Three stunt nematode species, Tylenchorhynchus leviterminalis, T. dubius and T. claytoni were characterized with segments of small subunit 18S and large subunit 28S rDNA sequence and placed in molecular phylogenetic context with other polyphyletic taxa of Telotylenchidae. Based upon comparably sized phylogenetic breadth of outgroups and ingroups, the 28S rDNA contained three times the number of phylogenetically informative alignment characters relative to the alignment total compared to the larger 18S dataset even though there were fewer than half the number of taxa represented. Tail shapes and hyaline termini were characterized for taxa within these subfamily trees, and variability discussed for some related species. In 18S trees, similar terminal tail thickness was found in a well-supported clade of three Tylenchorhynchus: broad-tailed T. leviterminalis branched outside relatively narrow-tailed T. claytoni and T. nudus. Terminal tail thickness within Merliniinae, Telotylenchinae and related taxa showed a mosaic distribution. Thick-tailed Trophurus, Macrotrophurus and putative Paratrophurus did not group together in the 18S tree. Extremely thickened tail termini arose at least once in Amplimerlinius and Pratylenchoides among ten species of Merliniinae plus three Pratylenchoides, and three times within twelve taxa of Telotylenchinae and Trophurinae. Conflicting generic and family nomenclature based on characters such as pharyngeal overlap are discussed in light of current molecular phylogeny. Contrary to some expectations from current taxonomy, Telotylenchus and Tylenchorhynchus cf. robustus did not cluster with three Tylenchorhynchus spp. Two putative species of Neodolichorhynchus failed to group together, and two populations of Scutylenchus quadrifer demonstrated as much or greater genetic distance between them than among three related species of Merlinius.
character analysis; evolutionary convergence; morphology; nomenclature; phylogeny; stunt nematode; systematics; tail; taxonomy; Tylenchorhynchus
A new Parasitorhabditis species with males and females was discovered from the southern pine beetle Dendroctonus frontalis and its galleries in loblolly pine, Pinus taeda, growing in Mississippi. Females of the new species have a cupola-shaped tail with a small spike; males possess a 2 + (3+2) + 3 ray pattern on the tail fan with ray 10 reaching the margin, and a distinctive stomatal tooth. Parasitorhabditis frontali n. sp. has some similarities to P. hylurgi Massey, 1974 from Hylurgops pinifex in New York, USA, P. terebranus Massey, 1974 from D. terebrans (Olivier, 1795) in Texas USA, P. ligniperdae Fuchs, 1915 from Hylergops ligniperda (Fabricius, 1787) and P. dendroctoni Rühm, 1956 from D. micans (Kugelann, 1794) in Europe, P. ateri Fuchs, 1915 isolated from the beetle Hylastes ater (Paykull, 1800) in Germany, and P. malii Devdariani and Kakulia,1970 from Scolytus mali (Bechstein, 1805) within the republic of Georgia. Morphometrics for 44 species of Parasitorhabditis are provided to update older keys. Parasitorhabditis frontali n. sp. was initially grown on Malt Extract (ME) agar with its own microbial contaminants that included a bacterium and fungus. The nematode also grew and reproduced after slices of ME agar with nematodes and microbial contaminants were transferred to water agar. It was killed by E. coli on NGM agar plates commonly used to raise other Rhabditida. Drawings of diagnostic anatomy and low-temperature SEM images of bodies, heads, and tails are provided for cultured specimens from pine beetle frass.
morphology; nematode; Parasitorhabditis frontali n. sp.; SEM; southern pine beetle; taxonomy; trophic interaction
The identity of a newly discovered population of pale potato cyst nematode Globodera pallida associated with potato in eastern Idaho was established by morphological and molecular methods. Morphometrics of cysts and second-stage juveniles were generally within the expected ranges for G. pallida with some variations noted. The Idaho population and paratype material from Epworth, Lincolnshire, England, both showed variations in tail shape, with bluntly rounded to finely pointed tail termini. Compared to literature values for the paratypes, second-stage juveniles of the Idaho population had a somewhat shorter mean body length, and cysts had a slightly higher mean distance from the anus to the nearest edge of the fenestra. PCR-RFLP of the rDNA ITS region, sequence-specific multiplex PCR and DNA sequence comparisons all confirmed the identity of the Idaho population as G. pallida. The ITS rDNA sequence of the Idaho isolate was identical to those from York, England, and the Netherlands. Species-specific primers that can positively identify the tobacco cyst nematode Globodera tabacum were also developed, providing a new assay for distinguishing this species from G. pallida and the golden potato cyst nematode Globodera rostochiensis.
Globodera; detection; diagnosis; molecular biology; morphology; Nicotiana tabacum; PCR; potato; rDNA; RFLP; Solanumtuberosum; taxonomy
A root-knot nematode Meloidogyne thailandica n. sp. was discovered on roots of ginger (Zingiber spp.) intercepted from Thailand in October 2002 by the U.S. Department of Agriculture Animal and Plant Health Inspection Service at the port of San Francisco. Comparison by light microscopy (LM) and scanning electron microscopy (SEM) to five other morphologically related species (M. incognita, M. arenaria, M. microcephala, M. megatyla, and M. enterolobii) revealed that the new species differs from these by one or more of the following: body, tail and hyaline tail length, shape of head, tail and tail terminus of second-stage juveniles; stylet length and shape of spicules in males; perineal pattern, stylet length and shape of knobs in females. The distinctive perineal pattern is oval to rectangular, with smooth to moderately wavy and coarse striae, and with characteristic radial structures present underneath the pattern area; the dorsal arch is high, sometimes round to rectangular, and striae in and around the anal area form a thick network-like pattern interrupted by lateral lines and large phasmids. Second-stage juveniles have a long, slender tail and long, gradually tapering hyaline tail region ending in a rounded terminus. Male spicules commonly have an acutely angled shaft with a bidentate terminus. Molecular data from the ribosomal large subunit D3 expansion segment revealed four haplotypes, two of which were unique and distinguish M. thailandica n. sp. from M. arenaria, M. incognita, and M. javanica.
ginger; intergenic spacer (IGS); internal transcribed spacer (ITS1); large subunit (LSU); Meloidogyne; morphology; new species; ribosomal DNA; root-knot nematode; scanning electron microscopy; taxonomy; Thailand
An unusual population of Meloidogyne hapla, earlier thought to be an undescribed species, was found causing large galls, without adventitious roots, and substantial damage to coffee in Maui, Hawaii. Only in Brazil had similar damage to coffee been reported by this species. Unlike M. exigua from South and Central America, this population reproduced well on coffee cv. Mokka and M. incognita-susceptible tomato but poorly on tomato with the Mi resistance gene. Characterization included SEM images, esterase isozymes, and five DNA sequences: i) the D3 segment of the large subunit (LSU-D3 or 28S) rDNA, ii) internal transcribed spacer (ITS-1) rDNA, iii) intergenic spacer (IGS) rDNA, iv) the mitochondrial interval from cytochrome oxidase (CO II) to 16S mtDNA, and v) the nuclear gene Hsp90. Sequences for ITS-1, IGS, and COII were similar to other M. hapla populations, but within species ITS-1 variability was not less than among species. One LSU-D3 haplotype was similar to a previously analyzed population with two minor haplotypes. Hsp90 exhibited some variation between Maryland and Hawaiian populations distinct from other species. Females were narrow with wide vulval slits, large interphasmidial distances, and more posterior excretory pores; 20% of perineal patterns had atypical perivulval lines. Males had a low b ratio (<12 µm). Juveniles had a short distance between stylet and dorsal gland orifice. Juvenile body length was short (<355 µm) and was different between summer and winter populations.
climate; Coffea arabica; Coffea robusta; detection; identification; India; Meloidogyne exigua; M. incognita; M. javanica; M. konaensis; molecular diagnostics; nematode; netherlands; resistance; taxonomy
We describe and illustrate a new needle nematode, Longidorus americanum n. sp., associated with patches of severely stunted and chlorotic loblolly pine, (Pinus taeda L.) seedlings in seedbeds at the Flint River Nursery (Byromville, GA). It is characterized by having females with a body length of 5.4-9.0 mm; lip region slightly swollen, anteriorly flattened, giving the anterior end a truncate appearance; long odontostyle (124-165 µm); vulva at 44%-52% of body length; and tail conoid, bluntly rounded to almost hemispherical. Males are rare but present, and in general shorter than females. The new species is morphologically similar to L. biformis, L. paravineacola, L. saginus, and L. tarjani but differs from these species either by the body, odontostyle and total stylet length, or by head and tail shape. Sequence data from the D2-D3 region of the 28S rDNA distinguishes this new species from other Longidorus species. Phylogenetic relationships of Longidorus americanum n. sp. with other longidorids based on analysis of this DNA fragment are presented. Additional information regarding the distribution of this species within the region is required.
DNA sequencing; Georgia; loblolly pine; Longidorus americanum n. sp.; molecular data; morphology; new species; neddle nematode; phylogenetics; SEM; taxonomy
A root-knot nematode, Meloidogyne floridensis n. sp., is described and illustrated from peach originally collected from Gainesville, Florida. This new species resembles M. incognita, M. christiei, M. graminicola, and M. hispanica, but with LM and SEM observations it differs from these species either by the body length, shape of head, tail and tail terminus of second-stage juveniles, body length and shape of spicules in males, and its distinctive female perineal pattern. This pattern has a high to narrowly rounded arch with coarsely broken and network-like striae in and around anal area, faint lateral lines interrupting transverse striae, a sunken vulva and anus, and large distinct phasmids. Molecular data from ribosomal IGS illustrate that M. floridensis n. sp. is different from the mitotic species M. arenaria, M. incognita, and M. javanica. Data from RAPDs confirm it and suggest that this new species lies in an intermediate phylogenetic position between the previous species and the meiotic species M. hapla, M. fallax, and M. chitwoodi. Differential host tests based on annual crops and on Prunus accessions are reported.
esterase phenotype; Florida; host range; meiotic parthenogenesis; Meloidogyne; morphology; new species; peach; rootknot nematode; scanning electron microscopy; taxonomy
Faces of lesion nematodes Pratylenchus teres (populations RTB and JK) and P. zeae or the bacterivore Distolabrellus veechi were observed on frozen specimens with low-temperature scanning electron microscopy and as chemically fixed, critical-point dried specimens with conventional scanning electron microscopy. Amphidial secretions were preserved in chemically fixed but not cryofixed lesion nematodes. Overhanging liplets of chemically fixed D. veechi may be artifactual because they appeared as variably filled, mostly empty membranes when cryofixed. The diagnostically useful lips of the frozen lesion nematodes exhibited six sectors of variable prominence that were absent in chemically fixed specimens. This variability may be due to different degrees of muscle contraction captured during cryofixation, which occurs in milliseconds. This is the first evidence that rarely observed lip sectors in Pratylenchus may be something other than an artifact of shrinkage.
amphid; cryofixation; Distolabrellus veechi; glutaraldehyde; face patterns; low temperature scanning electron microscopy; lip sectors; Pratylenchus teres; Pratylenchus zeae; Rhabditida; scanning electron microscopy; taxonomy; Tylenchida
Phylogenetic characters for Heteroderinae Luc. et al., 1988 are evaluated in Meloidodera which is believed to have primarily ancestral characters. Phasmid ultrastructure is observed in second-stage juveniles (J2), third-stage juvenile males, fourth-stage juvenile males, and fifth-stage males of Meloidodera floridensis and M. charis. Phasmid secretion occurs inside the egg before the J1-J2 molt. Before J2 hatch, concentric lamellar membranes occur within the sheath and socket cells. Some membranes become lamellae of the sheath cell plasma membrane; others become multilamellar bodies. During early molting, plasma membrane lamellae disappear and a distal dendrite segment appears in a rudimentary canal. After the molt, the distal dendrite is not present within the canal. The phylogenetic utility of phasmid features is discussed. In both species the ampulla shape and size between molts are stable features in juveniles and males. The posthatch J2 sheath cell receptor cavity may vary in a species specific manner, but comparative morphology requires precise timing after hatch.
end apparatus; Heteroderinae; male development; Meloidodera floridensis; Meloidodera charis; molting; multilamellar body; neuromorphology; phasmid; phylogeny; secretion; ultrastructure
Absence of the phasmid was demonstrated with the transmission electron microscope in immature third-stage (M3) and fourth-stage (M4) males and mature fifth-stage males (M5) of Heterodera schachtii, M3 and M4 of Verutus volvingentis, and M5 of Cactodera eremica. This absence was supported by the lack of phasmid staining with Coomassie blue and cobalt sulfide. All phasmid structures, except the canal and ampulla, were absent in the postpenetration second-stage juvenile (J2) of H. schachtii. The prepenetration V. volvingentis J2 differs from H. schachtii by having only a canal remnant and no ampulla. This and parsimonious evidence suggest that these two types of phasmids probably evolved in parallel, although ampulla and receptor cavity shape are similar. Absence of the male phasmid throughout development might be associated with an amphimictic mode of reproduction. Phasmid function is discussed, and female pheromone reception ruled out. Variations in ampulla shape are evaluated as phylogenetic character states within the Heteroderinae and putative phylogenetic outgroup Hoplolaimidae.
anaphimixis; ampulla; cell death; Cactodera eremica; Heterodera schachtii; Heteroderinae; parallel evolution; parthenogenesis; phasmid; phylogeny; ultrastructure; Verutus volvingentis