Balancing memory fidelity and representational stability in the female mouse accessory olfactory bulb

Sensory systems must balance the value of efficient coding schemes against the need to update specific memorized representations without perturbing other memories. Here we describe a unique solution to this challenge that is implemented by the vomeronasal system (VNS) to encode and remember multiple conspecific individuals as part of the Bruce Effect (BE). In the BE, exposure of a pregnant female mouse to the odors of an unfamiliar male leads to failure of the pregnancy (pregnancy block) via the VNS. Following mating and sensory exposure, however, the female becomes protected from a pregnancy block by the stud individual. While this form of natural learning has been proposed to depend on changes in the representation of his odors in her accessory olfactory bulb (AOB), a key VNS structure, there are no direct comparisons of in vivo sensory responses before and after imprinting. It has further been suggested that these changes simply render the AOB insensitive to stud odors. However, the combinatorial odor code used by the AOB and the significant overlap in the odor composition of different males means that silencing responses to one individual is likely to degrade responses to others, posing potential problems for more general sensory encoding. To identify the neuronal correlates of learning in the context of the BE, we recorded extracellular responses of AOB neurons in vivo in mated and unmated female mice upon controlled presentation of urinary chemosignals, including urine from both the stud and males of a distinct strain. We find that while initial sensory responses in the AOB (within a timescale required to guide social interactions) remain stable, responses to extended stimulation (as required for eliciting the pregnancy block) display selective attenuation of stud-responsive neurons. Based on our results, we propose a model that reconciles the formation of strong, selective memories with the need to sustain robust representational bandwidth by noting a distinction between the representations of brief and extended stimuli. This temporal disassociation allows attenuation of slow-acting endocrine processes in a stimulus-specific manner, without compromising consistent ongoing representations of stimuli that guide behavior.

Lethal and Sublethal Effects of Conventional and Organic Insecticides on the Parasitoid Trissolcus japonicus, a Biological Control Agent for Halyomorpha halys

The egg parasitoid Trissolcus japonicus is a natural enemy of Halyomorpha halys, a polyphagous invasive pest in Europe and North and South America. Integration of chemical and biological control tactics could facilitate effective and sustainable integrated pest management programs. This study was conducted to assess (i) the lethal effects of field rates, (ii) the sublethal effects of maximum and half field rates, and (iii) the lethal effects of different routes of exposure of three organic and two conventional insecticides against T. japonicus. Maximum field rates of spinosad and sulfoxaflor resulted in acute lethal toxicity to adult T. japonicus 1 week after residual contact exposure. Maximum and half field rates of pyrethrins, the mixture of azadirachtin and pyrethrins, and clothianidin caused sublethal effects to female wasps through residual contact exposure. Furthermore, all insecticides caused acute lethal effects 1 week after ingestion by unmated female wasps. Taken together, these results suggest that careful planning is necessary to ensure compatibility between biological and chemical control for H. halys. The insecticides evaluated in this study varied in toxicity to T. japonicus and should be used with caution to conserve this natural enemy for biological control of H. halys.

Effect of Constant Temperatures on Biological Parameters of Tuta absoluta (Meyrick, 1917) on Tomato Plants in Case of Asexual Reproduction (Parthenogenesis

Tomato leafminer Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae) is a key devastating pest worldwide, it has the capacity to develop on a wide range of Solanaceous plants but tomato (Solanum lycopersicum L.) is considered to be its preferred host. This study was carried out at the Agricultural Scientific Research Centre in Latakia in 2019 to estimate biological parameters of T. absoluta and evaluate the effect of temperature in its development, longevity, reproduction in parthenogenesis. The experiments were carried out at constant temperatures (10, 20, 30˚ C), 60-65% RH, and photoperiod (16L: 8D). Biological parameters were analyzed according to the theory of age-stage two-sex life table by using the computer program TWO-SEX MSchart. The highest value of intrinsic rate of increase (r), the final increase rate (λ), and net reproductive rate (Ro) were 0.0439±0.0028 females/female/day, 1.0449±0.0029, and 7.01±0.8705 females/female/generation, respectively, at 20˚C. The lowest value of net reproductive rate (Ro) was 0.92±0.1250 females/female/generation at 30˚C. Generation time (T) was the longest (44.3±0.203 days) at 20˚C and decreased to 26.38±1.156 days at 30˚C. T. absoluta completed its development at all these temperatures. The results obtained showed that the effect of temperature on the insect development from egg to adult decreased with increased temperature. The shortest development period on egg, larva and pupa development was 3.95±0.149, 11.975±0.075 and 4.95±0.086 days, respectively, at 30˚C. This means that the development time from egg to adult was shorter (20.8±1.151 days) at 30˚C as compared to 34.51±0.127 days at 20˚C, and longest at 10˚C (125.4±1.211 days). The female longevity was longer (61.35±0.25 days) at 20˚C. The highest rate of fecundity was 12.98±1.072 eggs/unmated female, and the lowest was 2.19±0.152 eggs/unmated female at 30˚C. Moreover, the unmated females kept at 10˚C did not lay eggs, and unfertilized eggs (asexually produced eggs) laid by unmated females at 20 or 30˚C did not hatch. The adult pre-oviposition period (APOP) of unmated females was 2.57±0.1368 days at 20˚C and 4.31±0.2629 days at 30˚C, whereas the total APOP of females was 36.86±0.1844 days at 20˚C and 24.21±0.3039 days at 30˚C. Keywords: Tomato leaf miner, Life tables, asexual reproduction, Parthenogenesis, Syria

Behavioural Evidence and Chemical Identification of a Female Sex Pheromone in Anagrus atomus (Hymenoptera: Mymaridae)

Anagrus atomus (L.) is an egg parasitoid involved in the biological control of Empoasca vitis (Göthe) in vineyards. Sex pheromones play a crucial role in mate finding for several parasitoid species and could be used for monitoring under field conditions. We carried out laboratory and field studies aimed at assessing the existence and identity of a possible A. atomus sex pheromone. We found that males were significantly attracted by virgin females independent of age. Males were not attracted to individuals of the same sex, but they were attracted by a crude extract from an unmated female and its polar fraction. Eugenol (4-allyl-2-methoxyphenol) was identified as the attractive substance and proved to be attractive not only in the olfactometer but also in another laboratory bioassay and under field conditions. Attraction of males, but not females, confirms that this is not an aggregation pheromone. This is the first sex-pheromone component identified in Mymaridae, however more compounds could be involved in the mating behaviour of A. atomus. The utility of a sex pheromone in A. atomus is discussed in the context of fitness returns.

Behavioural Evidence and Chemical Identification of a Female Sex Pheromone in Anagrus Atomus (Hymenoptera: Mymaridae)

Anagrus atomus (L.) is an egg parasitoid used for the biological control of Empoasca vitis (Goethe) in vineyards. Sex pheromones play a crucial role in mate finding process of several parasitoid species and could be used for monitoring under field conditions. We carried out lab and field studies aiming at assessing the existence and identity of a possible A. atomus sex pheromone. We found that males were significantly attracted by virgin female independently from female age. Males were not attracted from individuals of the same sex but they were attracted by crude extract of an unmated female and its polar fraction. Eugenol (4-allyl-2-methoxyphenol) was identified as the attractive substance and proved to be attractive not only in the olfactometer but also in another laboratory bioassay and under field conditions. Attraction of males, but not females, confirms that this is not an aggregation pheromone. This is the first sex-pheromone component identified in Mymaridae but more compounds could be involved in the mating behaviour of A. atomus. The utility of a sex pheromone in A. atomus is discussed in the context of fitness returns.

Quantification of the Life Time Flight Capabilities of the South American Palm Weevil, Rhynchophorus palmarum (L.) (Coleoptera: Curculionidae)

The life time flight capabilities of an invasive palm pest, Rhynchophorus palmarum, were assessed using flight mill assays under controlled conditions in the laboratory. A total of 101 weevils were used for experiments and subjected to repeat flight assays. A total of 17 flight trials were run, of which the first 14 provided useful data prior to weevil death. Male and female weevils exhibited a strong capacity for repeat long distance flights. Flight metrics of interest were not affected by weevil sex or mating status. Cumulative lifetime flight distances for male and female R. palmarum averaged ~268 km and ~220 km, respectively. A maximum lifetime cumulative flight distance of ~758 km and ~806 km was recorded for one male of unknown mating status and one unmated female weevil, respectively. Dispersal data for individual flights (i.e., trials 1 through 9, 10–14 combined) and all flight trial data (i.e., flights 1–14 combined) exhibited platykurtic distributions. The results presented here may have important implications for modeling the spread of this invasive pest and for the development of monitoring and management plans.

Biology of Raoiella indica Hirst. (Acari: Tenupalpidae) on Arecanut Leaves under Laboratory Conditions

Biology of Raoiella indica Hirst was studied under laboratory at 27 ± 2°C temperature and 79 ± 5.75 percent RH. The finding showed that life cycle of R. indica consisted of five stages viz., eggs, larva, protonymph, deutonymph and adult. The eggs incubation period of R. indica was 9.790 ± 1.94 days. The larval body measured 0.09 and 0.13 mm in length and 0.08 to 0.10 mm in width and lived for 8.35 ± 0.84 days. The total developmental period of female was 29.80 ± 2.73 days and male took 31.27±40 days. Mated female lived for longer time and laid higher number of eggs than unmated female.

Effects of Non-Lethal High-Temperature Stress on Bradysia odoriphaga (Diptera: Sciaridae) Larval Development and Offspring

Throughout China, the dipteran pest Bradysia odoriphaga significantly reduces Chinese chive production; therefore, identifying conditions that influence its growth and development is crucial for developing ecological regulation strategies. In this study, different non-lethal high temperatures and treatment durations were used to stress the third-instar larvae of B. odoriphaga, and the effects of this treatment on their growth and offspring were recorded and analyzed. The results showed that the average larval mortality increased with increased temperature and prolonged exposure times. After stress treatment at 40 °C for 2 h, 100% of larvae died within 5 days, which was not significantly different from the 5-day average larval mortality (90.66%) after stress at 37 °C for 4 h, but significantly higher than the 5-day average larval mortality (72.00%) after stress at 40 °C for 1 h. After 5 days, all still-living larvae could pupate, and there was no significant difference in average pupal period after pupation. However, the eclosion rate of subsequent pupae decreased with increased temperature and prolonged exposure times, and were only 43.00% and 42.73% after larvae were stressed at 37 °C for 4 h and 40 °C for 1 h, respectively. After eclosion into adults, there was no significant difference in the lifespan of unmated female adults, while the lifespan of unmated male adults was significantly reduced to 1.67 d and 2 d after larvae were stressed at 37 °C for 4 h and 40 °C for 1 h, respectively. However, there was no significant difference in male and female adult longevity after mating. There was no significant difference in oviposition or egg hatchability. This indicates that non-lethal high temperature at 37 °C for 4 h can hinder development and allow control of B. odoriphaga. There is great potential for non-lethal high temperature to be applied in the field to control agricultural pests.

Biology and rearing of the cogongrass gall midge, Orseolia javanica Kieffer & Docters van Leeuwen-Reijnvaan (Diptera: Cecidomyiidae)

ABSTRACTImperata cylindrica (L.) Beauv. (Poaceae) is one of the most harmful weeds in the world because of its ability to spread and form high density, monospecific stands that exclude other vegetation. The cogongrass gall midge, Orseolia javanica Kieffer & Docters van Leeuwen-Reijnvaan (Diptera: Cecidomyiidae), is a stem galling insect that is only known to develop in cogongrass and has only been found on the island of Java in Indonesia. The midge attacks very young shoots, which stimulates abnormal growth, resulting in the formation of a purplish, elongate stem gall tappered to a point at the apical end. The aim of the current research was to describe the biology of the midge and develop a rearing method. Orseolia javanica completed its life cycle in 12-38 days with average egg, larval, and pupal periodes of 4.0 ± 0.0, 13.5 ± 3.8, and 8.6 ± 6.6 days (mean ± SD), respectively. Mated female, unmated female, and male longevities were 1.7 ± 0.47, 1.2 ± 0.41, and 1.0 ± 0.00 days (mean ± SD). Galls began to appear 29 days after larval infestation, and stem death coincided with emergence of the adult midge. The midge may have potential for biological control of cogongrass if future studies confirm a restricted host range.

Biological traits and susceptibility of Delia antiqua (Meigen, 1826) (Diptera: Anthomyiidae) in onion

The pre-oviposition period of mated and unmated female reared on Bangladeshi and Indian onion was 4.5 ± 0.5, 4.37 ± 0.6 days and 4.11 ± 0.09, 4.45 ± 0.32 days, respectively. The oviposition period of mated and unmated female was 5.6 ± 0.6, 6.03 ± 0.6 days and 6.48 ± 0.39, 6.5 ± 0.34 days reared on Bangladeshi and Indian onion, respectively. The life cycle of Delia antiqua consisted of four definite stages: egg, larva, pupa and adult. The incubation period was1.38 ± 0.11 and 1.25 ± 0.05 days; larval period was 5.7 ± 0.7 and 5.4 ± 0.05 days; pupal period was 6.8 ± 0.2 and 6.08 ± 0.2 days, respectively. There were three larval instars in D. antiqua. To complete the total life cycle it required shorter period in Indian than in Bangladeshi onion. The total life cycle of female was 16.73 ± 0.89 and 15.29 ± 0.45 days, respectively on Bangladeshi and Indian onion. The difference between the life cycle of female was significant (p < 0.05) in Bangladeshi and Indian onion. Fecundity was higher in Indian than in Bangladeshi onion. The fecundity of female D. antiqua reared in Bangladeshi and Indian onion was 75.2 ± 4.09 and 89.2 ± 2.39, respectively and it was significantly (p < 0.05) varied. Female lived longer than male D. antiqua. It was more susceptible in Indian than Bangladeshi onion irrespective of the duration of life cycle and fecundity. Bangladesh J. Zool. 47(2): 325-332, 2019