Abaxial tail implantation in the emu, Dromaius novaehollandiae: Morphological characteristics and origin of a rare avian sperm defect

Abaxial tail implantation is a defect occurring in the neck region of spermatozoa and is characterized by misalignment of the centriolar complex relative to the head base. This defect has been described in a number of mammalian species, but is rarely reported in birds. In this study, a detailed desc...

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Bibliographic Details
Published in:Theriogenology 2012-04, Vol.77 (6), p.1137-1143
Main Authors: du Plessis, Lizette, Soley, John T.
Format: Article
Language:English
Subjects:
Abaxial tails
Animals
Dromaiidae
Dromaius novaehollandiae
Emu
emus
flagellum
Incidence
Male
Microscopy, Electron, Transmission - veterinary
Semen Analysis - veterinary
Sperm morphology
Sperm Tail - ultrastructure
spermatozoa
Spermatozoa - abnormalities
Spermatozoa - ultrastructure
testes
transmission electron microscopy
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Description
Summary:Abaxial tail implantation is a defect occurring in the neck region of spermatozoa and is characterized by misalignment of the centriolar complex relative to the head base. This defect has been described in a number of mammalian species, but is rarely reported in birds. In this study, a detailed description of the defect in emu sperm is presented as well as morphological evidence of its origin in the testis. Despite their low incidence defective sperm could readily be identified using light (LM) and transmission electron microscopy (TEM). Affected sperm displayed obvious misalignment of the head and flagellum with many cells additionally showing unilateral swelling and caudal extension of the nuclear base. This material overlapped the anterior aspect of the centriolar complex. More subtle forms of the defect which were not resolved by LM were revealed by TEM. Abaxial sperm development could be identified in the testis during the early elongated spermatid stage of spermiogenesis. At this stage the centriolar complex was clearly misaligned with respect to the longitudinal axis of the condensing and elongating nucleus. The rare occurrence and low incidence of this defect in the emu would suggest that it has little effect on fertility.
ISSN:0093-691X
1879-3231
DOI:10.1016/j.theriogenology.2011.10.018