Sex in Schistosomes – Signaling Mechanisms in the Female Gonads

Abstract

Besides their great medical importance as causative agents of schistosomiasis, an infectious disease affecting humans and animals in tropical and subtropical regions worldwide, schistosomes exhibit distinctive biological features. Living in the blood vessels of infected hosts, these blood flukes survive permanent attacks of the immune system over many years. Furthermore, schistosomes represent the only genus of the class trematoda which live doeciously. Their most remarkable attribute, however, is the continuous pairing-contact which is both obligatory for the development of the female reproductive organs and prerequisite for egg production Over decades great efforts have been undertaken to develop an effective vaccine against schistosomes, but without fundamental success. In addition, due to the upcoming fear for resistance against the commonly used drug praziquantel, there is a pressing need to find new drugs to fight this parasite. In this respect, the understanding of basic processes of schistosome biology, especially its reproductive development, is fundamental. Since egg production is closely associated with the clinical progression of schistosomiasis, elucidating the molecular principles of the male-induced sexual maturation of the female may lead to new strategies intervening in these processes to control parasite spread on the one hand and to limit egg-induced pathology on the other.

Whole-Organ Isolation Approach as a Basis for Tissue-Specific Analyses in Schistosoma mansoni

“… A) Crude preparation of intact testes (TE) together with a part of an incompletely digested male worm body (MB) and different types of cells (CE) (left) and an mature ovary (Om) surrounded mainly by S4-vitelline cells (VC) from the vitellarium (right); immature ovary (Oi) and ootype (OT) with vitelloduct (VD) and oviduct (OD) isolated from a unisexual female; the ootype was contrasted by brief staining with Ponceau S; asterisk: “hymen”-like morphological structure typical for ootypes of unisexual females [18], [108] B) Mechanical transfer by pipetting led to the enrichment of pure testes (TE), mature ovaries (Om) after collecting and concentrating. TL (testes lobe), Op (ovary - posterior part containing mature primary oocytes in the case of mature ovaries), Oa (ovary - anterior part containing immature, stem cell-like oogonia); vitellarium (VI) with vitelline lobes (VL); dashed arrow = continued from Figure 1.…”