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Changes in the Phenotype of the Rat Nematode, Nippostrongylus brasiliensis, after One and 150 Nematode Generations in Hamsters
J. Ralph Lichtenfels
The Journal of Parasitology
Vol. 57, No. 3 (Jun., 1971), pp. 517-525
Stable URL: http://www.jstor.org/stable/3277905
Page Count: 9
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Two host-adapted strains of Nippostrongylus brasiliensis (Travassos, 1914) that had been isolated from the same stock infection of laboratory rats, and thereafter maintained exclusively in either rats or Syrian hamsters for over 150 nematode generations, were used to study the immediate and longterm influence of host species on the phenotype of the nematode. Thirteen nematode characters were measured at 8 necropsy times from the 2nd to 13th days of infection. Observations also were obtained of the percentage development, growth, egg production, and length of survival in rats and hamsters. When raised in hamsters, both strains had significantly longer spicules than when raised in rats. In contrast, the hamster-adapted strain was significantly shorter in body length with significantly shorter spicules than the rat strain regardless of host. The size differences between the strains were found to be the result of different patterns of growth. Because: (1) hamster-adapted strain females showed a reduction in the number of eggs in the uterus earlier in hamsters than in rats; and (2) rat strain nematodes persisted longer in the intestines of rats than the hamster-adapted strain did in either rats or hamsters-it is suggested that the hamster develops an immune response to the nematode more quickly than does the rat. This factor may have resulted in selection for nematodes that complete growth more rapidly and have a shorter life-span.
The Journal of Parasitology © 1971 The American Society of Parasitologists