Population density dynamics of Pachymelania byronensis (Wood, 1828) (Gastropoda: Thiaridae) in the Cross River, Nigeria

The ecology of an exploited population of the commercially important molluscan species, Pachymelania byronensis (Wood, 1828) was studied (January-December, 2018) in the lower Cross River, Nigeria, using density [number per hectare (N. ha-1)] as measure of stock abundance. The results revealed that the river supports a considerable stock of the gastropod (density range: Drange = 508000 – 12510000 N. ha-1; mean: Dmean = 4849833N.ha-1). The density decreased by 12002N. ha-1 (i.e. 10001667N. ha-1 mo-1) between January and December, a reflection of the increasing human exploitation as the year progressed. However, the monthly density changes scored low stochasticity (randomness), a product of the resilience of the population to human exploitation. The monthly densities were significantly correlated with river limnological parameters, including surface temperature, discharge, water level, transparency, dissolved oxygen concentration and hydrogen ion concentration. The coefficients of determination showed the decreasing order of theimportance of these parameters as: transparency (67.8%), water level (57.0%), surface temperature (43.5%), pH (40.5%), dissolved oxygen concentration (36.1%) and discharge (34.3%). The monthly values of biotic potential (rmax) were used to show trends in the population dynamics. Major density decreases were noted in February (rmax = -5.456) and December (rmax = -2.931) whereas notable density increases were recorded in January (rmax = + 3.204) and November (rmax = + 3.052). The value of the annual mean biotic potential (mean: rmax(mean) = -0.191) portrayed the general effect of heavy human exploitation on the mollusc. Hence, the gastropod total mortality rate was high (Z = -3.204 yr-1) The river carrying capacity of the gastropod was estimated at 12510000N ha-1. The monthly biotic potential correlated significantly with habitat temperature and dissolved oxygen concentration, two important life support parameters. Keywords: Pachymelania byronensis; density; biotic potential; exploitation; Cross River; Nigeria.

Biological potential cestodes of Echinococcus granulosus in dogs and sheep in the Republic Dagestan

The article is devoted to the study of the biotic potential and the role of the cestode Echinococcus granulosus in the infection of shepherd dogs and sheep in the republic. It has been established that the average intensity of invasion (II) of the causative agent of echinococcosis in shepherd dogs in the surveyed areas (Kizlyarsky, Laksky, Nogaysky, Sergokalinsky, Suleiman – Stalsky, Khasavyurt, Tsumadinsky, Shamilsky, etc.) is 1768 ± 245; 2924 ± 369; 3456 ± 382; 4683 ± 597; 2249 ± 321; 1870 ± 263; 2633 ± 352; 2149 ± 286 specimens / specimen. Infection of adult sheep with echinococcosis occurs in all surveyed areas, with fluctuations in the intensity of invasion (II) from 14.8 ± 1.3 to 21.3 ± 1.9 specimens / specimen, on average 17.56 ± 1.53 specimens. /individual. In sheep of all age groups, with a complete helminthological autopsy, in 1 ml of echinococcal fluid, fertile larvocysts were found in an amount of 20.36 ± 1.15 specimens / individual, except for young sheep, up to 1 year old. In sheep under the age of 2 years, fertile larvocysts of Echinococcus granulosus are found in the amount of 9.2 ± 0.41 specimens / specimen 0.83 ± 0.076 thousand specimens. The average number of fertile larvocysts found in 1 ml of fluid in sheep at the age of up to 3 years is 15.8 ± 0.93 specimens / individual and 1.15 ± 0.098 thousand specimens; up to 4 years old – 20.5 ± 1.17 specimens / individual and 1.92 ± 0.17 thousand specimens; up to 5 years – 27.3 ± 1.69 specimens / individual and 2.58 ± 0.26 thousand specimens; up to 6 years old – 36.7 ± 1.88 specimens / individual and 3.06 ± 0.49 thousand specimens. These data indicate an increase in the role and activity of the ovine variant of the causative agent of echinococcosis Echinococcus granulosus.

Biotic potential and reproductive parameters of Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) in the laboratory

In this study we evaluate the biotic potential and reproductive parameters of Spodoptera cosmioides (Walker, 1858) under controlled conditions (25 ± 1 °C, 70 ± 10% RH and 14 hour photophase). Females, on average, (14.433 days) did not live significantly longer than their male counterparts (13.100 days). The mean durations of the pre-oviposition, oviposition and post-oviposition periods were 2.767, 10.600 and 1.067 days, respectively. The mean fecundity of females was 5,073.533 eggs and the mean fertility was 5,021.027 larvae. On average, females copulated 1.167 times. Fecundity was positively correlated with the number of copulations (r = 0.583, P <0.001). The number of copulations, however, was negatively correlated whit the duration of the pre-oviposition (r = -0.560, P = 0.007) and oviposition (r = -0.479, P = 0.048) periods, and overall longevity (r = -0.512, P = 0.031). The biotic potential was estimated at 6.547 x 1021 individuals/female/year. The net reproductive rate (Ro) was 2,193.722 times per generation and the mean generation time (T) was 46.407 days. The intrinsic rate of increase (rm) was 0.166, with a finite rate of increase (λ) of 1.180, per week.

Environmental elements for revitalization of entomophages in theforest plantations of the arid zone

Введение. Лесомелиоративное обустройство территорий малолесных регионов коренным образом преобразует ранее пустынные пространства. Позитивные изменения влажностнотеплового, почвенного, гидрологического режимов, обогащение аборигенной дендрофлоры новыми видами влечет за собой также и трансформацию животного мира, в том числе населения насекомых. Энтомосообщества формируются за счет представителей степной группы, обитателей естественных ценозов, а также группы лесных насекомых, в числе которых виды, являющиеся опасными вредителями и их энтомофаги. Цель работы анализ изменения разнообразия насекомыхэнтомофагов в насаждениях засушливой зоны различных параметров и состояния. Объекты исследований насекомыеэнтомофаги, обитающие в энтомокомплексах защитных насаждениях различного дендрологического состава ФНЦ агроэкологии РАН на территории Волгоградской области (кадастр. 34:34:000000:122 34:08:000000:6). Материалы и методика. Сбор материала проводили в насаждениях различного хозяйственного значения. Объектами исследования являлись полезные насекомые. Отбор проб проводили посредством окашивания крон энтомологическим сачком, визуальным осмотром модельных ветвей и ручным сбором хищников и паразитированных видов филлофагов с последующим выведением имаго в лабораторных условиях. Результаты и обсуждение. В сообществе полезных насекомых защитных лесных насаждений сухостепной зоны зафиксирован 221 вид энтомофагов, относящихся к 7 отрядам и 32 семействам. Различия экологических условий, ассортимент древесных растений в каждой из посадок, характер и интенсивность негативного внешнего влияния определяют особенности фаунистического населения, в т. ч. энтомофагов. Оценка распределения количественного обилия паразитов и хищников показала, что в лесных полосах хищников в среднем в три раза больше паразитических насекомых. Отчетливо прослеживаются вариации изменения разнообразия энтомофагов в насаждениях разного класса жизнеспособности. Конструктивные особенности, флористическая обедненность и сформировавшийся микроклимат существенно ограничивает жизнедеятельность энтомофагов в малорядных (23 ряда) насаждениях, численность которых здесь снижается в среднем в 2,5 раза по сравнению с многорядными посадками. В вертикальном градиенте посадок по мощности накопления биотического потенциала полезных насекомых выделяется травянистый ярус, наличие которого в лесополосе обусловливает увеличение числа особей энтомофагов в сообществе в 1,32,7 раза. Наименьшую роль в накоплении полезной группы насекомых играет наличие развитого подлеска. Заключение. Наличие в насаждениях энтомофильных древесных растений и развитого травостоя важнейшие экологические факторы для накопления биотического потенциала энтомофагов. Максимальный эффект обеспечивает совокупное влияние определяющих экологоструктурных элементов в многорядных посадках. Introduction. Forest reclamation area developmentpoor regions is radically transforms the previously desolate space. Positive changes in moistureheat, soil, hydrological regimes, enrichment of native dendroflora with new species also entails the transformation of the animal world, including the insect population. Entomologiste formed by the representatives of the steppe group of the inhabitants of the natural coenoses, and the group of forest insects, including species that are dangerous pests and their entomophages. The purpose of the analysis of changes in the diversity of insect entomophages in the plantations of the arid zone of different parameters and conditions. The objects of research insectsentomophages living in entomocomplexes protective plantation of different dendrological composition of the Federal scientific center for Agroecology wounds on the territory of the Volgograd region (the cadaster number is 34:34:000000:122 34:08:000000:6). Materials and methods. Collection of material was carried out in plantations of various economic importance. The objects of study were useful insects. Samples were collected by hilling crowns entomological net, by visual inspection of the model branches and handcollection of predators and parasitism species of phyllophagous with subsequent excretion of adults in the laboratory. Results and discussion. 221 species of entomophages belonging to 7 groups and 32 families were recorded in the community of useful insects of protective forest plantations of the dry steppe zone. Differences in environmental conditions, the range of woody plants in each of the plantings, the nature and intensity of the negative external influence determine the characteristics of the faunal population, including entomophages The estimation of distribution of quantitative abundance of parasites and predators showed that in forest bands of predators on average three times more parasitic insects. Variations in the diversity of entomophages in plantings of different classes of viability are clearly observed. Design features, floristic depletion and formed microclimate significantly limits the life activity of entomophages in smallrow (23 rows) plantations, the number of which is reduced by an average of 2.5 times compared to multirow planting. In the vertical gradient of plantings on the power of accumulation of biotic potential of useful insects, a grassy tier is allocated, the presence of which in the forest belt causes an increase in the number of entomophages in the community by 1.32.7 times. The least role in the accumulation of a useful group of insects is played by the presence of developed undergrowth. Conclusion. The presence of entomophilic woody plants and developed herbage in the plantations are the most important environmental factors for the accumulation of the entomophage biotic potential. The maximum effect provides a cumulative effect of determining ecological and structural elements in multirow landings.

Biotic Potential and Reproductive Parameters of Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae)

The fall armyworm, Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae), a native to the Americas and recently reported in Africa, Germany, the Netherlands and India, is a significant pest of many crop species. Although a widespread and important pest, information on its biology and development are incomplete and require detailed study. In this study, the biotic potential and reproductive parameters of S. frugiperda were evaluated under controlled conditions (25&plusmn;1 &deg;C, 70&plusmn;10% RH and 14 hour photophase). The longevity, pre-, post- and oviposition periods, fecundity, and fertility of 30 pairs were evaluated. The longevity of females (10.87 days) was not significantly different from that of males (10.90 days). The mean durations of the pre-, post- and oviposition periods were 2.63, 0.53 and 7.70 days, respectively. The mean fecundity was 2,370.66 eggs per female and mean fertility was 2,309.03 larvae per female. On average, a female copulated 1.6 times. The biotic potential of S. frugiperda was estimated at 2.086 &times; 1029 individuals/female/year. The net reproductive rate (Ro) was 1,079.73 times per generation and the mean generation time (T) was 32.00 days. The intrinsic rate of increase (rm) was 0.22, with a finite rate of increase (&lambda;) of 1.24 per day. This study evaluates and describes the biological parameters of S. frugiperda with special emphasis on its biotic potential and reproductive parameters. This information will improve the development of integrated pest management (IPM) and insect resistance management (IRM) for this species.

Biotic Potential and Life Tables of Chrysodeixis includens (Lepidoptera: Noctuidae), Rachiplusia nu, and Trichoplusia ni on Soybean and Forage Turnip

Loopers such as Chrysodeixis includens (Walker), Rachiplusia nu (Guenée), and Trichoplusia ni (Hübner) are important defoliators in soybean, sunflower, and crucifer crops, respectively, in countries of the Americas. The biotic potential of these polyphagous species of Plusiinae was comparatively examined considering crop rotation and succession scenarios in which crucifer crops are cultivated during or after Brazilian winter. All the species developed and reproduced on soybean (BRS 133 Embrapa) and forage turnip (Cati AL 1000, Wolf Seeds do Brasil). The development of C. includens was similar on both host plants. The survival of R. nu was lower on forage turnip than on soybean. In contrast, T. ni performance (survival, fecundity, pupal weight) was better on forage turnip than on soybean. This suggests that in crop rotation and succession scenarios of soybean after brassicacea, C. includens is likely to have a higher number of generations per year and could be potentially more harmful.