Temperature Effects on Survival and Development of Heleidomermis magnapapula in the Laboratory

The mermithid Heleidomermis magnapapula Poinar and Mullens, a parasite of the biting midge Culicoides variipennis (Coquillett), was exposed to constant temperatures in the laboratory. Survival of the free-living stages and development times of eggs and the parasitic phase were inversely related to temperature. Average preparasite longevity was 70, 46, 42, and 22 hours at 15.6, 21.1, 26.7, and 32.2 C, respectively. Females survived significantly longer than males. Longevity in days (females/males) at different temperatures was 17.3/11.0 at 4.4 C, 9.0/8.2 at 15.6 C, 5.9/5,1 at 21.1 C, 5.2/4.7 at 26.7 C, and 4.4/3.6 at 32.2 C. Embryogenesis required 44 ± 2 degree days above a thermal minimum of 10.1 C, while parasitic development in host larvae required 214 ± 10 degree days above a thermal minimum of 8.9 C. Parasite responses to temperature were very closely related to temperature-dependent host development patterns.     

Potential effects of warmer worms and vectors on onchocerciasis transmission in West Africa

Development times of eggs, larvae and pupae of vectors of onchocerciasis (Simulium spp.) and of Onchocerca volvulus larvae within the adult females of the vectors decrease with increasing temperature. At and above 25°C, the parasite could reach its infective stage in less than 7 days when vectors could transmit after only two gonotrophic cycles. After incorporating exponential functions for vector development into a novel blackfly population model, it was predicted that fly numbers in Liberia and Ghana would peak at air temperatures of 29°C and 34°C, about 3°C and 7°C above current monthly averages, respectively; parous rates of forest flies (Liberia) would peak at 29°C and of savannah flies (Ghana) at 30°C. Small temperature increases (less than 2°C) might lead to changes in geographical distributions of different vector taxa. When the new model was linked to an existing framework for the population dynamics of onchocerciasis in humans and vectors, transmission rates and worm loads were projected to increase with temperature to at least 33°C. By contrast, analyses of field data on forest flies in Liberia and savannah flies in Ghana, in relation to regional climate change predictions, suggested, on the basis of simple regressions, that 13–41% decreases in fly numbers would be expected between the present and before 2040. Further research is needed to reconcile these conflicting conclusions.     

Fergusobia/Fergusonina-induced Shoot Bud Gall Development on Melaleuca quinquenervia

Fergusobia nematodes and Fergusonina flies are mutualists that cause a variety of gall types on myrtaceous plant buds and young leaves. The biology of an isolate of the gall complex was studied in its native range in Australia for possible use in southern Florida as a biological control agent against the invasive broad-leaved paperbark tree, Melaleuca quinquenervia. Timed studies with caged Fergusonina flies on young branches of M. quinquenervia revealed that females are synovigenic with lifetime fecundities of 183 ± 42 (standard error; SE) eggs and longevities of 17 ± 2 days. None of the male flies but all dissected female flies contained parasitic female nematodes (range = 3-15), nematode eggs (12-112), and nematode juveniles (78-1,750). Female flies deposited eggs (34 ± 6; 8-77 per bud) and nematode juveniles (114 ± 15; 44-207 per bud) into bud apices within 15 days. Histological sections of shoot buds suggested that nematodes induce the formation of hypertrophied, uninucleate plant cells prior to fly larval eclosion. Enlarged size, granular cytoplasm, and enlarged nucleus and nucleolus characterized these cells, which appeared similar to those of other species galled by nematodes in the Anguinidae. Observations of ovipositional behavior revealed that female Fergusonina sp. create diagnostic oviposition scars. The presence of these scars may facilitate recognition of host use during specificity screening.     

Heat Stress Impedes Development and Lowers Fecundity of the Brown Planthopper Nilaparvata lugens (St?l)

This study investigated the effects of sub-lethal high temperatures on the development and reproduction of the brown plant hopper Nilaparvata lugens (Stål). When first instar nymphs were exposed at their ULT₅₀ (41.8°C) mean development time to adult was increased in both males and females, from 15.2±0.3 and 18.2±0.3 days respectively in the control to 18.7±0.2 and 19±0.2 days in the treated insects. These differences in development arising from heat stress experienced in the first instar nymph did not persist into the adult stage (adult longevity of 23.5±1.1 and 24.4±1.1 days for treated males and females compared with 25.7±1.0 and 20.6±1.1 days in the control groups), although untreated males lived longer than untreated females. Total mean longevity was increased from 38.8±0.1 to 43.4±1.0 days in treated females, but male longevity was not affected (40.9±0.9 and 42.2±1.1 days respectively). When male and female first instar nymphs were exposed at their ULT₅₀ of 41.8°C and allowed to mate on reaching adult, mean fecundity was reduced from 403.8±13.7 to 128.0±16.6 eggs per female in the treated insects. Following exposure of adult insects at their equivalent ULT₅₀ (42.5°C), the three mating combinations of treated male x treated female, treated male x untreated female, and untreated male x treated female produced 169.3±14.7, 249.6±21.3 and 233.4±17.2 eggs per female respectively, all significantly lower than the control. Exposure of nymphs and adults at their respective ULT₅₀ temperatures also significantly extended the time required for their progeny to complete egg development for all mating combinations compared with control. Overall, sub-lethal heat stress inhibited nymphal development, lowered fecundity and extended egg development time.     

Monitoring long-term evolutionary changes following Wolbachia introduction into a novel host: the Wolbachia popcorn infection in Drosophila simulans

Wolbachia may act as a biological control agent for pest management; in particular, the Wolbachia variant wMelPop (popcorn) shortens host longevity and may be useful for dengue suppression. However, long-term changes in the host and Wolbachia genomes can alter Wolbachia spread and/or host effects that suppress disease. Here, we investigate the phenotypic effects of wMelPop in a non-native host, Drosophila simulans, following artificial transinfection approximately 200 generations ago. Long-term rearing and maintenance of the bacteria were at 19°C in the original I-102 genetic background that was transinfected with the popcorn strain. The bacteria were then introgressed into three massbred backgrounds, and tetracycline was used to create uninfected sublines. The effect of wMelPop on longevity in this species appears to have changed; longevity was no longer reduced at 25°C in some nuclear backgrounds, reflecting different geographical origin, selection or drift, although the reduction was still evident for flies held at 30°C. Wolbachia influenced productivity and viability, and development time in some host backgrounds. These findings suggest that long-term attenuation of Wolbachia effects may compromise the effectiveness of this bacterium in pest control. They also emphasize the importance of host nuclear background on Wolbachia phenotypic effects.     

Increases in the longevity of desiccation-phase developing rice seeds: response to high-temperature drying depends on harvest moisture content

Background and Aims Previous studies have suggested that the drying conditions routinely used by genebanks may not be optimal for subsequent seed longevity. The aim of this study was to compare the effect of hot-air drying and low-temperature drying on subsequent seed longevity for 20 diverse rice accessions and to consider how factors related to seed production history might influence the results.Methods Seeds of rice, Oryza sativa, were produced according to normal regeneration procedures at IRRI. They were harvested at different times [harvest date and days after anthesis (DAA), once for each accession] and dried either in a drying room (DR; 15 % relative humidity, 15 °C) or in a flat-bed heated-air batch dryer (BD; 45 °C, 8 h d^–1) for up to six daily cycles followed by drying in the DR. Relative longevity was assessed by storage at 10·9 % moisture content and 45 °C.Key Results Initial drying in the BD resulted in significantly greater longevity compared with the DR for 14 accessions (seed lots): the period of time for viability to fall to 50 % for seeds dried in the BD as a percentage of that for seeds dried throughout in the DR varied between 1.3 and 372·2 % for these accessions. The seed lots that responded the most were those that were harvested earlier in the season and at higher moisture content. Drying in the BD did not reduce subsequent longevity compared with DR drying for any of the remaining accessions.Conclusions Seeds harvested at a moisture content where, according to the moisture desorption isotherm, they could still be metabolically active (>16·2 %) may be in the first stage of the post-mass maturity, desiccation phase of seed development and thus able to increase longevity in response to hot-air drying. The genebank standards regarding seed drying for rice and, perhaps, for other tropical species should therefore be reconsidered.     

Life Cycle and Mating Behavior of Belonolaimus longicaudatus in Gnotobiotic Culture

The life cycle of Belonolaimus longicaudatus was observed in vitro on excised roots of Zea mays. Roots were cultured on Gamborg''s B5 medium in petri dishes with 1.5% agar adjusted to pH 5.8 and incubated at 28 °C in darkness. Second-stage juveniles (J2) fed on the roots and started the second molt (M2) to the third-stage juveniles 2 days after inoculation (DAI). The third molt (M3) to the fourth-stage juveniles occurred 7 DAI, followed by the fourth molt (M4) to males 13 DAI or to females 14 DAI. Nematode gender differences were observed by the end of the fourth molt. The first male appeared 15 DAI and the first female 17 DAI, after which mating occurred. Males were attracted to females, and mating was observed. Mating was required for reproduction. Fertilized females began to lay eggs 19 DAI and continued egg laying without the further presence of males during a 90-day observation. All of the eggs hatched. Unfertilized females rarely laid eggs, and none of the eggs were able to hatch. Feeding took place between each molt and before egg deposition occurred. The first-stage juveniles molted in the eggs 4 days after deposition, and J2 hatched from eggs 5 days after egg deposition. The life cycle from J2 to J2 was completed in 24 days.     

First Record of Bourgelatia diducta (Nematoda: Chabertiidae) from Wild Boars in the Republic of Korea

This study describes the first record of Bourgelatia diducta (Nematoda: Chabertiidae) from wild boars in the Republic of Korea (=South Korea). Gastrointestinal tracts of 87 Korean wild boars (Sus scrofa coreanus) hunted in mountains in the south-western part of South Korea between 2009 and 2012 were examined for their visceral helminths. B. diducta, as identified by morphological characteristics of the head and tail, were recovered from the large intestine of 47 (54%) wild boars. The average length of adult female worms was 11.3±0.87 mm and the thickest part of the body measured 0.54±0.04 mm in maximum width, while those of males were 9.8±0.72 and 0.45±0.03 mm, respectively. The characteristic J-shaped type II ovejector was observed in females, and the type II dorsal ray with 2 rami on each side of the median fissure was uniquely seen in males. The buccal capsule was small, relatively thin-walled, cylindrical, very short, and ring-shaped. The externodorsal ray arose from a common stem with the dorsal ray. The cervical groove was absent. The anterior extremity was equipped with 20-22 external corona radiata, 4 cephalic papillae and 2 lateral amphids around the mouth. The eggs were 66.0×38.9 µm in average size. By the present study, B. diducta (Nematoda: Chabertiidae) is recorded for the first time in South Korea. Additionally, morphological characteristics and identification keys provided in the present study will be helpful in the faunistic or taxonomic studies for strongylid nematodes related.     

Identification and Prevalence of Globocephalus samoensis (Nematoda: Ancylostomatidae) among Wild Boars (Sus scrofa coreanus) from Southwestern Regions of Korea

This study describes the first record of Globocephalus samoensis (Nematoda: Ancylostomatidae) recovered in wild boars from southwestern regions of Korea. Gastrointestinal tracts of 111 Korean wild boars (Sus scrofa coreanus) hunted from mountains in Suncheon-si, Gwangyang-si, and Boseong-gun between 2009 and 2012 were examined for their visceral helminths. G. samoensis, as identified by morphological characteristics of the head and tail, were recovered from the small intestine of 51 (45.9%) wild boars. Worms were found from 7 of 28 wild boars (25.0%) from Suncheon-si, 40 of 79 (50.6%) from Gwangyang-si, and all 4 (100%) from Boseong-gun. The length of adult females was 7.2±0.5 mm, and the thickest part of the body measured the average 0.47±0.03 mm, while those of males were 6.52±0.19 and 0.37±0.02 mm, respectively. The buccal cavity was equipped with a pair of large and bicuspid subventral lancets near the base of the capsule. The average length of spicules of males was 0.45±0.02 mm. By the present study, G. samoensis is recorded for the first time in southwestern regions of Korea. Additionally, morphological characteristics and identification keys provided in the present study will be helpful in the faunistic and taxonomic studies for strongylid nematodes in both domestic and wild pigs. The infection of G. samoensis apparently did not elicit pathologic lesions, as revealed by macroscopic observation during the autopsy of all wild boars in this study.     

ON CHROMOSOME BALANCE AS A FACTOR IN DURATION OF LIFE

This paper presents a study of the influence of chromosome balance on duration of life in Drosophila. The balanced type of cells are shown to favor a longer life than are the unbalanced type. Under the identical conditions of the experiment, the type females live an average of 33.1±.6 days; the type males 28.9±.8 days; the triploid females 33.1±.8 days and the sex-intergrade females 15.0±.3 days. The unbalance of the chromosomes and therefore of the genes contained within them is evidently a fundamental factor in the probable life span of the individual. The magnitude of the effect is fully on a par with that found for other factors, i.e., different Mendelian genes for constitutional vigor, etc. It has been possible to show by a study of the various sex classifications within the sex-intergrade class that the presence or absence of ovarian or testicular tissue as such is not the primary cause of the difference in the life duration in the type males and females but that the cause is to be found deeper, sex determination and duration of life accompanying each other and resulting from the common cause, chromosome constitution. The survival curve of the sex-intergrade groups present a limiting curve of duration of life, a constant death rate for each day of age. The curves have different rates of degeneration. To account for this fact it is necessary to assume that for these particular organisms a different organ in the two groups has assumed major significance to life due to the gene complex which causes their differentiation. Recurrent chance environmental and hereditary agents acting on organs generate the type of probability curve observed. Triploid flies are made up of cells which are one-third larger than the cells of the type flies. It is not without significance to note that such individuals show no greater or less duration of life than do the ordinary flies when both groups have their chromosomes in balance.     

Taxonomic Status of Berntsenus brachycephalus (Nematoda: Aphelenchina)

Berntsenus brachycephalus is redescribed from original material collected by Thorne in Utah, and hololectotype and paralectotypes are designated. This species is characterized by an expanded lip region, offset head, heavily sclerotized stylet conus, and two rows of oogonia and spermatogonia. The hololectotype male is 720 µm long, and paralectotype males are 864 to 952 µm long. Paralectotype females are 840 µm long. Tails of both sexes are amucronate.     

The role of male accessory-gland substance on female reproduction with some observations of spermatogenesis in the stable fly

The bulbous tubular portion of the median ejaculatory duct functions as the accessory gland in the male stable fly, Stomoxys calcitrans. The gland started to enlarge after emergence when the fly was fed on sugar-water or blood. Implants of accessory glands from sugar-water or blood-fed males were effective in stimulating oviposition in virgin females. The injection into females of accessory-gland extracts from males fed blood prevented insemination; this extract was effective in concentration as low as 0.25 gland per female. Accessory-gland extracts from sugar-water fed males were only partially effective in preventing female insemination. However, the accessory-gland extracts of male stable flies had little effect on insemination when injected into three other species of female dipterans.Spermatogenesis was completed by the time of emergence, or shortly thereafter, a process independent of blood feeding. Three types of spermatids were identified, forming a continuum of spermiogenesis stages. Fat, fusiform spermatozoa elongated to become thin, elongate and mature spermatozoa.     

Observations on a Pasteuria Isolate Parasitic on Hoplolaimus galeatus in Peru

A Pasteuria isolate associated with a population of the lance nematode Hoplolaimus galeatus was discovered in Peru. The infective propagules adhered to adult stages and juveniles and were found filling the bodies of males and females. The endospore and central core diameters measured 4.5 ± 0.4 pm and 1.9 ± 0.2 μm, respectively, which differed from those reported for other Pasteuria isolates found iu North America on the same host. Examinations of endospore ultrastructure with scanning electron microscopy showed the presence of a thin layer of parasporal fibers surrounding the central core, a thin reduced layer of parasporal fibers in contact with the host''s cuticle, and a putative basal core ring.     

Degree-day Models for Predicting Egg Hatch and Population Increase of Criconemella xenoplax

A degree-day model was derived to predict egg hatch for Criconemella xenoplax. Eggs collected from gravid females were incubated in distilled water at constant temperatures of 10-35 C. Sixty-six percent of all eggs hatched between 13 and 32 C, and 42% hatched at 10 C. All eggs aborted above 32.5 C. Between 25 and 32 C, 8.5 ± 0.5 days were required for egg hatch. Degree-day requirement for egg hatch at 10-30 C was estimated to be 154 ± 5 with a base of 9.03 ± 0.04 C. This base of 9 C was adopted in studies of the relationship between degree-days and nematode population increase on Prunus seedlings grown 9-11 weeks in a greenhouse. Degree-day accumulations were based upon daily averages from maximum and minimum air temperatures. Ratios of final to initial population densities exhibited an exponential pattern in relation to degree-day accumulations with proportionate doubling increment of 0.100 ± 0.049 every 139 ± 8 degree-days. These results provide a means of predicting nematode population increase under greenhouse conditions and a basis for choosing sampling intervals when evaluating nematode multiplication.     

Variation in haematological parameters in children less than five years of age with asymptomatic Plasmodium infection: implication for malaria field studies

During the season of high malaria transmission, most children are infected by Plasmodium, which targets red blood cells (RBCs), affecting haematological parameters. To describe these variations, we examined the haematological profiles of two groups of children living in a malaria-endemic area. A cross-sectional survey was conducted at the peak of the malaria transmission season in a rural area of Burkina Faso. After informed consent and clinical examination, blood samples were obtained from the participants for malaria diagnosis and a full blood count. Of the 414 children included in the analysis, 192 were not infected with Plasmodium, whereas 222 were asymptomatic carriers of Plasmodium infection. The mean age of the infected children was 41.8 months (range of 26.4-57.2) compared to 38.8 months (range of 22.4-55.2) for the control group (p = 0.06). The asymptomatic infected children tended to have a significantly lower mean haemoglobin level (10.8 g/dL vs. 10.4 g/dL; p < 0.001), mean lymphocyte count (4592/µL vs. 5141/µL; p = 0.004), mean platelet count (266 x 103/µL vs. 385 x 103/µL; p < 0.001) and mean RBC count (4.388 x 106/µL vs. 4.158 x 106/µL; p < 0.001) and a higher mean monocyte count (1403/µL vs. 1192/µL; p < 0.001) compared to the control group. Special attention should be applied when interpreting haematological parameters and evaluating immune responses in asymptomatic infected children living in malaria-endemic areas and enrolled in vaccine trials.     

Leaching Soluble Salts Increases Population Densities of Tylenchulus semipenetrans

The effect of salinity on population densities of Tylenchulus semipenetrans was measured on 3-month-old salt-tolerant Rangpur lime growing on either loamy sand, sand, or organic mix and on 4-month-old salt-sensitive Sweet lime in organic mix. Salinity treatments were initiated by watering daily with 25 mol/m³ NaCl + 3.3 mol/m³ CaCl₂ for 3 days and every other day with 50 mol/m³ NaC1 + 6.6 mol/m³ CaC1₂ for one week, with no salt (NS) treatments as controls. Salinity was discontinued in one treatment (DS) by leaching with tap water prior to inoculation with nematodes, whereas the continuous salinity (CS) treatment remained unchanged. Overall, in Rangpur lime organic soil supported the highest population densities of T. semipenetrans, followed by loamy sand and sand. The DS treatment resulted in the highest (P ≤ 0.05) mean population densities of T. semipenetrans in the three soil types. Similarly, the DS treatment in Sweet lime resulted in the highest (P ≤ 0.05) nematode populations. The DS treatment predisposed citrus to nematode infection through accumulated salt stress, whereas leaching soluble salt in soil solution offered nematodes a suitable nonosmotic habitat. Nematode females under the DS treatment also had the highest (P ≤ 0.05) fecundity.     

Ditylenchus dipsaci Infestation of Trifolium repens. I. Temperature Effects,Seedling Invasion,and a Field Survey

Rates of development of stem nematode (Ditylenchus dipsaci) in white clover (Trifolium repens) seedlings were found to be linearly related to temperature. Basal developmental temperature (T_b) was 3 °C, and the thermal constant (S) for development of gravid adult females from freshly laid eggs was 270 accumulated day-degrees above the T_b. Only 12% at 20 °C and 4% at 4 °C of the gravid female nematodes inoculated into seedling axils successfully penetrated seedling epidermis. These nematodes slowly migrated within the seedling and after a lag of 5 days at 20 °C started to lay eggs. The maximal rate of egg production was temperature-dependent, being 0.8 and 3.1 eggs female⁻¹ day⁻¹ at 10 and 20 °C, respectively. Nematodes emigrated rapidly from infested stolons when they were immersed in water, with rates being highest at 25 °C and lowest at 4 °C. The sensitivity to temperature of many of the parameters that govern nematode population dynamics indicates that climatic changes will have a marked effect upon this host-parasite system. A study of infested stolons from the field indicated that nematode numbers increased up to 3,000 or more before tissue senesence, triggered by nematode damage, caused a mass emigration of nematodes from the stolon.     

Laboratory studies on the biology ofSpalangia nigra [Hym.: Pteromalidae]

At 21 °C,Spalangia nigra Latreille (Hymenoptera: Pteromalidae) averaged 29.3 days between exposure and emergence of 1^st progeny from host house flies,Musca domestica L. (Diptera: Muscidae). At 27 °C, the average developmental time to 1^st emergence was reduced to 26.6 days, and a majority of adult wasps emerged from host house fly puparia between 29 and 40 days postoviposition. The sex ratio of progeny ranged from 1.4 to 1.8 female-to-male, but all progeny of virgin females were male. Male wasps lived from 6.8–15 and females 11–17.8 days at 27 °C; honey as a food source increased longevity. No significant differences in parasitism byS. nigra were associated with host house fly pupal densities ranging from 1 to 200 pupae per female-male pair of wasps, but average percent parasitism decreased at host densities greater than 50. House fly pupae exposed to parasitism at ages ranging from 4 to 96 h did not differ in subsequent production of adult flies.S. nigra did not demonstrate preference for house flies or stable flies,Stomoxys calcitrans (L.) (Diptera: Muscidae) as hosts. The results of these studies indicate thatS. nigra may contribute significantly to previously unexplained mortality of house flies and stable flies.      

Morphological and Molecular Characterization of Gracilacus wuae n. sp. (Nematoda: Criconematoidea) Associated with Cow Parsnip (Heracleum maximum) in Ontario,Canada

Gracilacus wuae n. sp. from soil associated with cow parsnip in Ontario, Canada is described and illustrated. Morphologically, females have a long stylet ranging from 80 to 93 µm long, the lip region not offset from the body contour, without lateral lips but with large and flat submedian lobes, the mouth opening slit-like elongated laterally and surrounded by lateral flaps, the excretory pore is anterior to the knobs of the stylet; males without stylet and the pharynx degenerated. The fourth-stage juveniles lack a stylet, the pharynx degenerated, and can be differentiated into preadult females and males based on the position of the genital primordia. The third-stage juveniles are similar to females but smaller. Phylogenetic studies using the rDNA small subunit 18S, large subunit 28S D2/D3, and internal transcribed spacer (ITS) sequences collectively provide evidence of a grouping with other Gracilacus and some species of Paratylenchus with stylet length of females longer than 41 µm deposited in GenBank.