Effects of temperature, salinity, and air exposure on development of the estuarine pulmonate gastropod Amphibola crenata

The primitive pulmonate snail Amphibola crenata embeds embryos within a smooth mud collar on exposed estuarine mudflats in New Zealand. Development through hatching of free-swimming veliger larvae was monitored at 15 salinity and temperature combinations covering the range of 2-30 ppt salinity and 15-25 °C. The effect of exposure to air on developmental rate was also assessed. There were approximately 18,000 embryos in each egg collar. The total number of veligers released from standard-sized egg collar fragments varied with both temperature and salinity: embryonic survival was generally higher at 15 and 20 °C than at 25 °C; moreover, survival was generally highest at intermediate salinities, and greatly reduced at 2 ppt salinity regardless of temperature. Even at 2 ppt salinity, however, about one-third of embryos were able to develop successfully to hatching. Embryonic tolerance to low salinity was apparently a property of the embryos themselves, or of the surrounding egg capsules; there was no indication that the egg collars protected embryos from exposure to environmental stress. Mean hatching times ranged between 7 and 22 days, with reduced developmental rates both at lower temperature and lower salinity. At each salinity tested, developmental rate to hatching was similar at 20 and 25 °C. At 15 °C, time to hatching was approximately double that recorded at the two higher exposure temperatures. Exposing the egg collars to air for 6-9 h each day at 20 °C (20 ppt salinity) accelerated hatching by about 24 h, suggesting that developmental rate in this species is limited by the rates at which oxygen or wastes can diffuse into and from intact collars, respectively. Similarly, veligers from egg capsules that were artificially separated from egg collars at 20 °C developed faster than those within intact egg collars. The remarkable ability of embryos of A. crenata to hatch over such a wide range of temperatures and salinities, and to tolerate a considerable degree of exposure to air, explains the successful colonization of this species far up into New Zealand estuaries.     

Effect of Temperature on Pratylenchus penetrans Development

Reproduction and development of Pratylenchus penetrans were studied on genetically transformed ladino clover roots. Solitary females developing on transformed roots in nutrient gellan gum medium (pH 5.5) deposited 1.2, 1.5, 1.6, 1.8, and 2.0 eggs per day at the respective temperatures of 17, 20, 25, 27, and 30 °C. The number of eggs deposited was highly correlated with temperature. A reduction in egg-laying rates at the start of hatching was observed at all temperatures. Juvenile mortality was higher at 17 °C (50.4%), 20 °C (50.3%), and 30 °C (58.4%) than at 25 °C (34.6%) and 27 °C (37.6%). Life-cycle (egg deposition to egg deposition) duration was 46, 38, 28, 26, and 22 days at the respective temperatures. The developmental zero degrees (°C) and the effective accumulative temperatures (degree-days) required for hatching, female emergence, and onset of oviposition (completion of one generation) of P. penetrans were estimated to be 2.7 and 200, 4.2 and 548, and 5.1 and 564, respectively. Pratylenchus penetrans reproduces over a wide range of temperatures.     

Temperature impact on reproduction and development of congener copepod populations

The goal of this study was to relate the temperature response of all developmental stages and reproductive biology of two congener copepod pairs inhabiting different biogeographic regions to their geographic distribution patterns. Survival of adult females and egg production, embryonic development and hatching success of the genera Centropages and Temora from two stations, in the North Sea and the Mediterranean, were studied in laboratory experiments in a temperature range from 2 to 35 °C. Postembryonic development was determined from cohorts raised at temperatures between 10 and 20 °C with surplus food. Tolerance limits and optima of female survival, reproduction and development distinguished the northern species Centropages hamatus and Temora longicornis from the southern T. stylifera, while C. typicus, which is found in both regions, was intermediate. Thus, thermal preferences could in part explain distribution patterns of these species. While C. hamatus and the two Temora species showed distinct temperature ranges, C. typicus was able to tolerate different temperature conditions, resulting in its wide distribution range from the subarctic to the tropics. However, the thermal range of a species did not necessarily correlate with the optimal temperatures in the experiments. Optima of egg production and stage development were surprisingly low in T. stylifera, which has a mere southern distribution.     

Influence of Temperature on Multiplication and Egg Hatching of Longidorus africanus

Longidorus africanus multiplication on tomato was highest at 29 °C. Few nematodes were recovered after 6 weeks at soil temperatures of 35 °C or below 23 °C. The time to egg hatching was shortest and the percentage of eggs hatching was highest at 29 °C. The minimum temperature and the heat sum above this temperature required for egg development were calculated to be 14.3 °C and 94.08 degree-days, respectively. The thermal times required for egg development by L. africanus and L. elongatus were nearly identical. For both species the product of the base temperature and the heat sum was near constant, and at a temperature of 22.3 °C the rates of egg development were equal.     

Exposure Time to Lethal Temperatures for Meloidogyne incognita Suppression and Its Implication for Soil Solarization

Meloidogyne incognita eggs or J2 were incubated in test tubes containing sand:peat mix and immersed in a water bath heated to 38, 39, 40, 41, 42, 43, 44 and 45°C for a series of time intervals. Controls were maintained at 22°C. Nematodes surviving or hatching were collected from Baermann trays after three weeks of incubation. Regression analyses between percent survival or egg hatch and hours of heat treatment were performed for each temperature. Complete suppression of egg hatch required 389.8, 164.5, 32.9, 19.7 and 13.1 hours at 38, 39, 40, 41 and 42°C, respectively. Complete killing of J2 required 47.9, 46.2, 17.5 and 13.8 hours at 39, 40, 41 and 42°C, respectively. J2 were not completely killed at 38°C within 40 hours of treatment, but were killed within one hour at 44 and 45°C. Effect of temperature on nematode killing is not determined by heat units. Oscillating temperature between cool and warm did not interfere with the nematode suppressive effect by the heat treatment. Six-week solarization in the field during the summers of 2003 and 2004 in Florida accumulated heat exposure times in the top 15 cm of soil that surpassed levels required to kill M. incognita as determined in the water bath experiments. Although near zero M. incognita were detected right after solarization, the nematode population densities increased after a cycle of a susceptible pepper crop. Therefore, future research should address failure of solarization to kill nematodes in the deeper soil layers.     

Zur fortpflanzungsbiologie von mesostoma ehrenbergii (Focke, 1836) (Turbellaria)

1. At temperature levels from 10 to 25°C animals from resting eggs produce subitaneous eggs independent on temperature. In contrast animals from subitaneous eggs produce subitaneous eggs dependent on temperature. At a high rate subitaneous eggs are only formed at temperature levels above 20°C.
2. Below 10°C no development occurs in the juveniles. At temperatures of 30/22°C (24.7°C) the first subitaneous eggs are formed after 6–9 days, at 14/9°C (10.7°C) they are formed after 34 days. At different temperature levels the developmental rate of the young is from 10.5 to 42 days. One generation extends over 16.5 (30/22°C) to 75 days (14/9°C). The average egg production is 10–20 subitaneous eggs or 30–60 resting eggs. The maximum egg production of one individual is 50 subitaneous eggs or 84 resting eggs. 50% of the animals have just formed resting eggs, before the juveniles are hatched. Resting eggs in the first egg-batch are formed 6–20 days later than subitaneous eggs. The duration of life is between 65 (30/22°C) and 140 days (19/13°C).
3. Young worms in resting eggs have a dormance period of at least 15–30 days.

At room temperatures (20°C) no juvenile in resting eggs hatches from water. By combining room and refrigerator (3.5°C) temperatures the hatching rate increases to a maximum of 85%. To reach a hatching rate of 50–65% the influence of low temperatures must be at least 30 days. At room temperatures 60% of the young in resting eggs hatch from mud covered with water. Combining high and low temperatures the hatching success is between 67 and 81%, where the highest percentage of the young may hatch at room temperature. Up to 90 days low temperatures cause a maximum hatching rate of 79%. It decreases to approximately 30% after 180 days. At high temperatures resting eggs preserved in 100% moist mud, survive for two months. By adding a period of low temperatures the hatching rate increases to a maximum of 52%. Low temperatures are survived for more than 6 months. Up to 30 days preservation at 3.5°C causes a maximum hatching rate of 61%, up to 12o days it decreases to 30%. At room temperature the young in resting eggs are not resistant against air-dried mud (30–40% rel. air moisture). Combining high and low temperatures air-dried mud is endured 1 month (hatching rate 5–14%). Preservation of 30–120 days at 3.5°C and 70% rel. air moisture result in a hatching rate of 43–61%. li]4. In the open air in Middle-Europe there occur 5–6 generations of M. ehrenbergii per life-cycle. The first generation hatches from resting eggs in May, where the production of subitaneous eggs is independent on temperature. All other generations up to October hatch from subitaneous eggs. The egg-production of those worms is dependent on environmental factors. In summer subitaneous egg production prevails, in autumn resting egg production. The abundance during the life-cycle is dependent on the number of animals which produce subitaneous eggs. Resting eggs are predestinated to endure periods of dryness and cold. The life-cycles of the species M. lingua and M. productum are different from those of M. ehrenbergii in length and in the number of generations. In both species 7 generations occur over 8 to 8.5 respectively 5.5 months. M. nigrirostrum only forms resting eggs. The life-cycle consists of one generation from February/March to May/June.     

Feeding of the Nematode Acrobeloides nanus on Bacteria

Information on the effect of bacteria-feeding nematodes on bacterial populations in the soil is sparse. We have isolated, cultured, and microscopically examined bacteria and nematodes coexisting within an agricultural soil and have studied their feeding relationship. The bacterium Pseudomonas corrugata isolate 2140R is a biocontrol agent against the pathogenic fungus Gaeumannomyces graminis var. tritici. The nematode Acrobeloides nanus is a cosmopolitan, bacteria-feeding organism widespread in agricultural and arid soils throughout Australia. Using light and electron microscopy, we observed the ingestion and breakdown of P. corrugata in the pharynx of A. nanus and bacterial passage through the nematode intestine as well as the accumulation of fluorescent compounds from ingested and broken P. fluorescens in the lumen of the nematode''s intestine. We also observed A. nanus feeding, growing, and reproducing on the Gram-positive bacterium Clavibacter toxicus, the causative agent of the disease annual ryegrass toxicity, and detected crushed bacteria in the nematode''s intestine.     

Influence of Rhizoctonia solani on Egg Hatching and Infectivity of Rotylenchulus reniformis

The effects of culture filtrates of Rhizoctonia solani and root exudates of R. solani-infected cotton (Gossypium hirsutum) seedlings on hatching of eggs and infectivity of females of Rotylenchulus reniformis were evaluated in an attempt to account for the enhanced nematode reproduction observed in the presence of this fungus. Crude filtrates of R. solani cultures growing over sterile, deionized distilled water did not affect egg hatching. Exudates from roots of cotton seedlings increased hatching of R. reniformis eggs over that observed in water controls. Exudates from cotton seedling roots not infected or infected with R. solani did not differ in their effect on egg hatching. However, infection of cotton seedlings by reniform females was increased in the presence of R. solani, resulting in the augmented egg production and juvenile population densities in soil observed in greenhouse studies.     

Heterologous expression of antifreeze protein gene AnAFP from Ammopiptanthus nanus enhances cold tolerance in Escherichia coli and tobacco

Antifreeze proteins are a class of polypeptides produced by certain animals, plants, fungi and bacteria that permit their survival under the subzero environments. Ammopiptanthus nanus is the unique evergreen broadleaf bush endemic to the Mid-Asia deserts. It survives at the west edge of the Tarim Basin from the disappearance of the ancient Mediterranean in the Tertiary Period. Its distribution region is characterized by the arid climate and extreme temperatures, where the extreme temperatures range from − 30 °C to 40 °C. In the present study, the antifreeze protein gene AnAFP of A. nanus was used to transform Escherichia coli and tobacco, after bioinformatics analysis for its possible function. The transformed E. coli strain expressed the heterologous AnAFP gene under the induction of isopropyl β-D-thiogalactopyranoside, and demonstrated significant enhancement of cold tolerance. The transformed tobacco lines expressed the heterologous AnAFP gene in response to cold stress, and showed a less change of relative electrical conductivity under cold stress, and a less wilting phenotype after 16 h of − 3 °C cold stress and thawing for 1 h than the untransformed wild-type plants. All these results imply the potential value of the AnAFP gene to be used in genetic modification of commercially important crops for improvement of cold tolerance.     

Effects of Zinc Fertilization of Corn on Hatching of Heterodera glycines in Soil

Experiments were conducted to determine the effects of zinc fertilizers on hatching and soil population densities of Heterodera glycines. In vitro egg hatching in solutions of reagent-grade zinc sulfate and zinc chloride and fertilizer-grade zinc sulfate was significantly greater than hatching in deionized water, whereas zinc chelate fertilizer significantly inhibited egg hatching relative to deionized water. In greenhouse experiments, no differences in cumulative percentage egg hatch were detected in soil naturally infested with H. glycines amended with fertilizer-grade zinc sulfate and zinc chelate at rates equivalent to 0, 1.12, 11.2, and 112 kg Zn/ha and subsequently planted with corn (Zea mays L.). In a field experiment, no significant differences in H. glycines egg population densities and corn yields were detected among plots fertilized with 0, 11.2, and 22.4 kg Zn/ha rates of zinc chelate. Yields of H. glycines-susceptible soybean planted in plots 1 year after zinc fertilization of corn plots also were not significantly affected. Zinc compounds significandy affected H. glycines egg hatching in vitro, but had no effect on hatching in natural soils.     

Enhanced Hatching of Globodera tabacum solanacearum Juveniles by Root Exudates of Flue-cured Tobacco

Stimulation of hatching of a tobacco cyst nematode (Globodera tabacum solanacearum) by root exudates from resistant NC 567 and susceptible K 326 cultivars of flue-cured tobacco, Nicotiana tabacum, was investigated. Root exudates were collected by soaking seedlings in deionized water for 2 hours at 22 °C in the dark. Fifteen mature and uniformly sized cysts were exposed at 15, 20, or 25 °C to undiluted root exudate, root exudate diluted 1:1 or 1:3 with deionized water, or deionized water alone. Hatched juveniles were counted and removed at weekly intervals during 42 and 53 days of exposure in experiments conducted in 1994 and 1995, respectively. Root exudates from both susceptible cultivar K 326 and resistant cultivar NC 567 stimulated more hatching than deionized water at 25 °C in 1994, and at all three tested temperatures in 1995. In 1994, dilution of root exudates 1:3 reduced stimulation of hatching at 25 °C compared to undiluted exudate. Hatching at 25 °C was similarly stimulated by exposure to undiluted root exudate and exudate diluted 1:1. In 1995, both dilutions reduced stimulation of hatching by root exudates at all the temperatures.     

Effect of Artemisia vulgaris Rhizome Extracts on Hatching,Mortality, and Plant Infectivity of Meloidogyne megadora

The activity of an ethanolic rhizome extract of Artemisia vulgaris against hatching, mortality, host plant infectivity, and galling of the root-knot nematode Meloidogyne megadora was investigated. The extract inhibited egg hatch (50% inhibition by 2.35mg/ml) and caused second-stage juvenile mortality (50% lethality at 12 hours'' exposure to 55.67 mg/ml), both in a dose-dependent manner. Nematode infectivity on Phaseolus vulgaris ''Bencanta Trepar'', a susceptible host, decreased in a dose-responsive manner (50% inhibition at 6.28 hours exposure to extract). When applied directly to the soil, the extract reduced root galling on a susceptible host in a dose-dependent manner (50% inhibition by 32.36 mg/ml). After dilution in distilled water, the extract did not lose activity when stored in the dark at 25°C for 15 days.     

The life cycle of Anguina agrostis: Embryogenesis

Bpird A. F. and Sptynes B. A. 1981. The life cycle of Anguina agrostis: embryogenesis. International Journal for Parasitology11: 23–33. Egg development, from laying to hatching, of two widely separated populations of Anguina agrostis, has been followed over a range of temperatures. Development rates for these two populations have been shown to be identical with a thermal optimum between 18 and 20°C. The minimum time recorded for embryogenesis through to hatching was 9–10 days.Embryogenesis was inhibited by temperatures of 27°C and above and hatching by temperatures greater than 23°C.No significant differences were detected in the dimensions of eggs from either population. These eggs have an average length of 95 μm and an average width of 38 μm.Electron microscope studies of sections through eggs undergoing synchronous development show that the first and apparently only moult of the larva in the egg commences about 7 days after the start of embryogenesis under optimal conditions. The sequence of morphological events that occur throughout embryogenesis are described and recorded for whole specimens observed at low resolution and the moulting sequence is described from high resolution electron micrographs of the cuticles of synchronously developing embryos and larvae.     

Accelerated Movement of Nematodes from Soil in Baermann Funnels with Temperature Gradients

Baermann funnels were modified to eliminate or reverse the small temperature gradient (1-2 C/cm) across the soil layer that normally results from water evaporation. Effects of modifications on extraction efficiency were examined at various ambient temperatures and after overnight adaptation of three nematode species at 20 and 30 C. Extraction of Meloidogyne incognita from sandy loam, Tylenchulus semipenetrans from sandy clay loam, and Rotylenchulus reniformis from silt was greatly accelerated simply by covering funnels to prevent evaporation. In most cases, covering increased the nematodes extracted by 10-100 times after 5.5-48 hours. Faster and more efficient extraction of R. reniformis occurred over a wide range of ambient temperature (18-29 C). Effects of ambient temperature and temperature gradient direction on Baermann funnel extraction of R. reniformis were partly inconsistent with the behavior of R. reniformis in agar. Nematodes in agar moved toward cold at some ambient temperatures and toward heat at other temperatures. They always appeared to move toward cold on Baermann funnels. Differences were not attributable to blockage of gas exchange by covers. In agar and in funnels, the patterns of response to ambient temperature were shifted in the direction of the storage temperature.     

Influence of Inoculum Density,Host, and Low-temperature Period on Delayed Hatch of Meloidogyne javanica Eggs

Most eggs of M. javanica hatch within several days when incubated in water. Those that do not are said to show delayed hatching. Several experiments were conducted to determine the effect of specific conditions on the percentage of eggs with delayed hatch. Six initial inoculum densities ranging from 100 to 20,000 eggs per pot did not influence egg hatch within a 45-day incubation period. In a 60-day test, the percentage of eggs hatching after more than 20 days was low for egg masses removed from carrot and okra and high for those from pepper and bean. Increasing exposure to cold temperature (8 C) from 7 to 30 days tended to delay hatch.     

Glucose 6-phosphate dehydrogenase deficiency enhances germ cell apoptosis and causes defective embryogenesis in Caenorhabditis elegans

Glucose 6-phosphate dehydrogenase (G6PD) deficiency, known as favism, is classically manifested by hemolytic anemia in human. More recently, it has been shown that mild G6PD deficiency moderately affects cardiac function, whereas severe G6PD deficiency leads to embryonic lethality in mice. How G6PD deficiency affects organisms has not been fully elucidated due to the lack of a suitable animal model. In this study, G6PD-deficient Caenorhabditis elegans was established by RNA interference (RNAi) knockdown to delineate the role of G6PD in animal physiology. Upon G6PD RNAi knockdown, G6PD activity was significantly hampered in C. elegans in parallel with increased oxidative stress and DNA oxidative damage. Phenotypically, G6PD-knockdown enhanced germ cell apoptosis (2-fold increase), reduced egg production (65% of mock), and hatching (10% of mock). To determine whether oxidative stress is associated with G6PD knockdown-induced reproduction defects, C. elegans was challenged with a short-term hydrogen peroxide (H₂O₂). The early phase egg production of both mock and G6PD-knockdown C. elegans were significantly affected by H₂O₂. However, H₂O₂-induced germ cell apoptosis was more dramatic in mock than that in G6PD-deficient C. elegans. To investigate the signaling pathways involved in defective oogenesis and embryogenesis caused by G6PD knockdown, mutants of p53 and mitogen-activated protein kinase (MAPK) pathways were examined. Despite the upregulation of CEP-1 (p53), cep-1 mutation did not affect egg production and hatching in G6PD-deficient C. elegans. Neither pmk-1 nor mek-1 mutation significantly affected egg production, whereas sek-1 mutation further decreased egg production in G6PD-deficient C. elegans. Intriguingly, loss of function of sek-1 or mek-1 dramatically rescued defective hatching (8.3- and 9.6-fold increase, respectively) induced by G6PD knockdown. Taken together, these findings show that G6PD knockdown reduces egg production and hatching in C. elegans, which are possibly associated with enhanced oxidative stress and altered MAPK pathways, respectively.     

Effects of Temperature on Rate of Feeding of the Plant Parasitic Nematodes Rotylenchus robustus,Xiphinema diversicaudatum,and Hemicycliophora conida

Rotylenchus robustus, Xiphinema diversicaudatum, and Hemicycgiophora conida were observed feeding over a range of temperatures on perennial rye-grass (Lolium perenne) seedlings grown on agar plates. R. robustus fed between 0.5 and 42.5 C, X. diversicaudatum between 5.0 and 37.0 C and H. conida between 5.0 and 34.0 C. Between 10 and 25 C there was a direct relationship between temperature and rate of esophageal bulb contractions. Above 25 C the number of esophageal contractions/min did not increase at the same rate and eventually decreased. At the extremes of temperature range, abnormal feeding behaviour was observed. Rates of esophageal bulb contraction did not differ in the different nematode life stages and sexes, or at different feeding sites on the roots.     

Bemerkenswerte endogene Farbveränderung der Eischale von Chioninia delalandii (Duméril & Bibron, 1839) (Reptilia: Sauria: Scincidae)

The paper describes an unusual endogenous eggshell colouration observed in an egg of the Cap Verde skink Chioninia delalandii.A female specimen, kept in a terrarium, laid three eggs. Two of them were considered as fertilized (oval germ-disk, weakly pink). They were embedded 1 cm deep in a layer of moistened clay granules (substrate/water 2:1) and kept under different temperatures (egg 1 “cool”, 26-27 °C; egg 2 “warm”, 29-30 °C). There was a normal embryonic development in both eggs from their volume-enlargement and characteristic allometric growth (egg wide > egg length). The young hatch after 51 and 56 days.A change in eggshell colour, however, occurred in the “warm” kept egg during the last third of its incubation period. It started with a small spot (2-3 mm) in the outer area of the animal egg pole and spread into a dark-violet colouration over the whole eggshell within 15 days. After hatching of the young the shells of both eggs were examined. In the non-coloured egg there was no great difference in colour between the inner and outer egg layer, while in the coloured egg there was a distinct difference between the inner part, which was dark violet-gray, and the pale gray calcareous deck-layer. From the macroscopic view along the edge of the eggshell it was not identifiable, if the colour pigment was infiltrated into protein fibrils of the condensed surface layer.A possible explanation for the eggshell colouration could be an unusual embryonic pigmentation. This assumption is based on the first appearance of a restricted, point-like coloured area and its further regular extension. It might be that dark pigments (melanophores?) reached the eggshell (membrana testacea) and infiltrated the border-area to the condensed surface layer.     

Influence of Environmental Factors on the Hatch and Survival of Meloidogyne incognita

The influence of soil temperature and moisture on Meloidogyne incognita (Kofoid and White) Chitwood was examined in relation to hatching and survival of second-stage juveniles (J2). Nematodes were cultured on cotton (Gossypium hirsutum L. cv. Acala SJ2) under field conditions to provide populations similar to those found in the field in late autumn. Egg masses were placed in a temperature range (9-12 C and 21 C), and hatch was measured over a period equivalent to 20 degree days > 10 C (DD10). Hatch occurred below the reported 18 C activity threshold, was restricted below 12 C, and was inhibited below 10 C. Soil moisture influence on hatch was measured by placing egg masses in Hesperia sandy loam and subjecting them to suction pressures ranging from -1.1 bars to -4 .5 bars. Suction potentials of less than -2 bars reduced hatch and less than -3 bars inhibited hatch. J2 were placed in sandy loam soil with soil moisture near field capacity, and their motility was measured over a period of 500 DD10. In the absence of a host, more than 90% of J2 became nonmotile over this period.     

Development of Meloidogyne chitwoodi on Wheat

Postinfection development of Meloidogyne chitwoodi from second-stage juveniles (J2) to mature females and egg deposition on ''Nugaines'' winter wheat required 105, 51, 36, and 21 days at 10, 15, 20, and 25 C. At 25 C, the J2 induced cavities and hyperplasia in the cortex and apical meristem of root tips with hypertrophy of cortical and apical meristem cell nuclei, 2 and 5 days after inoculation. Giant cells induced by late J2 were observed in the stele 10 days after inoculation. Clusters of egg-laying females were common on wheat root galls 25 days after inoculation. Juveniles penetrated wheat roots at 4 C and above, but not at 2 C, when inoculum was obtained from cultures grown at 20 C, but no penetration occurred at 4 C when inoculum was stored for 12 hours at 4 C before inoculation. In northern Utah, J2 penetrated Nugaines wheat roots in the field in mid-May, about 5 months after seedling emergence. M. chitwoodi eggs were first observed on wheat roots in mid-July when plants were in blossom. Only 40% of overwintered M. chitwoodi eggs hatched at 25 C.