Effects of Photoperiod on Epididymal and Sperm Morphology in a Wild Rodent, the Viscacha (Lagostomus maximus maximus).

A. M. Cruceño,J. C. de Rosas,E. M. Chaves,L. Scardapane,C. Aguilera-Merlo,M. Fóscolo,S. Dominguez

doi:10.5402/2013/128921

Abstract

The viscacha (Lagostomus maximus maximus) is a seasonal South American wild rodent. The adult males exhibit an annual reproductive cycle with periods of maximum and minimum gonadal activity. Four segments have been identified in the epididymis of this species: initial, caput, corpus, and cauda. The main objective of this work was to relate the seasonal morphological changes observed in the epididymal duct with the data from epididymal sperm during periods of activity and gonadal regression using light and scanning electron microscopy (SEM). Under light and electron microscopy, epididymal corpus and cauda showed marked seasonal variations in structural parameters and in the distribution of different cellular populations of epithelium. Initial and caput segments showed mild morphological variations between the two periods. Changes in epididymal sperm morphology were observed in the periods analyzed and an increased number of abnormal gametes were found during the regression period. During this period, anomalies were found mainly in the head, midpiece, and neck, while in the activity period, defects were found only in the head. Our results confirm that the morphological characteristics of the epididymal segments, as well as sperm morphology, undergo significant changes during the reproductive cycle of Lagostomus.

Highlights

Animal species that develop their life cycle in contact with nature must adapt physiologically to the annual changes conditioned by the environment. e role of environment signals in synchronization has been described in previous reports, especially the circannual regulation of pituitary and gonadal function by photoperiod [1, 2]
The model animal used is the viscacha (Lagostomus maximus maximus), a South American rodent which lives in burrows built deep in the ground and only leaves its cave at dawn to look for food [8, 9]
The adult male exhibits a reproductive cycle characterized by three periods. e period of highest reproductive activity may be observed during long summer days and early autumn and is followed by a short period of ISRN Anatomy (a)

Summary

Introduction

Animal species that develop their life cycle in contact with nature must adapt physiologically to the annual changes conditioned by the environment. e role of environment signals in synchronization has been described in previous reports, especially the circannual regulation of pituitary and gonadal function by photoperiod [1, 2]. Animal species that develop their life cycle in contact with nature must adapt physiologically to the annual changes conditioned by the environment. Adult males have reproductive cycles that are expressed by morphological and biochemical changes in their reproductive organs [3]. Speci c proteins secreted by epithelial cells of the epididymis and factors generated by accessory glands modulate the structure and function of the sperm plasma membrane. E size and secretory activity of epithelia in the epididymis as well as in the accessory glands are in uenced by testosterone [7]. Studies carried out in our laboratory have demonstrated that this rodent has seasonal reproduction, the environmental photoperiod being the main synchronizer of the reproductive cycle along the year. The adult male exhibits a reproductive cycle characterized by three periods. e period of highest reproductive activity may be observed during long summer days and early autumn and is followed by a short period of ISRN Anatomy (a)

Methods

Results

Conclusion