Daily Oviposition Research Articles

Sublethal effects of spiromesifen on life table traits of Tetranychus urticae (Acari: Tetranychidae) and Neoseiulus californicus (Acari: Phytoseiidae)

The assessment of long-term negative effects of insecticides on the target and non-target insects can help assess the toxicity and side-effects of pesticides. In this study, the sublethal effects of a low concentration of spiromesifen (LC<sub>20</sub>) on life-history traits of T. urticae and its phytoseiid predator N. californicus were estimated for two successive generations (F0 and F1). According to the results, adult longevity, oviposition days, fecundity, and life table parameters (r<sub>m</sub>, R<sub>0</sub>, and T) exhibited significant negative impacts at LC<sub>20</sub> compared to the control. Meanwhile, significant effects of the LC<sub>20</sub> were found on most parameters of the life table (longevity, fecundity, oviposition days) of N. californicus. Also, spiromesifen had significant negative effects on the population parameters except for the net reproductive rate (R<sub>0</sub>) in N. californicus. On the other hand, the parameters of the consumption rate (finite predation rate (ω), stable consumption rate (ψ), and net consumption rate (C<sub>0</sub>)) in this predator exhibited significant negative impacts. Therefore, the results suggested that spiromesifen effectively controls the successive generation of T. urticae. Also, this compound adversely affected most parameters of N. califonicus, so it is inappropriate for IPM applications in the presence of this parasitoid.

Life table, survival and fecundity parameters of Aedes albopictus (Diptera: Culicidae) strains from desert and coastal regions of India

The Asian tiger mosquito, Aedes albopictus (Skuse, 1895) is the anthropophilic and day-biter mosquito, residing in peridomestic habitats and is responsible for vector-borne diseases, i.e., chikungunya and dengue. The knowledge of mosquito life demographics is very important to provide a foundation for a successful vector control program. In the present study, a comparative adult life table, survival, and fecundity parameters were evaluated on desert (Jodhpur, Rajasthan) and coastal (Kolkata, West Bengal) strains of Aedes albopictus (Diptera: Culicidae) from India under the standard laboratory conditions. The results showed significant differences between these strains for the life expectancy of males, fecundity (total eggs/cohort and eggs/female life span), oviposition days, intrinsic rate of increase (rm), finite rate of increase (λ), and doubling time (DT). Female mosquitoes lived longer than the males in both strains. Significant differences were observed in the net reproductive rate (R0) between Kolkata and Jodhpur strains. The coastal (Kolkata) strain showed a longer male life expectancy (5.6 days) than the desert strain (4.0 days). However, the fecundity (eggs/female lifespan) was higher in Kolkata (360.2) than the Jodhpur strain (229.7). The Kolkata strain showed higher R0, rm, λ, and the lower T, DT than the Jodhpur strain. Conclusively, the results indicate that the coastal strain of Ae. albopictus is more r-strategist than the desert strain. This study may help in the precise prediction of Ae. albopictus population dynamics surviving in these geographical areas for vector management.

Suitability of monotypic and mixed diets for development, population growth and predation capacity of Typhlodromus bagdasarjani (Acari: Phytoseiidae).

We quantified the life table parameters and predation capacity of a generalist predatory mite, Typhlodromus bagdasarjani Wainstein and Arutunjan on five monotypic diets, including Tetranychus urticae Koch (TSSM) eggs in the presence (SW) and absence (SN) of webs, Trialeurodes vaporariorum Westwood (GHWF) eggs (G), honeydew (H), and maize pollen (M) as well as three mixed diets, including SN + M, SN + G, and G + M. Our results showed that the individuals fed on the mixed diets had a considerably shorter developmental time and pre-oviposition period (APOP), higher oviposition days, higher fecundity and population growth rate than those raised on the monotypic diets. Furthermore, we found that the mixed diet of TSSM and GHWF eggs was the most favorable diet, resulted in the highest fecundity and population growth rate, shortest developmental time and APOP. While TSSM eggs alone in the presence of webs and honeydew were the worst diets resulted in the longest developmental time, lower oviposition day, higher fecundity and population growth rate. Our data determined that TSSM has more nutritional benefits than GHWF for T. bagdasarjani. We observed the positive effects of pollen addition to prey on the predatory mite's immature and adult life-history characters; however, it reduced the predation rate. Overall, maize pollen could enhance ecosystem services provided against spider mites and whiteflies by positively impacting the increase of T. bagdasarjani population. This predator may be more effective when two prey species are available than when only one species is present.

Cross-Resistance and Fitness Costs of the cis-Nitromethylene Neonicotinoid Cycloxaprid Resistance in Melon Aphid, Aphis gossypii (Hemiptera: Aphididae).

The melon aphid, Aphis gossypii Glover, is an important pest on various vegetables around the world and has developed resistance to neonicotinoids in fields. Cycloxaprid is a novel cis-nitromethylene configuration neonicotinoid insecticide that is different from trans-configuration neonicotinoids like imidacloprid and thiamethoxam. Herein, the cross-resistance to the other seven insecticides and fitness costs were investigated in the cycloxaprid-resistant A. gossypii strain (Cpd-R), which has developed 69.5-fold resistance to cycloxaprid. The results showed that the Cpd-R strain had very low levels of cross-resistance to imidacloprid (4.3-fold), acetamiprid (2.9-fold), thiamethoxam (3.7-fold), nitenpyram (6.1-fold), flupyradifurone (2.2-fold), and sulfoxaflor (4.5-fold), while it exhibited a cross-resistance to dinotefuran (10.6-fold). The fitness of the Cpd-R strain by life table analysis was only 0.799 compared to the susceptible strain (Cpd-S). This Cpd-R strain exhibited significantly reduction in fecundity, oviposition days, and developmental time of nymph stage compared to the Cpd-S strain. Moreover, the expression levels of some genes related to the development and reproduction, including EcR, USP, JHAMT, and JHEH were significantly up-regulated, while Vg was down-regulated in the Cpd-R strain. This study indicates that the Cpd-R strain possessed a certain fitness cost. The above research results are useful for rational application of cycloxaprid and implementing the appropriate resistance management strategy for A. gossypii.

Bottom-up effects of drought on the growth and development of potato, Leptinotarsa decemlineata Say and Arma chinensis Fallou.

Global climate change will result in increasingly arid weather that will have a significant impact on agriculture. The occurrence dynamics of plants, phytophagous insects and their natural enemies under drought conditions have attracted much attention. The consequences could be useful for controlling insect herbivores. Leptinotarsa decemlineata (Say) is one of the most important pests of potato, and causes serious damage to potato production. Arma chinensis (Fallou) is a parasitoid of L. decemlineata. However, how drought will affect tritrophic interactions between potato and these insects remains unknown. In this experiment, L. decemlineata and A. chinensis were released onto potato plants under water stress. Thereafter, plant height, stem diameter and yield of potato, growth and reproduction of L. decemlineata, and the longevity of A. chinensis adults were periodically recorded. The results showed that drought had crucial effects on height, stem diameter and yield of potato (p < 0.05); it also had a significant impact on pre-oviposition period, oviposition days, fecundity and life table parameters in L. decemlineata (p < 0.05). Moreover, drought significantly reduced the longevity (p < 0.05) and survival rate of A. chinensis adults. The longevity of adult A. chinensis was only 29.00 ± 3.00 days and the harvest rate of L. decemlineata adults was only 1.42% ± 0.07% under drought treatment. In this experiment, we evaluate the bottom-up effects of drought on tritrophic interactions involving potato, L. decemlineata and A. chinensis, and discuss the implications of the findings for integrated pest management programs involving the pest. Promising future research directions are proposed. © 2022 Society of Chemical Industry.

Transovarial toxicity matters: lethal and sublethal effects of hexythiazox on the two-spotted spider mite (Acari: Tetranychidae).

The effects of hexythiazox on life-history traits and demographic parameters of Tetranychus urticae Koch (Acari: Tetranychidae) were evaluated using the age-stage two-sex life table (in fecundity-based and fertility-based variants), with emphasis on its transovarial toxicity. Hexythiazox was applied when T. urticae females were either in the preovipositional period or in the first day of oviposition. In the F0 generation bioassay, treatments with concentrations of 50, 12.5 and 3.125mg/l significantly reduced the longevity of females and their fecundity. These effects were mostly the result of mortality of treated females (18-23%) over the 24-h exposure period. Even though the net reproductive rate (R0) decreased significantly, the intrinsic rate of increase (r), finite rate of increase (λ) and doubling time (D) were not significantly different from the control. The strongest transovarial toxic effect occurred within the first 4 days following treatment, when 52-89% of the eggs laid by treated females (96% in control) hatched. Fertility was significantly reduced by concentrations of 50, 12.5, 3.125, 0.781 and 0.195mg/l. These concentrations caused significant reductions in R0 (34-54%), r (12-24%) and λ (3-5%), whereas D was extended for 0.4-0.7days. In the F1 generation bioassay, 50, 12.5, 3.125, 0.781, 0.049 and 0.012mg/l caused significant reductions in R0 (34-92%), r (10-68%) and λ (3-17%), whereas extending D for 0.3-5.6days. These effects were mostly the consequence of transovarial toxicity. Application of the fecundity-based life table underestimated population-level effects of hexythiazox on T. urticae.

A sublethal concentration of afidopyropen suppresses the population growth of the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae)

The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is an important insect pest of cotton crops worldwide. The objectives of this study were to determine the acute toxicity of afidopyropen and whether there are any effects of sublethal concentrations of afidopyropen on the biological characteristics of A. gossypii. The results showed that afidopyropen possesses high acute toxicity to adult A. gossypii with a 72 h LC50 value of 1.062 mg L–1. A sublethal concentration (LC10) of afidopyropen significantly decreased adult longevity, fecundity and oviposition days of female adults in both F0 and F1 generations. The total pre-adult survival of F1 progeny was also significantly reduced by 30% at the LC10 of afidopyropen. In addition, the nymph developmental time, pre-adult period, adult pre-reproductive period (APRP), and total pre-reproductive period (TPRP) of the F1 progeny were significantly prolonged compared with the control. Several population parameters, including the net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (λ) of F1 progeny were significantly decreased by a sublethal afidopyropen concentration exposure. These results indicated that sublethal concentration of afidopyropen can significantly suppress A. gossypii population growth. It would be useful for assessing the overall effects of afidopyropen on A. gossypii.

Multigenerational Insecticide Hormesis Enhances Fitness Traits in a Key Egg Parasitoid, Trichogramma chilonis Ishii

Hormesis for the intractable pests can be dreadful, but for natural enemies of pests, it is a puissant strategy in optimizing their mass rearing. We report multigenerational stimulatory effects of widely used insecticide, imidacloprid, on the demographic traits of an important egg parasitoid Trichogramma chilonis Ishii. The study investigated the consequences of sublethal (LC5), low lethal (LC30), and median lethal (LC50) concentrations, as well as a control, for five continuous generations (F1 to F5). The initial bioassay experiments revealed imidacloprid exhibiting the highest toxicity for the parasitoid with a LC50 of 2 µg·L−1, whereas LC5 and LC30 were 0.07 µg·L−1 and 0.6 µg·L−1, respectively. Among biological traits, compared to the F1 individuals, a substantial increase in the fecundity of T. chilonis was observed in the F5 individuals by 54.92% and 46.81% when exposed to LC5 and LC30, respectively (p &lt; 0.00001). Further, there was a significant enhancement in the adult longevity as well as oviposition days of the F5 individuals at both these concentrations. Considering the population traits, along with gross reproductive rate (GRR), net reproductive rate (R0) was also enhanced by both LC5 and LC30 in F5 individuals than F1; whereas the intrinsic rate of increase (r) and finite rate of increase (λ) were enhanced only at LC30 upon comparing with control. On the other hand, LC50 exposure to T. chilonis did not result in notable differences in biological or population traits when compared across generations (F1 and F5). Low and sublethal concentrations of imidacloprid did not have a major influence on demographic traits of T. chilonis at initial generations of exposure but can induce hormetic effects in the subsequent generations. Overall, imidacloprid-induced hormesis stimulating the development of T. chilonis might be helpful under circumstances of mild exposure of imidacloprid in fields and could be leveraged for its mass rearing.

Suitability of spider mites and green peach aphids as prey for Eriopis connexa (Germar) (Coleoptera: Coccinellidae)

The ladybird Eriopis connexa is an important natural enemy of several pest arthropods in agroecosystems. High population of this predator is frequently observed in strawberry and soybean crops associated with spider mites. We used two-sex life table parameters to evaluate under laboratory conditions, the suitability of three species of spider mites (Tetranychus evansi, Tetranychus urticae, Tetranychus ogmophallos), and a species of aphid (Myzus persicae) as a prey for the predator E. connexa. Eriopis connexa completed immature development on all prey species except on T. evansi, in which all individuals of predator died before reaching the pupal stage. Among prey species that allowed the immature development of E. connexa, T. urticae and M. persicae provided a faster development time to the predator. Oviposition days, longevity and fecundity of E. connexa on T. urticae and M. persicae were substantially longer/higher than on T. ogmophallos. Net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) of E. connexa feeding on T. urticae and M. persicae were also higher than those on T. ogmophallos. Based on the overall performance of the ladybird, the order of suitability of prey species was M. persicae > T. urticae > T. ogmophallos > T. evansi.

Hatching in Coromandel Marsh Dart Damselfly Ceriagrion coromandelianum (Fabricius) (Zygoptera: Coenagrionidae): process and influence of the oviposition substrate

Coromandel Marsh Dart Damselfly Ceriagrion coromandelianum (Fabricius) breeds in stagnant pools, small garden tanks and ornamental cement ponds containing submerged and/or floating vegetation. Eggs were collected to observe two aspects of larval development: (1) The hatching rate of eggs deposited in different vegetation (Nymphaea nouchali, Lemna paucicostata, Hydrilla verticillata). Although C. coromandelianum prefers to oviposit in the broad leaves of N. nouchali, the highest rate of hatching was found in H. verticillata (95.8%) followed by N. nouchali (87.6%) and L. paucicostata (81.3%). Hatching commenced on Day 5 and was completed by Day 9. Maximum hatching (56%) was recorded on the sixth day of oviposition followed by the seventh day (20%) in all three substrates. (2) To document the process of hatching as follows: Around three minutes prior to hatching, the embryo exhibits cyclic pumping and pushing movements of the head (caused by the peristaltic movement of the mid- and hind- gut) of low intensity followed by high intensity and long pumping movements interspaced with smaller pulsating movements. Swelling of the head forces the apical chorion to split along the micropylar chute and like a lid, the apical tip topples over as a conical cap. This allows the prolarva to exit the egg. As it does so, it twists and the thorax swells breaking the prolarval sheath and releasing the first instar larva.

Strong decrease in egg mass on subsequent days of oviposition generates little variation in offspring performance in the pine‐tree lappet moth, Dendrolimus pini

AbstractThe pine‐tree lappet moth, Dendrolimus pini (L.) (Lepidoptera: Lasiocampidae), is a pest whose natural range mostly follows that of its host, Scots pine, Pinus sylvestris L. (Pinaceae). Under natural conditions, we observed differences in larval body size, pointing to different rates of their growth and development. This study aimed to check whether differences in egg mass can differentiate the growth and development rate of D. pini larvae. We assumed that decrease in egg mass on subsequent days of oviposition can have a large impact. Our results indicate that there is an unusually strong fecundity advantage of large female mass in D. pini, but with each day of laying, the mean mass of the eggs decreases. However, offspring phenotype and development in D. pini is not clearly correlated with egg mass. We also confirmed a strong decrease in the number and mass of eggs on subsequent days of oviposition. However, egg mass decline did not correspond with the performance of the offspring in a laboratory rearing because the specimens formed from ‘medium‐mass’ eggs were characterized by the highest fitness. Although we noted a significant impact of the day of oviposition on some offspring's fitness parameters (e.g., development stage duration, pupal mass, adult mass), the variation was not large. The offspring hatched from eggs on the 3rd day of oviposition were characterized by increased values of some parameters (e.g., higher mass, heavier cocoons, faster development). Variation in the development of the larvae could be a strategy to help offspring survive under short‐term unfavorable conditions, and also reduces intra‐species competition which is generally beneficial.

Effect of maternal age on primary and secondary sex ratios in the ectoparasitoid wasp Pachycrepoideus vindemmiae

Sex allocation is defined as the allocation of resources to produce male and female offspring during reproduction, and it is an important topic in evolutionary biology. As organisms with special haplo‐diploid sex determination, parasitoid wasps are particularly suited for the study of sex allocation. However, most studies focused on the secondary sex ratio (i.e., the eclosion sex ratio) because the oviposition ratio (the primary sex ratio) is difficult to study, especially in parasitoid species. The primary sex ratio may differ from the secondary sex ratio due to larval mortality and self‐superparasitism. The present study used microsatellites to explore the effects of female age on the primary and secondary sex ratio (male proportion) of the solitary ectoparasitoid Pachycrepoideus vindemmiae (Rondani) (Hymenoptera: Pteromalidae). The primary sex ratio showed a significant decreasing trend as the oviposition days increased, and the secondary sex ratio significantly increased. Self‐superparasitism, i.e., laying more than one egg in a host, was the cause of the variation in the secondary sex ratio in P. vindemmiae. When females practiced self‐superparasitism, they tended to lay female eggs. The application of microsatellites helped explore and improve the understanding of the primary sex ratio and self‐superparasitism in this ectoparasitoid species.

Diets for Tamarixia triozae adults before releasing in augmentative biological control

The effectiveness of augmentative biological control using parasitoids often depends on their physiological state and the pest population density at the time of release. Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) is a primary host-feeding parasitoid of a serious invasive pest Bactericera cockerelli (Šulc) (Hemiptera: Triozidae). Here we investigated the effects of adult diets (honey, water, yeast, and hosts) and timing of their provision on T. triozae fitness and oviposition patterns, providing knowledge for enhancement of its biological control potential. Adults fed with honey for four days with no access to hosts or with water or yeast for one day followed by host feeding for three days had similar longevity and lifetime pest killing ability. Adults fed with only water for one day before release had significantly greater intrinsic rate of increase, shorter doubling time, and higher daily fecundity peak. Adults fed with honey or yeast for one day followed by host feeding for three days significantly flattened their daily oviposition curves. These findings have several implications for augmentative biological control using T. triozae. First, honey diet may allow at least four days for successful shipment of host-deprived adults without compromising biological control effectiveness. Second, the release of host-deprived adults with one-day water feeding may achieve rapid pest suppression when the pest population density is high. Finally, releasing host-deprived adults with one-day honey or yeast feeding followed by three-day host feeding can increase their establishment success and reduce the risk of massive removal of hosts when the pest population density is low.

Sublethal effects of nitenpyram on the biological traits and metabolic enzymes of the white-backed planthopper, Sogatella furcifera (Hemiptera: Delphacidae)

Neonicotinoid insecticide nitenpyram is widely used in controlling rice hoppers including Sogatella furcifera (Horváth). At present, the effects of nitenpyram on the biological traits and metabolic enzymes of S. furcifera remain unclear. In this study, we applied an age-stage, two-sex life table to evaluate the sublethal effects of nitenpyram on S. furcifera under one- or multi-generation exposure. Fecundity of F0 individuals was significantly decreased in the LC25 treatment group compared to the control. Additionally, in contrast to control, the preadult period, male adult longevity, female adult longevity, longevity, total preoviposition period (TPOP), oviposition days and fecundity were significantly decreased in the F1 and F6 generations, while the development time of the 1st, 3rd and 5th -instar in the F6 generation were significantly shorter than the control and (or) the F1 generation. Moreover, except for the mean generation time (T) that was significantly decreased in the F1 and F6 generations, other population parameters such as the intrinsic rate of increase (ri), finite rate of increase (λ) and net reproductive rate (R0) were not influenced by nitenpyram exposure. The P450 and EST were both significantly increased in the F0 and F6 individuals after nitenpyram (LC25) treatment, and the P450 showed a higher activity in the F6 generation than F0. The mRNA levels of four P450 genes (CYP4CE3, CYP417A4, CYP439A3 and CYP6FJ3) were induced by nitenpyram (LC25) treatment in both the F0 and F6 generation, and these four P450 genes were also significantly upregulated in the F6 generation compared with F0. Our findings are useful for developing rational application strategies for using pesticides and understanding the metabolic resistance of nitenpyram in S. furcifera.

On the influence of environmental factors on the oviposition activity of necrophagous flies

Abstract1. Locating an optimal oviposition site can be a challenging task for female insects, especially when dealing with a patchy, unpredictable and ephemeral food source such as carrion. Understanding the biotic and abiotic parameters that influence the oviposition behaviour of necrophagous flies is not just of great biological importance but also essential for their application in legal investigations.2. In this study, we monitored the oviposition activity of necrophagous flies (Calliphoridae, Sarcophagidae) using mouse carcasses in an urban (city) and a rural (mixed forest) habitat in Frankfurt/Germany over a 2‐year period.3. Over 240 sampling days, 220,963 larvae of 4 blow fly species and 1 flesh fly were sampled. The most abundant species was the blow fly Lucilia ampullacea, followed by its family members Calliphora vicina and Lucilia caesar, the flesh fly Sarcophaga caerulescens and Lucilia sericata. Up to seven environmental parameters were statistically significant predictors for a colonisation of the carcasses, leading to unique patterns of seasonal and daily oviposition activity for all five species.4. Overall, the analysis showed that the seasonal adaption (the phenology of each species), the habitat (rural vs. urban) as well as temperature are the most important factors influencing the oviposition behaviour and activity of necrophagous blow flies and flesh flies.

Demography of Tetranychus urticae (Acari: Tetranychidae) under different nitrogen regimes with estimations of confidence intervals

In order to study the effect of nitrogen fertilization on the population growth rate of two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), life table data on common bean, Phaseolus vulgaris L. (Fabaceae), were collected at 25 ± 1 °C, 60 ± 5% RH and a photoperiod of 16:8 (L:D) h. Bean plants were treated with four nitrogen levels (0, 75, 150, and 225 kg N ha-1). Data were analyzed based on the age-stage, two-sex life table. The better performance of T. urticae (e.g., shorter total preadult duration, shorter total preoviposition period, longer adult longevity, more oviposition days, and higher fecundity) were observed with 225 kg N/ha (r = 0.2918 d-1) and 150 kg N/ha (r = 0.2744 d-1). Because the application of nitrogen fertilizer should be aimed to maintain optimal plant physiology while minimizing pest growth (i.e., optimize crop protection), we recommend the optimal N fertilization as 150 kg N/ha. By using the multinomial theorem, we demonstrated that 100,000 bootstrap resamplings can generate stable and precise estimates of population parameters and their confidence intervals. On the contrary, the 1000 bootstrap resamplings might underestimate the confidence intervals and lead to failure of pest control.

Improvement of Bemisia tabaci (Hemiptera: Aleyrodidae) Fitness on Chinese Kale upon Simultaneous Herbivory by Plutella xylostella (Lepidoptera: Plutellidae).

Simple SummaryDifferent herbivores feeding on the same plant can interact through plant-mediated effects. Cotton whitefly and diamondback moth are two of the most destructive pests in the world, and they often occur together in cruciferous plants. However, how the performance and fitness of them are affected when co-occurring in the same host plant remains unclear. The present study demonstrates that cotton whitefly has become a dominant competitor by gaining increased fitness benefits when it is mixed with DBM on the same host plant irrespective of sequences of their arrival, which may be one of the reasons for the rapid expansion and outbreak of the whitefly population worldwide.Bemisia tabaci and the diamondback moth (DBM), Plutella xylostella, are two major cosmopolitan pests that often occur together and cause severe economic losses to cruciferous crops. However, little is known about how they interact with each other. To determine the effects of defense responses induced by the two pests on the biology and population dynamics of the herbivores, we studied the performance and fitness of B. tabaci and DBM when they damaged Chinese kale simultaneously and in different orders. The results showed that DBM pre-infestation shortened the developmental duration, increased longevity, oviposition days, and fecundity of B. tabaci. Meanwhile, the intrinsic rate of increase (r), net reproductive rate (R0) and finite rate of increase (λ) of B. tabaci increased significantly with dual infection as compared with only B. tabaci infestation. In contrast, B. tabaci pre-infestation reduced the longevity and oviposition days of DBM, but the population parameters r, R0, and λ did not vary significantly compared with only DBM infestation. Thus, co-infestation of B. tabaci and DBM was beneficial to the performance of the B. tabaci population. The present findings highlight that B. tabaci has become a dominant competitor when mixing with DBM on the same host plant.

Reproductive behaviour before and after oestrus and oviposition in the captive short-beaked echidna (Tachyglossus aculeatus).

Most of our current knowledge regarding echidna reproductive behaviour is based on qualitative measurements; therefore, it is unclear if specific behavioural cues could be utilised in their captive reproductive management. This study aimed to identify quantitative changes in general and reproductive behaviour of echidna breeding pairs and pregnant females that might facilitate the detection of oestrus and impending oviposition and provide a summary of reproductive behaviour observed in a captive colony over a three-year observation period. Three echidna breeding pairs and two trios were monitored daily for seven reproductive and eight general behaviours during the 2020 breeding season. After confirmed copulation, females were monitored for four egg-laying and eight general behaviours until egg incubation. General observations of reproductive behaviours during the 2018-2020 breeding seasons were recorded as part of routine husbandry. For breeding pairs, there was a significant rate of change over time before and after copulation for the behaviours 'urogenital sniffing', 'rolling' and 'copulation attempt'. For pregnant females, time engaged in 'pacing' significantly increased while 'time eating' and the 'quantity of food eaten' significantly decreased on the day of oviposition. We were not able to identify oestrus from specific behaviours, but our observations suggest that the female echidna's period of receptivity is less than 24h. The frequency that males express 'urogenital sniffing', 'rolling' and 'copulation attempt' toward the female can be used to alert zookeepers that copulation has likely occurred. Increased pacing, reduced feeding time and quantity of food eaten can aid zookeepers to identify impending oviposition. This study demonstrates that there are quantifiable changes in specific echidna behaviours that can be incorporated into zoo husbandry practices to improve the reproductive management of this species.

Life cycle of the tick, Haemaphysalis (Kaiseriana) bispinosa (Acari: Ixodidae) under laboratory conditions

ABSTRACT Haemaphysalis (Kaiseriana) bispinosa is one of the widest–spread tick species in Southern Asia vectoring pathogens to wildlife and livestock animals. Understanding biological parameters of this species is of great importance, particularly when setting control plans or for epidemiological studies under laboratory conditions. The aim of this study was to figure out the biological aspects of H. (K.) bispinosa under laboratory conditions. Three continuous generations of this tick have been recorded. The study resulted in overall means of 10.6 ± 2.46, 8.7 ± 2.68, and 14.6 ± 2.39 days for pre-oviposition period, oviposition, and egg incubation, respectively. Larvae needed means of 4.10 ± 1.24 and 7.50 ± 1.57 days for feeding and pre–moulting periods, respectively, whereas nymphs required means of 5.10 ± 1.32 and 10.90 ± 2.39 days for feeding and pre–moulting periods, respectively. Adult females engorged for a mean of 8.0 ± 0.79 days. The entire life cycle averaged of 71.0 ± 12.0 days. Adult females weighted an average of 47.6 ± 14.8 mg, which produced egg masses that averaged 10.9 ± 3.5 mg. The oviposition rate was 557 ± 179.1 eggs/female with a peak oviposition on day 4. Hatchability rate with an average of 94.3 ± 2.19% was recorded. Significant linear correlations between weight of engorged females and weight of egg mass, and with number of eggs laid were recorded (r = 0.90; P > 0.01; r = 0.89; P > 0.01, respectively). The life cycle of this tick species was ambiguous over the past, and finally has been cleared; therefore, it could be used in the future biological, epidemiological, and control investigations concerning this tick species.

Allocation of more reproductive resource to egg size rather than clutch size of gregarious desert locust (Schistocerca gregaria) through increasing oogenesis period and oosorption rate

The desert locust, Schistocerca gregaria, shows a density-dependent reproductive trade-off by laying fewer but larger eggs in crowded conditions (gregarious phase) than in isolated conditions (solitarious phase). However, the physiological mechanisms controlling reproductive resource allocation remain unclear. We examined how egg production processes, including ovulation timing (i.e., oogenesis period), oocyte and ovarian growth rates, and oosorption rate (resorbing developing terminal oocytes), regulate reproductive outputs (egg biomass per clutch, egg size, and clutch size) during a reproductive cycle in S. gregaria by rearing them either under isolated or crowded conditions. We observed a common density-dependent negative correlation between egg size and clutch size, with no significant difference in egg biomass between the two rearing conditions. Dissection of female locusts after different days of oviposition revealed that the daily oocyte growth rate was almost similar between the two rearing conditions, but crowd-reared females ovulated later than isolated-reared ones, resulting in further oocyte growth in the former. Terminal oocytes were renewed by previous penultimate oocytes at the onset of a new reproductive cycle, and oosorption mainly occurred at an early stage in both rearing conditions; however, crowd-reared locusts displayed higher levels of oosorption compared to their isolated-reared counterparts. Crowding induced a high oosorption rate, resulting in a reduced clutch size and a prolonged oogenesis period, which in turn allowed oocytes to intake more yolk, which was probably recycled via oosorption. These results suggest that the length of the oogenesis period and oosorption rate are manipulated by maternal density, and these physiological modifications interactively regulate reproductive trade-off in S. gregaria.