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A Comparative Ultrastructural Study of the Shell Surrounding the Mature Acanthor Larvae of 13 Acanthocephalan Species

Bernard Marchand
The Journal of Parasitology
Vol. 70, No. 6 (Dec., 1984), pp. 886-901
DOI: 10.2307/3281634
Stable URL: http://www.jstor.org/stable/3281634
Page Count: 16
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
A Comparative Ultrastructural Study of the Shell Surrounding the Mature Acanthor Larvae of 13 Acanthocephalan Species
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Abstract

The acanthor shell of 13 acanthocephalan species were examined by electron microscopy: 5 Eoacanthocephala, 6 Paleacanthocephala, and 2 Archiacanthocephala. In each of them it was possible to distinguish 4 solid envelopes (E1-E4) interspersed by fluid granular spaces (G1-G4). E1 is the outermost envelope, sometimes separated into 2 parts: a fertilization membrane derivative found in all Acanthocephala, and a fibrillar structure. The latter is present among all Eoacanthocephala, rarely present among Paleacanthocephala, and absent from Archiacanthocephala. E2 is a keratin-like layer. It may or may not have lateral extensions. It is a thin layer in the Eoacanthocephala, a thicker layer in the Paleacanthocephala, and a very thick layer in Archiacanthocephala. In the first two, it is constituted of parallel filaments about 8 nm in diameter; in the latter, it is composed of interlaced filaments about 5 nm in diameter. The appearance of E3 often varies depending on the different orders. In Eoacanthocephala, it is most often composed of a single membrane-like structure about 8 nm thick. Among the Paleacanthocephala, it is composed of 2 closely connected elements. In the Archiacanthocephala, it is composed of 4 stacked layers, with the innermost being made of hexagonally shaped crystals. E4 is more or less homogeneous among all Acanthocephala. It is composed of 3 to 5 parallel structures.

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