Pre-reproductive Period Research Articles

Water deficit and aphid resilience on wheat: examining Sitobion avenae F. and their bacterial symbionts interplay under controlled laboratory conditions.

Climate change has far-reaching effects on food security and agriculture, affecting crop yields and food distribution. Agriculture relies heavily on water for irrigation and production, making it vulnerable to water scarcity. Additionally, climate change can affect crop pest insects, leading to increased global crop losses, particularly in cereals, an important component of the human diet. Aphids are major crop pests and have a symbiotic relationship with bacterial endosymbionts that can contribute to their success as pests under a climate change scenario. To test the effect of drought on aphids, we examined varying levels of water deficit and endosymbiont composition on the grain aphid (Sitobion avenae) performance on wheat under controlled laboratory conditions. We measured the intrinsic rate of population increase (rm), the body weight of adult aphids, and the pre-reproductive period for different genotypes of the grain aphid (including Chilean superclones) under different irrigation regimes. We also analyzed the relative abundance of their endosymbionts under the different water treatments. Our findings revealed that water deficit affects each aphid genotype differently, impacting various traits. For instance, the body weight of adult aphids was notably affected by different water treatments, with aphids grown under intermediate water deficit (IW) being significantly bigger. The relative abundance of endosymbionts also varied among genotypes and water treatments-specifically Regiella insecticola had a noticeably higher abundance under IW (P < 0.05). This study provides valuable insights into the impact of water deficit on aphid performance and the role of endosymbionts in mitigating the effects of water deficit. © 2024 Society of Chemical Industry.

Effect on Temperature Influences of the Life Table Studies for Aphid, Aphis craccivora Koch. in Cowpea under Laboratory Condition

Aim: To study the life table aphid, Aphis craccivora in cowpea at different temperature. Study Design: Simple random sampling design with two treatments and 12 replications. Place and Duration Study: Agricultural College and Research Institute, Madurai and 2019-2020. Methodology: We used a simple random sampling design, which included two temperature variables (30 and 35°C) and 12 repetitions for A. craccivora. The female adult aphids were placed in dishes with leaf dishes and 12 hours light appropriate temperature. Female adult aphids were placed in dishes containing leaf discs and incubated at the appropriate temperature, with a 12-hour light phase. They were transferred to new dishes as needed. We evaluated the pre-reproductive and reproductive periods under a stereomicroscope every 24 hours, and we determined the number of nymphs produced and their longevities at each temperature. Results: Aphid, Aphis craccivora Koch. is most important pest in Pulses ecosystem and life table studies on cowpea, the net reproductive rate (22.53 individuals / female at 300 C; 14.23 individuals / female at 350 C, mean generation time 11.41days at 300C; 10.39 at 350C, population doubling time (2.710 days at 300C, 2.539 at 350C in Cowpea. The age specific survivorship curve revealed that the population followed Type III curve and 50 per cent mortality of A. craccivora 9 days at 300C and 7.5 days at 350C in cowpea. Conclusion: The life table aphids insects parameters of net reproductive rate, population doubling time, mean generation time and age specific curve was maximum in 300C than 350C in Cowpea.

Realized heritability and fitness costs of flupyradifurone resistance in the cowpea aphid, Aphis craccivora Koch

The cowpea aphid, Aphis craccivora Koch (Homoptera: Aphididae) is a serious insect pest that infests legume crops. Flupyradifurone (FPF) is a butenolide insecticide that selectively targets sucking insects including aphids and whiteflies. However, the realized heritability (h2) and fitness costs associated with resistance to FPF have not yet been assessed with A. craccivora. In this study, A. craccivora showed the potential to develop resistance to FPF under continuous selection, with an overall mean estimated h2 of resistance of 0.21. Results of fitness costs showed no differences in the developmental time (except for N2 and N3), longevity, fecundity, adult pre-reproductive period (APRP), total pre-reproductive period (TPRP), and oviposition days (Od) of the FPF-R strain compared to the S-strain. In contrast, all population growth parameters, including the growth reproductive rate (GRR), net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), mean generation time (T), and doubling time (DT), were significantly lower in the FPF-R strain than in the S-strain. Fitness cost studies revealed that resistance to FPF decreased the relative fitness of the FPF-R strain to 0.76 compared with that of the S-strain. The estimation of realized heritable h2 and identification of resistance fitness costs provide a basis for designing insecticide resistance management (IRM) programs to sustain susceptibility in insect populations.

Intergenerational Sublethal Effects of Flonicamid on Cotton Aphid, Aphis gossypii: An Age-Stage, Two-Sex Life Table Study.

Flonicamid is a novel systemic insecticide widely used against aphids. However, the intergenerational sublethal effects of flonicamid on cotton aphid, Aphis gossypii, have not been fully studied. This study aimed to evaluate the sublethal effects of flonicamid on the biological parameters of adult A. gossypii (F0) and its subsequent intergenerational effects on the offspring (F1 generation) through age-stage, two-sex life table analysis. The results of the bioassays indicate that flonicamid exhibits significant toxicity toward adult A. gossypii, as evidenced by an LC50 value of 0.372 mg L-1 after a 48-h exposure period. The longevity, fecundity, and reproductive days of adult cotton aphids (F0) were significantly decreased when treated with the sublethal concentrations of flonicamid. The pre-adult stage exhibited an increase, whereas the adult longevity, total longevity, and fecundity experienced a notable decrease in F1 aphids after the exposure of F0 aphids to sublethal concentrations of flonicamid. Furthermore, the key demographic parameters, including r, λ, R0, and RPd, showed a significant decrease, while the total pre-reproductive period (TPRP) experienced a significant increase in the F1 generation. Collectively, our findings indicate that sublethal concentrations of flonicamid impact the demographic parameters of A. gossypii, resulting in suppression of population growth. This study presents comprehensive information on the overall impact of flonicamid on A. gossypii, which could potentially aid in managing this major pest.

Juvenile survival increases with dispersal distance and varies across years: 15 years of evidence in a prairie perennial.

Juvenile survival is critical to population persistence and evolutionary change. However, the survival of juvenile plants from emergence to reproductive maturity is rarely quantified. This is especially true for long-lived perennials with extended pre-reproductive periods. Furthermore, studies rarely have the replication necessary to account for variation among populations and cohorts. We estimated juvenile survival and its relationship to population size, density of conspecifics, distance to the maternal plant, age, year, and cohort for Echinacea angustifolia, a long-lived herbaceous perennial. In 14 remnant prairie populations over seven sampling years, 2007-2013, we identified 886 seedlings. We then monitored these individuals annually until 2021 (8-15 years). Overall, juvenile mortality was very high; for almost all cohorts fewer than 10% of seedlings survived to age 8 or to year 2021. Only two of the seedlings reached reproductive maturity within the study period. Juvenile survival increased with distance from the maternal plant and varied more among the study years than it did by age or cohort. Juvenile survival did not vary with population size or local density of conspecific neighbors. Our results suggest that low juvenile survival could contribute to projected population declines.

Transgenerational effect of a tea saponin–matrine mixture promotes fecundity and alters associated bacteria in the fall armyworm Spodoptera frugiperda

The fall armyworm Spodoptera frugiperda is a one of the most invasive and damaging pests that causes serious economic losses in several crops. Botanical insecticides such as tea saponin and matrine, as environmentally acceptable biopesticides, are widely used for controlling pests. Insecticide stress affects both individuals and the associated bacteria in insects. However, it remains unclear that if sublethal effects and bacteria are the drivers for the adaptive mechanisms of insecticides in fall armyworm. We examined the effectiveness of a 10:1 v/v mixture of biological insecticides against the fall armyworm and the impacts of several biological parameters and demographic variables of the armyworm targeting two generations at primary exposure. Moreover, the influence of the insecticide mixture on the associated bacteria of the fall armyworm was assessed via 16 S rRNA sequencing. The results showed that the mixture was highly toxic to fall armyworms, and the fecundity of the initially exposed generation (F0) significantly decreased; however, there was no significant effect on longevity. The larval duration, the total pre-reproductive period, longevity, fecundity, and mean generation time of the fall armyworm in the F1 significantly increased; yet the intrinsic and finite rates of the increase and the net reproductive rate remained fairly constant. Additionally, the population of associated bacteria was affected in both generations, with an increase in the microbial diversity within the fall armyworm compared to that of the F0 generation. Also, an increase in abundance of several genera of bacteria, including Acinetobacter, Serratia, Enterococcus, and Pseudomonas, was noted following treatment with the insecticide mixture. These results broaden our understanding of the impact of sublethal insecticide concentrations on the fall armyworm and its associated bacterial community.

Thiamethoxam-Induced Intergenerational Sublethal Effects on the Life History and Feeding Behavior of Rhopalosiphum padi

Thiamethoxam, a second-generation neonicotinoid insecticide is widely used for controlling sap-sucking insect pests including Rhopalosiphum padi. The current study aimed to investigate the life-history parameters and feeding behavior of R. padi following treatments with sublethal concentrations of thiamethoxam. The lethal concentration 50 (LC50) value of thiamethoxam against adult R. padi was 11.458 mg L−1 after 48 h exposure. The sublethal concentrations of thiamethoxam (LC5 and LC10) significantly decreased the adult longevity, fecundity, and reproductive days in the directly exposed aphids (F0 generation). In the progeny R. padi (F1), the developmental durations and total prereproductive period (TPRP) were decreased while the adult longevity, fecundity, and reproductive days (RPd) were increased at both thiamethoxam concentrations. The demographic parameters including the net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) were prolonged only at the LC5 of thiamethoxam. The EPG results indicated that the sublethal concentrations of thiamethoxam increases the total duration of non-probing (Np) while reducing the total duration of E2 in directly exposed aphids (F0). Interestingly, the E2 were significantly increased in the progeny generation (F1) descending from previously exposed parental aphids (F0). Overall, this study showed that thiamethoxam exhibited high toxicity against directly exposed individuals (F0), while inducing intergenerational hormetic effects on the progeny generation (F1) of R. padi. These findings provided crucial details about thiamethoxam-induced hormetic effects that might be useful in managing resurgences of this key pest.

Comparative biology and life tables of sorghum aphid Melanaphis sorghi (Theobald) (Hemiptera: Aphididae) from Mexico, at different temperatures

The sorghum aphid Melanaphis sorghi (Theobald, 1904) is the most critical pest in sorghum crops grown in the USA and Mexico. The cultivated area of sorghum was reduced by more than 30% between 2016 and 2019 in northern Mexico, Guanajuato, Morelos, and other regions. This study provides essential information to support an Integrated Pest Management of this insect. M. sorghi field colonies from Guanajuato, Mexico, were identified by morphometric criteria and reared on Sorghum bicolor var. UPM-219 leaf discs using a bioclimatic chamber under different temperatures: 5, 10, 15, 20, 25, 30, 35 and 40 °C. The highest mortality occurred in extreme temperatures: 40 °C (100%). The lowest temperature assessed (5 °C) shows no reproduction, but the pre-reproductive period spread to 62.5 days, allowing an average of 88.2 days of the insects' survival. At 20 °C, M. sorghi produced a supernumerary N5 stage that prolonged the development by 7.1 days, while at the highest temperature (40 °C), N1s died after 0.9 days. The most prolonged reproductive period was 33.2 days (0.6 nymphs/day) at 10 °C, in contrast to 4.1 days (0.4 nymphs/day) at 35 °C. The most extended post-reproductive period (22.4 days) was observed at 10 °C and the shortest (4.2 days) at 35 °C. The highest fertility average (79.06 nymphs) was reached at 25 °C. The heat units required for each generation were 158.9, while theoretical thermal thresholds were 2.0 and 40 °C. Population parameters show that 25 °C is the optimal temperature for this aphid, estimating Ro (79.06), Rm (0.44), T (10.01), DT (1.59), and λ (1.55).

Effects of nanoplastics exposure on ingestion, life history traits, and dimethyl sulfide production in rotifer Brachionus plicatilis

Microplastics (MPs) and nanoplastics (NPs) have gained global concern due to their detrimental effects on marine organisms. We investigated the effects of 80 nm polystyrene (PS) NPs on life history traits, ingestion, and dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP) production in the rotifer Brachionus plicatilis. Fluorescently labeled 80 nm PS NPs were ingested by the rotifer B. plicatilis and accumulated in the digestive tract. The lethal rates of B. plicatilis exposed to NPs were dose-dependent. High concentrations of PS NPs exposure had negative effects on developmental duration, leading to prolonged embryonic development and pre-reproductive periods, shortened reproductive period, post-reproductive period, and lifespan in B. plicatilis. High concentrations of PS NPs exposure inhibited life table demographic parameters such as age-specific survivorship and fecundity, generation time, net reproductive rate, and life expectancy. Consequently, the population of B. plicatilis was adversely impacted. Furthermore, exposure to PS NPs resulted in a reduced ingestion rate in B. plicatilis, as well as a decreased in DMS, particulate DMSP (DMSPp) concentration, and DMSP lyase activity (DLA), which exhibited a dose-response relationship. B. plicatilis grazing promoted DLA and therefore increased DMS production. PS NPs exposure caused a decline in the increased DMS induced by rotifer grazing. Our results help to understand the ecotoxicity of NPs on rotifer and their impact on the biogeochemical cycle of dimethylated sulfur compounds.

Selection parameters in lines of Drosophila melanogaster Meig., obtained from populations living in territories with different levels of radiation pollution: approbation of the Crow’s method

Man-made disasters, such as the accidents at the Chornobyl NPP and the Fukushima NPP-1, have raised questions about the radiation risks associated with the use of atomic energy in a new and acute way. The purpose of the study was to investigate the features of the action of natural selection in the lines of Drosophila melanogaster Meig., obtained from natural populations living in territories with different levels of radiation pollution. One of the aims was to test Crow's method on a model object, such as Drosophila. This method makes it possible to estimate the total intensity of selection, as well as to determine the contribution of its individual components, such as differential fecundity and differential mortality. The study was carried out on three lines of Drosophila melanogaster Meig.: the Haidary line (radiation background in the territory from which the line originates: 0.12 μSv/h, β-radiation flux: 0 particles/cm2/min), the KhPTI line (radiation background: 0.12–0.20 μSv/h, β-radiation flux: 0 particles/cm2/min), the Chornobyl line (radiation background: 0.20–0.22 μSv/h, β-radiation flux: 7–8 particles/cm2/min). According to the obtained results, the lines did not differ among themselves in egg production of females. In terms of the number of adult offspring, the Chornobyl line was inferior to the Haidary and KhPTI lines by 48.9% and 57.8%, respectively. Mortality in the pre-reproductive period of development (indicator pd), which includes embryonic and pupal mortality, was the highest in the Chornobyl line and exceeded the pd value in the Haidary and KhPTI lines by 1.4 times. As a result, the Chornobyl line, obtained from the territory contaminated with radionuclides, significantly exceeded the Haidary and KhPTI lines, obtained from the territories where the radiation situation does not go beyond the norm, by both components of selection – both by the component of differential fecundity (If), and by differential mortality (lm). The total selection indices (Itot) were quite close in the Haidary and KhPTI lines, and in the Chornobyl line this index was 2,1–2,6 times higher than in the other two lines. The results of the study support the view that ionizing radiation can promote evolution by accelerating evolutionary change. They indicate an increased mortality rate, a reduced level of fitness and an increased selection pressure in the line of fruit flies, which originates from the population living in the radiation-contaminated territory in the Chornobyl exclusion zone.

Estimation of estuarine habitat degradation and its influence on the reproduction process of the crab Eriocheir sinensis in the Yangtze River Estuary

BackgroundThe provision of habitat for fishery species in estuaries is highly valued and represents one of the most challenging ecosystem service values to quantify. However, quantifying this value is challenging due to complex relationships between habitat change, ecological processes, and environmental variations. This study aims to estimate estuarine habitat degradation and its impact on the reproduction process of the crab Eriocheir sinensis by characterizing the changes in breeding habitat and investigating relationships between the species and its habitat in the Yangtze River Estuary.MethodsA species distribution model recently developed was applied to estimate the extent and quality of breeding habitat changes from 2014–2021. The intrinsic (physiological) and external (structural) reproductive attributes of the breeding process were measured to assess the effects of habitat change. The relationships among habitat change, reproductive attributes and environmental factors were analyzed to understand the underlying driving forces of habitat degradation for breeding process by multivariate statistical analysis.ResultsAbout 34.24% of essential habitat was lost, mainly in highly suitable areas due to reclamation and waterway construction. Habitat degradation significantly affects female distribution and their reproductive processes, particularly gonad development during the pre-reproductive period and fecundity during the reproductive period, without altering population structure. These results indicated that the main ecological function served by the highly suitable breeding ground was the provision for development of gonad and improvement of fecundity. Increases of salinity and turbidity, caused by hydrodynamic changes from large-scale waterway construction, were identified as the environmental determinants contributing to cumulative habitat degradation. These influences ultimately led to a decrease in the fecundity of E. sinensis.ConclusionsOur research sheds light on the quantification of habitat degradation in the Yangtze River Estuary and its implications for the reproduction process of E. sinensis, which can serve as a foundation for assessing and quantifying the ecosystem service values provided by these breeding grounds. This information is valuable for policymakers and resource managers in making informed decisions regarding habitat conservation and the sustainable utilization of fishery resources.

Biology of aphid, Aphis gossypii Glover in cumin

The experiment on biology of aphid, Aphis gossypii infesting cumin crop was conducted under ambient conditions in the Entomology Laboratory, Agricultural Research Station, Mandor, Jodhpur. The study was conducted on potted plants of cumin variety GC-4. The aphid, A. gossypii nymphs were moulted four times before attaining the adult stage. The mean body length, width, antennal length and cornicle length of first, second, third and fourth instar nymphs were 0.50 ± 0.04, 0.28 ± 0.03, 0.28 ± 0.02 and 0.036 ± 0.01 mm; 0.90 ± 0.04, 0.38 ± 0.04, 0.40 ± 0.03 and 0.065 ± 0.01 mm; 1.11 ± 0.05, 0.49 ± 0.04, 0.54 ± 0.03 and 0.095 ± 0.01 mm and 1.31 ± 0.06, 0.65 ± 0.05, 0.64 ± 0.04 and 0.175 ± 0.01 mm, respectively. The mean body length, width, antennal length and cornicle length of adult aphid were 1.68 ± 0.06, 0.71 ± 1.53, 0.88 ± 0.02 and 0.266 ± 0.01 mm, respectively. The mean duration period of first, second, third and fourth instar nymphs were 1.30 ± 0.42, 2.05 ± 0.62, 2.40 ± 0.52 and 1.45 ± 0.45 days, respectively. The total nymphal duration was 7.75 ± 1.61 days. The mean longevity of adult aphid was 9.65 ± 1.75 days with an entire life span of 17.75 ± 2.91 days. The pre-reproductive, reproductive and post-reproductive periods were 1.35 ± 0.56, 7.20 ± 1.47 and 1.75 ± 0.71 days, respectively. The fecundity of the adult female was 24.45 ± 6.21 nymphs per female and the intrinsic rate of single female per day was an average of 4.80 ± 2.01 nymphs/day.

Biology of &lt;i&gt;Aphis gossypii&lt;/i&gt; Glover on Cotton and Brinjal as Observed in Mass Rearing

The aptness of two hosts viz., cotton and brinjal for mass rearing of Aphis gossypii Glover under laboratory conditions was investigated using the age-stage and two-sex lifetable method. The results showed that A. gossypii could complete its entire lifecycle on both hosts. The total nymphal duration (7.93± 0.33 days), reproductive period (6.95± 0.60 days), adult longevity (8.11± 0.68 days) and fecundity (24.66± 2.34 days) were significantly higher on brinjal than on cotton. The differences in pre-reproductive and post-reproductive periods on both hosts were not statistically significant. The mean reproductive period was longer on brinjal (6.95± 0.56 days) than that on cotton (5.06± 0.47 days); consequently, the fecundity was also significantly high in brinjal (24.66± 2.34 nymphs/ female) compared to cotton (14.11± 1.31 nymphs/female). The difference in an intrinsic rate of increase, infinite rate of increase and doubling time were non-significant. In contrast, the net reproductive rate, gross reproduction rate, and mean generation time on brinjal were significantly higher. Lifetable parameters such as age-stage-specific survival rates, fecundity, life expectancy and reproductive value of A. gossypii were higher on brinjal compared to cotton. The results of this study indicate that brinjal is a better host than cotton for the mass rearing of A. gossypii.

Morph-specific fitness throughout the life cycle of the grain aphid, nonhost-alternating, holocyclic Sitobion avenae (Hemiptera: Aphididae).

Aphids exhibit seasonally alternating asexual and sexual reproductive modes. Different morphs are produced throughout the life cycle. To evaluate morph-specific fitness during reproductive switching, holocyclic Sitobion avenae were induced continuously under short light conditions, and development and reproduction were compared in each morph. Seven morphs, including apterous and alate virginoparae, apterous and alate sexuparae, oviparae, males, and fundatrices, were produced during the life cycle. The greatest proportions of sexuparae, oviparae, males, and virginoparae were in the G1, G2, G3, and G4 generations, respectively. Regardless of asexual or sexual morphs, alate morphs exhibited a marked delay in age at maturity compared with that of apterous morphs. Among the alate morphs, males had the longest age at maturity, followed by sexuparae and virginoparae. Among the apterous morphs, sexuparae were older at maturity than the fundatrices, virginoparae, and oviparae. The nymphs of each morph had equal survival potentials. For the same wing morphs, apterous sexuparae and oviparae exhibited substantial delays in the pre-reproductive period and considerable reductions in fecundity, compared with those of apterous virginoparae and fundatrices, whereas alate sexuparae and alate virginoparae had similar fecundity. The seven morphs exhibited Deevey I survivorship throughout the life cycle. These results suggest that sexual production, particularly in males, has short-term development and reproduction costs. The coexistence of sexual and asexual morphs in sexuparae offspring may be regarded as an adaptive strategy for limiting the risk of low fitness in winter.

Impact of sublethal concentrations of flonicamid on key demographic parameters and feeding behavior of Schizaphis graminum.

Flonicamid is a novel systemic insecticide that efficiently controls sap-sucking insect pests. However, the impact of sublethal concentrations of flonicamid on key demographic parameters and the feeding behavior of greenbug, Schizaphis graminum has not yet been studied. In this study, we used the age stage, two-sex life table approach, and electrical penetration graphs (EPGs) to investigate the sublethal effects of flonicamid on the biological traits and feeding behavior of S. graminum. Bioassays showed that flonicamid possesses high toxicity to adult S. graminum with LC50 of 5.111 mg L-1 following 48 h exposure. Sublethal concentrations of flonicamid (LC5 and LC10) significantly decreased the longevity and fecundity of directly exposed parental aphids (F0), while the reproductive days were reduced only at LC10. The pre-adult stage and total pre-reproductive period (TPRP) increased in F1 individuals after exposure of F0 aphids to the sublethal concentrations of flonicamid. Furthermore, the adult longevity, fecundity and key demographic parameters (R0, r, and λ) were significantly reduced in progeny generation (F1). EPG recordings showed that the total duration of phloem sap ingestion and concurrent salivation (E2) decreased substantially in F0 and F1 aphids after exposure to LC5 and LC10 of flonicamid. Taken together, our results showed that the sublethal concentrations of flonicamid affect the demographic parameters and feeding behavior that ultimately suppress the population growth of S. graminum. This study provides in-depth information about the overall effects of flonicamid on S. graminum that might help to manage this key pest.

Effects of desalination brine on the fecundity of brine shrimp Artemia franciscana fed on rice bran

Abstract Brine water drained from the desalination stations represents environmental concerns because of its extremely high salinity. Artemia (brine shrimp) is one of the crustaceans that can live in increased saline water. So, it can live in the desalination brine water. This study investigated the possibility of growing Artemia (Artemia franciscana), an essential live food for the aquaculture industry, in the brine water disposed of during the desalination process. Nine reproductive characteristics were examined for Artemia growing in desalination brine water, compared to seawater. Both types of water were brought from the Rumaila water desalination facility on the Mediterranean Sea in Marsa Matrouh, Egypt. The experiment included brine water of salinities: 50, 60, 70, and 80 ppt and two seawater salinities: 38 and 50 ppt. The food source used was the rice bran suspension to feed Artemia during the experiment. The results illustrated that the pre-reproductive and reproductive periods and % offspring encysted had higher values in higher salinities of brine water than seawater. The rate of offspring encysted in the brine water of 70 ppt reached 72.42%, followed by the brine water of 60 ppt. The results showed that the Artemia could grow in the brine water of the desalination plants till the adult stage. The results show no significant difference between both types of water in some variables.

A sublethal concentration of chitosan oligosaccharide suppresses the population growth of the wheat aphid, Rhopalosiphum padi (Linnaeus)

AbstractThe bird cherry‐oat aphid Rhopalosiphum padi (L.) (Hemiptera: Aphididae) is a key pest of wheat in China. Chitosan oligosaccharide (COS) has been widely used due to its biocompatibility, antibacterial activity, environmental friendliness and convenient extraction. This study was aimed at determining the acute toxicity of COS on R. padi and transgenerational effects of sublethal concentrations of COS on the biological characteristics of R. padi. The results indicated that COS possessed acute toxicity against R. padi after 48 h of exposure (LC50: 1227.35 mg/L). The sublethal concentration of COS (LC15: 260 mg/L) induced a decrease in adult longevity, adult prereproductive period and fecundity in the first filial generation (F1). Moreover, in F1 progeny, nymphal (1st–3rd), preadult and total prereproductive period significantly enhanced due to sublethal dose. Moreover, finite rate of increase (λ), the intrinsic rate of increase (r) and net reproductive rate (R0) of F1 progeny were significantly decreased, whereas a sublethal COS concentration exposure significantly increased the mean generation time (T) of F1 progeny. Overall, the study shows that sublethal concentration of COS can significantly suppress population growth of R. padi F1 generation, showing the potential of COS as a biorational option to manage aphids.

Monthly variation in the lipid composition and content of Pacific oysters, \(\textit{Crassostrea gigas}\), cultured in Van Don, Quang Ninh

We conduct a study to investigate the year-round fluctuation of lipid composition and content in Pacific oysters (Crassostrea gigas) cultured in Van Don, Quang Ninh, for the first time. Our results showed that the total lipid content of oysters ranged from 1% to 1.6%, with the highest levels observed during their pre-reproductive period (July and December). Polyunsaturated fatty acids were the most abundant type of lipids in oysters, ranging from 41.66% to 53.36%. We identified six lipid classes in Pacific oysters, with the three dominant classes being PoL, ST, and TG, which exhibited significant variation, with the highest variability observed in May and June and the lowest in July. The primary fatty acids in oyster lipids were 14:0, 16:0, 18:0, 18:1n-7, 20:4n-6, 20:5n-3, and 22:6n-3. In summary, our study provides novel insights into the lipid composition and content of Pacific oysters cultured in Van Don, Quang Ninh.The results demonstrate the temporal variability in lipid classes and fatty acid composition throughout the year, with the highest lipid content observed during the pre-reproductive period. These findings could contribute to better understanding the nutritional value of Pacific oysters and inform future aquaculture practices.

Alopecia in Two Species of Insectivorous Bats during the Critical Time Period of Female Reproduction

Alopecia in bats has been related to multiple stressors, such as ectoparasite infestations, environmental contaminant exposure, idiopathic disease, and reproductive stress. Here we note occurrences of alopecia in 2 species of insectivorous bats, including a federally endangered species. In the summer of 2022, we encountered 3 Eptesicus fuscus (Big Brown Bat) and 7 Myotis grisescens (Gray Bat) with alopecia during mist-net and harp-trap surveys at multiple locations in Tennessee, USA. Seven of the 10 bats with bald spots were adult lactating or post-lactating females, 1 was an adult pregnant female, and 2 were adult nonreproductive males. No bats with alopecia were encountered after the lactation or post-lactation time period, despite continued mist-net and harp-trap surveys. The cause of the alopecia is unknown and warrants further investigation of prevalence across pre-reproductive (pre-pregnancy), reproductive (pregnancy, lactation, and spermatogenesis), and post-reproductive (pup volancy) periods in these populations. Understanding natural molt cycles versus alopecia as an outward sign of stress in individuals is critical for assessing the health of bat populations.

Seasonal gonadal changes in adult male lizards of Liolaemus cuyanus (Iguania: Liolaemidae) from the Monte desert, Argentina

Male reproductive cycles in lizards can be continuous or seasonal depending on the environmental conditions and female availability. The aim of this study is to investigate whether adult males of the psammophilus lizard Liolaemus cuyanus present seasonal changes of reproductive traits throughout the reproductive cycle. In order to carry out this task, sampling of specimens (N = 27) was carried out monthly from October to March in Valle de Matagusanos, Ullúm, San Juan, Argentina (31°06′46.08′’ S, 68°38′03.84′’ W; altitude: 945 m), a semi-arid zone. The animals captured in different months were grouped based on reproductive criteria according to three relevant periods: pre-reproductive (PrR), reproductive (R) and post-reproductive (PsR). In order to identify and characterize these periods, several male reproductive traits were obtained, like morphometric parameters (body mass, snout-vent length, testes and abdominal fat body mass), tubular surface and estimation of the interstitial tissue coverage, combined with histological and cell seminiferous tubule observations (germ cells types, histological and ultrastructural details) and presence of sperm in the cauda epididymis. During the PrR period, which occurred during spring, well-developed testes with free tubular sperm cells were present, but these were less frequent than during the R period. On the other hand, luminal sperm cells were evident at the seminiferous tubules from the beginning of the R period, in conjunction with the maximum testes mass and seminiferous tubular surfaces. This was also coincident with a higher abundance of sperm cells in the cauda epididymal lumen. At the end of this period, the initial regression of the seminiferous epithelium was corroborated by organelle regression which was observed in the ultrastructure of spermatogenic cells. At the beginning of the PsR period, before autumn, a marked decrease in male reproductive traits above described was detected. Instead, an increase in abdominal fat body mass could be observed indicating the onset of the lethargy period. The results obtained suggest that this population of L. cuyanus has a seasonal reproductive cycle, with its reproductive activity occurring during the spring-summer months (PrR-R periods) and finishing in late summer (PsR).