Effect of group rearing on the life table parameters of the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae)

The effect of rearing density on immune responses of hepatopancreas and intestine in Litopenaeus vananmei against Vibrio paraheamolyticus E1 challenge

As global aquaculture fish production continues to expand, an improved understanding of how environmental factors interact in fish health and production is needed. Significant advances have been made toward economical alternatives to costly fishmeal-based diets, such as grain-based formulations, and toward defining the effect of rearing density on fish health and production. Little research, however, has examined the effects of fishmeal- and grain-based diets in combination with alterations in rearing density. Moreover, it is unknown whether interactions between rearing density and diet impact the composition of the fish intestinal microbiota, which might in turn impact fish health and production. We fed aquacultured adult rainbow trout (Oncorhynchus mykiss) fishmeal- or grain-based diets, reared them under high- or low-density conditions for 10 months in a single aquaculture facility, and evaluated individual fish growth, production, fin indices, and intestinal microbiota composition using 16S rRNA gene sequencing. We found that the intestinal microbiotas were dominated by a shared core microbiota consisting of 52 bacterial lineages observed across all individuals, diets, and rearing densities. Variations in diet and rearing density resulted in only minor changes in intestinal microbiota composition despite significant effects of these variables on fish growth, performance, fillet quality, and welfare. Significant interactions between diet and rearing density were observed only in evaluations of fin indices and the relative abundance of the bacterial genus Staphylococcus. These results demonstrate that aquacultured rainbow trout can achieve remarkable consistency in intestinal microbiota composition and suggest the possibility of developing novel aquaculture strategies without overtly altering intestinal microbiota composition.

A study was conducted using life table parameters to assess the relative resistance in eleven botswana sorghum varieties all local, namely ‘town’, ‘PMK 132’, ‘PL 174’, ‘PsA 158’, ‘PsA 161’, ‘PMK 110’, ‘PL 177’ ‘PMK 109’, 'sephala’, ‘PMK 108’ and ‘PMK 129’ against sugarcane aphid Melanaphis sacchari (Zehntner). biological fitness of the aphid was determined using population and life table parameters: developmental rate, fecundity and survival, longevity/lifespan, intrinsic rate increase (rm), net reproduction rate (Ro), generation time (T), doubling time (DT) as well as finite rate of increase (λ). Life table and population parameters of the aphids varied significantly among varieties. A significant reduction in fecundity and survival rate was observed in ‘town’, ‘PL 174’ and ‘PMK 132’. In addition aphid life table analysis showed significantly lower net reproduction rate (Ro), intrinsic rate of increase (rm), finite rate of increase (λ) and prolonged generation time (T) and doubling time (DT) on ‘town’, ‘PL 174’ and ‘PMK 132’compared to others. the negative impact of ‘town’, ‘PL 174’ and ‘PMK 132’ on biological fitness of M. sacchari suggest antibiosis mechanism of resistance in these varieties.

The old world date mite,Oligonychus afrasiaticus(McGregor) (Acari: Tetranychidae) is a severe spider mite pest of date palm in most of the Middle East and North Africa. Considering that nothing is known about the performance of phytoseiid predators againstO. afrasiaticus, biology, predation, and life table parameters ofCydnoseius negevi(Swirski and Amitai) andNeoseiulus barkeriHughes (Acari: Phytoseiidae), collected from date palm orchards, were studied under laboratory conditions (25, 35°C and 35 ± 10% RH) as a first step to understand their effectiveness against all mobile life stages ofO. afrasiaticus. For both predators, oviposition period was significantly shorter at 35°C than at 25°C. The following parameters were obtained forC. negeviandN. barkeriat 25 and 35°C, respectively: female longevity, 31.8, 20.1, 35.7, 27.4 d; fecundity, 21.6, 38.0, 18.8, 34.8 eggs per female; oviposition period, 23.9, 13.7, 25.9, 18.1 d. Total predation ofC. negeviandN. barkerifemale was 246.0, 270.0, 227.6, 205.3 prey at 25 and 35°C, respectively. Rectal plugs were observed attached to the opisthosoma of some adult females ofN. barkeri, which often cause the mite to stick to the surface. Life table parameters were estimated as net reproductive rate (R0) 10.44, 17.35, 10.19, 13.84, intrinsic rate of increase (rm) 0.14, 0.19, 0.13, 0.16 d−1, finite rate of increase (λ) 1.15, 1.21, 1.12, 1.17 d−1, generation time (T) 17.03, 15.17, 17.83, 16.61 d, doubling time (DT) 04.95, 03.64, 05.33, 04.33 d forC. negeviandN. barkeriat 25 and 35°C, respectively. The values of intrinsic rate of increase and net reproductive rate were higher inC. negevithanN. barkeriat both temperature regimes. Therefore, it could be concluded thatC. negeviperformance was better thanN. barkeriagainstO. afrasiaticusand can be considered as a valuable addition to the existing methods for spider mites control.

The present investigation was conducted to determine the effects of fenpyroximate on life history traits (development and reproductive parameters) and population growth of F1 generation of Tetranychus urticae when F0 females were treated. Fenpyroximate 5% EC was applied at the LC10, LC20 and LC30 by leaf dip method under laboratory conditions. Results indicated that fenpyroximate exhibited relative toxicity with an LC5 0 of 23.10 ppm, while LC1 0, LC2 0, LC3 0 were 1.74, 4.23, and 8.02 ppm (mg commercial product/L), respectively, for T. urticae females. Sublethal exposure significantly prolonged the developmental duration of immature stages, particularly at the LC3 0 treatment, with an increase in egg stage duration in both sexes. The longevity of females and males decreased significantly at relatively high concentrations, and the total lifespan was reduced at LC2 0 and LC3 0 treatments. Reproductive parameters were also adversely affected by different concentrations. Although the adult preoviposition period did not differ significantly among the treatments, it was shorter than that of the control. The oviposition period and total fecundity decreased with increasing concentration, with the lowest fecundity observed at the LC3 0 (23.71 eggs/female). The life table parameters showed a concentration-dependent reduction in the population growth metrics. The net reproductive rate (R 0), gross reproductive rate (GRR), intrinsic rate of increase (r), and finite rate of increase (λ) decreased significantly as the concentration increased, whereas the mean generation time (T) remained unaffected. The daily survival curves revealed reduced longevity in the treated groups, and age-specific fecundity (m x ) peaked at lower values in the treated mites than in the control mites. The age-stage specific survival rate (S xj ), life expectancy (e xj ), and reproductive value (V xj ) further confirmed the adverse impacts of fenpyroximate. These findings highlight the importance of considering sublethal effects in resistance management and integrated pest control strategies against T. urticae.

Phytoseiid mites are important for biological control of some pest species including phytophagous mites and small insects. The species, Phytoseius corniger Wainstein is one of the most abundant predatory mite in fruit orchards and urban green spaces in Razavi Khorasan province, Iran. Biological parameters of this predatory feeding on the two-spotted spider mite Tetranychus urticae Koch was studied for the first time under the laboratory conditions (25±2 ºC, 55±5 % RH and 16L: 8D photoperiod). The results indicated that the mean developmental periods for egg, larva, protonymph and deutonymph were 1.12±0.09, 0.73±0.03, 1.01±0.03, and 3.05±0.09 days for females, and 0.95±0.37, 0.67±0.39, 1.05±0.88, and 3.05±0.85 days for males, respectively. The pre-oviposition, oviposition, post-oviposition periods and adult longevity for females were 4.63±0.11, 11.63±0.16, 7.93±0.13 and 24.18±0.21 days, respectively. The females laid an average of 0.48 eggs per day, and 5.60 eggs during their life span. In addition, larvae of P. corniger may molt to the protonymph stage without feeding. Consumption rate during nymphal stage was 1.95 prey per day. The highest rate of prey consumption was recorded during the oviposition period, with an average of 3.35 prey items prey per day. Regarding life-history traits, the intrinsic rates of increase (rm) of this predatory mite 0.064±0.02 (♀♀/♀/day) and its finite rate of increase (λ), net reproduction rate (R0), generation time (T), and doubling time (DT) were 1.066±0.23 (day-1), 3±0.07 (♀♀/♀/generation), 17.14±0.11 (days), and 10.83±0.65 (days), respectively. Further laboratory and field studies regarding its diet preference and predation capacity are needed.

Demographic parameters of the turnip aphid, Lipaphis erysimi (Kaltenbach) (Hemiptera: Aphididae), which is a serious pest of Brassica crops worldwide, were evaluated on five major Brassica vegetables (three varieties of Brassica oleraceae (Linnaeus) (Brassicaceae: Brassicales); kohlrabi, cabbage and ornamental cabbage, and two subspecies of Brassica rapa (Linnaeus) (Brassicaceae: Brassicales); Chinese cabbage and bak choi). The study was carried out under laboratory conditions at 25 ± 1°C, 70 ± 5% RH and 16:8 (L:D) h. Preadult developmental time, survival rate, female longevity, reproduction, and life table parameters were evaluated according to the age-stage specific life table method. The highest population growth parameters, i.e., net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) were recorded on kohlrabi (R0 = 30.45 offspring, r = 0.2174 d-1, λ = 1.2429 d-1). These parameters were the lowest on Chinese cabbage (R0 = 13.00 offspring, r = 0.1503 d-1, and λ = 1.1621 d-1) and bak choi (R0 = 16.30 offspring, r = 0.1614 d-1, λ = 1.1752 d-1). The results attained from population growth parameters, together with population projection estimation based on the age-stage, two-sex life table theory, indicated that both Chinese cabbage and bak choi were less suitable hosts for turnip aphids and should be considered as a possible source for developing resistance in breeding programs and integrated pest management strategies.

Aphis gossypii Glover and Acyrthosiphon gossypii Mordvilko (Hemiptera: Aphididae) are important pests of cotton (Gossypium hirsutum L.) in Xinjiang, China, that reduce yield and lint quality. We studied competition between the two aphid species in laboratory arenas to better understand population change and competitive advantage between the two and to provide a theoretical basis for the observed population outbreak of aphids in cotton fields. To study intraspecific competition, densities of 5, 10, and 15 aphids per 5-cm-diameter leaf disc were established in individual 6-cm-diameter arenas. Equal numbers of each species were placed on leaf discs in the arenas to establish densities of 3, 5, and 10 aphids of each species per leaf disc to assess interspecific competition. In intraspecific competition assays, the mean generation time (T) and the net reproductive rate (Ro) of both species decreased as aphid density increased, while the intrinsic rate of increase (r) and finite rate of increase (λ) of Acy. gossypii increased as density increased. In interspecific competition assays, population growth of A. gossypii was higher than with Acy. gossypii at the same density, while the mean generation time of A. gossypii was less than with Acy. gossypii. The net reproductive rate, intrinsic rate of increase, and finite rate of increase were higher in A. gossypii than in Acy. gossypii. Density is a key factor affecting competition between A. gossypii and Acy. gossypii. The higher the density, the more intense the interspecific competition, with interspecific competitiveness of A. gossypii stronger than that of Acy. gossypii.

Trichogramma achaeae Nagaraja and Nagarkatti (Hymenoptera: Trichogrammatidae) is currently used as biological control agent for several lepidopteran pests. Knowledge of thermal requirements is essential to optimize its rearing procedures and inundative releases. The biological characteristics and two-sex life table parameters of T. achaeae were determined at five constant temperatures (15, 20, 25, 30, and 35 °C) using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. T. achaeae was able to develop and survive from 15 °C to 30 °C, but not at 35 °C. Temperature significantly affected the preadult development time and adult longevity, decreasing when temperature increased from 15 °C to 30 °C. Temperature significantly altered the sex ratio, being female biased between 15 °C and 25 °C. Age-stage, two-sex life table analysis indicated that net reproductive rate (R0) was highest at 20 °C. Both the intrinsic rate of increase (r) and finite rate of increase (λ) increased with increasing temperature, while the mean generation time (T) decreased significantly. In addition, functional response of T. achaeae was studied, being significantly affected by temperature and host egg density, displaying a Holling type-I at 15 °C and a Holling type-II at 25 °C. The relevance of these results is discussed for the use of T. achaeae as biological control agent.

This study evaluated the functional response and life table parameters of the predator Orius vicinus (Ribaut) (Hemiptera: Anthocoridae) when fed on immature stages of the polyphagous pest Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae). Biological and life table parameters, including development, survival, reproduction, and population growth rates, were assessed using two-sex age–stage life table analysis. Functional responses of adult O. vicinus to the egg, larval, and pupal stages of B. tabaci were determined separately under controlled conditions of 26 ± 1 °C, 60 ± 10% relative humidity (RH), and a 16:8 h light: dark (L: D) photoperiod. Results showed that egg development lasted 4.67 ± 0.06 days, total nymphal development was 13.65 ± 0.13 days with a survival rate of 77.32%, and mean fecundity per female was 60.89 ± 2.76 eggs. Female and male adult longevities were 16.95 ± 0.55 and 12.27 ± 0.54 days, respectively. Adult preoviposition period (APOP) and total preoviposition period (TPOP) were 4.14 ± 0.12 and 22.7 ± 0.23 days, respectively, while the oviposition period lasted 11.23 ± 0.53daysThe estimated life table parameters were the intrinsic rate of increase ( r ) of 0.113 day⁻¹, the net reproductive rate ( R 0 ) of 24.8 offspring, the finite rate of increase ( λ ) of 1.12 day⁻¹, and the mean generation time ( T ) of 28.4 days. Functional response analysis revealed a Type III response to eggs and larval stages, and a Type II response to pupae. These results indicate that O. vicinus could be effectively integrated into Biological control programs against B. tabaci .

This study aimed to evaluate the biotic potential, life table parameters and fertility of Spodoptera albula (Walker, 1857) under controlled conditions (25 ± 1°C, 70 ± 10% RH and 14 hour photo phase). The longevity, pre, post and oviposition periods, fecundity and fertility of 13 couples were evaluated. The longevity of females (13.500 days) was significantly higher than those of males (11.154 days). The mean durations of the pre, post and oviposition periods were 2.615, 1.769 and 9.385 days, respectively. The mean fecundity was 1.417.69 eggs and mean fertility was 1.340.401 larvae, per female. On average, females copulated 1, 231 times. A strong positive correlation was observed between the number of copulations and fecundity (r = 0.847, p <0.001), as well as a strong negative correlation between the number of copulations and the duration of the pre-oviposition period (r = -0.762, p = 0.002), and longevity (r = -0.788, p = 0.001). The biotic potential of S. albula was estimated at 8.768 x 1022 individuals / female / year. The net reproductive rate (Ro) was 353,904 times per generation and the mean generation time (T) was 37.187 days. The intrinsic rate of increase (rm) was 1,105, with a finite rate of increase (λ) of 3,019.

ABSTRACTThe objective of this work was to evaluate the potential of the use of lima bean (Phaseolus lunatus) as hosts of the mite Tetranychus neocaledonicus. For such, the biology and fertility life table of T. neocaledonicus on P. lunatus plants were evaluated. The experiment was carried out in a controlled environment at 25 ± 1°C and 75 ± 10% relative humidity (RH), with a 12-h photoperiod. The eggs used in the experiments were from inventories. Evaluations were performed twice daily in the immature stage. While in the adult stage, a single evaluation was carried out, in which reproductive aspects of T. neocaledonicus were analysed, being determined the daily oviposition and the longevity of females and males. The average life cycle of females and males was 11.94 and 11.48 days, respectively. For females, the development of the mobile period of larva, protonymph, and deutonymph presented an average of 2.23, 1.17, and 1.24 days, respectively, and for males, an average of 2.20, 1.06, and 1.21 days, respectively. Regarding the post-embryonic non-mobile periods of protochrysalis, deutochrysalis, and teleiochrysalis, the averages obtained were 0.66, 0.76, and 0.78 days, respectively, for females and males 0.62, 0.68, and 0.73 days, respectively. The sex ratio was 0.77 and the average longevity of females and males was 44.30 and 48.30 days, respectively. In the life table parameters, the following variables were measured: intrinsic rate of increase (rm), 0.14 f/f/d; mean generation duration (T), 21.2 days; net reproductive rate (R0), 24.7 individuals; finite rate of increase (λ), 1.16 f/f; and population doubling time, 4.64 days. Therefore, lima bean allows the development and reproduction of the mite T. neocaledonicus. The rapid development, allied to the high viability of immature forms and the high oviposition of females, suggests that this mite can achieve pest status in this crop.

PDF HTML阅读 XML下载 导出引用 引用提醒 UV-B长期胁迫对麦长管蚜子代种群动态的影响 DOI: 10.5846/stxb201611172338 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（39970112，20470268）；高校博士点基金（20130204110004）；陕西省科技厅国际合作项目（2012） Effect on population dynamics of the offspring of Sitobion avenae Fabricius (Hemiptera: Aphididae) exposed to long term UV-B stress Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了探明UV-B长期辐射亲代麦长管蚜Sitobion avenae Fabricius后对其子代种群动态的影响。采用特定年龄生命表方法，设置不同强度（0，0.50，0.70 mW/cm2）UV-B连续多代处理麦长管蚜成虫，统计麦长管蚜分别经历UV-B辐射一代，六代，十一代，十五代后其子代麦长管蚜存活率和繁殖力、繁殖参数、种群参数的变化。结果表明：（1）经UV-B处理亲代麦长管蚜后，其子代种群的内禀增长率r与周限增长率λ在低强度处理组各世代之间无显著差异，在高强度处理组各世代之间呈先上升后下降的趋势。（2）处理组麦长管蚜种群繁殖力F、净增殖率R0、平均世代周期T、产卵天数和成蚜寿命均在G7代达到最大值，且与对照组无显著差异。（3）亲代麦长管蚜经UV-B胁迫处理后对子代种群的存活率影响显著。研究结论：亲代麦长管蚜经过不同代数的UV-B胁迫，可显著影响子代的生长发育与繁殖，且对处于不同世代的子代生态学指标产生不同影响。研究的创新点在于探究亲代麦长管蚜经历紫外胁迫后对其子代生长、发育与繁殖的影响，为逆境胁迫下蚜虫的生态遗传与进化机理提供理论依据。 Abstract:Recently, ultraviolet-B radiation (UV-B) has been proven to have a strong selection pressure on the biosphere and ecological environment, significantly influencing living organisms. The rapid increase of solar UV-B reaching the surface of the earth is owing to stratospheric ozone depletion caused primarily by the Industrial Revolution. The responses of insect physioecology and growth to ultraviolet radiation enhancement have received increasing attention in the scientific community. Sitobion avenae Fabricius (Hemiptera:Aphididae) is a common wheat pest. It affects plants by ingesting sap from the ears, stems, leaves, and other tender plant parts. It also transmits viruses (e.g., barley yellow dwarf virus) during feeding, thereby reducing wheat yield and quality. It is a good subject for research because of its special characteristics of parthenogenesis and high fecundity. The increase of UV-B levels may fundamentally affect the population dynamics of S. avenae by altering its normal growth, development, and fecundity. The two-sex life table analysis is a common method to indicate biological growth, development, and fecundity, and includes the entire population (males, females, and those that die before the adult stages), so that the result is more realistic than analyses based only on the means of development time. To explore the effect on population dynamics of the offspring of S. avenae by exposing the mother generation to UV-B for a long time, the age-specific life table of S. avenae was established to evaluate life-table parameters of offspring of S. avenae. The mother generation was radiated to different intensities of UV-B (0, 0.5, 0.7 mW/cm2) for one, six, eleven, and fifteen generations. The results showed that:(1) There were no significant differences in the intrinsic rate of increase (r) and finite rate of increase (λ) among the treatment group of each generation under low intensity of UV-B, whereas the parameters of r and λ first increased and then fell with generations under high intensity of UV-B. (2) The effect of UV-B on the fecundity (F), net reproductive rate (R0), mean generation time (T), oviposition duration, and adult longevity peaked in the seventh generation. Moreover, no significant difference was found in the seventh generation between the control and treatment groups. (3) When S. avenae were under different intensity of UV-B radiation in the same generation, most parameters in the treatments groups were significantly lower than those in the control except the parameter T in the second and sixteenth generation. However, no significant difference was found in the seventh generation between the control groups and treatment groups, whereas F, R0, T, oviposition days, and adult longevity all had significant differences, but there were no significant differences between other parameters in the twelfth generation. (4) The survival rate of offspring of S. avenae exposed to UV-B stress was significantly influenced. Our research showed that the effect of long-term UV-B stress on S. avenae was accumulated in the progeny, had different impacts in different generations. Our research showed the population dynamics of the offspring of S. avenae after the mother generation was influenced by UV-B; thus, the results may provide a theoretical basis for ecological genetics and evolutionary mechanisms of aphid under adversity stress. 参考文献 相似文献 引证文献

The cultivated Eastern oyster (Crassostrea virginica) is sold in a niche market seeking rounder and thicker oysters. While most of the research conducted on optimal rearing densities focuses on survival and length growth, the present study looks at the oyster's shape. Three initial length classes were used for this study and reared in floating bags at different densities. The effects of the tested rearing densities were more pronounced on oyster shape than on length growth. In the smaller oysters, the three lower densities produced the rounder shape while thicker ones were obtained with the 500 densities. For the medium oysters, rounder and thicker shape was obtained with the two lower densities. The shape of the larger oysters was not influenced by the tested densities. This study showed that there was significant impact of rearing densities on smaller and medium oysters’ growth and shape, while only length growth of larger ones was impacted by this factor. Based on these findings, oyster farmers should target rearing density of 500 oysters per bag for the 20–35 mm stage, 250 oysters for the 35–50 mm oysters and 200 oysters for the larger ones (50–65 mm). The latest recommendations are based on technical considerations.

Tuta absoluta (Meyrick), a tomato leaf miner, is one of the destructive pests of tomatoes, which is native to South America, and has been considered as a quarantined pest for Iran since 2010 while it has quickly spread all around the country and is known as a key pest in tomato-cultured regions since 2012. In the current study, the life table parameters of T. absoluta were studied on cut leaves of three greenhouse cultivars of tomato including 'Atabay', 'Cluse', and 'Perenses'. Data were analyzed based on the age-stage, two-sex life table analysis. Results showed differences in the duration of egg, larvae, pupae, and adults. Meanwhile, the life table parameters including intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R0), and gross reproductive rate (GRR) were categorized increasingly based on the feeding on Cluse, Atabay, and Perenses, respectively. The findings of the current study showed that the Cluse could be nominated as an unsuitable host for tomato leaf miner among cultivars because of its negative influences on the pest's biological parameters. Moreover, these results may develop the finding and screening process of relatively resistant cultivars to be used in the management of T. absoluta.