MORPHOLOGIC VARIABILITY AND VALUE OF THE CHARACTERS USED FOR SPECIES IDENTIFICATION IN PARATRICHODORUS SIDDIQI, 1974 (NEMATODA: )

BY

W. DECRAEMER Koninklijk Belgisch Instituut voor Natuurwetenschappen, Vautierstraat 29, B-1040 Brussel, Belgium

The variability of characters used for species identification in ParatrichodorusSiddiqi, 1974 are studied and their taxonomic value discussed. The thirteen characters considered valid for the genus database and conforming to the NEMAID identification computer program are: onchiostyle length, spicule length, number of precloacal supplements, presence of spermatheca, number of ventromedian cervical papillae, cloacal opening with bilobed lip, shape of vulva in ventral view, sperm structure, pharyngo-intestinal junction, presence of males, shape of vaginal sclerotizations, shape of spicules and geographical distribution. Additionally, three very specific characters included in the species identification system, although restricted to few species, are: a conoid tail shape with acute tip, the presence of medioventral body pores in female and the presence of two postcloacal papillae in the male. Keywords:Paratrichodorus, identification, variability, .

Fortuner & Wong (1984) proposed a computer program, NEMAID, to help identification of species in plant-parasitic genera. In addition to the creation of a genus database for Paratrichodorus, the taxonomic value and intraspecific variability of the characters used for species identification, are studied. So far, 26 species have been described within the genus Paratrichodorus Sid- diqi, 1974, of which 23 are still valid (Table I). Very few studies have been published on the variability of characters used in the taxonomy of the genus. In only 11 species out of 26 have more than one population been examined, often based on a restricted number of specimens. The variability of quan- titative characters used for the identification of species in Paratrichodorus was extensively studied for T. christiei ( = P. minor) by Bird & Mai ( 1968). The influ- ence was shown of host species, host variety, host physiology, and geographical origin of a population on the extent of variation in morphometric and allometric characters. The influence of fixation on most measurements and other morphological features was demonstrated for two species: T. flevensis ( = P. teres) by Kuiper & Loof (1962) and P. weischeri by Sturhan (1985). Sturhan (1985) found 26 9lo (0") to 30% shrinkage of the body in fixed specimens compared to fresh 38

TABLE I

List of Paratrichodorus species

. The shrinkage was less in the anterior body region and involved dif- ferences between fixed and fresh specimens in the position and shape of other characters. In his compendium of ( = Trichodorus + Paratrichodoru.s) Esser (1971) also referred to the influence of fixation on morphological features. In the present study data of fixed specimens only are taken into account. In many descriptions only the range of the observed value was given without a mean value and rarely the standard deviation coefficient of variation of the measurements. Following Fortuner & Wong (1984), in the present paper the mid-range was calculated as an approximation of the mean value of each measurement for use until the actual valucs of the means are available from paratypes or other specimens.