Paratylenchus minutus, n. sp., a Nematode Parasitic on Roots 1 
Maurice B. Linford, Juliette M. Oliveira, and Mamoru Ishii 2 
Members of the genus Paratylenchus Mico- 
letzky (1921: 605-607) (Criconematinae, An- 
guillulinidae ) have been reported from soil 
samples taken about the roots of various plants 
and, less often, from within the root cortex 
from a number of localities in Europe, the 
British Isles, North America, and the Nether- 
lands Indies; but nowhere has the abundance of 
these nematodes been sufficient to facilitate an 
investigation of their biology. Certain reports, 
including descriptions of two species, have been 
based upon individual nematodes. The most 
comprehensive and most recent paper on Para- 
tylenchus is that of Goodey (1934), who con- 
cluded that the genus is monotypic and estab- 
lished P. macrophallus (de Man) Goodey as 
the type species. Although recognizing that 
some former workers had found this nematode 
within the cortex, Goodey determined that it 
occurred chiefly on the surface among the root 
hairs. He found one individual still attached by 
its stylet to the surface of a processed root. 
Goodey regarded this nematode as a semi-para- 
site, a term that seems to imply incomplete 
dependence upon the living root for sustenance. 
Over a period of years in this laboratory a 
small representative of this genus that appears 
to be a distinct species has been taken in mod- 
erate numbers from soil samples from pine- 
apple fields and has been found sparingly in or 
attached to the roots of pineapple plants and 
of various weeds (Oliveira, 1940: 368). Later 
1 Published with the approval of the Director as 
Technical Paper No. 182 of the Pineapple Research 
Institute. Manuscript received April 29, 1948. 
2 Pathology Department, Pineapple Research Insti- 
tute. Juliette M. Oliveira is now Mrs. C. K. Went- 
worth, Editor, University of Hawaii. 
investigations have disclosed that it frequently 
is the most abundant nematode found about the 
roots of pineapple plants in certain old fields 
on the island of Oahu, Hawaii. Methods em- 
ployed earlier had resulted in grossly under- 
estimating its abundance: its very small size 
permits it to pass readily through the finest 
sieves suitable for separation of nematodes from 
soil suspensions, whether 200-mesh bolting silk 
or 32 5 -mesh brass screen. Its predominantly 
ectoparasitic habit results in there being rela- 
tively few individuals within roots prepared for 
microscopic study, even if plants are grown in 
very heavily infested soil. Utilizing natural 
infestations, in which other nematodes of known 
pathogenic nature also occurred, we have in- 
vestigated certain phases of the biology of this 
little parasite, including especially its feeding 
habits. We have not yet established, however, 
the pure cultures of this species that would be 
required to determine its significance as a 
pathogen. 
Paratylenchus minutus Linford, n. sp. 
Measurements. — $ : 0.24-0.31 mm., mean 
0.267 mm.; a =16-24, mean 19.1; /J=3.4-4.1, 
mean 3.68; y=12— 18; V=80-84; stylet 16-21 
fx. $ : 0.22-0.27 mm., mean 0.258 mm.; 
a=22-27, mean 24.4; /d=3. 5-4.1, mean 3.82; 
y=12-19, mean 14.4; spicula 16-19 /a; tail 
14-19 /a. Larvae: As small as 0.130 mm. long 
and 9 /* in diameter. 
Diagnosis. — Paratylenchus of small size, with 
fine cuticular annulation interrupted by narrow 
lateral fields. Buccal stylet only moderately vari- 
able in length, degenerate in male. Esophagus 
[ 111 ] 
