- Title
- Formation and dissociation of sperm bundles in monotremes
- Creator
- Nixon, Brett; Ecroyd, Heath; Dacheux, Jean-Louis; Dacheux, Francoise; Labas, Valerie; Johnston, Steve D.; Jones, Russell C.
- Relation
- Biology of Reproduction Vol. 95, Issue 4, p. 1-11
- Publisher Link
- http://dx.doi.org/10.1095/biolreprod.116.140491
- Publisher
- Oxford University Press
- Resource Type
- journal article
- Date
- 2016
- Description
- As monotremes are the earliest offshoot of the mammalian lineage, the platypus and short-beaked echidna were studied as model animals to assess the origin and biological significance of adaptations considered unique to therian mammals: epididymal maturation and subsequent capacitation. We show that spermatozoa from both species assemble into bundles of approximately 100 cells during passage through the epididymis and that an epididymal protein, secreted protein, acidic, cysteine-rich (osteonectin) (SPARC), is involved in bundle formation. The bundles persisted during incubation in vitro for at least 1 hour under conditions that capacitate therian spermatozoa, and then underwent a time-dependent dissociation to release spermatozoa capable of fertilization. Only after this dissociation could the spermatozoa bind to the perivitelline membrane of a hen's egg, display an altered form of motility reminiscent of hyperactivation, and be induced to undergo an acrosome reaction. It is concluded that the development of sperm bundles in the monotreme epididymis mandates that they require a time dependent process to be capable of fertilizing an ovum. However, as this functional endpoint was achieved without overt changes in protein tyrosine phosphorylation (a hallmark of capacitation in therians) it is concluded that the process in monotremes is distinctly different to capacitation in therian mammals.
- Subject
- capacitation; echidna; sperm maturation; epididymis; fertilization; monotreme; platypus; SPARC; sperm; sperm competition; sperm cooperation
- Identifier
- http://hdl.handle.net/1959.13/1337058
- Identifier
- uon:27768
- Identifier
- ISSN:1529-7268
- Language
- eng
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