The Mature Oncosphere of Hymenolepis diminuta

Abstract

The hymenolepidid oncosphere consists of a muscular parenchyma, three pairs of distinctive hooks, a binucleate medullary center, and epidermal glands, and is invested by a thin cuticle. Something is already known of the development and morphology of other oncospheres (Ogren, 1957); however, few descriptions exist of the morphology of the hexacanth embryo of Hymenolepis diminuta. The morphology and development of Dilepis undula has recently been described (Ogren, 1958a, 1959a,b). Dilepid oncospheres are of the hymenolepidid type (Ogren. 1957) and thus are similar in structure and development to Hymenolepis diminuta. The present investigation was undertaken to study this similarity in detail and to elaborate on an earlier report (Ogren, 1958b). Description will be restricted to mature and post-mature oncospheres, both considered to be infective. The term post-maturation condition has been introduced by the writer to designate the state of the oncosphere and protective envelopes in the most gravid terminal proglottids of the strobila. These also are the oncospheres found in the stools. Their appearance has been described for Dilepis and may represent a more resistant condition (Ogren, 1959a).