A morphological comparison of seven hypotriploid populations of Meloidogyne arenaria was made to clarify their taxonomic status, using light and scanning electron microscopy. All populations differed from each other and from the typical triploid M. arenaria by certain features. Differences were not regarded as sufficient to justify recognition of the variants as distinct species. Morphological divergence of populations from the typical M. arenaria was gradual. The most useful characters were stylet and head morphology of males and stylet morphology of females. Perineal patterns and cephalic, stylet, and tail morphologies of second-stage juveniles were of little taxonomic value. Host races 1 and 2 could not be distinguished morphologically. Populations E445 and E551 with the atypical esterase phenotypes M3-F1 and S1-M1, respectively, were morphologically more similar to the typical M. arenaria than populations E255 and E467, which have the most common A2 esterase phenotype of M. arenaria.
biochemistry; cytology; host race; hypotriploid; light microscopy; Meloidogyne arenaria; morphology; nematode; root-knot nematode; scanning electron microscopy; taxonomy; triploid; variation
A morphometric comparison of seven hypotriploid populations with five pooled triploid populations of Meloidogyne arenaria was made using standard descriptive statistics, stepwise discriminant analysis (SDA), and cluster analysis. Six morphometric characters of females, 14 of second-stage juveniles (J2), and 18 of males were measured for each population. Useful differentiating characters included: body length in J2; stylet length in females and J2; stylet-knob dimensions in females and males; dorsal esophageal gland orifice distance in all three life stages; esophagus-length ratio in males and J2; excretory pore position in J2; and spicule length in males. SDA and cluster analysis showed that in each life stage, the hypotriploid populations were set off to varying degrees from the triploid populations. In addition, the relationships among populations differed when different life stages were compared. No consistent relationships could be detected among the populations, when morphometric data of the present study and morphological findings of the same populations in a parallel study were considered. Morphometric differences were not sufficient to propose any of the hypotriploid populations as new species.
cluster analysis; cytological race; enzyme phenotype; host race; hypotriploid; light microscopy; Meloidogyne arenaria; morphology; morphometrics; nematode; root-knot nematode; stepwise discriminant analysis (SDA); taxonomy; triploid; variation
Meloidogyne morocciensis n. sp. is described from specimens parasitic on peach rootstock from Morocco. This species exhibits a combination of morphological characters similar to M. arenaria, M. incognita, and M. javanica. The perineal pattern of females is oval to squarish with a moderately high to high dorsal arch, and widely spaced, smooth striae; lateral lines are absent. The stylet, 16.5 μm long, has transversely ovoid, set-off knobs. Males have a set-off, annulated head region. The large, rounded labial disc is distinctly demarcated from the crescent-shaped medial lips; lateral lips are absent. The robust stylet, 24.6 μm long, has large, rounded knobs that taper slightly posteriorly. Mean second-stage juvenile (J2) length is 401 μm. The set-offhead region has incomplete annulations; the lip structures are dumbbell shaped. The stylet, 12.3 μm long, has rounded knobs that slope posteriorly. The J2 tail, 52.6 μm long, has irregularly sized annules in the posterior region and ends in a bluntly rounded tip. Tomato, tobacco, pepper, and watermelon are good hosts; cotton and peanut are not hosts. Meloidogyne morocciensis n. sp. reproduces by mitotic parthenogenesis and has a somatic chromosome number of 47-49. Its esterase phenotype is identical with the three-banded phenotype (A3) of M. arenaria.
host range; light microscopy; Meloidogyne morocciensis n. sp.; Morocco; morphology; morphometrics; new species; peach rootstock; Prunus persica; root-knot nematode; scanning electron microscopy; taxonomy
A morphological and morphometric comparison using light microscopy and scanning electron microscopy was made of six populations of Meloidogyne javanica belonging to three host races (infective on pepper, peanut, or noninfective on both). The variability of certain morphological characters was studied within these populations, and the reliability of these taxonomic traits was evaluated for usefulness in species identification. The most useful diagnostic characters of M. javanica were head and stylet morphology of males and stylet morphology and perineal patterns of females. Males have an offset head region, usually lacking annulations, and a distinct, narrow head cap with slightly raised labial disc. The stylet has a cone markedly wider than the shaft at the junction and large, transversely ovoid knobs that are offset from the shaft. Females have a robust stylet with a dorsally curved cone and large, transversely ovoid knobs. Perineal patterns are oval to squarish in shape, usually with coarse, broken striae and with conspicuous lateral lines. The host races could not be differentiated on a morphological basis.
Arachis hypogaea; Capsicum frutescens; host race; light microscopy (LM); Meloidogyne javanica; morphology; morphometrics; peanut; pepper; root-knot nematode; scanning electron microscopy (SEM)
Meloidogyne mayaguensis n. sp. is described and illustrated from specimens obtained from galled roots of eggplant, Solanum melongena L., from Puerto Rico. The perineal pattern of females is round to ovoid with fine, widely spaced striae. It has occasional breaks of striation laterally and a circular tail tip area lacking striae. The stylet, 15.8 μm long, has reniform knobs that merge gradually with the stylet shaft. Males have a high, rectangular, smooth head region, not set off from the body contour. The labial disc is continuous with the medial lips which do not slope posteriorly. The styler, 22.9 μm long, has large rounded backward sloping knobs; the shaft is of uneven diameter. Mean body length of second-stage juveniles is 453.6 μm. The truncate head region is not annulated, and the rounded, slightly raised labial disc and the crescentic medial lips form dumbbell-shaped lip structures. The stylet, 11.6 μm long, has rounded, posteriorly sloping knobs. The slender tail, 54.4 μm long, gradually tapers to a bluntly pointed tip. Tomato, tobacco, pepper, and watermelon are good hosts; cotton and peanut are not hosts. M. mayaguensis n. sp. reproduces by mitotic parthenogenesis and has a somatic chromosome number of 2n = 44-45. The enzyme patterns are unique among Meloidogyne species.
taxonomy; morphology; new species; host range; scanning electron microscopy; Solanum melongena L.; eggplant; Meloidogyne mayaguensis n. sp.; root-knot nematode; Puerto Rico
Spicules of 9 Meloidogyne, 2 Heterodera, 3 Globodera, and 12 other plant-parasitic, insect-parasitic, and free-living nematodes were excised and examined using scanning electron microscopy (SEM). Gubernacula of some of the species were also excised, and their structure was determined. The two spicules of all species examined were symmetrically identical in morphology. The spicule typically consisted of three parts: head, shaft, and blade with dorsal and ventral vela. The spicular nerve entered through the cytoplasmic core opening on the lateral outer surface of the spicule head and generally communicated with the exterior through one or two pores at the spicule tip. Spicules of Xiphinema sp. and Aporcelaimellus sp. were not composed of three typical parts, were less sclerotized, and lacked a cytoplasmic core opening and distal pores. Spicules of Aphelenchoides spp. had heads expanded into apex and rostrum and had very arcuate blades with thick dorsal and ventral edges (limbs). Gubernaculum shapes were stable within a species, but differed among species examined. The accessory structures of Hoplolaimus galeatus consisted of a tongue-shaped gubernaculum with two titillae at its distal end and a plate-like capitulum terminating distally in two flat, wing-like structures. A comparison of spicules of several species of Meloidogyne by SEM and light microscopy revealed no striking morphological differences.
spicule; gubernaculum; capitulum; titillae; scanning electron microscopy; light microscopy; Aphelenchoides; Aporcelaimellus; Belonolaimus; Dolichodorus; Globodera; Heterorhabditis; Heterodera; Hoplolaimus; Meloidogyne; Mesorhabditis; Panagrellus; Tylenchorhynchus; Xiphinema
Meloidogyne hispanica n. sp. is described and illustrated from specimens obtained from peach rootstock, Prunus persica silvestris Batsch, from the Seville district of Spain. The perineal pattern of the female is oval shaped to rectangular with low dorsal arch and often widely spaced lateral lines with fringe-like striae. The stylet, 14.1 μm long, has broad, distinctly set off knobs. Males have a high, rounded head cap that slopes posteriorly. Labial disc and medial lips are fused to form elongate lip structures. The robust styler, 23.5 μm long, has large, rounded knobs that are slightly set off from the shaft. Mean second-stage juveniles length is 392.6 μm. The truncate head region is generally not annulated. The distinctly rounded and raised labial disc and the crescent-shaped medial lips form dumbbell-shaped lip structures. The stylet, 11.1 μm long, has rounded, posteriorly sloping knobs. The slender tail, 46.4 μm long, has large irregular-sized annules in the posterior region and ends in a bluntly rounded tip. Tomato was a good host; tobacco, pepper, and watermelon were poor hosts; cotton and peanut were nonhosts. Meloidogyne hispanica n. sp. reproduces by mitotic parthenogenesis and has a somatic chromosome number of 2n = 33-36. The esterase pattern is unique among Meloidogyne species.
taxonomy; morphology; new Meloidogyne species; host range; scanning electron microscopy; Prunus persica silvestris
Seven populations, representing cytological race A (triploid, 3n = 51-56) and the two host races (infective and noninfective on peanut) of Meloidogyne arenaria were studied with light microscopy (LM) and scanning electron microscopy (SEM). Characteristics of root-knot nematodes, recently recommended as useful taxonomic traits, were reexamined among these populations, and their variability both within and between populations was ascertained. We found that stylet morphology of females and head and stylet morphologies of males and second-stage juveniles were the most reliable characters for identification. The two host races of M. arenaria could not be distinguished morphologically. Two of the populations could be separated consistently from the remainder but were not sufficiently divergent to be considered new species. These two variant populations were similar; neither produced males in culture, and they differed from the typical populations in female perineal patterns (LM) as well as in cephalic structure (SEM) and tail shape (LM) of second-stage juveniles. In morphometric studies, most characters of the variant populations differed significantly from those of the typical M. arenaria.
root-knot nematodes; cytological races; host races; morphometrics; taxonomy; scanning electron microscopy; light microscopy
Meloidogyne microcephala n. sp. is described and illustrated from specimens obtained from tobacco (Nicotiana tabacum L.) in Thailand. The female perineal pattern usually has a low dorsal arch, coarse striae, and a series of small cuticular flaps around the tail terminus. The stylet of the female is 14.4 μm long, with large, square to rectangular stylet knobs, The distinctive male head region is narrow, small, and truncate with a low, flattened head cap. The stylet length is 20.6 μm, and the knobs are small, angular, and set off from the shaft. Mean length of second-stage juveniles is 457.5 μm, and stylet length is 9.3 μm. The tail tip in the juveniles is set off from the rest of the tail as a small finger-like projection. M. microcephala reproduces by mitotic parthenogenesis, and has a chromosome number of 2n = 36.
taxonomy; morphology; new Meloidogyne species; host range; scanning electron microscopy
Meloidogyne platani n. sp. is described and illustrated from specimens obtained from roots of American sycamore, Platanus occidentalis, in Virginia. This new species shows certain similarities with M. arenaria but differs from it by a number of distinctive characters. The perineal pattern of females is rounded with fine, wavy to zig-zag striae and raised, convoluted striae in the inner lateral line regions. The stylet of females is 16.5 μm long with large, rounded stylet knobs set off from the shaft. Males have a low head cap and smooth head region. The styler length is 22.0 μm, and the stylet knobs are rounded and set off from the shaft. Mean second-stage juvenile length is 443.0 μm, and stylet length is 12.2 μm. The head region of juveniles is not annulated, and the tail has a definite terminus. This nematode causes severe galling and reproduces well on sycamore. Other good hosts include white ash and tobacco cv. NC 95. M. platani n. sp. reproduces by mitotic parthenogenesis and has a somatic chromosome number of approximately 45 (2n).
taxonomy; morphology; new Meloidogyne species; host range; scanning electron microscopy
Head shape and stylet morphology of males of 90 populations of M. arenaria, M. hapla, M. incognita, and M. javanica from geographic regions of the world were compared by light microscopy (LM). In addition, stylets of one population each of M. arenaria, M. incognita, and M. javanica and three different chromosomal forms of M. hapla race A and two of race B were excised and examined with a scanning electron microscope (SEM). Differences among species occurred in both head and stylet morphology. Head morphology differed in size and shape of the head cap, annulation of the head region, and width of the head region relative to the first body annule. Differences in stylets occurred in size and shape of the cone, shaft, and knobs. All populations of M. hapla, except one, had similar head morphology, but stylet morphology was different between cytological races A and B. Populations of M. javanica varied with respect to the presence of head annulations. Head shape and stylet morphology of males are recommended as additional characters useful in the identification of root-knot nematodes.
Meloidogyne arenaria; M. hapla; M. incognita; M. javanica; root-knot nematodes; cytological races; intersexes; scanning electron microscopy; taxonomy
The external morphology of female heads of three populations of each of two cytological races of Meloidogyne hapla (race A-meiotic, race B-mitotic) and single populations of M. arenaria, M. incognita, and M. javanica was compared by light (LM) and scanning electron microscopy (SEM). Perineal patterns of all nine populations were observed with a LM and then examined with a SEM. In addition, female stylets of each population were excised, viewed with a SEM, and compared with observations made with a LM. Head morphology of the females, including shape of medial and lateral lips, expression of sensilla, and head annulation, was distinct for each species, each race of M. hapla, and each population of M. hapla race A. The morphology of a given perineal pattern appeared similar with the SEM and the LM. The SEM emphasized surface details, whereas the LM revealed subcuticular structure as well. Stylet morphology was unique for each species but similar in all populations of M. hapla. There were differences between species in the shape of the cone, shaft, and knobs and in the distance of the dorsal esophageal gland orifice from the stylet knob base. Several of the morphological characters first detected in the SEM were seen subsequently with the LM and are helpful in species identification.
cytological races; root-knot nematodes; Meloidogyne hapla; M. arenaria; M. incognita; M. javanica; scanning electron microscopy
Males of five populations of Meloidogyne hapla were compared by scanning electron microscopy (SEM). Three populations of race A had haploid chromosome numbers of 15, 16, and 17 and reproduced by facultative parthenogenesis. Race B consisted of two mitotically parthenogenetic populations with somatic chromosome numbers of 45 and 48. Males of one population each of M. arenaria, M. incognita, and M. javanica were also examined to delineate species differences. The populations of M. arenaria, M. incognita, and M. javanica had 54, 41-43, and 44 chromosomes, respectively, and reproduction was by mitotic parthenogenesis. Observations were made on head structures, lateral field, excretory pore, and tail. The expression of labial and cephalic sensilla, shape and proportion of labial disc and lips, and markings on the head region were distinctly different for each species. The head morphology of the two cytological races of M. hapla was dissimilar. Populations of race A were different from each other and showed intrapopulation variation. Populations of race B were morphologically similar and stable in head morphology. The structure of the lateral field, excretory pore, and tail was of little value in distinguishing species or populations because of inter- and intrapopulation variation. The results are discussed in relation to earlier SEM observations of second-stage juveniles of the same populations.
cytological races; root-knot nematodes; Meloidogyne hapla; M. arenaria; M. incognita; M. javanica
External morphology of second-stage juveniles of six populations of Meloidogyne hapla, hclonging to two cytological races (A and B), and one population each of M. arenaria, M. incognita, and M. javanica was compared by scanning electron microscopy (SEM). Race A of M. hapla included three facultatively parthenogenetic populations with haploid chromosome numbers of 15. 16, and 17; race B consisted of three mitotically parthenogenetic populations with somalic chromosome numhers of 45, 45, and 48. The mitotically parthenogenetic populations of M. arenaria, M. incognita, and M. javanica had 54, 41-43, and 44 chromosomes, respectively. Observations were made on head structures, lateral field, excretory pore, anal opening, and tail. Head morphology, including shape and proportion of labial disc and lips, expression of labial and cephalic sensilla, and markings on head region, was distinctly different for each species. M. hapla populations of race A were distinct from each other but showed much intrapopulatiou variation in head morphology. Populations of race B were different from those of race A and were very stable and quite similar in head morphology. Considerable inter- and intrapopulatiou variation made the structure of the lateral field, excretory pore, anal opening, and tail of little value in distinguishing species or populations. The results are discussed in relation to earlier SEM observations on the genus Helerodera.
M. arenaria; M. incognita; M. javanica
Anguina plantaginis n. sp., parasitic on Plantago aristata, is described and illustrated. This new species is most closely related to A. klebahni, A. millefolii, A. mobilis, and A. moxae and is characterized as follows: moderate body size for the genus; absence of esophageal "storage organ"; postvulval uterine sac extending about 45% of vulva-anus distance; crustaformeria of young females longer than spermatotheca or uterus proper; spicules with 2 sclerotized thickenings; long, conical tail in both sexes, narrowing at about 1/6 of its length to peg-like tip; parasitic only on P. aristata. Two nematode generations that are morphologically similar but differ in body size develop in one plant gall. The postembryogenesis, studied with respect to morphological development of the larval stages, is similar to that of Ditylenchus. The sexes can be differentiated from the second molt on. The infective larva is the third stage, which is morphologically distinct from the regularly developing third-stage larva.
Chromonema heliothidis n. gen., n. sp. is described as an entomophilic nematode of Heliothis zea and other lepidopterous larvae; the diagnosis of the family Steinernermatidae is emended. In most morphological and host-parasite features, this nematode is similar to neoaplectanid nematodes; however, males are different in having a peloderan bursa and straight to slightly curved spicules. Although the infective-stage juveniles only give rise to hermaphrodites, the nematode is heterogonic, with both males and females being produced in the second generation. Parasitized hosts are brick-red in color and luminescent in the dark because of the association of a chromogenic, bioluminescent bacterium with the nematode. The nematode is capable of parasitizing a wide range of insects with lepidopterous larvae being most susceptible.
entomophilic nematode; morphology; taxonomy
The fine structure of the stylet, "guiding apparatus," anti protractor muscles of males of Meloidogyne incognita and Heterodera glycines is ehtcittated and compared. In both nematodes, the stylet cone is of greater electron density than the shaft. The cone is heterogeneous; shaft material extends into it for most of its length, whereas the shaft proper and knob regions are relatively homogeneous. The stylet lumnen is round throughout its length in H. glycines, but in M. incognita changes from round, posteriorly, to irregular, triradiate, and oblong near the styler tip. The various layers of the lining of the stylet shaft are continuous with those of the cuticular lining of the esophageal lumen. Similarly, cuticular layers of the stomatal lining and vestibule extension are continuous with the body wall cuticle. The stylet "guiding apparatus" is formed by linings of the stomatal opening, vestibule, and vestibule extension, together with transversely folded membranes, which extend further posteriorly and attach near the junction of shaft and cone. Noncontractile regions of the three stylet protractor muscles originate in the esophagus. Contractile portions extend anteriorly from the stylet knobs and branch into a total of 10 elements that attach near the basal ring of the cephalic framework and the vestibule extension. A second, noncontractile region is present at the anteriormost part of the protractor muscles in H. glycines.
Cyst nematode; root-knot nematode; stylet; stylet "guiding apparatus"; stylet protractor muscles