Seasonal changes in the intertubular tissue of the camel testis (Camelus dromedarius)

The morphology and morphometry of camel testicular intertubular tissue are reported for different seasons of the year. The intertubular tissue occupies a comparatively large portion of the camel testis ranging from about 24% in autumn to about 39% in spring. The volume percentages of the different intertubular tissue constituents, namely Leydig cells, blood vessels, lymph vessels and various connective tissue components, also display clear seasonal changes. Early in winter, the intertubular tissue is richly vascularized by blood vessels (about 18% of the intertubular volume), whereas lymph vessels constitute only about 3%. This remarkable abundance of blood vessels coincides with the presence of voluminous and active Leydig cells that represent about 44% of the total. In spring, an immense expansion of the lymph vessels is observed (up to about 10% of intertubular tissue), but no change is seen in blood vessels. The Leydig cells in this season constitute only about 19% of the total. In summer, the vascular compartment occupies nearly the same volume as in early winter but with fewer blood and more lymph vessels. The Leydig cell volume percentage is markedly increased (39.3%) as compared with spring. In autumn, blood and lymph vessels record their lowest volume percentages (12% and 2.5%, respectively) and Leydig cell volume is also decreased as compared to summer. The Leydig cell morphology evidently points to two periods of elevated activity during the year. The first period occurs early in winter and is characterised by voluminous Leydig cells (average volume: 1614 microns3) with a well developed and highly organised SER. By spring, the cells are reduced in size (926 microns3) due to a decrease in the amount of SER. The second period of elevated Leydig cell activity is observed in summer and is again characterised by an increased cell volume (1420 microns3) as a consequence of SER development. In summer, however, the SER is not as highly organised as in early winter. The absolute number of Leydig cells per testis also shows clear changes from season to season, being lowest in autumn (3.68 x 10(9) cells) and highest in late winter and spring (6.04 x 10(9) cells). Thus, camel Leydig cells are subject to a permanent turnover. Degenerating Leydig cells are replaced the year round by undifferentiated fibroblastic precursors, whereas Leydig cell mitoses are a rare observation. The strongest waves of replacement seem to follow the peaks of increased Leydig cell activity and occur between summer and autumn as well as in late winter and spring.