Effects Of Adult Density Research Articles

The effect of adult density on the reproductive output and hatching performance of the lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

Abstract Commercial availability of insect biomass for food and feed calls for the methodical investigation of all the complications that can deteriorate the insect farming efficiency. An appropriate stocking density is thus instrumental for the establishment of sustainable and cost effective insect farming protocols; high densities may lead to reduced insect fitness and reproduction, while low densities will result to a proportionally lower per capita yield. The present study deals with the estimation of the optimum adult density of the lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), a species with great potential as food and feed source based on its high growth performance and reproductive output. However, limited data is available so far regarding the effect of adult density on its reproductive performance. Four different adult densities, ranging from 1.1 to 8.2 cm2 per adult, were evaluated in laboratory experiments in terms of reproductive output (number of eggs) and larval emergence for a period of 45 days of continuous oviposition. According to our results, the reproduction output, expressed as the cumulative number of eggs per adult and the cumulative larval hatching rate, was not affected by the adult densities tested here. Although high hatching rates that in most of the cases exceeded 85% were observed within the initial oviposition interval, these rates were in all treatments drastically reduced to 48-56% after 30 to 36 d. High adult survival (over 93%) was observed during the trial. In this experiment, the maximum reproductive output was observed in the highest density of adults that were left to oviposit continuously for a month. Data as such provide an opportunity to further exploit A. diaperinus in high-throughput production systems.

Influence of Seasonal Extreme Flows on Brook Trout Recruitment

AbstractPopulations of Brook TroutSalvelinus fontinalisexhibit large variation in annual recruitment (abundance of young of the year [age 0]), which is likely a product of density‐dependent and density‐independent factors. Quantifying the importance of each of these mechanisms in regulating Brook Trout recruitment would be valuable to managers that are responsible for the conservation of this iconic species throughout its native range. We analyzed a time series of age‐0 and adult Brook Trout density data collected from 10 streams in the Sinnemahoning Creek watershed, north‐central Pennsylvania (2010–2019), using Bayesian hierarchical modeling to partition the density‐dependent effects of adult density and the density‐independent effects of elevated streamflow on Brook Trout recruitment. Multiple models were examined, and the top‐ranked model showed that Brook Trout recruitment followed a Ricker stock–recruitment relationship, with annual recruitment negatively influenced by maximum streamflow during the spring season (March–April). This model will be useful in predicting future variation in Brook Trout recruitment under climate change scenarios in which the frequency and intensity of high‐flow events are expected to increase.

Effect of adult density on egg production, egg hatching success, adult mortality, nauplii cannibalism and population growth of the tropical calanoid copepod Acartia tropica

Present study evaluated the impacts of adult density on key biological parameters of a tropical estuarine calanoid copepod A. tropica. Egg production, egg hatching success (EHS), adult mortality (%), nauplii cannibalism (% hour−1), population growth and intrinsic rate of population increase in response to five different adult densities viz. 125, 250, 500, 1000 and 2000 adults/L were assessed. The highest individual egg production (IEP, eggs/female/day) was recorded at 125 adults/L treatment while relative egg production (REP, eggs/L/day) was highest at 1000 adults/L. EHS (24 h and 48 h) showed significant difference (p < 0.05) among the treatments with highest EHS recorded at 125 adults/L treatment and lowest EHS recorded at 2000 adults/L treatment. Moreover, the adult mortality and nauplii cannibalism were negatively correlated to adult density with significantly highest cumulative adult mortality (65 ± 3) and nauplii cannibalism (4.49 ± 0.27) recorded at 2000 adults/L. The highest population count after 8 days culture was recorded at 2000 adults/L treatment. However the lowest intrinsic rate of whole, live and adult population increase after 8 days culture was recorded at 2000 adults/L treatment. It is also observed that the population with an initial adult density of 2000/L decreases to a new stable equilibrium of 1000 adults/L after 8 days culture. Our results suggest to maintain A. tropica at a density of 1000 adults/L in batch culture with daily harvest of eggs and nauplii to maximise its productivity as live feed in aquaculture hatcheries.

Inter-class competition in stage-structured populations: effects of adult density on life-history traits of adult and juvenile common lizards.

Ecological and evolutionary processes in natural populations are largely influenced by the population's stage-structure. Commonly, different classes have different competitive abilities, e.g., due to differences in body size, suggesting that inter-class competition may be important and largely asymmetric. However, experimental evidence states that inter-class competition, which is important, is rare and restricted to marine fish. Here, we manipulated the adult density in six semi-natural populations of the European common lizard, Zootoca vivipara, while holding juvenile density constant. Adult density affected juveniles, but not adults, in line with inter-class competition. High adult density led to lower juvenile survival and growth before hibernation. In contrast, juvenile survival after hibernation was higher in populations with high adult density, pointing to relaxed inter-class competition. As a result, annual survival was not affected by adult density, showing that differences in pre- and post-hibernation survival balanced each other out. The intensity of inter-class competition affected reproduction, performance, and body size in juveniles. Path analyses unravelled direct treatment effects on early growth (pre-hibernation) and no direct treatment effects on the parameters measured after hibernation. This points to allometry of treatment-induced differences in early growth, and it suggests that inter-class competition mainly affects the early growth of the competitively inferior class and thereby their future performance and reproduction. These results are in contrast with previous findings and, together with results in marine fish, suggest that the strength and direction of density dependence may depend on the degree of inter-class competition, and thus on the availability of resources used by the competing classes.

Packaging conditions for the field release of the fruit fly parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae)

AbstractThe effects of adult density, hypoxia conditions, temperature and photoperiod on the emergence, mating, flight ability, survival and fecundity of adult Diachasmimorpha longicaudata (Ashmead) were evaluated when insects were packaged in a 20 l cylindrical container for field release. Survival was the only parameter that was significantly affected by density and hypoxia. Emergence and fecundity were noticeably delayed with decreased temperature, although survival increased. Mating depended mainly on temperature, but photoperiod was not a determinant; however, the presence of light significantly increased fecundity and flight ability of adults. Adult emergence averaged 60%, but in high packaging densities a greater incidence of damage to antennae occurred, likely because of mating behaviours in overcrowded conditions. The information generated by this study is useful for the field release of higher quality parasitoid adults in projects intended to utilise augmentative biological control to suppress fruit fly pest populations.

Density dependent growth changes through juvenile and early adult life of North East Atlantic Mackerel (Scomber scombrus)

Density dependence of somatic growth has an important, but overlooked, impact on fisheries management advice. We therefore examined how growth relates to abundance in a case where growth has been observed to vary substantially in recent years, namely North East Atlantic mackerel, one of the most widespread and commercially important fish stocks in the North Atlantic. Growth of juvenile and early adult North East Atlantic mackerel was found to be decreasing since the late 1990s. Modelling showed that growth was related to density. Mean growth rate during the first year was tightly correlated with the density of juveniles and especially with juveniles from the previous cohort. This putative effect of juvenile density could be tracked in the length-at-age up to adult mackerel at commercially targeted sizes. However, as the mackerel grew towards adulthood, the effects of the same cohort became dominant. The effect of adult density was minor, but increasing with age. The ontogenetic progression in density dependant regulation of growth appeared to reflect the spatial dynamics (migration patterns) in the feeding season. This is the first time growth patterns quantified in the adult mackerel population have been linked to density related processes occurring within the nursery areas during the first year. These aspects of mackerel production have a substantial and direct impact on the management plan evaluations used when fisheries scientists provide advice for fisheries management.

Egg cannibalism in Acartia tonsa: effects of stocking density, algal concentration, and egg availability

Cannibalism in copepod culture may limit its production yield and therefore affect the economic interests associated with the use of copepods as live feed in aquaculture. The effects of adult density, egg density, and algal availability were tested on the calanoid copepod Acartia tonsa to understand how these parameters affect cannibalism rates on eggs. The overall cannibalism within the range of adult densities tested (120–1,000 adult L−1) was solely influenced by the egg and algal density, and not by the adult density. The increased densities of eggs lead to higher occurrences of cannibalism. Increasing the availability of alternative diets (e.g., algae) significantly diminished the adults’ cannibalistic behavior. The highest cannibalistic rates per adult were observed at low densities of adults and high densities of eggs (120 ind L−1 and 20,000 eggs L−1, respectively) and resulted in consumption rates >20 eggs ind−1 h−1. In this experiment, cannibalistic behavior reached 20 % of adult weight ind−1 h−1 under the aforementioned parameters. Additionally, the present study suggests that at high adult copepod density, the interactions between adults result in a decreased “time to feed.” Finally, it is argued that the separations of eggs from adult copepods, as well as the continuous access to an alternative food source, are necessary for decreasing the effects of cannibalism in copepod cultures.

Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in cotton: vertical distribution of egg masses, effects of adult density and plant age on oviposition behavior

The objective of this work was to determine the most suitable density of adults per plant, ideal plant age, and vertical distribution of eggs in different parts of the plant in a greenhouse investigation for future resistance studies and improvement of S. frugiperda management practices in cotton. The experiments of Spodotera frugiperda oviposition in relation to adult density, relationship between cotton plant age and Spodoptera frugiperda oviposition, Spodoptera frugiperda non-preference for oviposition on cotton varieties were conducted with plants of cotton variety BRS Ita 90. The experiments were conducted with plants of cotton variety BRS Ita 90. Non-preference (antixenosis) for oviposition was studied in FiberMax 966, FiberMax 977, DeltaOpal, DeltaPenta, Acala 90, Coodetec 408, Coodetec 409, Coodetec 410, BRS Cedro, BRS Ipê, BRS Aroeira, IPR 96, IPR 20, BRS Araçá, IAC 24, and BRS Ita 90 varieties. We concluded that the fall armyworm S. frugiperda prefers to oviposit on plants with approximately 60 days of age, on the lower surface of leaves located in the upper third of the plant tests under greenhouse conditions. A density of at least three pairs of S. frugiperda adults per plant was sufficient to conduct non-preference-for-oviposition tests under greenhouse conditions. Coodetec 408, BRS Aroeira, BRS Araçá, BRS Ita 90 and DeltaPenta varieties showed non-preference-for-oviposition resistance to S. frugiperda. In regions with high infestations of S. frugiperda, it would be prudent for the cultivation the use of BRS Ita 90 cotton variety.

Population dynamics of the mussel Mytilus edulis: spatial variations in age-class densities of an intertidal estuarine population along environmental gradients

Population dynamics of the mussel Mytilus edulis: spatial variations in age-class densities of an intertidal estuarine population along environmental gradients

Daily Patterns of Reproductive Activity and the Influence of Adult Density and Exposure to Host Plants on Reproduction in the Diamondback Moth (Lepidoptera: Plutellidae)

Daily patterns of activity and the effects of adult density and exposure to host plants on the onset of reproductive activities and age-specific fecundity of the diamondback moth, Plutella xylostella (L.), were determined under constant conditions of 21°C, 70%RH, and a 16:8 (L:D) photoperiod. More than 50% of adult emergence occurred in the first 8 h of the photophase. Although calling occurred throughout the scotophase, >70% of mating and oviposition took place in the first 4 h. Approximately 90% of females had begun to call, mate, and lay eggs, and the females contained ≥1 mature egg by night 4 when kept with males and host plants in individual pairs. In contrast, only 27% of females kept with males but without host plants had mated by night 4, and only 64% contained mature eggs. Individually caged females laid eggs at a rate >50% of their maximum daily oviposition on nights 3–5, and for females caged in groups of 50 males and 50 females this occurred on nights 4–10. Ovarian development also was consistently slower in the group-caged females than in the individually caged females, the former containing 16 to 93% as many mature eggs as the individually caged females, depending on age and prior exposure to plants. Male sexual maturation was not complete at adult emergence, and only 54% of day-l males were able to fertilize 4-d-old, virgin females. By night 4,98% of males were able to do so regardless of whether or not they were exposed to host plants. Females mated to day-4 males that were exposed to plants for the first three nights produced significantly more viable eggs compared with females mated to day-4 males that were not previously exposed to host plants.

Interspecific Competition between Drosophila melanogaster and Drosophila simulans: Effects of Adult Density, Species Frequency, Light, and Dietary Phosphorus-32 on Fecundity

Fecundity (number of eggs per surviving female) of Drosophila simulans st and D. melanogaster Or-R-C was measured over consecutive 12-h periods for 7 days post-eclosion in replicated experiments where adult density (6 levels), species frequency (6 levels), and P32 tissue content (2 levels) were varied factorially. Phosphorus-32 tissue content was introduced as a factor so that eggs of the two species could be distinguished in mixed-species populations. A similar experiment was done for D. simulans st and D. melanogaster yw. Least-squares analyses of variance indicated that: (1) D. melanogaster Or-R-C had highest fecundity, followed by D. melanogaster yw, then D. simulans st. (2) Competing D. melanogaster strains influenced fecundity of D. simulans st-fecundity being higher when yw was the competitor. (3) Fecundity changed with female age, but each strain displayed a unique pattern. (4) Increasing density reduced fecundity for all strains; similarly for st and yw, but more severely for Or-R-C. (5) Effects of species frequency were significant only for D. simulans st, its fecundity decreasing as its frequency increased. (6) P32 lowered fecundity. (7) Light (i.e., day vs. night) had a significant effect on fecundity for all strains. Effects of density and of its own frequency on the fecundity of D. simulans st apparently were due to intraspecific interactions affecting mating-an increasing proportion of females remaining unmated with increase in density or frequency. Reduced fecundity with increasing density in the D. melanogaster strains and effects on the proportions of eggs laid in the day and night in all three strains were explainable in terms of differing disruption at oviposition due to activity differences among the strains. Different patterns of relationship of fecundity with species frequency at the different densities for the two D. melanogaster strains were not simply interpretable, either in terms of inter-or intraspecific interactions.

Interspecific competition between Drosophila melanogaster and Drosophila simulans: Effects of adult density on adult viability

Survival (viability) of newly eclosed adults of D. simulans st and D. melanogaster Or R-C, which had excess quantities of dead yeast available throughout life, was measured daily for 7 days in an experiment where adult density (6 levels), species frequency (6 levels) and 32P tissue content (2 levels) were varied factorially. A separate experiment comparing viability in different types of experimental unit also was done. Similar experiments were done for D. simulans st competing against D. melanogaster y w. The entire data were subjected to a least-squares (unbalanced, missing-plot) analysis of variance. D. melanogaster Or R-C had a higher average viability than D. melanogaster y w or D. simulans st, which were equal. The competing strain of D. melanogaster influenced D. simulans st viability — viability being higher when y w was the competitor. Viability decreased over the seven day period but at different rates for the three strains. Increasing density reduced viability for all three strains, but species frequency effects, although significant, were generally not consistent. Females had higher viability than males in both D. melanogaster strains, but the reverse was true in D. simulans st. 32P lowered viability and experimental unit type altered viability. Numerous interactions were significant. Adult density was shown to have a delayed effect on viability — the delay before the appearance of the effect (an increase in death rate) being decreased as density rose. The term ‘variably delayed density dependent’ has been adopted to describe the fitness component, adult viability. Some high density populations showed a readjustment (a decrease) in their death rate as a reaction to the effect of reduced density caused by high early mortality.