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
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)
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.
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.