scholarly journals Effects of Food Concentration and Photoperiod on Egg Production, Female Life Expectancy and Population Dynamics of the Paracalanid Copepod, Bestiolina amoyensis

2021 ◽  
Vol 8 ◽  
Author(s):  
Lin Wang ◽  
Shuhong Wang ◽  
Chaoshu Zeng ◽  
Yuyue Wang ◽  
Chunxiao Zeng
Keyword(s):  
Population Dynamics ◽  
Life Expectancy ◽  
Egg Production ◽  
Intrinsic Rate ◽  
Food Concentration ◽  
Population Increase ◽  
Larval Rearing ◽  
Culture Techniques ◽  
Female Life Expectancy ◽  
Final Population

The paracalanid copepod, Bestiolina amoyensis, is a widely distributed species occurring in subtropical inshore waters across the Pacific Ocean. Its small size, herbivorous feeding habit, and high adaptability make the species one of the most promising candidates as potential live feed for hatchery larval rearing. This study investigated effects of different feeding density of microalgae Isochrysis spp. (1 × 105, 2 × 105, 3 × 105, 4 × 105, and 5 × 105 cells ml–1) and photoperiod (8L:16D, 12L:12D, and 16L:8D) on productivity-related parameters, including egg production, female life expectancy and population dynamics of B. amoyensis. Results showed that total egg output over female lifespan, final population size and intrinsic rate of population of 12L:12D photoperiod treatments were always the highest among three photoperiod conditions, especially at the food concentration of 4 × 105 cells ml–1, indicating B. amoyensis had high reproductive performance and the population was in a more stable status. The number of nauplii from 4 × 105 cells ml–1 algal concentration treatment accounted for 75% of the population, and the ratio of females to males approaching 1:1 when photoperiod was 12L:12D; female life expectancy was 10.5 ± 0.6 days. In conclusion, our results showed that Isochrysis spp. is a suitable feed for B. amoyensis with an optimal concentration at 4 × 105 cells mL–1; the optimal photoperiod for B. amoyensis rearing is 12L:12D. The relatively long reproductive lifespan and high intrinsic population increase rate make B. amoyensis a good candidate to develop culture techniques for hatchery larval rearing.

Asplanchna-kairomone induces life history shifts in Brachionus angularis (Rotifera)

2018 ◽  
Vol 54 ◽  
pp. 13 ◽  
Author(s):  
Ling Pan ◽  
Yi-Long Xi ◽  
Jing Gu ◽  
Shan Jiang ◽  
Han Zhu ◽  
...  
Keyword(s):  
Population Growth ◽  
Egg Production ◽  
Scenedesmus Obliquus ◽  
Intrinsic Rate ◽  
Population Increase ◽  
Food Level ◽  
Reproduction Rate ◽  
Inducible Defenses ◽  
Rapid Population Growth ◽  
Sexual Offspring

Predator-derived kairomones play an important role in ecological and evolutionary processes that enable the prey to survive predation pressure. In the presence of predatory Asplanchna, some Brachionus and Keratella species develop morphological and behavioral defenses, but whether rapid population growth and diapause are inducible defenses largely remains unknown. In the present study, parental B. angularis females cultured at 1.0 × 106 and 2.0 × 106 cells · mL−1 of Scenedesmus obliquus were indirectly exposed to 0, 40, 80 and 160 ind. L−1 of A. brightwelli using mesh enclosure, and their life-table demographic parameters, population growth rates and morphological characters were calculated and measured. The results showed that Asplanchna-released kairomone decreased significantly average lifespan, life expectancy at hatching, generation time and net reproduction rate, but increased the proportion of sexual offspring of parental B. angularis females. The threshold Asplanchna density required for significant effects varied with food level. Kairomone released by Asplanchna at 80 ind. L−1 increased significantly the intrinsic rate of population increase of B. angularis cultured at 2.0 × 106 cells · mL−1 of S. obliquus, which would offset the mortality of exposed females from predation. The accumulation of kairomone in aquatic environments enhanced the indirect effect of Asplanchna on the population growth of B. angularis. The present results indicated that rapid population growth of B. angularis induced by Asplanchna kairomone might facilitate the coexistence of preys with predators, and higher proportion of sexual offspring and then resting egg production might help the preys avoid the predator in time instead of facing the enemy through defenses.

Combined effects of oxytetracycline concentration and algal food level on the life-table demography of Brachionus calyciflorus (Rotifera)

2018 ◽  
Vol 54 ◽  
pp. 28
Author(s):  
Shan Jiang ◽  
Yi-Long Xi ◽  
Han Zhu ◽  
Bing-Xing Zhang ◽  
Jin-Hang Yu
Keyword(s):  
Life Expectancy ◽  
Life Table ◽  
Generation Time ◽  
Intrinsic Rate ◽  
Brachionus Calyciflorus ◽  
Population Increase ◽  
Reproduction Rate ◽  
Net Reproductive Rate ◽  
Environmental Concentration ◽  
Net Reproduction

Oxytetracycline (OTC) is commonly used for aquaculture and livestock, and its environmental concentration has increased to a considerable level and displays potential environmental risk. In the present study, the life-table demography of Brachionus calyciflorus exposed to sublethal concentrations (30.0, 60.0, 90.0, 120.0, 150.0 and 180.0 mg L−1) of OTC was investigated at 1.0 × 106, 2.0 × 106 and 4.0 × 106 cells mL−1 of Scenedesmus obliquus. The results showed that at each algal density, OTC concentration affected significantly life expectancy at hatching, net reproductive rate, generation time and intrinsic rate of population increase (P < 0.01), but did not affect proportion of mictic offspring of the rotifers (P > 0.05). Compared to the controls, and at 2.0 × 106 cells mL−1 of S. obliquus, treatments with OTC at 30.0–150.0 and 60.0–120.0 mg L−1 significantly prolonged life expectancy at hatching and generation time, treatments with OTC at 30.0–120.0 and 30.0–90.0 mg L−1 increased net reproduction rate and intrinsic rate of population increase, respectively, but the reverse was also true for those with OTC at 180.0 mg L−1. Higher and lower algal densities decreased the magnitude of stimulatory effects of lower concentrations of OTC but enhanced that of inhibitory effects of high concentration of OTC on the survival, asexual reproduction and population growth of the rotifers. At the three algal densities, net reproduction rate was more sensitive to OTC than the other endpoints, and significant concentration- effect relationship existed between OTC concentration and each of all the life-table demographic parameters except the proportion of mictic offspring.

Plant Resistance in Some Modern Soybean Varieties May Favor Population Growth and Modify the Stylet Penetration of Bemisia tabaci (Hemiptera: Aleyrodidae)

2021 ◽  
Author(s):  
Mauricélia F Almeida ◽  
Clébson S Tavares ◽  
Euires O Araújo ◽  
Marcelo C Picanço ◽  
Eugênio E Oliveira ◽  
...  
Keyword(s):  
Population Growth ◽  
Bemisia Tabaci ◽  
Intrinsic Rate ◽  
Reproductive Rate ◽  
Genetically Engineered ◽  
Population Increase ◽  
Net Reproductive Rate ◽  
Bt Toxin ◽  
Demographic Performance

Abstract Complaints of severe damage by whiteflies in soybean fields containing genetically engineered (GE) varieties led us to investigate the role of transgenic soybean varieties expressing resistance to some insects (Cry1Ac Bt toxin) and to herbicide (glyphosate) on the population growth and feeding behavior of Bemisia tabaci (Gennadius) MEAM1 (Hemiptera: Aleyrodidae). In the laboratory, the whiteflies reared on the GE Bt soybeans had a net reproductive rate (R0) 100% higher and intrinsic rate of population increase (rm) 15% higher than those reared on non-GE soybeans. The increased demographic performance was associated with a higher lifetime fecundity. In electrical penetration graphs, the whiteflies reared on the GE soybeans had fewer probes and spent 50% less time before reaching the phloem phase from the beginning of the first successful probe, indicating a higher risk of transmission of whitefly-borne viruses. Data from Neotropical fields showed a higher population density of B. tabaci on two soybean varieties expressing glyphosate resistance and Cry1Ac Bt toxin. These results indicate that some GE soybean varieties expressing insect and herbicide resistances can be more susceptible to whiteflies than non-GE ones or those only expressing herbicide resistance. Most likely, these differences are related to varietal features that increase host-plant susceptibility to whiteflies. Appropriate pest management may be needed to deal with whiteflies in soybean fields, especially in warm regions, and breeders may want to consider the issue when developing new soybean varieties.

Population dynamics of large and small mammals: Graeme Caughley's grand vision

2009 ◽  
Vol 36 (1) ◽  
pp. 1 ◽  
Author(s):  
Charles J. Krebs
Keyword(s):  
Population Dynamics ◽  
Population Control ◽  
Population Increase ◽  
Control Mechanisms ◽  
Relative Role ◽  
Top Down ◽  
Large Herbivores ◽  
Disturbed Systems ◽  
Herbivorous Mammals ◽  
Grand Vision

Ecologists that study the population dynamics of large and small herbivorous mammals operate in two worlds that overlap only partly, and in this paper I address whether the conjecture that these worlds represent two distinct and valid paradigms is currently justified. I argue that large mammals fall into three groups depending on whether they have effective predators or not, and whether they are harvested by humans. Because of human persecution of large predators, more and more large herbivorous mammals are effectively predator-free and are controlled bottom-up by food. But in less disturbed systems, large herbivorous mammals should be controlled top-down by effective predators, and this can lead to a trophic cascade. Small herbivorous mammals have been suggested to be controlled top-down by predators but some experimental evidence has challenged this idea and replaced it with the notion that predation is one of several factors that may affect rates of population increase. Intrinsic control (territoriality, infanticide, social inhibition of breeding) appears to be common in small herbivorous mammals with altricial young but is absent in species with precocial young, in ecosystems with strong stochastic weather variation (deserts) and in areas of human-induced habitat fragmentation in agricultural monocultures. The extrinsic control of large herbivores with precocial young validates part of Graeme Caughley’s Grand Vision, but the relative role of intrinsic and extrinsic mechanisms for small herbivores with altricial young is still controversial. An improved knowledge of population control mechanisms for large and small herbivores is essential for natural resource management.

The population dynamics of metacercariae of Apatemon gracilis (Trematoda: Digenea) in three species of lake-dwelling leeches

Parasitology ◽  
1986 ◽  
Vol 93 (3) ◽  
pp. 517-530 ◽  
Author(s):  
S. M. Spelling ◽  
J. O. Young
Keyword(s):  
Population Dynamics ◽  
Relative Density ◽  
Sexual Maturity ◽  
Egg Production ◽  
Seasonal Pattern ◽  
Distinct Pattern ◽  
The Other ◽  
Mean Intensity ◽  
Density Values ◽  
Host Mortality

SUMMARYMonthly samples of the leeches Erpobdella octoculata, Glossiphonia complanata and Helobdella stagnalis were taken over a two-year period from an eutrophic, English lake to detect metacercariae of the trematode, Apatemon gracilis. In each cohort of each of the three leeches, prevalence was low in young individuals, rose to a peak in autumn/winter, and then declined until the cohort had almost died out; in E. octoculata and H. stagnalis a final brief increase occurred. Mean intensity and relative density values followed a similar seasonal pattern of change to that of prevalence in these last two species, but in G. complanata values fluctuated irregularly with no distinct pattern. The frequency distribution of the parasite in G. complanata was highly over-dispersed, but less so in the other two species. Infected E. octoculata reached sexual maturity. The parasite reduced egg production in G. complanata and H. stagnalis, but only by maximum values of 2·5 and 9% respectively. This reduction in fecundity is low compared to the subsequent high mortality, at 95% or more, of newly recruited young from as yet unidentified causes. Parasite-related host mortality was difficult to assess in young leeches, but there was some evidence for its occurrence in older leeches of E. octoculata and H. stagnalis. However, this is unlikely to play a prominent role in the control and regulation of lacustrine leech populations.

scholarly journals Population dynamics of five riverbed breeding bird species on the lower Drava River, NE Slovenia

Acrocephalus ◽  
2017 ◽  
Vol 38 (174-175) ◽  
pp. 85-126
Author(s):  
Luka Božič ◽  
Damijan Denac
Keyword(s):  
Population Dynamics ◽  
Bird Species ◽  
Breeding Population ◽  
Population Increase ◽  
General Situation ◽  
Breeding Bird ◽  
Main River Channel ◽  
Extreme Flood ◽  
Gravel Bars ◽  
Gravel Bar

AbstractIn 2006–2017, annual censuses of breeding bird species regarded as indicators of natural rivers were carried out on the 38.9 km long lowland stretch of the Drava riverbed between Maribor and Zavrč with altered flow regime due to the operating hydropower plants. Gravel bar habitats were surveyed in four years of the study period by combining orthophoto analysis and analysis of field photographs. Effects of gravel bar management were evaluated based at 20 locations. The Little Ringed PloverCharadrius dubiusoccurred on 39.8% of the gravel bars, but most were occupied only in a few years and held just one breeding pair. Low numbers between 2009 and 2012 (< 30 pairs) were followed by a steep population increase from 2014 onwards to a maximum of 66–73 pairs (1.7–1.9 p/km). Such population dynamics was attributed to the lack of large discharges (>500 m3/s) and consequent overgrowing of riverbed in the first part of the study period, while the increase in the second part was due to the creation of extensive shingle areas (from 20,6 ha in 2009/10 to 37,8 ha in 2014) by the extreme flood in early November 2012, subsequent regular occurrence of large discharges outside the breeding seasons and large-scale removals of woody vegetation. Breeding population of Common SandpiperActitis hypoleucosremained at a rather similar low level (<20 p) during most of the period studied after an initial decline, and did not reflect changes in the overall surface area of riverbed habitats. Contrary to the general situation, the number of breeding pairs on gravel bars subjected to management increased several-fold. Maximum number of pairs on these bars was reached up to four years after the initiation of management measures, as only then the optimal mosaic of early successional stages interspersed with shingle areas developed at main sites. The species was widespread only on lower part of the Drava. KingfisherAlcedo atthiswas fairly widely distributed along the riverbed, but occurred in rather low densities throughout (c. one pair on 2–3 km of the studied riverbed on average), probably as a result of limited bank erosion and consequent overgrowing/lack of suitable nest sites. The population was estimated as stable with effects of harsh winter conditions on breeding numbers in some years. The majority of nest holes were excavated in eroded river banks along the main river channel (77.8%), followed by similar sites located in mouth areas of small tributaries of the Drava (14.8%). Regular breeding of Sand MartinRiparia ripariasince 2012 (up to 259, mostly at only one location annually) was almost exclusively the result of the annual artificial nest site preparation programme. Fairly large gravel bar-breeding population of White WagtailMotacilla alba, monitored since 2013 and predominantly ground nesting in sparsely vegetated areas, seems unusual considering the prevalent breeding habits of the species at the European scale. Conservation implications and guidelines for future management efforts are discussed.

scholarly journals Seasonal dynamics of <I>Pseudocalanus minutus elongatus</I> and <I>Acartia spp.</I> in the southern Baltic Sea (Gdańsk Deep) – numerical simulations

2006 ◽  
Vol 3 (4) ◽  
pp. 1157-1202
Author(s):  
L. Dzierzbicka-Głowacka ◽  
L. Bielecka ◽  
S. Mudrak
Keyword(s):  
Population Dynamics ◽  
Baltic Sea ◽  
Seasonal Dynamics ◽  
Egg Production ◽  
Phytoplankton Bloom ◽  
Individual Growth ◽  
Initial Development ◽  
Southern Baltic Sea ◽  
Gdansk Deep ◽  
Southern Baltic

Abstract. A population dynamics model for copepods is presented describing a seasonal dynamics of Pseudocalanus minutus elongatus and Acartia spp. in the southern Baltic Sea (Gdansk Deep). The copepod model was coupled with an one-dimensional physical and biological upper layer model for nutrients (total inorganic nitrogen, phosphate), phytoplankton, microzooplankton and an early juvenile of herring as predator. In this model, mesozooplankton (herbivorous copepods) has been introduced as animals having definite patterns of growth in successive stages, reproduction and mortality. The populations are represented by 6 cohorts in different developmental stages, thus assuming, that recruitment of the next generation occurs after a fixed period of adult life. The copepod model links trophic processes and population dynamics, and simulates individual growth within cohorts and the changes in biomass between cohorts. The simulations of annual cycles of copepods contain one complete generation of Pseudocalanus and two generations of Acartia in the whole column water, and indicate the importance of growth of older stages of 6 cohorts each species to total population biomass. The peaks of copepods biomass, main, at the turn of June and July for Pseudocalanus and smaller, in July for Acartia, lag that phytoplankton by ca. two mouths due to growth of cohorts in successive stages and egg production by females. The numerical results show that the investigated species could not be the main factor limiting the spring phytoplankton bloom in the Gdansk Deep, because the initial development was slow for Acartia and faster for Pseudocalanus, but main development formed after the bloom, in both cases. However, the simulated microzooplankton biomass was enough high to conclude, in our opinion, that, in this case, it was major cause limiting phytoplankton bloom. Model presented here is a next step in understanding how the population dynamics of a dominant species in the southern Baltic Sea interact with the environment.

Potential Rates of Increase of a Harbour Porpoise (Phocoena phocoena) Population Subjected to Incidental Mortality in Commercial Fisheries

1991 ◽  
Vol 48 (12) ◽  
pp. 2429-2435 ◽  
Author(s):  
Thomas H. Woodley ◽  
Andrew J. Read
Keyword(s):  
Gulf Of Maine ◽  
Intrinsic Rate ◽  
Frequency Equation ◽  
Harbour Porpoise ◽  
Population Increase ◽  
Intrinsic Rate Of Increase ◽  
Natural Mortality ◽  
Phocoena Phocoena ◽  
Rate Of Increase ◽  
Incidental Mortality

We estimated the potential intrinsic rate of increase (r) of the harbour porpoise (Phocoena phocoena) population in the Bay of Fundy and Gulf of Maine using empirical data on reproductive rates (mx) and several hypothetical survival (Ix) schedules. Schedules of Ix, to maximum ages of 12 and 15 yr, were calculated from two potential natural mortality (nx) schedules combined with several schedules of incidental mortality (hx) estimates. The most realistic results were obtained when nx of non-calves were calculated from Caugley's (1966. Ecology 47: 906–918) smoothed age-frequency equation for Himalayan thar (Hemitragus jemlahicus) and applied in conjunction with a range of calf natural mortality estimates, this model indicates that harbour porpoises have a limited capacity for population increase, and populations are unlikely to sustain even moderate levels of incidental mortality (4% of the population per year). Extending the maximum age used in the models from 12 to 15 yr does little to increase estimates of r for the harbour porpoise population, and hence their susceptibility to incidental mortality.

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