The Aphelenchoidea (Fuchs, 1937; Thorne, 1949) is a large group of stylet bearing nematodes that have adapted to a wide range of ecological relationships including phytoparasitism, predation, fungus feeding, association with insects in soil and obligate insect parasitism (Nickle, 1970). The majority of studied members are fungal feeders (Hunt, 1993). However, only
In an attempt to investigate the nematode biodiversity in Hainan Province, a population of
Nematodes were extracted from soil and root samples using the modified Cobb sieving and flotation-centrifugation method (Jenkins, 1964). For morphometric studies, nematodes were killed and fixed in hot formalin (4% formaldehyde) and processed to ethanol-glycerin dehydration according to Seinhorst (1959) as modified by De Grisse (1969) and mounted on permanent slides. Measurements were made on mounted specimens and light micrographs and illustrations were produced using a Zeiss microscope equipped with a Zeiss AxioCam MRm CCD camera.
DNA samples were prepared according to Li et al. (2008). Four sets of primers (synthesized by Invitrogen, Shanghai, China) were used in the PCR analyses to amplify sequences of the near full-length 18S region, D2-D3 expansion segments of 28S, and ITS of ribosomal RNA genes (rDNA). The 18S region was amplified with primers 988F/1912R and 1813F/2646R (Holterman et al., 2006). The 28S D2 to D3 region was amplified with primers D2A/D3B (De Ley et al., 1999), and the ITS was amplified using primers TW81/AB28 (Tanha Maafi et al., 2003). PCR conditions were as described by Ye et al. (2007) and Li et al. (2008). PCR products were separated on 1% agarose gels and visualized by staining with ethidium bromide and products of sufficiently high quality were purified for cloning and sequencing by Invitrogen, Shanghai, China.
The sequences of the near full-length 18S region and D2 to D3 expansion segments of 28S of
The body of female is long, cylindrical, slightly ventrally arcuate or straight when heat relaxed. Cuticle is weakly annulated, lateral field with 10 incisures (i.e., 9 ridges) (reduced to 6 incisures at the tail end). Lip region is low, rounded, not offset. Stylet is 14.3 (13.2-15.2) µm long without basal swelling, conus forming ca two-fifths of total length. Procorpus is cylindrical ca 3-4 times stylet length. Median bulb (metacorpus) is well developed, ovoid, and conspicuous valve plates situated centrally. Dorsal esophageal gland orifice opening into lumen of median bulb mid-way between anterior end of metacorpal valve and anterior end of median bulb. Esophago-intestinal junction located 20 to 25 µm posterior to base of metacorpus, 91 to 114 µm from the anterior end. Esophageal gland lobe is slender, ca 3 times body diam., overlapping intestine dorsally. Nerve ring is located ca one metacorpal valve length posterior to metacorpus. Excretory pore is located posterior to the nerve ring. Hemizonid is slightly posterior to excretory pore, but sometimes at the same level of excretory pore. Reproductive system is monodelphic, prodelphic, occupying ca 45 to 55% of body length, consisting of ovary, oviduct, spermatheca, crustaformeria, uterus, vagina and post-uterine sac (PUS), with developing and developed oocytes arranged in a single row in anterior part and posterior part of ovary. Oviduct is comparatively longer, connecting ovary and spermatheca. Spermatheca is round or oblong, containing round sperm, present in majority of specimens. Uterus is thick-walled. Vagina wall is parallel not sclerotised, vulva pore shape, and lips simple without flap. In some specimens, vulval region appears sunken. PUS is well developed, extending for ca 44.5 to 82.7% of vulva to anus distance. Rectum and anus are visible. Tail is straight, cylindrical, ca 2.7 times longer than anal body diam. Tail tip is broad and bluntly rounded.
The body of male is cylindrical, posterior region slightly curved, Cuticle, and anterior region similar to female. Testis is outstretched,
This population was found in the rhizosphere of
Holotype female, 12 female and 14 male paratypes (slide numbers F11-1 to F11-9) were deposited in the nematode collection of Ningbo Customs Technical Center, China. Three paratype females and one paratype male (T572) deposited in the Canadian National Collection of Nematodes, Ottawa, Canada.
The species is named after the type locality.
Up to now, genus
Another species i.e.
The new species differs from
It differs from
It is different from
The new species differs from
The new species can be distinguished from
It differs from
The new species differs from
It differs from
Finally, it differs from
Furthermore, the new species differs from all other known species by having an unbalanced adult ratio, i.e., more males than females, while in all other described species males were not found or rare. In addition, the PUS of
The sequences of nearly full-length 18S (1707 bp, GenBank accession numbers MT396110- MT396111), 28S D2-D3 region (772 bp, MT396108-MT396109) and ITS region of rDNA (661 bp, MT396103-MT396104) of
The Bayesian phylogenetic tree of the 18S gene represented a high support (Posterior Possibility PP = 100) clade of Aphelenchidae (Fuchs, 1937) which is consisted of two genera,
In the 28S D2-D3 gene tree,
No phylogenetic tree based on the ITS sequence was carried out in the present study since the high sequence divergences and lack of support in the posterior probabilities among related species. However, the sequence divergence of
Morphologically, the
The genus
The
Morphometrics of
Female | Male | ||
---|---|---|---|
Character | Holotype | Paratypes | Paratypes |
n | – | 15 | 15 |
L | 792 | 793 ± 71.9 (639-877) | 756 ± 59.6 (647-863) |
a | 31.0 | 30.5 ± 2.7 (26.9-33.6) | 31.9 ± 3.4 (26.7-37.0) |
b | 9.6 | 7.7 ± 1.0 (6.2-8.8) | 7.5 ± 0.7 (6.1-8.7) |
b′ | 5.0 | 4.8 ± 0.6 (3.9-5.7) | 4.5 ± 0.4 (3.8-5.3) |
c | 19.5 | 21.0 ± 3.1 (16.7-27.1) | 26.7 ± 2.6 (22.1-30.4) |
c′ | 3.1 | 2.7 ± 0.4 (2.3-3.8) | 1.8 ± 0.2 (1.5-2.2) |
V or T | 72.7 | 72.8 ± 3.8 (65.2-77.6) | 70.5 ± 7.1 (59.4-89.0) |
Lip region height | 3.1 | 3.6 ± 0.3 (3.1-4.2) | 3.4 ± 0.5 (2.5-4.2) |
Lip region width | 8.3 | 8.8 ± 0.5 (8.1-9.5) | 8.5 ± 0.5 (7.8-9.5) |
Stylet length | 13.7 | 14.3 ± 0.7 (13.2-15.2) | 13.8 ± 1.0 (12.2-15.7) |
Body diam. | 25.5 | 26.2 ± 3.1 (19.2-31.7) | 23.9 ± 2.1 (19.2-28.2) |
Median bulb width | 15.3 | 16.1 ± 1.5 (13.1-19.6) | 13.8 ± 1.0 (12.2-15.7) |
Median bulb length | 22.5 | 22.3 ± 1.8 (18.6-24.5) | 20.1 ± 1.2 (17.8-21.9) |
Median bulb length/diam. Ratio | 1.5 | 1.4 ± 0.1 (1.2-1.5) | 1.5 ± 0.1 (1.3-1.7) |
E. pore from anterior end | 113.6 | 107.9 ± 7.2 (96.6-123.3) | 106.5 ± 7.2 (91.5-116.7) |
Ovary length or Testis | 436.3 | 407.4 ± 50.2 (280.2-458.3) | 531.4 ± 54.1 (452.6-610.9) |
Post-uterine sac | 112.1 | 100.7 ± 15.5 (66.3-120.2) | – |
Vulva to anus distance | 176.3 | 166.9 ± 22.3 (131.2-195.0) | – |
Post-uterine sac length/vulva to anus (%) | 63.6 | 60.9 ± 10.4 (44.5-82.7) | – |
Anal (cloacal) body diameter | 13.1 | 14.2 ± 2.0 (10.6-17.3) | 15.4 ± 1.0 (13.9-17.3) |
Tail length | 40.6 | 38.4 ± 5.9 (24.2-44.9) | 28.4 ± 2.4 (23.6-32.2) |
Spicule (curved median line) | – | – | 28.0 ± 2.0 (24.3-31.3) |
Spicule (Chord) | – | – | 28.7 ± 1.7 (25.8-32.3) |
Gubernaculum | – | – | 13.2 ± 0.4 (12.2-13.7) |
Hemizonid | 115.3 | 110.1 ± 5.5 (100.1-117.3) | 108.5 ± 7.3 (96.1-121.3) |
Head to pharyngo-intestinal junction | 92.9 | 103.2 ± 6.9 (91.0-113.5) | 100.6 ± 5.5 (86.0-109.3) |
Head to pharyngeal gland end | 159.6 | 163.9 ± 12.1 (139.6-181.0) | 165.9 ± 12.0 (149.3-188.2) |
Vulva to tail terminus | 203.1 | 213.1 ± 28.6 (156.3-251.8) | – |