Female annual reproductive cycle of Rhinolophus ferrumequinum korai (Chiroptera: Rhinolophidae): morphological changes and prolonged sperm storage and sperm fate of the female reproductive tract according to month

Abstract

Morphological changes and prolonged sperm storage and loss of female reproductive tract per year and site as well as reproductive cycle were investigated by using an optical microscope, scanning electron microscope and transmission electron microscope in Rhinolophus ferrumequinum korai. The size and morphological characteristics of the uterus were found to be highly relevant to mating and the delivery period. In particular, some of the sperm ejaculated to the female reproductive tract became extinct due to phagocytosis by leukocytes starting from the end of August, which continued until the end of February. Accordingly, this period may be called the cleansing period. The sperm became extinct mainly in the uterine lumen, and an extremely small amount of sperm became extinct by secretion from the uterine gland and the phagocytosis by leukocytes. Such phagocytosis seemed to result in maintaining the clean intrauterine environment to facilitate the implantation of the fertilized egg. Also, phagocytosis by leukocytes was considered as a physiological mechanism to kill the sperm breaking into the female reproductive tract by recognizing them as alien materials, to maintain an appropriate number of sperm at the fertilization site of the fallopian tubes, so as to improve fertility. Only the sperm reaching the caudal isthmus of oviduct were found to be involved in fertilization in the next year. Ovulation and fertilization occurred approximately at the end of March. Embryogenesis appeared consecutively with implantation. The pregnancy period was approximately 70 days; delivery occurred approximately early- and middle June; and the nurturing period was approximately 80 days.

Keywords

• female annual reproductive cycle
• cleansing period
• prolonged sperm storage
• sperm fate
• phagocytosis