Nematode Morphometric Parameters

                                                                                                                                        Revised: 11/20/2019

De Man Formulae

The following set of parameters used to characterize nematode species were developed initially by De Man in 1876 and 1880 and have been added to, modified and amended by Cobb (1914), Thorne (1949) and many others. They are often known as the De Man Formulae or the De Man Indices.

n = number of specimens on which measurements are based

L = overall body length

V = % distance of vulva from anterior

a = body length / greatest body diameter

b = body length / distance from anterior to esophago-intestinal valve

b' = body length / distance from anterior to base of esophageal glands

MB% = % distance from anterior to median bulb relative to length of esophagus

c = body length / tail length

c' = tail length / tail diameter at anus or cloaca

s = stylet length / body diameter at base of stylet

T = % length of male gonad relative to body length

o = % distance of dorsal esophageal gland opening from stylet knobs in relation to stylet length

P = % distance of phasmid from anus in relation to length of tail

Pa = % distance of anterior phasmid from anterior of nematode in relation to body length

Pp = % distance of posterior phasmid from anterior of nematode in relation to body length

G1 = % length of anterior female gonad in relation to body length

G2 = % length of posterior female gonad in relation to body length

Tail = portion of body from anus or cloaca to posterior terminus

 s = stylet or spear length (stomatostyle or odontostyle)

 SE = distance from anterior end to excretory pore in µm

 SE/L = SE/L (measured in same units) expressed as %).

 SV/s = distance from base of stylet to median bulb valve/stylet length.

 s/L = stylet length/body length (measured in same units as %).

 m = conus of stomatostyle/total stomatosyle length

  o = (distance of dorsal esophageal gland opening from stylet knobs x 100)/(length of stylet)

  p = (distance of phasmid(when not erratic) from anus x 100)/( length of tail)

 VA = distance from vulva to anus

 R = total number of body annules

   Rex = number of body annules between anterior and excretory pore

   RV = number of body annules between vulva and tail tip

  Ran = number of body annules between anus and tail tip

   RVan = number of body annules between vulva and anus

Other useful measurements:

      stylet extension (odontophore) length in µm
      gubernaculurn length in µm
      spicule length in µm
      capitulum length in µm

In descriptions of the characteristics of nematode species, parameters of the De Man Formula are expressed as means and ranges, with the units of the means indicated for the measures that are not ratios:

For n=20 females, L = 1.2 (0.9-1.45) mm, a = 32 (26.8- 35.1), b = 9.2 (7.8-10.3), b' = 6.3 (5.2-7.3), c = 72 (65-78), o = 16 (14-18) %, P = 45 (41-48) %, G1 = 34 (28-48) %, G2 = 31 (27-34) %, V = 53 (50-56) %, stylet = 25 (23-28) µm.

For n=13 males........similar and including male-specific parameters.

 

Loof-Coomans Formulae

Loof and Coomans (1970) defined an additional set cof morphometric charvctaers applicable to the Order Dorylaimida in which there are five esophageal (pharyngeal glands.  The parameters define the relative location of gland orifices and nuclei in relation to the length of the esophagus.

 

     DO = orifice of dorsal gland (e.g. 51-55 %)

     DN = dorsal gland nucleus at center of nucleolus (e.g. 54-58 %).

     S1O = orifice of the first pair of ventrosublateral glands (e.g. 65-68%).

     S1N1 = anterior nucleus of the first pair of ventrosublateral glands (e.g. 69-72 %).

     S1N2 = posterior nucleus of the first pair of ventrosublateral glands (e.g. 70-74 %).

     S2O = orifice of the second pair of ventrosublateral glands (e.g. 84-86 %).

     S2N1 = anterior nucleus of the second pair of ventrosublateral glands (e.g. 84-86 %).

     S2N2 = posterior nucleus of the second pair of ventrosublateral glands (e.g. 88-90 %).

    K = Distance DN-S1N1 as a percentage of distance DN-S1N2.

    K' = Distance DO-S1O as a percentage of DOS2O.

 

References

Caveness, F.E. 1964. A Glossary of Nematological Terms. Ibadan, Nigeria.

Cobb, N.A. 1914. Antarctic marine free-living nematodes of the Shakelton expedition. Contributions to a Science of Nematology 3-33.

De Man, J.G. 1876. Onderzoekingen over vrij in de aarde levende nematoden. Tijdschr. Ned. Dierk. Ver.  2: 78-196.

De Man, J.G. 1880. Die Eingheimischen, frei in der reinen erde und im süssen wasser lebends Nematoden. Tijdschr. Ned. Dierk. Ver.  5: 1-104.

Loof, P.A.A. and Coomans, A. 1970. On the development and location of the oesophageal gland nuclei in the Dorylaimina. Proc. IX Int. Nem. Symp (Warsaw, 1967) 1970.

Thorne, G. 1949. On the classification of the Tylenchida, new order (Nematode, Phasmidia). Proc. Helmithol. Soc. Washington 16:37-73.