds, which all elicit a strong antennal response, attracts mated grapevine moth females from a distance, by upwind orientation flight. These 10 grape volatiles are in part behaviorally redundant, since attraction to a 3-component blend of beta-caryophyllene, (E)-beta-farnesene and (E)-4,8-dimethyl-1,3,7-nonatriene was not significantly different from the 10-component blend. Blending these three compounds had a strong synergistic effect on female attraction, and omission of any one compound from this 3-component blend almost abolished attraction. It was nonetheless possible to substitute the three compounds with the other grape volatiles which are perceived by the female antenna, to partly restore attraction. Several blends, of varying composition, elicited significant attraction. The observed behavioral plasticity in response to grape volatile blends probably reflects the variation of the natural plant signal, since females oviposit on different grape varieties, in different phenological stages.     

Evaluating the phototactic behavior responses of the diamondback moth,Plutella xylostella,to some different wavelength LED lights in laboratory and field

Light traps equipped with light emitting diodes (LEDs) have been applied to manage some phototactic insect pests. The diamondback moth, Plutella xylostella, is a cosmopolitan insect pest to be seriously harmful to many cruciferous plants. The present research focused on evaluating the phototactic behavior responses of the moths to several wavelengths and photon flux densities of LED lights under laboratory and field conditions. The results from the laboratory showed that the highest phototactic behavior responses of P. xylostella moths were recorded for UV (380 nm) LED light under 1.5 µmol m⁻² s⁻¹ and 2.5 µmol m⁻² s⁻¹. The moths were more attracted to light traps equipped with 4 LEDs and 6 LEDs of 380 nm, respectively, between 20:00 and 22:00 than the other groups and night times in the field. The finding from the field was consistent with the results from the laboratory. We found that the 380 nm LED light results in the strongest attraction rate of the moths by 92.4 % and the moths caught in light trap with the UV LEDs was 1.62 times more than that with a black light. These data clearly demonstrate that P. xylostella moths have a high sensitivity to 380 nm, therefore, a 380 nm LED light trap could be useful for monitoring and controlling the moths.     

Relationships in six groups of rhesus monkeys II. Dyads

Dyadic relationships are described for rhesus monkeys living in six groups. The kinds, frequencies, directionality, and overall patterning of interactions are examined over a twelve-month period for adult males, adult females, and young monkeys. Kinship, sex, age, reproductive conditions, time, events, and other social relations all affected dyadic relationship. Certain patterns of interactions characterized different relationships, such as those termed “special,” “tense,” “affiliative,” “conflicting.” A component approach is recommended for the understanding of relationships based on an appraisal of attraction, familiarity, and deference between individuals. The importance of assessing relationships in the group context is stressed.     

Attraction of the sexes inFormica lugubris Zett (Hymenoptera: Formicidae)

Summary Sexuals ofFormica lugubris fly to mating places, where females attract males by using a sex pheromone. Females collected on the nest surface before departing on a mating flight are much less attractive than those collected on the mating place after the mating flight, suggesting that the mating flight triggers the release of the sex pheromone. Olfactory cues are essential for males to locate females while they patrol. Males probably use visual cues to locate females once they have alighted nearby them. Males are also attracted by aggregations of other males on the ground, probably because one or several females are likely to be close to male aggregations.     

Facial correlates of sociosexuality

Previous studies have documented variation in sexual behaviour between individuals leading to the notion of ‘restricted’ individuals (i.e., people who prefer long-term relationships) and ‘unrestricted’ individuals (i.e., people who are open to short-term relationships). This distinction is often referred to as sociosexual orientation. Observers have been previously found to distinguish sociosexuality from video footage of individuals, although the specific cues used have not been identified. Here we assessed the ability of observers to judge sexual strategy based specifically on cues in both facial composites and real faces. We also assessed how observers' perceptions of the masculinity/femininity and attractiveness of faces relate to the sociosexual orientation of the pictured individuals. Observers were generally able to identify restricted vs. unrestricted individuals from cues in both composites and real faces. Unrestricted sociosexuality was generally associated with greater attractiveness in female composites and real female faces and greater masculinity in male composites. Although male observers did not generally associate sociosexuality with male attractiveness, female observers generally preferred more restricted males' faces (i.e., those with relatively strong preferences for long-term relationships). Collectively, our results support previous findings that androgenisation in men is related to less restricted sexual behaviour and suggest that women are averse to unrestricted men.     

Alternative attractors in an ecological-genetic model of populations with non-overlapping generations

This study classifies and analyzes various bifurcations of fixed points of the simple model of population dynamics with its number described by Ricker’s model and intrapopulation parameters determined by a single di-allelic locus. The model considered shows such nonlinear phenomena as multistability and coexistence of alternative attractors, which can violate the simple combination of the action of evolutionary-genetic and density-dependent ecological-dynamic processes, where gene elimination is determined by the genotypes’ resource parameters and the population number stability depends on their Malthusian parameters. The most interesting pattern in this regard is existence of polymorphic attractors, when the resource parameter of heterozygotes is not maximal. It presents a clear violation of the principle of natural selection optimality, which is caused precisely by the multistable phenomena of nonlinear dynamics. By which of the alternative attractors the dynamics is characterized by depends sensitively on the initial conditions, even small external influences can became significant, as they can shift the system from one attraction basin to another, and thus fundamentally change the dynamic mode and nature of the evolutionary process.     

Improvement of protein bait produced from beer yeast waste for controlling Bactrocera dorsalis (Diptera: Tephritidae) in China

In the present study, preservatives and antibiotics were applied in a variety of doses to assess their effects on the beer waste-based protein bait, a product widely used to control populations of Bactrocera dorsalis (Diptera: Tephritidae). Screening was performed using the inhibition zone method against the dominant bacteria in deteriorated protein bait. Additionally, the attractiveness of the bait was assessed after respectively adding different doses of methyl eugenol, brown sugar solution, ammonium acetate, and guava essence, as determined by bio-cage tests. The results showed that the four selected preservatives had different inhibition effects at different dose levels, and that the level of inhibition increased with dose: at the highest dose of 1:1 (v:v), sodium benzoate can significantly inhibit Staphylococcus spp., potassium sorbate can significantly inhibit Lactobacillus spp., sodium nitrite can significantly inhibit Escherichia spp. and ethyl p-hydroxybenzoate can significantly inhibit Staphylococcus spp. and Xanthomonas spp. Among three antibiotics, kanamycin was the most effective in suppressing a mix of all four bacteria for all tested doses. In terms of lure performance, the addition of four substances in various ratios into the protein bait were found to have varying effects on its attractiveness to B. dorsalis females and males. Specifically, the addition of a high-dose of guava essence could significantly enhance the attractiveness of the bait. Our findings will help to enhance the effectiveness of protein bait applications by prolonging the quality guarantee period and improving its attractiveness toward both female and male B. dorsalis.