Comparative investigations of the morphology and chemical composition of the eggshells of Acanthocephala

Abstract

Eggshells of the eoacanthocephalansNeoechinorhynchus rutili (Neoechinorhynchidae) andParatenuisensis ambiguus (Tenuisentidae) were investigated for their fine structure and their chemical composition. The acanthor larvae ofP. ambiguus are surrounded by four eggshells (E1–E4) separated by electron-lucent interstices (G1–G4). This resembles the stratification of the eggshells of archiacanthocephalans and palaeacan-thocephalans. However, an additional outer envelope (E0) exists inN. rutili. In mature eggs of this species, the broad interstice between E0 and E1 is densely packed with polysaccharides, but the other interstices also showed an intense Thiéry label. In both species, E2 along with its outer protuberances contains keratin, as does E2 in archiacanthocephalans and palaecanthocephalans, whereas E4 does not contain chitin, which contrasts with findings in the eggs of the two other classes of acanthocephalans. The results are discussed with respect to the classification of the Acanthocephala and to their transmission to the intermediate hosts.