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Morphological Differences between Ancylostoma duodenale and Necator americanus in the Fourth Larval Stage

Yukio Yoshida
The Journal of Parasitology
Vol. 52, No. 1 (Feb., 1966), pp. 122-126
DOI: 10.2307/3276402
Stable URL: http://www.jstor.org/stable/3276402
Page Count: 5
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Morphological Differences between Ancylostoma duodenale and Necator americanus in the Fourth Larval Stage
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Abstract

An attempt was made to distinguish morphologically the fourth-stage larvae of Ancylostoma duodenale and Necator americanus obtained from experimental animals. The observed differential features are as follows: (1) The number of teeth on the base of the provisional buccal capsule is four in A. duodenale and three in N. americanus. (2) The genital primordium, still recognizable as a small oval structure in the early fourth stage, and the vulva, which appears at the end of this stage, are situated posterior to the middle of the intestine in A. duodenale and slightly anterior to it in N. americanus. (3) The caudal end of A. duodenale, both in male and female, is needlelike, markedly sharper than that of N. americanus. This is considered to be the most useful differential feature. (4) The provisional buccal capsule is relatively small in A. duodenale, large in N. americanus. Differential points described in (1), (3), and (4) are useful both in male and female and in any phase of the fourth larval stage. However, those described in (2) are utilizable only in the initial fourth stage of both sexes and at the end of the fourth stage in the female.

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