- Title
- Reproduction in the male echidna (Tachyglossus aculeatus) with particular emphasis on the epididymis
- Creator
- Djakiew, Daniel
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 1982
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- The thesis describes studies on the kinetics of spermatogenesis and the production of spermatozoa and the structure and function of the epididymis. The epididymal studies involved stereological and ultrastructural work, and determination of the maturation of spermatozoa and the reabsorption of fluid and protein and the secretion of specific proteins. It was found that the rate of spermatogenesis of the echidna (55.32 days) is within the range of values that have been estimated for other mammals. However, compared to most mammals that have been studied the echidna is peculiar in that more than one stage of spermatogenesis occurs per tubular cross section and the daily production of spermatozoa per gram of testis is low. The ductuli efferentes of the echidna are structurally similar to the ductuli of therian mammals which have been studied in that they are lined by a low epithelium composed of principal and ciliated cells, and there are few spermatozoa in the lumen of the duct. The ductuli reabsorb most of the fluid which leaves the testis and selectively reabsorb protein from the lumen of the duct. The ductus epididymidis of the echidna is differentiated into two structurally distinct segments, an initial and terminal segment. The initial segment is very long and the lining epithelium has the same cellular composition as has been reported for eutherian mammals. It is composed of principal, basal, apical, narrow and halo cells. Further, the ultrastructure of principal cells within the initial segment of the echidna is similar to principal cells within the initial segment of the therian mammals which have been studied. It is concluded that the initial segment of the ductus epididymidis of the echidna is histologically and ultrastructurally uniform along its length except that spermatozoa gradually become concentrated within the lumen of the duct. It reabsorbs luminal fluid and secretes all (6 proteins) of the specific proteins secreted by the epididymis. It is also the site where maturation of spermatozoa occurs. This process involves most of the major changes associated with the extra testicular maturation of mammalian spermatozoa (i.e., mi 1ration of the cytoplasmic droplet, development of motility, changes in the properties of the plasmalemma). Further, spermatozoa acquire a coating of flocculent electron dense material over the periacrosomal plasmalemma during transit through the initial segment. It is shown that six proteins specific to the ductus epididymidis (they are not present in blood plasma or rete testis fluid) are secreted into the lumen of the initial segment. Their molecular weights (Xl0 3 ) are; 82.5, 48.5, 39.0, 32.0, 20.0 and 19.0 daltons. Some of these proteins (39.0xlO 20.0xl0 3 , 19.0xl0 3) are similar in molecular weight to epididymal proteins that have been studied in eutherian mammals. The terminal segment of the ductus epididymitis of the echidna is very short and contains no apical or narrow cells and few basal and halo cells. The lining epithelium forms villi and is involved in considerable apocrine secretion. The terminal segment is surrounded by a thick muscular tunic which is the effector which ensures that spermatozoa are immediately accessible for ejaculation. Compared to the initial segment of the ductus epididymitis the terminal segment contains less protein. Spermatozoa are formed into bundles within the terminal segment and are coated with a flocculent electron dense material which adheres to their plasmalemmas. These spermatozoa are dilute compared to spermatozoa within the terminal segment of the ductus epididymitis of the eutherian mammals which have been studied. In conclusion it is proposed that, (i) since the echidna produces fewer sperm/gram testis/day and the storage capacity of the terminal segment of the ductus epididymidis is low compared to the eutherian mammals which hove been studied the rate of sperm output (ir, terms of the number ejaculated per day) must be less, in relation to body size, than for other mammals such as the rat, rabbit, ram and bull. Further, (ii) the evolution of the ductus epididymidis of therian mammals has involved the development of additional middle segments, which seem to be involved in the maturation of spermatozoa.
- Subject
- echidnas; Tachyglossus aculeatus; reproduction; epididymis; short-beaked echidna; THESIS 884
- Identifier
- http://hdl.handle.net/1959.13/1489668
- Identifier
- uon:52744
- Rights
- Copyright 1982 Daniel Djakiew. This thesis © 1982 by Daniel Djakiew is licensed under CC BY-NC 4.0: https://creativecommons.org/licenses/by-nc/4.0/. Unless otherwise noted, any third-party material reproduced within is © the respective owner and is excluded from this licence.
- Language
- eng
- Full Text
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