Lower Number Of Eggs Research Articles

Trichome Density and Antibiosis Affect Resistance of Tomato to Fruitborer and Whitefly Under Laboratory Conditions

Abstract The tomato fruitborer, Helicoverpa armigera Hub., and the whitefly, Bemisia tabaci Genn., can not be easily controlled in tomato, Lycopersicon esculentum Mill. The insects are capable of rapidly evolving resistance to insecticides. Exploiting resistance mechanisms is a sustainable strategy to combat these pests. Resistance to these pests was identified in tomato accessions by evaluating resistance mechanisms. Among the accessions screened for whitefly resistance, ‘LE 598’ had more trichomes (72/mm2) on both leaf surfaces. Similarly, ‘LE 104’ had 53.0/mm2, and is resistant to fruitborer. Whiteflies preferred to lay more eggs on the abaxial (4.0 to 31.5/leaf) than on the adaxial leaf surface (1.0 to 24.5/leaf). Accession ‘COTLCVRH 1’ had the lowest number of eggs on the abaxial surface (4.0 eggs/leaf) and 1.0 egg/leaf on the adaxial surface. There was a linear relationship between trichome density and oviposition preference by whitefly (r = 0.91). Trichomes were most dense on ‘LE 104’ and it was pr...

Lifelong heterogeneity in fecundity is insufficient to explain late-life fecundity plateaus in Drosophila melanogaster

Previous studies have demonstrated that fecundity, like mortality, plateaus at late ages in cohorts of Drosophila melanogaster. Although evolutionary theory can explain the decline and plateau in cohort fecundity at late ages, it is conceivable that lifelong heterogeneity in individual female fecundity is producing these plateaus. For example, consistently more fecund females may die at earlier ages, leaving only females that always laid a low number of eggs preponderant at later ages. We simulated fecundity within a cohort, assuming the two phenotypes described above, and tested these predictions by measuring age of death and age-specific fecundity for individual females from three large cohorts. We statistically tested whether there was enough lifelong heterogeneity in fecundity to produce a late-life plateau by testing whether early female fecundity could predict whether that female would live to lay eggs after the onset of the population fecundity plateau. Our results indicate that heterogeneity in fecundity is not lifelong and thus not likely to cause late-life fecundity plateaus. Because lifelong heterogeneity models for fecundity are based on the same underlying assumptions as heterogeneity models for late-life mortality rates, our test of this hypothesis is also an experimental test of lifelong heterogeneity models of late life generally.

Behavioral and Physiological Resistance of the German Cockroach to Gel Baits (Blattodea: Blattellidae)

A gel bait-resistant German cockroach, Blattella germanica (L.), strain Cincy was collected in Cincinnati, OH. This strain exhibited a high level of behavioral resistance to Avert (0.05% abamectin) and Maxforce FC (0.01% fipronil) gel baits. Topical application assays indicated moderate levels of physiological resistance of the Cincy strain to abamectin and fipronil. Resistance ratios (based on LD50 values from topical applications) to abamectin and fipronil were 2.5 and 8.7, respectively. The Cincy strain of had a significantly lower LD50 value to abamectin than a nonaverse field strain (Dorie) and similar LD50 values to fipronil as the Dorie strain. The aversion behavior (avoidance of gel baits) was therefore caused by food ingredients in the gel baits. The Cincy strain showed avoidance of agar containing fructose, glucose, maltose, and sucrose, which are phagostimulants to the laboratory strain. Modifications of the inert ingredients in the Maxforce FC gel bait significantly improved the efficacy against the Cincy strain. The Cincy strain produced significantly smaller oothecae and lower numbers of eggs in each egg capsule than the nonaverse Jwax and Dorie strains of cockroaches, suggesting fitness costs are associated with resistance.

Behavioral and Physiological Resistance of the German Cockroach to Gel Baits (Blattodea: Blattellidae)

A gel bait-resistant German cockroach, Blattella germanica (L.), strain Cincy was collected in Cincinnati, OH. This strain exhibited a high level of behavioral resistance to Avert (0.05% abamectin) and Maxforce FC (0.01% fipronil) gel baits. Topical application assays indicated moderate levels of physiological resistance of the Cincy strain to abamectin and fipronil. Resistance ratios (based on LD50 values from topical applications) to abamectin and fipronil were 2.5 and 8.7, respectively. The Cincy strain of had a significantly lower LD50 value to abamectin than a nonaverse field strain (Dorie) and similar LD50 values to fipronil as the Dorie strain. The aversion behavior (avoidance of gel baits) was therefore caused by food ingredients in the gel baits. The Cincy strain showed avoidance of agar containing fructose, glucose, maltose, and sucrose, which are phagostimulants to the laboratory strain. Modifications of the inert ingredients in the Maxforce FC gel bait significantly improved the efficacy against the Cincy strain. The Cincy strain produced significantly smaller oothecae and lower numbers of eggs in each egg capsule than the nonaverse Jwax and Dorie strains of cockroaches, suggesting fitness costs are associated with resistance.

Shedding consistency of strongyle-type eggs in dutch boarding horses

Faeces of 484 horses were sampled twice with an interval of 6 weeks while anthelmintic therapy was halted. Faecal eggs counts revealed that 267 (55.2%) horses had consistently low numbers of eggs per gram faeces (EPG) (EPG < 100 or = 100), 155 (32.0%) horses had consistently high EPGs (EPG > 100). Horses with consistently high EPGs were more often mares with access to pasture, aged less than 6 or more than 23 years, that were dewormed at intervals longer than 6 months, and were treated for the last time more than 3 months before the start of the study. Horses with consistently low EPGs were more often male horses with no or limited access to pasture, that were dewormed at maximally 6-month intervals, and were aged between 6 and 23 years. The results are an indication that some horses have consistently low EPGs and perhaps could be used as non-treated animals in a selective anthelmintic treatment scheme aimed at the prevention of the development of anthelmintic resistance.

Resistance to locust leafminer (Coleoptera: Chrysomelidae) in black locust.

Locust leafminer, Odontota dorsalis (Thunberg), activity was observed for 2 yr on 70 black locust, Robinia pseudoacacia L., trees grown from seed collected from its native range. Four black locust seedlings from Tennessee had low numbers of eggs, larvae, pupae, and mines, and were selected for clonal propagation. These clonal propagules were resistant to locust leafminers collected from three different counties in Maryland. This resistance was also observed in controlled choice and no-choice tests in outdoor screen houses. Adults showed different ovipositional preferences for black locust trees from different seed sources, which were reflected in lower numbers of larvae, pupae, and mines in resistant clones. It was concluded that antixenosis and antibiosis were involved in the mechanisms of resistance to the locust leafminer in black locust.

Pulp handling by vertebrate seed dispersers increases palm seed predation by bruchid beetles in the northern Amazon

Abstract The simultaneous use of fruits and seeds by invertebrate seed predators and vertebrate seed dispersers produces complex ecological interactions that reduce the predictability of seed fate. Cocosoid palm seeds in the Neotropics are subject to high mortality by bruchid beetle infestation and such attack is the major cause of mortality for seeds of the palm Attalea maripa at our study site in the northern Brazilian Amazon. The exocarp and mesocarp of 1400 fruits were manipulated in different ways to simulate handling by vertebrates. No eggs of the bruchid beetle, Pachymerus cardo, were laid on intact control fruits, while the highest numbers of eggs were received by fruits whose exocarp and mesocarp had been partially removed, as if by primates and rodents (mean of 15.9 and 18.9 eggs fruit−1, respectively, during the peak fruiting season). Fruits with intact mesocarp but no exocarp, and fruits with all mesocarp and exocarp removed, received low numbers of eggs (mean of 4.6 and 6.6 eggs per fruit, respectively, during the peak fruiting season). Thus both exocarp and mesocarp deter oviposition, and removal of these fruit structures increases fruit susceptibility to infestation. Oviposition rates declined as the fruiting season progressed, but oviposition preferences remained the same. Seed mortality was high for any fruit on which eggs were laid. Large rodents and primates, which have been considered among the most effective seed dispersers for large‐seeded Neotropical trees such as palms, actually increased the susceptibility of seeds to bruchid beetle attack. Removal of (intact) seeds by other dispersers may be necessary to ensure seed survival. These results indicate that the reliability of seed dispersers cannot be gauged without a complete understanding of variables that affect seed viability.

The impact of grain quantity on the biology of Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae): oviposition, distribution of eggs, adult emergence, body weight and sex ratio

Studies were conducted to observe the effect of grain quantity on the oviposition, distribution of eggs, adult emergence, adult body weight and sex ratio of Sitophilus zeamais, an important pest of maize. Three quantities of maize grains (200, 400 and 800 grains/glass jar of 1 l) were used under laboratory conditions (301C and 70% r.h.). Twenty five male/female pairs of maize weevil were introduced into each glass jar for 12 d. The greatest and lowest number of eggs was laid on batches of 800 and 200 grain kernels, respectively. The total number of grains attacked followed a similar trend. The aggregation of eggs expressed as a ratio of the variance to mean increased as the amount of maize grains was increased. The aggregation parameter k ranged from 2.35 on 200 grains to 4.49 on 800 grains. On average, a significantly higher proportion of grains were infested (90%) when less grain was present. Emergence of adult weevils was, however, maximal (472 individuals/glass jar) when the grain quantity was highest. The mean weight of the emerged adults was not significantly influenced by grain quantity, but female weevils were heavier than males (mean weight 3.16 vs. 3.05 mg) irrespective of maize quantity and eggs laid. Sex ratio (males/100 females) of emerged adults did not differ amongtreatments. The importance of grain quantity, and of oviposition, in internally feeding granivores and the possibility that there is an adaptive reproductive strategy are discussed. r 2002 Elsevier Science Ltd. All rights reserved.

Family differences in success of triploid induction and effects of triploidy on fecundity of catarina scallop ( Argopecten ventricosus)

Mass induction of triploidy in the catarina scallop ( Argopecten ventricosus) results in low success in the percentage of triploids produced. To understand whether this is a treatment effect affecting all eggs equally, families were individually induced to triploidy with cytochalasin-B (CB), comparing their survival from egg to D-larvae and spat, and the percent of triploidy within families. Differences in percent triploidy success were evident between families, obtaining some with no triploids, and some with high triploidy. Among the possible causes for these differences are quality of eggs, different developmental rates, and differences in susceptibility to the treatment (CB or DMSO) itself. Regardless of those differences, overall triploidy production was increased by inducing individually eggs of each scallop rather than in mixed egg batches. In the first experiment, it was improved by 17%, and in the second experiment by 42%, as indicated by the weighted mean of triploids among the families, and when compared with previous results with this same species, where triploidy success was 58%. In a second experiment with three different families, the growth and fecundity of triploid and diploid catarina scallops were evaluated. The growth superiority of triploids was confirmed. The results indicated that triploid catarina scallops had a significantly reduced fecundity when compared with diploid scallops. The reduced fecundity appears to be mostly of a random nature, possibly associated with a reduced capability to produce balanced gametes. Whereas the successful production of tetraploid catarina scallop from fertile triploid scallops is in principle possible, the low number of eggs shed by triploid catarina scallops could diminish that success rate, even more if single triploid females are required to optimize tetraploid induction.

Effect of season on the productivity of camels (Camelus dromedarius and the prevalence of their major parasites in eastern Ethiopia.

The productivity and the prevalence rates of the major parasites of camels (Camelus dromedarius) kept under traditional management conditions at Errer valley, Ethiopia were assessed for a year (October 1997-September 1998). The daily milk offtake was significantly higher (p < 0.05) during the wet season (3.12 +/- 0.03 L) than during the dry season (1.49 +/- 0.04 L). Likewise, significantly higher (p < 0.05) daily weight gains (50.68 +/- 0.54 g) were observed during the wet season than during dry season in immature camels aged 1-4 years. Trypanosoma evansi, Sarcoptes scabiei and strongyle parasites were present throughout the year, but their prevalence rates were higher during the rainy months than during the dry months. The minimum and maximum point prevalence rates for T. evansi were 5.4% and 20.6%, respectively. Similarly, the point prevalence rates for S. scabiei also varied from 4.7% during the dry season to 21.7% during the rainy months. The highest strongyle egg counts per gram of faeces and highest point prevalence rate (85.7%) were observed in October, a rainy month, whereas the lowest number of eggs per gram of faeces and the lowest point prevalence rate (61.5%) were recorded in April, a dry month.

Effect of Diet and Mating on Oviposition in the Twospotted Stink Bug &lt;I&gt;Perillus bioculatus&lt;/I&gt; (F.) (Heteroptera: Pentatomidae)

Control females of the twospotted stink bug, Perillus bioculatus (F.), and those given an artificial diet mated repeatedly over their lifetimes when held with males. The average number of observed matings was 4 and 8.4 in the controls and those given the artificial diet, respectively. Mating and an adequate diet are prerequisites for laying a full compliment of eggs in this insect. Virgins laid an average of 22 eggs compared with 138 in the multiply mated controls, 84 in singly mated females and 42 in multiply mated females given an artificial diet. The number of clutches deposited was not significantly affected by treatment, but the number of eggs per clutch was significantly lower in virgins and those given the artificial diet than in the controls or once mated females. The number of eggs per clutch showed no significant changes as the female aged. Oviposition rates were calculated over 5-d periods for each female and presented as eggs per day. In all experimental groups the number of eggs deposited per interval decreased as the females aged. By 27.5 d after the start of oviposition, females from all treatments laid one or fewer eggs per day. The decrease in eggs per day deposited by females as they aged is attributed to an increase in the time between clutch deposition. Egg viability showed no significant differences among the multiply mated controls, once mated females, or the multiply mated females given the artificial diet. This suggests that multiple mating is not required to maintain egg viability, but is necessary to maintain oviposition over the lifetime of the female. Low numbers of eggs oviposited by females given the artificial diet is attributed to the production of fewer mature follicles than in the controls and not to an impairment of the process of oviposition. In contrast, the lower number of eggs laid by virgin females results from an impairment of the oviposition process and not the impairment of ovarian follicle maturation.

Offspring Produced by Nuclear Transfer Can Evaluate the Developmental Competency of the Nucleus and Cytoplasm of Oocytes from Old Mice

Objective: Decline of human reproduction potential with increasing maternal age can be attributed to several factors including low egg number and an increased rate of aneuploidy. This latter problem has been hypothesized to be associated with a cytoplasmic defect(s) during oocyte maturation. However, there is no suitable animal model to test this hypothesis. An age-related decline in fecundity has also been noted in mice. This project evaluates whether cytoplasmic or nuclear defects impact on the developmental competency of oocytes from aged mice.

On the development and reproduction of Botryllus schlossen (Tunicata) colonies from the eastern Mediterranean Sea: plasticity of life history traits

Summary Analysis of developmental patterns of Botryllus schlosseri colonies from the eastern Mediterranean coast has been performed on 143 genets under different temperature regimens (15,20,27 °C) for up to 22 weeks. While the average maximal size as the length of the blastogenic cycle (BC) varied in respect to water temperature, ontogeny at all temperatures was characterized by 4 developmental stages: 1. the lag phase (the first 1–3 BCs, 1 bud/BC), 2. the exponential growth phase (5.5–7.8 BCs, up to 3 buds/BC), 3. the plateau phase, (7.4–8.2 BCs, 1 bud/BC), 4. the degenerative or the variable phase. Many (40.6%) colonies were not sexually reproductive, the others were male only (30.1%) or hermaphrodites. Colonies at the peak of reproduction develop 1.2 oocytes/zooid, and up to 57.7% produced >4 clutches. Analysing onset of reproduction with maximal colony size revealed 4 patterns, two for “male only” colonies and two for hermaphrodites that varied at different sea water temperatures. In two patterns, the onset of reproduction precedes colony maximal size, and in the others it starts at the peak size or thereafter. Zooids at the colony's periphery developed almost twice as many buds as did zooids at the center, but produced significantly lower numbers of eggs. Fragmentation was recorded in large colonies and was temperature dependent. Results are compared with the data available on populations from other localities indicating for dramatically different developmental modes characteristic to this cosmopolitan species.

Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae) oviposition on seven naturally co-occurring Eucalyptus species

Gonipterus scutellatus is a significant insect pest of eucalypts in most countries where that genus has been introduced, but is usually only of minor significance in its native Australia. Because of this, much of the research on its biology and host preferences has been done outside Australia. This fact has the potential to produce misleading results as the insect may be forced to choose less preferred hosts, if normally preferred species are unavailable. In part of its native range, in Tasmania, oviposition of G. scutellatus was recorded on seven naturally co-occurring Eucalyptus species that were planted in even aged, replicated plots. Among the seven species were the economically important species, E. globulus and E. viminalis, which have been previously reported as highly preferred hosts. Within plots, oviposition occurred most commonly on three peppermint species ( E. pulchella, E. tenuiramis and E. amygdalina) and was rare or absent on the other species ( E. globulus, E. viminalis, E. ovata and E. obliqua). Of the peppermints, E. pulchella was the most preferred species for oviposition at this site. A low percentage of peppermints in mixed forest (containing these seven species) immediately adjacent to plots was always matched by low numbers of G. scutellatus eggs within plots; but high percentages of peppermints outside plots could either be matched by high or low numbers of eggs within plots. In the discussion, we suggest that previous studies of G. scutellatus host range may have been limited because the insect was not exposed to hosts it naturally encounters.

Effect of temperature on oviposition in four species of the melanogaster group of Drosophila.

Experiments were conducted to test the effect of temperature on oviposition in four species of the melanogaster group of Drosophila: D. ananassae, D. bipectinata, D. malerkotliana and D. biarmipes. In each species, two wild strains were used and eggs laid by females at three different temperatures (19 degrees C, 24 degrees C and 30 degrees C) were counted for four days at 24 h interval. It is evident from the results that females of D. ananassae, D. bipectinata, D. malerkotliana and D. biarmipes lay low number of eggs at low temperature (19 degrees C). Thus oviposition in these four species of Drosophila is significantly reduced at low temperature.

Differential life history responses of several pelagic Daphnia clones differing in migratory behaviour

Females of the hybrid Daphnia galeata × hyalina were isolated from a natural population in Lake Maarsseveen and from these individuals clones were cultured in the laboratory. Some clones were assumed to be migrating and some non-migrating. Life history experiments were performed with these clones in the presence and absence of fish kairomones. Results show that clones differed in life history strategy in concert with their presumed migration strategies which suggests a link between life history and behaviour. However, no sharp border exists between migrating and non-migrating clones since a gradual response pattern was found for the traits investigated. In the absence of fish kairomones, the relation between length at maturity and number of eggs was found to differ between the clones of the non-migrating and the migrating group. The latter had a lower number of eggs at similar length values. In the presence of fish kairomones, the length–clutch size relation was the same. However, non-migrating clones were smaller at the age at maturity and had fewer eggs. Although clones of both groups were thus found to differ significantly, overlap existed. Age at maturity was found to be the same.

Impact of antifibrotic treatment of the course of Schistosoma mansoni infection in murine model.

Administration of an antifibrotic agent as an adjunct to antihelmintic treatment with the objective of morbidity reduction was investigated in the murine schistosomiasis mansoni model. Antifibrotic, beta-aminopropionitrile treatment has a profound effect on the cellular matrix composition of the liver granuloma of Schistosoma mansoni infected mice when given alone, resulting in increase macrophage infiltration. These macrophages, in response to stimulation with soluble egg antigen or lipopolysaccharide produced elevated levels of nitric oxide but low levels of tumor necrosis factor alpha compared to untreated infected mice. This also correlated with reduced liver granuloma size. In spite of low numbers of eggs in the liver, mice receiving a combine treatment had a high level of resistance to a challenge infection compared with mice receiving only praziquantel. Those mice also exhibited a reduced lymphocyte proliferative response, similar to that of infected untreated mice. Antifibrotic treatment has an impact on the dynamic of the cellular nature of granulomas and impacts on the host immunity of infection.

Role of granivory and insectivory in the life cycle of the carabid beetle Amara similata

1. The cereal field carabid beetle Amara similata was selected to elucidate the role of seeds and insects as food sources. Three experiments were performed to rank different weed seeds and insects in terms of food value: (i) fecundity in relation to adult diet, (ii) larval survival in relation to diet and (iii) larval survival in relation to parental diet.2. Seeds were found to be of high value and insects of low value both for adults and larvae. Adding insects to a seed diet gave no significant improvement. The value of single species of seeds varied within adults and larvae, but also between adults and larvae. This is the first report that Amara larvae are granivorous.3. The value of different insects varied by species. Cereal aphid species were of the lowest value both for adult and larval beetles. On a diet of mixed insects, the adults were able to produce a low number of eggs but the larvae all died before pupation.4. There was no simple relation between survival of the larvae and the quality of the parents’ diet.

Coccidial and helminth infections in goats kept indoors in the Netherlands

An investigation was carried out on coccidial and helminth infections in goats kept indoors on five farms in the Netherlands. The goats were individually sampled. Coccidial oocysts were identified and nematode eggs counted. Larval cultures were made and infective larvae identified to the generic or species level. The goats were divided into three groups according to their age: kids, those weaned but not served, and older goasts. Oocysts were found in 26 out of 27 kids (96.3%), in 52 out of 55 weaned but not served goats (94.5%), and in 72 out of 110 older goats (65.5%). Eimeria ninakohlyakimovae was the most common species in all groups with an overall prevalence of 82%, followed by Eimeria arloingi (78%) and Eimeria aspheronica (53.3%). Other species present were Eimeria alijevi (50%), Eimeria christenseni (39.3%), Eimeria caprina (38.7%), Eimeria hirci (28.7%) and Eimeria jolchijevi (7.3%). Nematode eggs were seen on four of the five farms. It appeared that on two farms some goats, although now kept indoors, had been on pasture in the past. These goats excreted low numbers of eggs of Ostertagia and/or Trichostrongylus, Strongyloides papillosus, Haemonchus contortus, Trichuris spp. and larvae of Muellerius capillaris. In goats that were kept exclusively indoors, infections with Strongyloides papillosus were found on two farms in the older group and on one farm also in the group weaned but not served. On two farms Skrhabinema ovis was incidentally observed by the farmer in older goats. This was confirmed by faecal examinations on one farm. All kids were free of nematode infection.

PENGAMBILAN TELUR DARI INDUK NILA MERAH (Oreochromis sp.) PENGARUHNYA TERHADAP KECEPATAN BERPIJAH KEMBALI

Removing eggs from red nila female during spawning period were observed to know an appropriate time of removal and its effect on inter-spawning period of female broodstock. Spawning experiment was conducted with three replicates in the hapa. The female that cared fertilized eggs were cathed on 7th day, 21th, 28th day, and 35th day after stocking. Other spawning experiment with three relications were cared out to test the effect of removing eggs. On 7th day after spawning produced the highest number of spawned female reduced yhe inter-spawning interval, but there was no effect of male stocking on re-spawning rate of female. The low number of eggs per spawner together with asynchronus spawning would be problems faced on mass production of red nila seed.