The structure and function of the gametes of the striped field mouse (Rhabdomys pumilio)

Abstract

This study was initiated in an attempt toadd the four-striped field mouse (Rhabdomys pumilio) to the small group of mammals that are used to study and develop assisted reproductive technologies. To accomplish this, a complete knowledge of both the male and female gametes was necessary, as well as a repeatable and successful IVF protocol. The gametes of the field mouse, both the falciformspermand the mature oocytes, were shown to be similar in several respects to those of many other rodent species. The induction of both the capacitated state and the acrosome reaction in the sperm were readily achieved. The success of retrieving mature oocytes was very low, with the rare occurrence of polar bodies within ovulated oocytes. The difficulties with oocytes was either related to the lack of a regular oestrous cycle, or to the hormonal regime used to induce superovulation. Although several protocols were used to accomplish superovulation in this species, it was seldom achieved. In in vitro fertilization trials, sperm were found to attach to both the cumulus oophorus and the zona pellucida of the oocytes. However, fertilization was never accomplished. This failure to achieve fertilization was probably related to the immaturity of the oocytes. Without further studies on Rhabdomys pumilio and further attempts at accomplishing in vitro fertilization, it would seem that this species would not easily be introduced as an animalmodelfor assisted reproduction.