scholarly journals Characteristics of survivors: growth and nutritional condition of early stages of the hake species Merluccius paradoxus and M. capensis in the southern Benguela ecosystem

2012 ◽  
Vol 69 (4) ◽  
pp. 553-562 ◽  
Author(s):  
Britta Grote ◽  
Werner Ekau ◽  
Erling K. Stenevik ◽  
Catriona Clemmesen ◽  
Hans M. Verheye ◽  
...  
Keyword(s):  
Selection Pressure ◽  
Larval Mortality ◽  
Larval Growth ◽  
Threshold Level ◽  
Nutritional Condition ◽  
Complex Relationship ◽  
Early Stages ◽  
Benguela Upwelling ◽  
Selection For ◽  
High Selection

Abstract Grote, B., Ekau, W., Stenevik, E. K., Clemmesen, C., Verheye, H. M., Lipinski, M. R., and Hagen, W. 2012. Characteristics of survivors: growth and nutritional condition of early stages of the hake species Merluccius paradoxus and M. capensis in the southern Benguela ecosystem. – ICES Journal of Marine Science, 69: 553–562. Larval mortality in marine fish is strongly linked to characteristic traits such as growth and condition, but the variability in these traits is poorly understood. We tried to identify the variability in growth in relation to conditions leading to greater survival chances for early stages of Cape hake, Merluccius paradoxus and M. capensis, in the Benguela upwelling ecosystem. During two cruises in 2007 and one cruise in 2008, hake larvae and juveniles were caught. Otolith microstructures revealed a larval age ranging from 2 to 29 days post-hatching (dph), whereas juvenile age was 67–152 dph. RNA:DNA ratios, used to evaluate nutritional condition, were above the relevant threshold level for growth. No strong coupling between growth and condition was detected, indicating a complex relationship between these factors in the southern Benguela ecosystem. Merluccius paradoxus juveniles caught in 2007 (the surviving larvae of 2006) had significantly higher larval growth rates than larvae hatched in 2007 and 2008, possibly indicating selection for fast growth in 2006. High selection pressure on growth could be linked to predation avoidance, including cannibalism.

scholarly journals Not Only a Formulation: The Effects of Pickering Emulsion on the Entomopathogenic Action of Metarhizium brunneum

2021 ◽  
Vol 7 (7) ◽  
pp. 499
Author(s):  
Nitsan Birnbaum ◽  
Victoria Reingold ◽  
Sabina Matveev ◽  
Chandrasekhar Kottakota ◽  
Michael Davidovitz ◽  
...  
Keyword(s):  
Ricinus Communis ◽  
Larval Mortality ◽  
Acute Infection ◽  
Larval Growth ◽  
Disease Process ◽  
Pickering Emulsion ◽  
Broad Host Range ◽  
High Humidity ◽  
Conventional Agriculture ◽  
Metarhizium Brunneum

Growing global population and environmental concerns necessitate the transition from chemical to eco-friendly pest management. Entomopathogenic fungi (EPF) are rising candidates for this task due to their ease of growing, broad host range and unique disease process, allowing EPF to infect hosts directly through its cuticle. However, EPF’s requirement for high humidity negates their integration into conventional agriculture. To mitigate this problem, we formulated Metarhizium brunneum conidia in an oil-in-water Pickering emulsion. Conidia in aqueous and emulsion formulations were sprayed on Ricinus communis leaves, and Spodoptera littoralis larvae were introduced under low or high humidity. The following were examined: conidial dispersion on leaf, larval mortality, conidial acquisition by larvae, effects on larval growth and feeding, and dynamic of disease progression. Emulsion was found to disperse conidia more efficiently and caused two-fold more adhesion of conidia to host cuticle. Mortality from conidia in emulsion was significantly higher than other treatments reaching 86.5% under high humidity. Emulsion was also found to significantly reduce larval growth and feeding, while conferring faster fungal growth in-host. Results suggest that a Pickering emulsion is able to improve physical interactions between the conidia and their surroundings, while weakening the host through a plethora of mechanisms, increasing the chance of an acute infection.

scholarly journals Selection for Reinforcement-Free Learning Ability as an Organizing Factor in the Evolution of Cognition

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Solvi Arnold ◽  
Reiji Suzuki ◽  
Takaya Arita
Keyword(s):  
Selection Pressure ◽  
Learning Ability ◽  
Environmental Complexity ◽  
Baldwin Effect ◽  
Neural Structure ◽  
Neural Organization ◽  
Environmental Structure ◽  
Selection For ◽  
Efficient Learning ◽  
Complexity Thesis

This research explores the relation between environmental structure and neurocognitive structure. We hypothesize that selection pressure on abilities for efficient learning (especially in settings with limited or no reward information) translates into selection pressure on correspondence relations between neurocognitive and environmental structure, since such correspondence allows for simple changes in the environment to be handled with simple learning updates in neurocognitive structure. We present a model in which a simple form of reinforcement-free learning is evolved in neural networks using neuromodulation and analyze the effect this selection for learning ability has on the virtual species' neural organization. We find a higher degree of organization than in a control population evolved without learning ability and discuss the relation between the observed neural structure and the environmental structure. We discuss our findings in the context of the environmental complexity thesis, the Baldwin effect, and other interactions between adaptation processes.

scholarly journals Toxicity of Imidacloprid and Diafenthiuron to Chrysoperla Carnea (Stephens) (Neuroptera: Chrysopidae) in the Laboratory Conditions

2009 ◽  
Vol 49 (3) ◽  
pp. 290-296 ◽  
Author(s):  
Gnanadhas Preetha ◽  
Johnson Stanley ◽  
Thiagarajan Chandrasekaran ◽  
Sasthakutty Kuttalam
Keyword(s):  
Plant Protection ◽  
Larval Mortality ◽  
Plant Protection Products ◽  
Threshold Level ◽  
Adult Mortality ◽  
Recommended Dose ◽  
Chrysoperla Carnea ◽  
Laboratory Studies ◽  
Egg Mortality ◽  
Laboratory Conditions

Toxicity of Imidacloprid and Diafenthiuron toChrysoperla Carnea(Stephens) (Neuroptera: Chrysopidae) in the Laboratory ConditionsInsecticides are unavoidable in pest management programs especially when the pest crosses Econimic Threshold Level (ETL). Nevertheless, often the plant protection products kill the natural enemy population making the pest to resurge and thus demanding more sprays. Therefore, insecticides used in IPM programs should be selective enough to spare the beneficials. Laboratory studies were conducted to find out the toxicity of imidacloprid and diafenthiuron to the eggs, larvae and adults ofChrysoperla carnea.Imidacloprid at the recommended dose of 0.28 ml/l caused 15.38% egg mortality, 26.67 and 33.33% larval mortality by ingestion and contact, respectively and 50.00% adult mortality. The egg mortality was about 15.38% and larval mortality of 23.33% and adult mortality of 26.67% was caused by diafenthiuron. Based on the classification given by IOBC/WPRS working group on Pesticides and non-target invertebrates, both the insecticides were classified as harmless toC. carnea, since the recommended dose caused less than 50% mortality in the laboratory conditions.

scholarly journals Conjugated linoleic acid as a novel insecticide targeting the agricultural pest Leptinotarsa decemlineata

2019 ◽  
Author(s):  
Justin Clements ◽  
Russell L. Groves ◽  
JoAnn Cava ◽  
Caroline Barry ◽  
Scott Chapman ◽  
...  
Keyword(s):  
Linoleic Acid ◽  
Conjugated Linoleic Acid ◽  
Colorado Potato Beetle ◽  
Leptinotarsa Decemlineata ◽  
Larval Mortality ◽  
Larval Growth ◽  
The United States ◽  
Feeding Preference ◽  
Agricultural Pest ◽  
Potato Beetle

AbstractThe Colorado Potato Beetle, Leptinotarsa decemlineata, is a major agricultural pest of solanaceous crops in the United States. Historically, a multitude of insecticides have been used to control problematic populations. Due to increasing resistance to insecticides, novel compounds and methodologies are warranted for the control of beetle populations. Mixed-isomer conjugated linoleic acid has been studied in-depth for its beneficial properties to mammalian systems. At the same time, studies have demonstrated that conjugated linoleic acid can manipulate fatty acid composition in non-mammalian systems, resulting in embryo mortality. Consequently, experiments were conducted to assess the effects of foliar-applied conjugated linoleic acid on larval growth, embryogenesis, and feeding preference in Colorado potato beetle. Both maternal and deterrent effects of dietary conjugated linoleic acid were assessed. Conjugated linoleic acid demonstrated desirable insecticidal properties, including increased larval mortality, slowed larval development, antifeedant effects, and decreased egg viability after maternal ingestion.

A SECONDARY EFFECT OF DDT UPON THE AQUATIC MICROFLORA AND MICROFAUNA

1958 ◽  
Vol 4 (5) ◽  
pp. 445-452 ◽  
Author(s):  
Marshall Laird
Keyword(s):  
Selection Pressure ◽  
Developmental Stages ◽  
Larval Mortality ◽  
Fourth Instar ◽  
Anopheles Maculipennis ◽  
Field Investigations ◽  
Laboratory Colony ◽  
Time Required ◽  
Early Developmental ◽  
Heavy Infestation

Observations were made on the microflora and microfauna of infusions in which larvae of Anopheles maculipennis atroparvus were being subjected to DDT selection pressure (2 μg/ml). Comparisons with controls indicated that the insecticide influenced neither the species representation nor the succession of the organisms concerned. However, heavy initial larval mortality took place. Dead larvae remaining in the containers overnight became centers of very rapid bacterial multiplication, and the maturation of the experimental infusions was accelerated. The larval cultures became polysaprobic after about two weeks, by which time the surviving larvae were in the fourth instar. These survivors were large and healthy, having spent their early developmental period in the presence of a rich supply of infusion organisms answering their food requirements, and successfully withstood the deteriorating environmental conditions and consequent heavy infestation with epibionts (Chlamydobacteriales and peritrichous ciliates). On the other hand, fourth instar larvae from similar infusions in the laboratory colony of A, m. atroparvus were often undersized and sickly because of early overcrowding linked with the initially longer time required for the development of an adequate yield of food organisms. Such larvae, also pupae, frequently died of exhaustion due to undernourishment and complicated by the hampering of their activity by a vestiture of bacteria and ciliates. This explained the paradox that adults derived from the laboratory colony tended to be less robust than those hatching from developmental stages subjected to DDT selection pressure. Besides pointing to the importance of paying due regard to larval environmental factors in resistance studies, these observations suggest the need for field investigations of the significance of similar chains of events in nature.

scholarly journals Phenotypic, genotypic and biochemical changes during pyrethroid resistance selection in Anopheles gambiae mosquitoes

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Maxwell G. Machani ◽  
Eric Ochomo ◽  
Daibin Zhong ◽  
Guofa Zhou ◽  
Xiaoming Wang ◽  
...  
Keyword(s):  
Public Health ◽  
Insecticide Resistance ◽  
Anopheles Gambiae ◽  
Selection Pressure ◽  
Pyrethroid Resistance ◽  
Natural Populations ◽  
Biochemical Changes ◽  
Moderate Intensity ◽  
Agricultural System ◽  
Selection For

Abstract The directional selection for insecticide resistance due to indiscriminate use of insecticides in public health and agricultural system favors an increase in the frequency of insecticide-resistant alleles in the natural populations. Similarly, removal of selection pressure generally leads to decay in resistance. Past investigations on the emergence of insecticide resistance in mosquitoes mostly relied on field survey of resistance in vector populations that typically had a complex history of exposure to various public health and agricultural pest control insecticides in nature, and thus the effect of specific insecticides on rate of resistance emergency or resistance decay rate is not known. This study examined the phenotypic, genotypic, and biochemical changes that had occurred during the process of selection for pyrethroid resistance in Anopheles gambiae, the most important malaria vector in Africa. In parallel, we also examined these changes in resistant populations when there is no selection pressure applied. Through repeated deltamethrin selection in adult mosquitoes from a field population collected in western Kenya for 12 generations, we obtained three independent and highly pyrethroid-resistant An. gambiae populations. Three susceptible populations from the same parental population were generated by removing selection pressure. These two lines of mosquito populations differed significantly in monooxygenase and beta-esterase activities, but not in Vgsc gene mutation frequency, suggesting metabolic detoxification mechanism plays a major role in generating moderate-intensity resistance or high-intensity resistance. Pre-exposure to the synergist piperonyl butoxide restored the susceptibility to insecticide among the highly resistant mosquitoes, confirming the role of monooxygenases in pyrethroid resistance. The rate of resistance decay to become fully susceptible from moderate-intensity resistance took 15 generations, supporting at least 2-years interval is needed when the rotational use of insecticides with different modes of action is considered for resistance management.

Growth and Seed Return of Auxin-Type Herbicide Resistant Wild Mustard (Brassica kaber) in Wheat

Weed Science ◽  
1996 ◽  
Vol 44 (4) ◽  
pp. 871-878 ◽  
Author(s):  
Daniel J. Debreuil ◽  
Lyle F. Friesen ◽  
Ian N. Morrison
Keyword(s):  
Selection Pressure ◽  
Dry Matter ◽  
Dry Matter Accumulation ◽  
Recommended Dosage ◽  
Herbicide Resistant ◽  
Wild Mustard ◽  
Phenoxy Herbicide ◽  
High Selection ◽  
Brassica Kaber ◽  
Very High

The growth and seed return of auxin herbicide resistant (R) wild mustard was compared to that of a susceptible (S) biotype in wheat in the field. In the absence of herbicide, the S biotype accumulated shoot dry matter more quickly than the R biotype throughout most of the growing season. However, in only one of the two years did the S biotype set substantially more seed than the R biotype (3120 versus 2520 seeds plant−1). The recommended dosage of 2,4-D for wild mustard control (420 g ai ha−1) killed all S plants in both years of the study, and severely inhibited growth and seed return of R plants. Shoot dry matter accumulation and seed return of treated R plants were reduced 75 to 90% compared to the untreated control. However, at a density of 20 plants m−2R seed return was still very high; 9000 and 5700 seeds m−2in 1992 and 1993, respectively. The recommended dosage of dicamba (300 g ha−1) did not inhibit the growth and seed return of either S or R wild mustard to the same extent as 2,4-D. Dicamba at 300 g ha−1reduced S shoot dry matter and seed return 80 to 90%, while R shoot dry matter and seed return was reduced 60 to 65%. The results of this study indicate a very high selection pressure for R wild mustard at recommended dosages of 2,4-D. Despite a high selection pressure, and considering the long history of phenoxy herbicide usage on the Prairies, the relatively rare occurrence of phenoxy herbicide resistant weeds implies that the frequency of resistant individuals is very low. From a mathematical model it was determined that the frequency of R wild mustard in an unselected population may be in the order of 10−30.

Heritability of frost tolerance in white clover (Trifolium repens)

1990 ◽  
Vol 114 (2) ◽  
pp. 151-155 ◽  
Author(s):  
J. R. Caradus ◽  
A. C. Mackay ◽  
J. Van Den Bosch ◽  
S. Wewala ◽  
D. H. Greer
Keyword(s):  
White Clover ◽  
Trifolium Repens ◽  
Size Effects ◽  
Leaf Size ◽  
Frost Damage ◽  
Frost Tolerance ◽  
Method Of Calculation ◽  
Selection For ◽  
Heritability Estimates ◽  
High Selection

SUMMARYWhite clover genotypes selected for frost tolerance and susceptibility were pair-crossed in various combinations with unselected genotypes of Grasslands Huia. Progeny lines and parent genotypes were artificially frosted at −8°C and scored for percentage of leaves damaged. Progeny from crosses between frost-tolerant genotypes were less damaged by frost than progeny from crosses involving either susceptible genotypes or unselected Grasslands Huia genotypes. Heritability estimates for frost tolerance or susceptibility were high, ranging from 0·75 to 0·93, depending on method of calculation. Removal of leaf-size effects from scores of frost damage reduced heritability estimates to 0·54–0·73. It was concluded that, because heritability for frost tolerance was high, selection for this character and incorporation of frost tolerance into agronomically suitable but frost-sensitive cultivars by breeding would be successful.

Effect of index selection for reduced backfat thickness and increased growth rate on sow weight changes through two parities in swine

1992 ◽  
Vol 72 (2) ◽  
pp. 403-408 ◽  
Author(s):  
R. M. McKay
Keyword(s):  
Growth Rate ◽  
Key Words ◽  
Selection Pressure ◽  
Backfat Thickness ◽  
Index Selection ◽  
Weight Changes ◽  
Selection For ◽  
The Impact

The impact of continued selection for reduced backfat thickness and improved growth rate on weight changes in Yorkshire and Hampshire sows, from breeding as gilts to weaning their second litter, was studied. Results suggest that some sow weight changes may have been influenced by selection pressure exerted. Key words: Sows, Canadian Yorkshire, Hampshire, liveweight change

larval growth and mortality of japanese spanish mackerel (scomberomorus niphonius) in the central seto inland sea, japan

2005 ◽  
Vol 85 (5) ◽  
pp. 1255-1261 ◽  
Author(s):  
jun shoji ◽  
tsutomu maehara ◽  
m. tanaka
Keyword(s):  
Fish Larvae ◽  
Larval Mortality ◽  
Larval Growth ◽  
Survival Strategies ◽  
Seto Inland Sea ◽  
Larval Feeding ◽  
Spanish Mackerel ◽  
Daily Increments ◽  
Absolute Growth ◽  
Scomberomorus Niphonius

growth and mortality rates of larval japanese spanish mackerel (scomberomorus niphonius) were estimated by using otolith daily increments in 1997 and 1998 in the sea of hiuchi, central seto inland sea. there was no day–night difference in the abundance and size-distribution of s. niphonius larvae in the 3–10 mm size-classes, indicating the larvae were efficiently collected by the larva-net used for sampling (1.3 m mouth diameter, 0.5 mm mesh). mean absolute growth rate (0.748 mm d−1 in 1997, 0.821 mm d−1 in 1998), weight specific growth coefficient (g: 0.402 in 1997, 0.444 in 1998) and mortality coefficient (m: 0.784 in 1997 and 0.625 in 1998) were among the highest reported for marine fish larvae. scomberomorus niphonius seems to have evolved survival strategies characterized by fast growth with strong piscivory that can reduce duration of the larval period with the high mortality. in 1997, spatial distribution of the larvae was not well corresponded to that of their prey, clupeid larvae, and the larval feeding incidence was lower than in 1998. recruitment potential assessed by examining the ratio of g:m was lower in 1997 (0.513 in 1997, 0.711 in 1998) due to the lower g and higher m values. prey fish availability may be one of the important determinants for the recruitment potential by controlling the larval mortality due to starvation and/or starvation-related predation.

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