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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Crossonema

Crossonema Mehta & Raski, 1971 (ref. ID; 5848)

Order Tylenchida: Family Criconematidae (ref. ID; 7649)

Family Criconematidae (ref. ID; 5948)

N.Synonym Croserinema Khan et al., 1975 (ref. ID; 5848)

ref. ID; 5848

Diagnosis (emended)

Female body 0.29-0.86 mm. Annules 40-60 with fringe of spines or scales, longitudinal rows of scales or palmate projections in alternate rows. At least some cuticular projections of body annules bearing knobbed, clubbed, bifurcated, serrated or refractive tip elements. Head annules two, set off, smooth to crenate, first annule wider than second. Lip region elevated, round. Stylet 64-114 µm. Vulval lips conical, conspicuously withdrawn from body contour. Tail three to eight annules, rounded. Cuticular structures on tail longer than at midbody especially around vulva. VL/VB 0.8-1.1. (ref. ID; 5848)
  • Juveniles (Fourth stage): Cuticle with eight longitudinal rows of broad, flattened semicircular protuberances with four to six prominent conical spines. (ref. ID; 5848)
  • Male: Lateral incisures four, bursa small, spicules 33-35 µm. (ref. ID; 5848)

    Notes

    Crossonema differs from Pateracephalanema by fewer body annules (40-60 vs. 70-98), two head annules (one in Pateracephalanema) and cuticle with modified spines or scales on body and tail (cuticule with unmodified scales on body and tail in Pateracephalanema). Khan et al. (1976) proposed the monotypic genus Croserinema because of alternating rows of palmate body projections and submedian lobes in C. palmatum. DeGrisse (1977), however, demonstrated under SEM that C. palmatum has six pseudolips; submedian lobes are absent. Crossonema palmatum is closely related to C. civellae, type species of Crossonema, having similar stylet length, number of annules, vulva structure and position, tail and head structures, and juvenile cuticular characteristics. The species differ in that C. civellae has a fringe of spines whereas C. palmatum has alternate rows of palmate body projections; both species have alternate rows of palmate projections on the tail. The cuticular difference between the two species is considered specific in nature and insufficient for acceptance of Croserinema as a distinct genus since the cuticle in Crossonema species is highly variable and modified. Croserinema is therefore rejected and synonymized with Crossonema. (ref. ID; 5848)

    Type species

    Crossonema civellae (Steiner, 1949) Mehta & Raski, 1971 (ref. ID; 5848)

    Nominal species

    Crossonema chrisbarnardi (Heyns, 1970) Loof & DeGrisse, 1973 (ref. ID; 5848)
    1. Crossonema abies Andrassy, 1979
      See; Neocrossonema abies (ref. ID; 5848)
    2. Crossonema aculeatum (Schneider, 1939) (ref. ID; 5948)
    3. Crossonema aquitanense (Fies, 1968) Mehta & Raski, 1971
      See; Neocrossonema aquitanense (ref. ID; 5848)
    4. Crossonema capitospinosum Ebsary, 1979 (ref. ID; 5848, 5948 original paper)
      See; Neocrossonema capitospinosum (ref. ID; 5848)
    5. Crossonema chrisbarnardi (Heyns, 1970) Loof & DeGrisse, 1973 (ref. ID; 5848)
    6. Crossonema civellae (Steiner, 1949) Mehta & Raski, 1971 (ref. ID; 5848)
    7. Crossonema coronatum (Schuurmans-Stekhoven & Teunisson, 1938) Mehta & Raski, 1971 (ref. ID; 5848)
    8. Crossonema fimbriatum (Cobb, in Taylor, 1936) Mehta & Raski, 1971 (ref. ID; 5848, 5948)
      See; Neocrossonema fimbriatum (ref. ID; 5848)
    9. Crossonema fimcivatum Khan et al., 1976 (ref. ID; 5848)
    10. Crossonema insulicum (Choi & Geraert, 1975) n. comb. (ref. ID; 5848)
      Syn; Neolobocriconema insulicum Choi & Geraert, 1975 (ref. ID; 5848)
    11. Crossonema latens Mehta & Raski, 1971 (ref. ID; 5848)
    12. Crossonema melanesicum (Andrassy, 1979) n. comb. (ref. ID; 5848)
      Syn; Seriespinula melanesica Andrassy, 1979 (ref. ID; 5848)
    13. Crossonema menzeli (Stefanski, 1924) Mehta & Raski, 1971 (ref. ID; 5848, 5948)
      See; Neocrossonema menzeli (ref. ID; 5848)
    14. Crossonema multisquamatum (Kirjanova, 1948) Mehta & Raski, 1971 (ref. ID; 5848)
    15. Crossonema palmatum (Siddiqi & Southey, 1972) Mehta & Raski, 1971 (ref. ID; 5848)
    16. Crossonema pectinatum (Colbran, 1962) n. comb. (ref. ID; 5848)
      Syn; Pateracephalanema pectinatum (Colbran, 1962) Mehta & Raski, 1971 (ref. ID; 5848)
    17. Crossonema pellitum (Andrassy, 1979) n. comb. (ref. ID; 5848)
      Syn; Pateracephalanema pellitum Andrassy, 1979 (ref. ID; 5848)
    18. Crossonema proclive (Hoffmann, 1973) Andrassy, 1979
      See; Neocrossonema proclive (ref. ID; 5848)
    19. Crossonema punici (Edward et al., 1971) n. comb. (ref. ID; 7649)
      Syn; Criconema punici Edward, Misra, Peter & Rai, 1971 (ref. ID; 7649)
    20. Crossonema quercum (Choi & Geraert, 1975) n. comb. (ref. ID; 5848)
      Syn; Criconema querci Choi & Geraert, 1975 (ref. ID; 5848)
    21. Crossonema taylatum Khan et al., 1976 (ref. ID; 5848)
    22. Crossonema taylori (Jairajpuri, 1964) Mehta & Raski, 1971 (ref. ID; 5848)

    Crossonema aculeatum (Schneider, 1939) (ref. ID; 5948)

    Descriptions

    See the description of Crossonema menzeli. (ref. ID; 5948)

    Crossonema capitospinosum Ebsary, 1979 (ref. ID; 5848, 5948 original paper)

    See

    Neocrossonema capitospinosum (ref. ID; 5848)

    Differential diagnosis

    Crossonema capitospinosum new species is most similar to C. menzeli, C. fimbriatum, and C. abies. It differs from C. menzeli by a greater number of body annules (66-77 vs. 53-68), and by a more anterior vulva and anus (annules 13-17 and 8-10 vs. 10-14 and 4-8, respectively). It differs also by the long, thin head spines, about 30 per annule (12-20, short thick spines in C. menzeli), and by the thin, irregularly alinged body spines. Crossonema capitospinosum differs from C. fimbriatum by more body annules (66-77 vs. 51-63), more anterior vulva and anus (annules 13-17 and 8-10 vs. 10-14 and 4-6, respectively), by spined, equal width head annules (head annules crenate, first wider than second in C. fimbriatuum) and by the thin irregulary aligned body spines (short and thick in C. fimbriatum). Crossonema capitospinosum differs from C. abies by having two head annules, each fringed with 30 long thin spines (one head annule with about 20 short, thick spines in C. abies), a shorter stylet (86-99 µm vs. 102 µm), and by the excretory pore on annules 23-27 (annule 20 in C. abies). It should be noted that the longitudinal lines on the spines of C. abies as described by Andrassy (1979) also occur in C. menzeli, C. fimbriatum, and C. capitospinosum new species. The body spines in these species are hollow; the longitudinal lines are the lateral margins of the lumen in the spines. This finding weakens the value of spine structure in C. abies as a specific character. (ref. ID; 5948)

    Descriptions

  • Female: Head annules two, set off, anteriorly directed, equal in width. Annules with about 30 prominent round tipped, this spines, 3-5 µm and 2 µm long on annules one and two respectively. Head spines distinct in sagittal section. Lip region elevated, round. Pseudolips six, laterals larger. Submedian lobes absent. Amphids slit-like on oral disc. Oral aperture I shaped. Stylet flexible, delicate. Prorhabdion 82 µm (73-86), stylet knobs 7-8 µm in diameter. Annules from anterior end to base of style 16-18, esophagus 20-24, and excretory pore 23-27. Annules with continuous fringe of about 50 spines at midbody. Spines long, slender, tips slightly clavate, irregularly alinged on body. Spine length on anterior body 5 µm, midbody 7-8 µm, tail 5 µm. Vulva closed on annules 13-17 from terminus. Vulval lips prominent reaching contour of body spines. Anterior lip slightly overlapping posterior lip, smooth, hemispherical in ventral view. Vagina oblique to body axis. Anus conspicuous, 8-10 annules from terminus. Ovary terminus varies from midbody to posterior of stylet knobs. Spermatheca small, round, sperm filled. Tail conical tapering to pointed terminus. (ref. ID; 5948)
  • Juvenile female (Molting Fourth Stage): Head annules two, set off, anteriorly directed, each annule 12 µm wide, fringed with very short round spines. Molted prorhabdion 62 µm long. Cuticle with 12 longitudinal rows of scales at midbody. Each scale with semicircular base (similar to that of C. menzeli), subcylindrical posterior extension, and three (two to five) fine, sharp spines tips. Tail conical pointed. (ref. ID; 5948)
  • Male: Unknown. (ref. ID; 5948)

    Type host and locality

    Specimens collected in 1969 by Dr. R.V. Anderson and Mr. R.H. Mulvey from most moss and grass on rotting logs, highway 101, 80 km south of Timmins in northern Ontario. CNCN No.5903. (ref. ID; 5948)

    Type deposited

  • Holotype: Specimens on slide 242 deposited in CNCN, Ottawa. (ref. ID; 5948)
  • Paratypes: Twelve females, one juvenile, on slides 242a-242n deposited as follows: seven females, one juvenile, and one en face and ventral section in CNCN, Ottawa; one female each at the following institutions: USDANC, Beltsville, Maryland; UCNSC, Davis, California; PD, Wageningen, The Netherlands; R.U.G., Gent, Belgium. (ref. ID; 5948)

    Measurements

  • Holotype (female): L=0.49 mm; a=8.5; b=3.6; c=5.4; V=82; stylet 95 µm; body annules 67. (ref. ID; 5948)
  • Paratypes (12 females): L=0.46(0.41-0.50) mm; a=8.3(6.8-9.4); b=3.7(3.6-3.8); c=5.6(5.2-6.1); V=84(80-90); stylet 94(86-99) µm; body annules 70(66-77). (ref. ID; 5948)

    Crossonema fimbriatum (Cobb, in Taylor, 1936) Mehta & Raski, 1971 (ref. ID; 5848, 5948)

    See

    Neocrossonema fimbriatum (ref. ID; 5848)

    Descriptions

  • Juvenile female (Fourth Stage): Head annules two, set off, first anteriorly directed 10 µm wide, cup-like. Second annule 12 µm wide, rounded. Both annules crenate. Body annules retrorse with 10 longitudinal rows of scales at midbody. Scales similar in structure to C. capitospinosum but with four (two to five) fine spines at scale tips. Tail conical, pointed. (ref. ID; 5948)
  • Juvenile male (Molting Fourth Stage): Juvenile cuticle similar to juvenile female but with eight rows of scales. Prorhabdion 49 µm long. Male head broadly rounded of six annules, continuous with body contour. Cephalic framework well developed, crecentic. Esophagus degenerate, obscure. Stylet absent. Annule width at midbody 3 µm. Lateral incisures three, about 3 µm wide. Spicules slender, 40 µm long, arcuate. Spicules constricted near proximal end. Gubernaculum 5 µm long. Outer lateral incisures crenate to about 40 µm anterior of cloaca. Tail 45 µm, conical terminus sharply pointed. (ref. ID; 5948)

    Measurements

    Juvenile female (Fourth Stage): L=0.31 mm; a=7.5; b=3.0; stylet 65 µm; body annules 63. (ref. ID; 5948)

    Crossonema menzeli (Stefanski, 1924) Mehta & Raski, 1971 (ref. ID; 5848, 5948)

    See

    Neocrossonema menzeli (ref. ID; 5848)

    Descriptions

    Juvenile female (Fourth Stage): Head annules two, set off, finely spined. First annule anteriorly directed, 9 µm wide, second annule rounded, 11 µm wide. Body annules retrorse with 12(11-13) longitudinal rows of scales at midbody, similar in structure to C. capitospinosum. Each scale tipped with two (one to four) fine, sharp spines. Tail conical, pointed. (ref. ID; 5948)

    Notes

    Menzel (1914) schematically illustrated a molting (male?) juvenile of C. menzeli and indicated six longitudinal rows of rounded scales and bluntly rounded continuous head with a distinct fringe of long spines similar to the adult female. The Canadian juveniles differ significantly having two set off, finely spined head annules and 11-13 longitudinal rows of scales tipped with one to four fine, sharp spines at tips. Andrassy (1979), without explanation, synonymized C. aculeatum (Schneider, 1939) with C. menzeli. Crossonema aculeatum was considered distinct from C. menzeli by spination differences; sharply pointed in aculeatum, rounded in menzeli. Mehta and Raski (1971) suggested that the observations of Schneider (1923) and Stefanski (1924) might be questioned. Table 1 compares measurements of C. aculeatum reported by Schneider (1923), Stefanski (1924), and Trave (1954) with those of C. menzeli reported by Mehta and Raski (1971); the measurements strongly overlap. Similarities also occur in head, tail, and vulval structures, the only apparent difference being in body spination. Specific separation based on dubious spination differences is not considered justified. I concour with Andrassy's synonymization of C. aculeatum with C. menzeli. (ref. ID; 5948)

    Measurements

    Juvenile female (Fourth Stage): L=0.32(0.29-0.34) mm; a=6.2(5.7-6.7); b=3.1(3.0-3.2); stylet 79(78-82) µm; body annules 66(65-68) (n=7). (ref. ID; 5948)

    Crossonema multisquamatum (Kirjanova, 1948) Mehta & Raski, 1971 (ref. ID; 5848)

    Notes

    Diagrams of the head of C. multisquamatum do not adequately depict the number and shape of the head annules or the nature and location of head crenations or lip structure. Tail spines, although stated to be divided into lobules were not illustrated. Type specimens were not retained to enable clarification and, until additional specimens are collected, this species should be considered as inadequately described and placed in species inquirenda. The synonyzation of C. civellae with C. multisquamatum by Andrassy (1979) is not accepted at this time. (ref. ID; 5848)

    Crossonema punici (Edward et al., 1971) n. comb. (ref. ID; 7649)

    Synonym

    Criconema punici Edward, Misra, Peter & Rai, 1971 (ref. ID; 7649)

    Descriptions

    Lip region with two annules, the first one directed anteriorly. Submedian lobes absent. Stylet 57 µm long with anteriorly directed basal knobs. Each annule bearing eight lobular outgrowths in the middle of the body but in the oesophageal region the number is six. Each scale is triangular in outline. Vulva located on 13th annule from tail terminus. Spermatheca distinctly oval in shape. Tail pointed. Anus could not be located. (ref. ID; 7649)
  • Male: Not found. (ref. ID; 7649)

    Remarks

    The present female resembles Criconema punici Edward et al., 1971 in the number of body annules, location of vulva and the number of cuticular projections on each annule. It shows some morphological variations in greater length. Shorter stylet, smaller spermatheca and a slightly different tail shape. Also the spines on the body are slightly longer than Edward's specimens. Mehta and Raski (1971) revised the subfamily Criconematinae and proposed four new genera, Crossonema, Neolobocriconema, Blandicephalanema and Pateracephalanema, raising the total number of the genera in the subfamily to eight. Criconema and Crossonema were differentiated by the presence or absence of submedian lobes, these being absent in the latter genus. Because of the absence of submedian lobes, Criconema punici should be placed in the genus Crossonema Mehta and Raski 1971. It, however, does not fit into either Crossonema or Seriespinula, the two subgenera proposed under the genus Crossonema by Mehta and Raski (1971). It resembles the subgenus Crossonema in the presence of a continuous fringe of blunt scales but differs in these scales being arranged in longitudinal rows. Criconema punici resembles the subgenus Seriespinula in the longitudinal arrangement of scales but differs in the number and shape of the scales in each annule. So, although Criconema punici is transferred to the genus Crossonema, it is not placed under either of the two subgenera till the time more characters are found to differentiate between these two subgenera. (ref. ID; 7649)

    Host

    From around the roots of grass (Unidentified). (ref. ID; 7649)

    Locality

    Dalhousie, Himachal Pradesh. (ref. ID; 7649)

    Deposited materials

    Paratype female: Slide no.RM/C/1. (ref. ID; 7649)

    Measurements

    Female: L=0.45 mm, a=8.3, b=5, c=?, V=82%, R=66, RSt=11, ROes=16, RV=13, Stylet 57 µm. (ref. ID; 7649)