Andrassy, I.

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Short notes
Acknowledgments
This work was financed by the Departmental Research
Support Programme of the University Grants Commission,
New Delhi.
References
CHl1WOOD, B. G. & CHI1WOOD, M. B. (1974). An Introduction
10 Ne ma IOlogy. Monumental Printing Press, Baltimore,
241 p.
Rt\SKI, D. J. & COOMANS, A. V. (1990). Five new species of
Aphanolaimus (Nemata : Araeolaimida) with a key to spe-
cies. NemalOlogica, 26 : 22-54.
A SHORT CENSUS OF FREE-LIVlNG NEMATODES
Istvan ANoRAssy
Ei:itvos Lorand Tudomanyegyetem, Allatrendszertani és Okolôgiai TanszeR., Budapest, Puskin u. 3, Hungary.
Accepted for publication 31 January 1991.
Key-words : Census, nematodes.
Of the sum 1380, 603 genera (44 %) are marine and
777 (56 %) continental *. As for the subclasses, 472
genera (34 %) belong to the Torquentia, 406 (30 %) to
the Secementia and 502 (36 %) to the Penetrantia. These
nearly equal numbers do serve a good argue again that
1989 is not far from two thousand : 1793. The actual
number of valid genera, however, cannot be given so
definitely. The reason is well known : the valuation of
genera, i.e. what someone looks upon as " good " genus,
is more subjective. One would regard every smalt group
of species as a separate genus, the other prefers ta unite
even quite evident genera. In having been somewhere in
the mean, 1 calculate with good reason that 1380 genera
may be considered as valid (Table 1). That means, 77 %
of the nominal generic taxa are good and 23 % (413
genera) synonyms or incerlae.
Table 1. Free-living genera.
Of them
37
405
335
777
435
1
167
603
marine continental
VaJid genera
472 (34 %)
406 (30 %)
502 (36 %)
1380Together
Subclasses
Torquentia
Secementia
Penetrantia
As far as 1 know the exact number of Nematoda
species has not been counted for a semi-century, only
sorne, more or less rough, calculations were published in
a few cases. Let us see sorne examples : Tarjan (1960) :
about 9000 species; Meyl (1961) : 5000 free-living
species; Kaestner (1965) : 10 000 species, but in the
validiry at least 100000 species; Hope and Murphy
(1972) : 438 marine genera and 5000 marine species;
Ayoub (1980) : 50 % of the known species marine, 35 %
free-living (continental) and 15 % parasitic; Maggenti
(1981) : about 15000 nominal species, and 250-300
families; Plan and Warwick (1983) : 20000 nominal
species, of them 4000 species marine; Poinar (1983) :
about 15 000 described species but at least 500000
actually living species; Siddiqi (1986) : 216 genera and
2200 species in the order Tylenchida - and we could
continue the enumeration. According ta these calcu-
lations, 10 000 to 20 000 species - free-living and para-
sitic tagether - are supposed as having been described
ta the present.
Unfortunately 1 cannat give exact data about parasitic
nematades, about free-living ones *, however, 1 dare
outline sorne picture. During forry years having worked
on these animais 1 currently registered alt the taxa ever
described. Welt, how many genera and species of
Nematada have been registered ta science?
Genera
The total number of nominal genera and subgenera of
free-living nematodes established to the end of the year
* Under " free-Iiving " nematodes 1 mean ail the marine,
limnic and rerrestrial forrns including those associated on or in
plants. The" true " parasites are those forms which live in
animais and in the man.
* Although there are sorne - few - genera which occur in
both spheras, on the basis of majority of species, however, they
may be regarded as marine or terres trial, respectively.
Vol. 1S, nO 2 - J992 187
I. Andrassy
• On1y [wo (or three) species, lhus practically none.
Table 2. Free-living species.
Species
The number of valid species of free-living Nematoda
having been described hitherto is Il 050. Of them, 5450
are marine and 5600 continental (Table 2), that means
that both the main spheras - sea and land - have been
populated, according to our present-day knowledge, by
the same number of nematode species!
A close balance of species number we can see in the
subc1asses as weil: 3650 species (33 %) belong to the
Torquentia, 3120 species (28 %) to the Secementia and
4280 species (39 %) to the Penetrantia. If we look,
however, at the two brief regions of the Earth, we can
find strong differences in the subclasses. Of marine
nematodes 3380 species (62 %) belong to the Torquen-
tia, 2070 species (38 %) to the Penetrantia and only 2 (or
3) species « 1 %) to the Secementia. Of the continental
Nematoda, the number of species is the richest in the
Secementia (3120 species, 56 %), fairly rich in the
Penetrantia (2210 species, 39 %) but poor in the Tor-
quentia (270 species, 5 %).
TARJAN, A. C. (1960). Check-list ofplant and soil nematodes. A
nomenclatorial compilarion. Gainesville, USA, Society of
Nematologists, 200 p.
From an other point of view, the valid species of
Torquentia are in 93 % marine and in 7 % continental,
of Secernentia in less than 1 % marine, i.e. practically in
100 % continental, and of Penetrantia in 48 % marine
and in 52 % continental.
But let us see also sorne examples on the relation
between nominal (all hitherto described) and valid spe-
cies of continental - terrestrial and !imnic - Nema-
toda. The total number of nominal species is 6810, of
them 5600 (82 %) may be accepted as good and 1210
(18 %) synonyms or incerlae. That means that every 5th
or 6th of species is invalid taxonomically. In Torquentia :
nominal 411, valid 270 (66 %), synonyms etc. 141 (34 %);
in Secementia : nominal 3731, valid 3120 (84 %), syno-
nyms etc. 611 (16 %); in Penetrantia : nominal 2673,
valid 2210 (83 %), synonyms, etc. 463 (17 %).
In free-living continental nematodes the richest orders
are the Tylenchida (2240 species, 40 %), the Dorylaimida
(1880 species, 34 %) and the Rhabditida (870 species,
16 %). The Enoplida are represented by hardly 6 %, and
all the Torquentia by less than 5 % of species.
The above sums refleet the presently known status of
genus and species number. We may not forget that the
actual number of nematode species must be much far
greater. Cautious and unanimous opinions of experts
presume that al/easl 100000 nematodes species do exist
in all the world!
MAGGENTI, A. (1981). General nematology. New York, Heidel-
berg & Berlin, Springer Verlag, 372 p.
MEYL, A. H. (1961). Die freilebenden Erd- und Süsswasser-
nematoden (Fadenwürmer). In : Die Tierwelt Mùre!europas,
1 (5a) Leipzig, 164 p.
PLATT, H. M. & WARWICK, R. M. (1983). Free-living marine
nematodes. Pan 1. British enoplids. Cambridge University
Press, 307 p.
POINAR, G. O. Jr. (1983). The natural history of nematodes.
Englewood Cliffs, USA, Prentice-Hall, 323 p.
SIDDIQI, M. R. (1986). Tylenchida parasites of planlS and
inseets. Farnham Royal, UK, CABl, 645 p.
References
AYOUB, S. M. (1980). Plant nematology. An agriculcuraltrain-
ing aid. Sacramento, USA, CDFA, 195 p.
HOPE, W. D. & MURPHY, D. G. (1972). A taxonomie hierarehy
and ehecklist of the genera and higher taxa of marine nema-
todes. Washington, Smithsonian Contributions to Zoology,
No. 137, 101 p.
KAESTNER, A. (1965). Lehrbuch der Spezielien Zoologie. Band
I. Wirbeliose. 1. Teil. Protozoa, Mesozoa, Parazoa, Coelente-
rata, Protostomia. Jena, 845 p.
Valid species Of them
marine continental
3650 (33 %) 3380 270
3120 (28 %) * 3120
4280 (39 %) 2070 2210
11050 5450 5600Together
Subclasses
Torquentia
Secementia
Penetrantia
ail the three subclasses are approximately of the same
taxonomic " gravity ". But this balance dissolves if we
look at the marine and the continental forms separately.
In marine habitats the Torquentia are on the top
(435 genera, 72 %), the Penetrantia much fewer (167 gen-
era, 28 %) and the Secementia represented by a sole
genus (Ha/enchus, < 1 %). In continental relation the
Secementia are predominant (405 genera, 52 %), they
are followed by the Penetrantia (335 genera, 43 %), while
the Torquentia are the poorest (37 genera, 5 %). In other
words, the genera of Torquentia are in 92 % marine and
only in 8 % continental, those of Secementia hardly in
1 % marine, thus practically in 100 % continental, and
those of Penetrantia in 33 % marine and in 67 %
continental.
It is worthy to mention that 21 % of the nominal
generic taxa - or 26 % of the valid genera - were
described in the last twelve years. Of the valid marine
genera 13 %, of the limnic and terrestrial ones 37 % (!)
were established in the last dozen of years.
188 Fundam. appl. Nematol.


A short census of free-living nematodes

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