Studies of Male Reproduction in the Greater Bilby <i>Macrotis lagotis</i>
2010
Johnston, S D | Rumph, C | Lucht, M | Stenzel, D | Nicolson, V | Blyde, D | Keeley, T
<p>Despite its vulnerable conservation status there is scant information on male Greater Bilby <i>Macrotis lagotis</i> reproduction. Observations of gross anatomy revealed a testis to body weight ratio of 0.08 - 0.'7% (n = 4), the presence of a carrot shaped prostate with an oblique coronal segmentation of ventral and dorsal orientated prostatic tissue, an elongated membranous urethra, two bulbourethral glands and a bifurcated urethra in the glans penis (n = 1). The testis contained a high proportion of Leydig tissue (37.5 ± 2.7%) and a seminiferous epithelial cell cycle (8 stages identified) with a predominance of pre-meiotic stages (61.4 %) and Sertoli cells with unusually large nuclei. A GnRH stimulation test conducted on four different intact sexually mature Bilbies using 2pg Buserelin resulted in maximal plasma androgen secretion 30 to 60 mins after injection. While steps of <i>M. lagotis</i> spermiogenesis were similar to those described in peramelid marsupials, the morphology of the Bilby spermatozoan at spermiation, was radically different to that of the bandicoot sperm cell. Similar to the bandicoot, <i>M. lagotis</i> spermatozoa in the corpus epididymidis dislocated their neck insertion from the primary implantation fossa, so that by the time the sperm cell had reached the cauda epididymidis, the acetabulum had migrated cranially into a secondary implantation fossa and the nucleus had become streamlined with respect to the flagellum. This study reports the first description of large crystalloid inclusions in the principal cells of the caput epididymidal epithelium, the significance of which remains unknown. Male Bilby reproduction reported in this study supports the present taxonomic position of the Thylacomyidae.</p>
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