The specific gravity of old Caenorhabditis briggsae was shown to be greater than that of young nematodes. The possible explanations for this age-associated change are discussed.
aging; specific gravity; methods
'Vernal' alfalfa was grown for 30 weeks in nematode-free soil and in soil infested with Pratylenchus penetrans. Charlottetown fine sandy loam soil was used at its pH of 4.4 and at adjusted reactions of 5.2, 6.4 and 7.3. Nematode reproduction was significantly greater at pit 5.2 and 6.4 and was not related to alfalfa root production over the full pH range studied. A significant nematode infestation X soil pit interaction on forage yield was recorded. Nematode infestation significantly decreased forage yields at ptt 5.2 and 6.4 but not at pH 4.4 and 7.3.
root lesion nematode; interaction; Medicago sativa; soil reaction
Both Neodiplogaster pinicola and Panagrellus redivivoides reproduce amphimictically, with XO type of sex determination. In N. pinicola, primary spermatocytes have six bivalent chromosomes and one univalent; after two meiotic divisions, sperm are produced with either six or seven chromosomes. In primary oocytes, with seven bivalents, meiosis is initiated by entrance of a sperm. After two meiotic divisions, three polar nuclei are produced, and egg and sperm pronuclei fuse. Cleavage begins after the egg is laid. Males have a 2n number of 13 chromosomes; females, 14. In P. redivivoides, primary spermatocytes have four bivalents and one univalent. After two meiotic divisions, spermatids are produced with either four or five well separated chromosomes. In primary oocytes, the first maturation division is initiated after penetration of a sperm; after two meiotic divisions, each egg has five chromosomes. Cleavage begins immediately after fusion of egg and sperm pronuclei, and embryonic development and hatching occur within the uterus. Males have a 2n chromosome number of 9; females, 10.
Tylenchorhynchus dubius was observed to feed on 'Toronto' creeping bentgrass and 'Merion' Kentucky bluegrass, and was a key participant in reducing the vegetative growth of both grass species. The severity of foliar and root macrosymptoms incited by T. dubius to 'Toronto' bentgrass was greater on plants grown at 16 C than on plants maintained at 21, 27 and 32 C. These parasitized plants exhibited a suppression of secondary stolon formation, shortened internodes and premature inflorescence initiation. Initial inoculum densities of 500 and 1000 nematodes/test pot produced similar pathogenic effects on the host. Feeding was primarily on root hairs and epidermal cells immediately behind the meristematic region. No necrotic lesions or other diagnostic symptoms were visible at the feeding sites. Nematodes were not observed inside the roots.
stunt nematode; temperature; feeding
The insect-parasitic female of Sphaerularia bombi everts its uterus and associated reproductive structures into the body cavity of its bumblebee host. This uterine sac then takes over the normal functions of the parasite and leads an independent existence. An examination of this sac shows that the surface of the uterine cells are differentiated into a network of saccular indentations separating off fine cytoplasmic extensions. The folding of adjacent cytoplasmic extensions around portions of the host's hemolymph results in the formation of pinocytotic vacuoles. Intracellular vacuoles are also formed at the base of the saccular indentations. It appears that the first stage of intracellular digestion in S. bombi initially occurs by pinocytosis in the outer surface of the uterine cells. The inner and outer surfaces of the ovary and oviduct are modified into lobelike projections to increase the absorptive surface area, and electron-dense droplets originating in this tissue were also observed in the developing eggs. The hypothesis is presented that soluble nutrients are passed into the ovary-oviduct tissue where, after being reconstituted into droplets, they enter the developing eggs.
nourishment; parasite; bumblebee
Heterodera schachtii developed to maturity and reproduced on the lateral roots of defoliated sugarbeet which were buried to a depth of 2.5 cm in sterilized soil and inoculated with cysts. Nematodes did not develop on detached lateral roots or on roots of young defoliated beets which did not have a large tap root. The storage roots of large rooted plants were sliced, placed in small jars, inoculated with cysts, covered with moist granulated agar or soil and incubated at 24°C 12-62 days. The sugarbeet nematode developed in root slices of sugarbeet, red table beet, icicle and globe radish, turnip and rutabaga. Only a few males developed on slices of potato tubers. Neither males nor females developed on root slices of carrot, salsify or parsnip. H. schachtii also developed on the cut surfaces of growing sugarbeet and radish.
sugarbeet nematode; culture; root slices
The relative DNA content of hypodermal nuclei of preparasitic, 2nd-stage larvae was determined cytophotometrically in 19 populations belonging to 13 species of Meloidogyne, Heterodera and Meloidodera. In Meloidogyne hapla, M. arenaria, M. incognita and M. javanica, total DNA content per nucleus is proportional to their chromosome number, indicating that chromosomal forms with high chromosome numbers are truly polyploid. M. graminicola, M. grarninis and M. ottersoni have a DNA content per chromosome significantly lower than that of the other Meloidogyne species. Within Heterodera, species with high chromosome numbers have proportionally higher DNA content, indicating again polyploidy. DNA content per chromosome in Meloidogyne is one third that of Heterodera and one haft that of Meloidodera floridensis. The karyotypic relationships of the three genera are still not clearly understood.
aneuploidy; parthenogenesis; nematodes
A procedure for extracting eggs of Meloidogyne spp. from soil was developed by modifying and combining certain existing techniques. Egg masses were elutriated from the soft, gelatinous matrices of the egg masses were dissolved, and the dispersed eggs were stained to facilitate counting. Data on egg population densities thus obtained facilitate the study of population dynamics of Meloidogyne spp. and the analysis of root-knot epidemics.
egg extraction; population dynamics; root knot
Invasion of 2-day-old seedlings of 'Buffalo' alfalfa and 'Kenland' red clover by larvae of M. incognita and adults of P. penetrans, during 1-3 day periods of incubation at 24 C, was investigated in 50-mm petri dishes on 1% agar. Penetration by both nematodes increased arithmetically with increased numbers in inocula. P. penetrans invaded alfalfa more readily than red cover, but M. incognita invaded red clover more readily than alfalfa. Both nematodes inhibited root-elongation of alfalfa more than that of red clover. In combinations of 10 and 50 of both nematodes, invasion of both plants by both nematodes was the same as for each nematode alone. Penetration by M. incognita into alfalfa, but not into red clover, was significantly reduced when combinations of 50 M. incognita and 200 P. penetrans were inoculated simultaneously. In the presence of large numbers of entrant P. penetrans in both plants, penetration by M. incognita was highly significantly reduced. Penetration by P. penetrans was unaffected in the reciprocal situations.
Meloidogyne hapla egg-laying was unaffected by a 3-day immersion in 40 ppm concentrations of 6-azauracil, 5-bromodeoxyuridine, or streptomycin sulfate in physiological saline. Comparable exposure to 1-20 ppm cycloheximide irreversibly inhibited egg-laying, but with exposures of 1, 3, or 9 hr, the effect was partly reversible. Of the few eggs laid after the nematodes were transferred to physiological saline, many were abnormally developed. Most of the unlaid eggs extracted from the uteri of cycloheximide-treated nematodes were nonviable. Oogenesis was irreversibly inhibited by the treatment. Cycloheximide stimulated embryonic development and some early hatching, but later hatching was inhibited.
Cycloheximide; Meloidogyne hapla; oogenesis; embryogenesis; egg-laying
Soybean-cyst nematode larvae survived in water up to 630 days, depending on incubation temperature. Most larvae were killed when ice crystals formed in water, and all died after 1 day at 40 C. At temperatures of 0, 4, 8 and 12 C, larvae survived for the duration of the experiments (630 days). From 16 to 36 C, survival was inversely correlated with temperature. In naturally infested soil, nematode survival was similax but more extended and related to moisture level. Larvae survived 7-19 months in flooded soil, 29-38 months in dry soil, and for 90 months in soil maintained near its field capacity.
The biology and morphology of Chromadorina bioculata is presented. Tile nematode was abundant on the alga Cladophora of one lily pond, but absent from similar habitats in nearby ponds. The setae, caudal glands, high Iocomotory rates and positive photo response have been interpreted in relation to maintenance on, amongst and between algal filaments, suspended over large volumes of water.
When placed in tap or distilled water, C. bioculata became inactive and died. The influence of pH buffers, tonicity, temperature and starvation on activity were investigated. C. bioculata survived longer in artificial sea water diluted 10 or 100 times with distilled water, or in NaCl isotonic with sea water diluted 100 or 1000 times, than in tap or distilled water. No evidence of wide osmotic toleration or osmoregulation was observed. Activity was influenced by temperature, with peak activities occurring at the seasonal normal temperature. These findings are discussed in terms of general hematology and habitat selection.
osmotic tolerance; activity; behavior; distribution; morphology; setae; caudal glands
Biochemical changes occurred in roots of bur marigold and grapevine infected with Longidorus africanus. Phenols of infected root tips differed quantitatively from those of healthy root tips (optical density of 0.68 and 0.32, respectively). Column chromatography of the phenol extracts resulted in more fractions in the infected than in the healthy root extract. Of the enzymes involved in phenol metabolism, three were tested. No polyphenol oxidase activity was detected and no difference in catalase activity was found between healthy and infected roots. Peroxidase activity, however, was much higher in infected roots. The extra peroxidase was associated mainly with the cortical cells of the infected root tips.
Galled roots contained twice the amount of simple sugars and inulin as did the healthy roots. A cytokinin-active fraction was found only in the noninfected roots.
The effects of four soil types, soil porosity, particle size, and organic matter were tested on survival and migration of Xiphinema americanum. Survival and migration were significantly greater in silt loam than in clay loam and silty clay soils. Nematode numbers were significantly greater in softs planted with soybeans than in fallow softs. Nematode survival was greatest at the higher of two pore space levels in four softs. Migration of X. americanum through soft particle size fractions of 75-150, 150-250, 250-500, 500-700, and 700-1,000 μ was significantly greater in the middle three fractions, with the least occurring in the smallest fraction. Additions of muck to silt loam and loamy sand soils resulted in reductions in survival and migration of the nematode. The fulvic acid fraction of muck, extracted with sodium hydroxide, had a deleterious effect on nematode activity. I conclude that soils with small amounts of air-filled pore space, extremes in pore size, or high organic matter content are deleterious to the migration and survival of X. americanum, and that a naturally occurring toxin affecting this species may be present in native soft organic matter.
Associations among nematode communities were studied in 18 Indiana mixed-hardwood stands of varying composition, soils, physiography, and past management practices. All sites were sampled in April, July, and October of 1968 and 1969. A total of 175 species representing eight orders were found, with 18 species occurring in all 18 sites, and approximately half the total species occurring in more than 50% of the sites. Taxonomic similarity, based on nematode species composition, was determined for the woodlots by means of a resemblance equation. Woodlots containing similar nematode species also showed similarities in dominant tree species and in soil types. Sites that had undergone major disturbances were the most dissimilar.
Indiana hardwood stands; resemblance equation
The optimum temperature for embryogenesis in Meloidogyne javanica lies between 25 and 30 C. Embryogenesis is slightly more rapid at 30 C (9-10 days), but more eggs complete development at 25 C (11-13 days). At temperatures of 25, 27.5, and 30 C, embryogenesis is about twice as rapid as at 20 C (23-25 days), and about four times as rapid as at 15 C (46-48 days). Time-lapse studies showed that the thermal optimum is similar throughout the different stages of embryonic development.
embryo; larva; ciné time-lapse
In Florida, Tylenchulus semipenetrans on citrus has two high and two low population levels each year. High levels occur in April-May and November-December, and low levels, in February-March and August-September. Population increases occur about 4-5 weeks after the spring and fall flush of root growth. Populations of Pratylenchus coffeae on citrus varied widely, and were not related to season. Populations of P. brachyurus showed seasonal variation with a high in June-July and a low in March-May. Males of T. semipenetrans and P. coffeae were found throughout the year, whereas males of P. brachyurus were rare and were found only during November and December.
The fine structure of the gelatinous matrix of Meloidogyne javanica in both moist and dry states was studied by means of chemical fixation and thin sectioning techniques and the freeze-etch method. The matrix consists of an irregular meshwork when hydrated and a uniform granular mass of much greater density when dehydrated. The spaces in the hydrated meshwork are presumed to contain water. The change from a hydrated to a dehydrated state is accompanied by an overall shrinkage and hardening of the egg mass with a change in color from yellow to reddish-orange. The possible functions of this unusual glycoprotein are discussed.
freeze-etch; shrinkage; glycoprotein; electron microscope
The feeding apparatus of Pratylenchus penetrans (Cobb) Chitwood and Oteifa was studied by means of the electron microscope. The stomatostylet is composed of tooth, shaft, and basal knobs. The tooth and shaft are closely interlocked. The tooth forms the outer covering and the inner lining of the anterior half of the stylet, whereas the shaft extends from the basal knobs to the level of the stylet opening. It is proposed that the shaft and knobs are living tissues, whereas the tooth is the product of sclerotized secretion. Stylet protractor muscles are attached to the basal knobs, and they become forked and split into 10 bundles as they extend anteriorly. Two types of secretory granules are observed in the dorsal esophageal gland, and they are different from those produced in the subventraI glands.
stomatostylet; protractor muscle; esophageal gland
The pathogenicity and interactions of Meloidogyne naasi, Pratylenchus penetrans, and Tylenchorhynchus agri on 'Toronto C-15' creeping bentgrass, Agrostis palustris, was studied in a long-term greenhouse experiment. Based on dry weights of roots and clippings, M. naasi alone and in all combinations with P. penetrans and T. agri was highly pathogenic to creeping bentgrass. P. penetrans and T. agri alone and in combination inhibited root growth but adversely affected top growth only when the two were co-inoculated. In combination, the effects of each species on top growth were additive, with M. naasi the dominant pathogen. Creeping bentgrass was an excellent host for M. naasi and T. agri, but a poor host for P. penetrans. T. agri inhibited population increase of M. naasi, indicating nematode-nematode competition, but neither T. agr/ nor P. penetrans was affected by any of the combinations.
Agrostis palustris; root-knot nematode; lesion nematode; stunt nematode; pathogenicity; population dynamics; nematode complexes
Soil samples were collected from three native Iowa prairies and analyzed for plant paiasitic nematodes and selected soil properties. Sites or nematodes were clustered with similarities related to habitat by a cluster analysis of site by nematode species and of nematodes by site. Some nematodes occurred in a wide range of prairie habitats, whereas others were more restricted. For example, greater numbers of Xiphinema americanum were in the low, well-drained sites than in the low wet sites or upland dry sites. Wet sites contained fewer nematodes than well-drained sites. Well-drained sites contained mainly Tylenchorhynchus maximus, Helicotylenchus pseudorobustus, and X. americanum. Wetter sites contained almost exclusively X. chambersi, H. hydrophilus, Telylenchus joctus, and an undescribed species of Tylenchorhynchus.
habitat relationships; H. leiocephalus; Aorolaimus torpidus; T. nudus
Contortylenchus barberus is synonymized with C. brevicomi because their original separation was based on minor morphometric variations that are considered here to be intraspecific rather than interspeciflc. The ranges of body length and body width in measured specimens of C. brevicomi encompass those of the original description of C. brevicomi and C. barberus. The presence or absence of the caudal mucro is considered not a valid criterion for species differentiation. Several of the morphometric details of the two species overlap and thus are not considered suitable for species differentiation. Such variation may be due to stresses of the host-parasite relationship. The respective hosts of the two nematodes, Dendroctonus brevicomis and D. barberi, have been synonymized into the former species. The description of the larval stages of C. brevicomi is presented.