The puzzle of the acanthocephalan male reproductive organs and their role in copulation and sexual selection

Abstract text

Introduction

Reproduction of the Acanthocephala always received less attention. Many unanswered questions and mysteries on some processes in male and female reproductive apparatus. Among some taxa of invertebrates, such as the Insecta and Acanthocephala, several behavioral and physiological adaptations of males may help to avoid the second inseminations of the same female. One of these adaptations is a copulatory cap or chastity belt produced by the male accessory gland secretions as a plug within the female genital apparatus. Acanthocephalan male reproductive system includes testes, vas efferentia, seminal vesicle, cement glands, cement reservoir, Saetttigen"s pouch, copulatory bursa and penis. One of the most distinctive elements in the genital apparatus of male acanthocephalans are cement glands and their products have considerable importance in the reproductive process.

Objectives

Here we present the aspect of cement glands of species belonging to 4 classes of this phylum. Moreover, due to lack of information on relationship between different parts of male reproductive system herein ultrastructure of cement reservoir, seminal vesicle and Saefftigen"s pouch will be detailed.

Materials & Methods

From the intestine of fish and bird definitive hosts of different acanthocephalan species several males were selected and dissected and the whole genital apparatus were fixed for light and electron microscopy.

Results

In Acanthocephala cement glands vary in shape, number and arrangement in different classes of the taxon, generally each gland has an outer cytoplasmic layer containing nuclei and surrounding a space for storage of the cement material within the gland. The nuclei have an irregular outline and the cytoplasm of the cells contains round, membrane-bound secretory granules. Current study documented the fine structure of Saetttigen"s pouch and close contact between this organ and seminal vesicle, cement reservoir.

Conclusion

All species of Acanthocephala are polygamous, the capping behaviour evolved in response to sexual selection and such a cap will delay or prevent the introduction of sperm by another male. No work has been carried out on the ultrastructure of different organs of male reproductive apparatus. We report herein the first photographic evidence on ultrastructure of the Saetttigen"s pouch and its close contact with copulatory bursa, this organ is essential for extrusion of the male copulatory bursa.