Peak Of Larvae Research Articles

Occurrence of juvenile Dermacentor reticulatus ticks in three regions in Poland: the final evidence of the conquest

BackgroundTwo populations of Dermacentor reticulatus ticks (Western and Eastern) in Poland are among the most dynamic tick populations in Central Europe. Expansion and settlement of ticks in new localizations depend on the presence of suitable hosts, for both adult and juvenile ticks.MethodsThe current study was planned to complement our previous studies on questing adult ticks and was focused on a collection of juvenile D. reticulatus ticks from rodents from three regions in Poland, defined by the presence/absence of adult ticks (regions of the Western and Eastern tick population and the gap area between them) to confirm the existence of stable populations. Rodent trapping was conducted in open habitats (fallow lands, wasteland and submerged meadows) in 2016–2018 in June, July and/or August to encompass seasonal peaks of larvae and nymph activity.ResultsAltogether, three tick species were collected, 2866 D. reticulatus, 2141 Ixodes ricinus and 427 Haemaphysalis concinna. Dermacentor reticulatus was the most common (72.3%) and abundant (mean 17.94 ± 2.62 ticks/rodent) tick species on rodents from the Eastern region; in the Western region infestation of rodents was only 6.8%. Ixodes ricinus was found in all three regions and was the only tick species collected from rodents from the gap area. Haemaphysalis concinna was noted only in the Western region. The highest infestation of juvenile D. reticulatus was recorded on voles (Myodes and Microtus spp.), infestation of I. ricinus was the highest on Apodemus mice, and the majority of H. concinna ticks were collected from root voles Alexandromys oeconomus.ConclusionsOur study confirmed a stable population of D. reticulatus in Eastern and Central Poland and a lower prevalence and mean abundance of this tick species among rodents from the Western region. A lack of juvenile D. reticulatus on rodents in Niewiadów confirmed the existence of the gap area, free of D. reticulatus ticks.Graphical abstract

Phenology of Amblyomma sculptum in a degraded area of Atlantic rainforest in north-eastern Brazil

Amblyomma sculptum is the principal vector of Rickettsia rickettsii, the main agent of spotted fever rickettsiosis in Brazil. Little information is available regarding the population dynamics of this tick in some regions, including north-eastern Brazil, where cases of spotted fever rickettsioses are increasingly reported. Herein, we studied the phenology of A. sculptum in a rural area in north-eastern Brazil. Ticks were collected from the environment, using dry ice-baited traps, monthly for two consecutive years. In total, 1500 ticks were collected: 94 females (6.3%), 74 males (4.9%), 468 nymphs (31.2%), and 864 larvae (57.6%). All nymphs and females were identified as A. sculptum. Males were tentatively identified as A. sculptum and larvae as Amblyomma spp. Ticks were more numerous during spring and summer, followed by autumn and winter. Peaks of larvae and nymphs were recorded during summer and spring, respectively, whereas adults were more frequently collected in spring. A total of 380 ticks were tested by PCR for the gltA gene of Rickettsia spp., but none of them were positive. While our results revealed a seasonal pattern for A. sculptum in north-eastern Brazil that is distinct from the seasonal pattern in south-eastern Brazil, we caution that the observed pattern could have been biased by the relatively low number of ticks collected. Finally, the absence of Rickettsia-infected ticks does not rule out the possibility that rickettsial organisms are circulating in the study area and further long-term studies are warranted.

Ecological Studies on Beet Fly Pegomyia mixta (Vill) Infesting Sugar Beet Plants and Their Associated Predators in Sharkia Governorate, Egypt

The present work was carried out at Diarb- Nigm district, Sharkia Governorate, during the two sugar beet seasons 2015/2016 and 2016/2017, to study the seasonal fluctuation and number of generations of Pegomyia mixta (Vill) and seasonal fluctuation of the predators Coccinella undecimpunctata (L.), Paederus alfierii (Koch.), Chrysoperla Carnea(Stephens), Scymnus sp.andtrue spiders. The seasonal fluctuation of P. mixta (eggs and larvae) on sugar beet plants recorded two peaks during each season. Peaks of eggs were recorded in 22nd of February and 11th of April, in the first season, while the second season, these peaks were recorded in 27th of February and 17th of April. Peaks of larvae were recorded in 7th of March and 18th of April in the first season while the second season, it recorded in 13th of March and 24th of April. P. mixta eggs and larval were recorded were recorded three generations during each season. The peak of C. undecimpunctata and P. alfierii has occurred in 21th of March and 20th of March for the first and second seasons. The peak of C. Carneawas recorded in 14th of March and 13th of March for the two seasons. The peak of true spiders was recorded in 11th of April and 17th of April for the two seasons. The numbers of Scymnus sp was decreased for the two seasons.

Seasonal dynamics, geographical range size, hosts, genetic diversity and phylogeography of Amblyomma sculptum in Argentina

The aim of this work was to generate knowledge on ecological aspects of Amblyomma sculptum in Argentina, such as seasonal dynamics, geographical range size, hosts, genetic diversity and phylogeography. Adult and immature A. sculptum ticks were collected in different localities of Argentina to know the geographical range size and hosts. The genetic diversity of this tick was studied through analyses of 16S rDNA sequences. To describe the seasonal dynamics, free-living ticks were monthly collected from October 2013 to October 2015. A. sculptum shows a marked ecological preference for Chaco Húmedo eco-region and “Albardones” forest of the great rivers in the wetlands in the Chaco Biogeographical Province, and for Selvas Pedemontanas and Selva Montana in the Yungas Biogeographical Province. This species has low host specificity, and it has large wild and domestic mammals as principal hosts to both immature and adult stages. Amblyomma sculptum is characterized by a one-year life cycle. Larvae peak in early winter, nymphs peaked during mid-spring, and adults during late summer and mid-summer. The genetic divergence was low and the total genetic variability was attributable to differences among populations. This fact could be associated to stochastics process linked to micro-habitat variations that could produce a partial restriction to gene flow among populations. The geographic regions do not contribute much to explain the A. sculptum population genetic structure, with an ancestral haplotype present in most populations, which gives rise to the rest of the haplotypes denoting a rapid population expansion.

Chrysodeixis chalcites nucleopolyhedrovirus (ChchNPV): Natural occurrence and efficacy as a biological insecticide on young banana plants in greenhouse and open-field conditions on the Canary Islands.

Chrysodeixis chalcites, an important pest of banana crops on the Canary Islands, is usually controlled by chemical insecticides. The present study aimed to evaluate the efficacy of the most prevalent isolate of the Chrysodeixis chalcites nucleopolyhedrovirus (ChchNPV, Baculoviridae) as a biological insecticide. Overall the prevalence of ChchNPV infection in C. chalcites populations was 2.3% (103 infected larvae out of 4,438 sampled), but varied from 0–4.8% on Tenerife and was usually low (0–2%) on the other islands. On Tenerife, infected larvae were present at 11 out of 17 plantations sampled. The prevalence of infection in larvae on bananas grown under greenhouse structures was significantly higher (3%) than in open-field sites (1.4%). The ChchNPV-TF1 isolate was the most abundant and widespread of four genetic variants of the virus. Application of 1.0x109 viral occlusion bodies (OBs)/l of ChchNPV-TF1 significantly reduced C. chalcites foliar damage in young banana plants as did commonly used pesticides, both in greenhouse and open-field sites. The insecticidal efficacy of ChchNPV-TF1 was similar to that of indoxacarb and a Bacillus thuringiensis (Bt)-based insecticide in one year of trials and similar to Bt in the following year of trails in greenhouse and field crops. However, larvae collected at different time intervals following virus treatments and reared in the laboratory experienced 2–7 fold more mortality than insects from conventional insecticide treatments. This suggests that the acquisition of lethal dose occurred over an extended period (up to 7 days) compared to a brief peak in larvae on plants treated with conventional insecticides. These results should prove useful for the registration of a ChchNPV-based insecticide for integrated management of this pest in banana crops on the Canary Islands.

Ecology and genetic variation of Amblyomma tonelliae in Argentina.

The ecology of Amblyomma tonelliae (Ixodida: Ixodidae), including its seasonal distribution and the development periods of each stage, was investigated during a study carried out over two consecutive years in northwestern Argentina. In addition, the genetic variation of this tick was studied through analyses of 16S rDNA sequences. Amblyomma tonelliae has a 1-year lifecycle characterized by a long pre-moult period in larvae with no development of morphogenetic diapause. Larvae peak in abundance during late autumn and early winter; nymphs peak in abundance in spring, and adults do so from late spring to early summer. Amblyomma tonelliae shows a marked ecological preference for the driest areas of the Chaco ecoregion. In analyses of 16S rDNA sequences in genes from different populations of A. tonelliae, values for nucleotide diversity and the average number of nucleotide differences showed genetic diversity within this species to be low. No significant differences were found in comparisons among populations.

Behavior constrains the dispersal of long-lived spiny lobster larvae

Behavior such as ontogenetic vertical migration (OVM) limits the transport of marine larvae with short pelagic larval durations (PLDs), but its effect on the supposed long-distance disper- sal of larvae with long PLDs is unknown. We conducted laboratory tests of ontogenetic change in lar- val phototaxis and examined size-specific patterns of larval distribution in the plankton to character- ize OVM in the Caribbean spiny lobster Panulirus argus during its long (6 mo) PLD. We then used a coupled biophysical model to explore the consequences of OVM and hydrodynamics on larval P. argus dispersal in the Caribbean Sea. Larvae reared in the laboratory were positively phototatic for the first 2 mo and then avoided light thereafter, similar that seen in the planktonic distribution of same-sized larvae. Simulations of larval dispersal from 13 spawning sites in the Caribbean Sea pre- dicted that twice as many larvae would recruit to nurseries if they displayed OVM compared with passive dispersers. Larvae with OVM typically settled 1000 km away. OVM also produced an asymmetrical bimodal pattern of dispersal dominated by larvae that settled near their origin (~60%), but showed a second peak of larvae that dispersed over long distances (~20%). Hydrodynamics created subregional differ- ences in the potential for self-recruitment. Our findings suggest that (1) larval behavior constrains the dispersal of even long-lived larvae, particularly in tandem with retentive oceanographic environ- ments, and (2) larval sources of P. argus in the Caribbean Sea cannot be estimated from passive trans- port and surface circulation.

Seasonal Dynamics of Ixodes ricinus in a 3-Year Period in Northern Spain: First Survey on the Presence of Tick-Borne Encephalitis Virus

No cases of tick-borne encephalitis (TBE) in humans have ever been diagnosed in Spain. However, it is not clear if the necessary conditions for TBE virus (TBEV) persistence and transmission exist there, particularly synchrony in larval and nymphal activity, which has been related to the appearance of TBE in several countries. This synchrony allows ticks to cofeed on the same rodent host, facilitating transmission of TBEV between tick stages. From March 2006 to October 2008, 182 tick samplings were carried out on a monthly basis in six field sites in northern Spain using the blanket dragging technique. A total of 964 tick adults, 10,117 nymphs, and 73,534 larvae were counted. Ixodes ricinus was the predominant tick species. More number of adults, nymphs, and larvae were captured during the first year (2006) compared with the second or third years (p<0.05). Adults and nymphs were more active between April and June, whereas the peak of larvae appeared between May and September. Good synchrony between larvae and nymphs was observed only in two sampling sites, where mean maximum temperatures were below 10 °C from November 2006 to March 2007, but this synchrony was not maintained during the third year. Significant associations were found between abundance of I. ricinus larvae and temperature. Presence of TBEV was investigated by real-time reverse transcriptase polymerase chain reaction in 1800 nymphs analyzed in pools of 5 and in 630 adults processed individually, and all of them were negative. We therefore concluded that TBEV prevalence is either very low or absent in the investigated regions in northern Spain and current conditions there do not seem to favor TBEV maintenance. However, active and extensive surveillance based on epidemiological data collection, including data on changes in livestock, temporal fluctuations in density of small mammals, as well as tick seasonal population dynamics, is indispensable to predict the appearance of new TBE foci and recommend preventive measures.

Factors Affecting Localized Abundance and Distribution of Lesser Mealworm in Earth-Floor Broiler Houses in Subtropical Australia

Factors that influence the localized abundance and distribution of lesser mealworm, Alphitobius diaperinus (Panzer), in litter of two compacted earth-floor broiler houses in subtropical Australia were studied using various experimental manipulations. Numbers of lesser mealworms substantially increased inside caged areas and under uncaged empty feed pans placed in open areas of the houses. These populations were found to be localized and independent of chicken-feed, manure, and high beetle populations that normally occur under existing feed pans. Substantial horizontal movement of larvae to under feed pans was recorded. Placing metal barriers around these pans significantly restricted this movement. In almost all treatments, lesser mealworms typically peaked in numbers during the middle of the flock time. This temporal pattern of abundance also was observed under pans within barriers, where relatively low insect numbers occurred, but it was not observed in uncaged open areas (where chickens had complete access). It is likely that larvae do not establish in open areas, but fluctuate in numbers as they either move to refuges away from chickens or suffer high rates of mortality. In these refuges, larvae peak in numbers and then leave the litter environment to pupate in the earth floor before the end of the flock time. This behavior might be exploited for management of lesser mealworm by targeting applications of control agents.

Factors Affecting Localized Abundance and Distribution of Lesser Mealworm in Earth-Floor Broiler Houses in Subtropical Australia

Factors that influence the localized abundance and distribution of lesser mealworm, Alphitobius diaperinus (Panzer), in litter of two compacted earth-floor broiler houses in subtropical Australia were studied using various experimental manipulations. Numbers of lesser mealworms substantially increased inside caged areas and under uncaged empty feed pans placed in open areas of the houses. These populations were found to be localized and independent of chicken-feed, manure, and high beetle populations that normally occur under existing feed pans. Substantial horizontal movement of larvae to under feed pans was recorded. Placing metal barriers around these pans significantly restricted this movement. In almost all treatments, lesser mealworms typically peaked in numbers during the middle of the flock time. This temporal pattern of abundance also was observed under pans within barriers, where relatively low insect numbers occurred, but it was not observed in uncaged open areas (where chickens had complete access). It is likely that larvae do not establish in open areas, but fluctuate in numbers as they either move to refuges away from chickens or suffer high rates of mortality. In these refuges, larvae peak in numbers and then leave the litter environment to pupate in the earth floor before the end of the flock time. This behavior might be exploited for management of lesser mealworm by targeting applications of control agents.

Metabolism of [3H]-ecdysone in embryos and larvae of the tick Ornithodoros moubata.

The fate of [3H]-ecdysone ([3H]-E) was investigated in hanging drop cultures of embryos and larvae of the tick Ornithodoros moubata using HPLC. The hormone was metabolized more slowly during described periods of increasing endogenous ecdysteroid (ES) titers than during periods of low titers except for young embryos. Three different classes of metabolites were produced: 1) apolar products (AP) corresponding to C-22 fatty acid ester conjugates of E and, in some cases, of 20-hydroxyecdysone (20E), 2) unidentified polar products (PP) more polar than E, one peak of which had the same retention times as 20,26-dihydroxyecdysone, and finally, 3) 20E verified by comigration of cold standards on RP-18 and silica columns. Hydroxylation of E to 20E first became evident in cultures of 2 day old embryos and was present in all cultures of older animals. Highest production of free 20E occurred during increasing endogenous ES titers in embryos and during the ES peak in larvae. Conjugation of E to AP occurred in all stages investigated, but was more pronounced during periods of low endogenous ES titers, and may correspond to a detoxification mechanism. In contrast, PP were produced during high 20E production in embryos and during periods of high and decreasing endogenous titers in larvae.

Seasonality and Abundance of Ichthyoplankton in Great South Bay, New York

The seasonality and abundance patterns of ichthyoplankton were investigated during 1985–1986 in Great South Bay, New York, USA. Eggs representing 17 species and larvae representing 23 species of fish were identified. Bay anchovy, Anchoa mitchilli, was the most abundant ichthyoplankter, comprising >96% of the eggs and >69% of the larvae collected. Bay anchovy spawned throughout the bay from late May through August, with peak baywide densities of >200 eggs and 6 larvae m−3. Eggs of windowpane flounder (Scophthalmus aquosus) ranked second in abundance and were present in both spring and fall. Other dominant larvae were winter flounder (Pleuronectes americanus) and American sand lance (Ammodytes americanus). Their combined density reached 8 m−3 and accounted for the winter peak in larvae. The seasonality of abundance of larval fish was strongly correlated with reported densities of copepod nauplii prey.

Distribution of trichostrongylid nematodes in the abomasum of sheep

The distributions of Haemonchus contortus, Ostertagia circumcincta and Trichostrongylus axei during their development in lambs were studied by freezing and sectioning the abomasum and then recovering the worms from the contents and mucosa of each section. In previously worm-free lambs, the distribution of fourth stage H. contortus was very regular, the frequency of larvae being highest in the anterior fundic area and then decreasing in each section towards the pylorus. The distributions of the early larval stages of O. circumcincta and T. axei were variable but tended to be biomodal, with one peak of larvae in the fundic area and a second in the pyloric area. It is suggested that the difference in distribution between H. contortus and the other two species may be due to a difference in the rate of response of exsheathed third stage larvae to stimuli in the abomasum. In the later stages of development, H. contortus and O. circumcincta tended to migrate towards the pyloric area. In previously infected lambs, the distribution of inhibited early-fourth stage H. contortus was similar to that of normally developing fourth stage larvae in previously worm-free lambs and appeared to be unaffected by the host response which caused an altered distribution and rejection of late-fourth stage and adult worms. The rate of rejection of adult O. circumcincta differed between the fundic and pyloric areas of the abomasum, which suggests that the host response in these two areas may be different.

ヤノネツヤコバチ放飼園におけるヤノネカイガラムシの捕食者キイロテントウムシダマシの発生消長

Saula japonica is a native predator of Unaspis yanonensis in Japan. The seasonal prevalence and spatial distribution of S. japonica on citrus trees were examined in 1984 in an orchard where Coccobius fulvus, an introduced parasitoid of U. yanonensis had been released. The seasonal prevalence of both larvae and adults showed two peaks. The peaks of larvae were well synchronized with those of U. yanonensis, but those of the adults were not synchronized. Abundance of both larvae and adults did not vary with the part of the tree. More larvae and adults were, however, found on the undersurface of leaves as compared with the uppersurface.

The contribution of overwintering pasture larval infection and the spring rise as sources of Ostertagia circumcincta infection in lambs

An investigation was made to study the acquisition of infection with Ostertagia circumcincta by lambs on land carrying residual infection, infection following the spring rise and both infections. Dry weather in June modified the usual pattern of herbage larval infection by delaying the peak of larvae derived from residual infection and cutting out the first half of the diphasic peak normally associated with the spring rise. It is suggested that prediction of the time when damaging infections develop on the herbage may be possible by a study of meteorological observations.

Some Observations of the Stored-product Pests for Confection in Kochi

This paper reports results of studies on the stored-product pests in confections conducted from August 1968 to November 1969 at six survey areas in Kochi and of experimental studies on Oryzaephilus mercator, which was first found to be resident in the district of Kochi in our present study, in comparison with O. surinamensis, a common species in Japan of the same genus, and a species of another genus, Plodia interpunctella, as well. Laboratory studies on the development of O. mercator and O. surinamensis depending on different ages of parents and temperatures were made.To sum up briefly, the important ones among these results are as follows. (1) Out of the total observed number of 1722 of confections, high infestation rates of pests, 2.67% (15 species) and 18.2% (26 species), were found in samples taken from confections for sale and those of return, respectively. And as the results of our survey for a year, we could recognize three common species of pests, O. surinamensis, O. mercator and P. interpunetella. (2) Among different confections, biscuits were most severely infected as compared with chocolate and caramel confections. (3) High infestation rates were observed on the shops at rural areas in Kochi, on the shops of miscellaneous goods and on the wholesale store, hence we may well safely consider that the pest infection of confections is apt to occur severely in goods remaining long unsold and badly controlled at confection retail stores. (4) Seasonal fluctuations of O. mercator in the number collected by traps every week at confectioners factories distinct three peaks of adults and four peaks of larvae in the period from May to February, and it turns out that this pest may have four generations in a year (Fig. 19). But its fluctuation in number at the store of wholesale trade and retail stores never indicates such distinct peaks. (5) Developmental periods (egg to emergency) at 28°C did not show any distinct difference between both species, O. surinameusisand O. mercator, except that O. suriuamensis could not emerge, while another species could do at 32°C, both species emerging at 15°C. (6) In our study, we were aware of the fact that these two species of Oryzaephilus have intensive positive thigmotaxis (stereotaxis). (7) Faculty of boring polyethylene paper (0.02mm thickness), used for chocolate cover, becomes greatest for O. mercator when the population is of intermediate density (32 per cage in size 30cm3), whereas it becomes smaller in cases of lower or higher densities. (8) In O. mercator, the developmental period of offspring of parents of older ages (13 days old or more) was reduced by about two days as compared with that of parents younger than 13 days old, and the length and width of the thorax of offspring became shorter, P. interpunctella has the same tendency. (9) As three pairs of ovariole are found in both species of Oryzaephilus, it is possible that a female of these lays six eggs a day. The breeding period were six months at longest. (10) As to insecticidal activity for two species exposed to DDVP, O. mercator and O. surinamensis were found to be almost equal in LD50 values obtained by the topical application method (24hrs, 28°C). As the result of other experiments, which is shown in Fig. 22 in the LT50 values (y) observed at different distances (x) from DDVP-plates to pests, the relationship between the distances and insecticidal activity for pests seems to be formularized by y=0.433x+14.700. (11) P. interpunctella has 4th instar larval stages, periods of egg to emergence being about 30 days, and the pest comes to maturity in several hours after emergence and periods of egg-laying are almost a week.