One‐Sided Ejaculation of Echidna Sperm Bundles

We report for the first time an unusual ejaculatory mechanism in the short‐beaked echidna in which each side of the bilaterally symmetrical, rosettelike glans penis is used alternately, with the other being shut down. This is unparalleled in mammals but is reminiscent of the use of hemipenes in squa...

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Bibliographic Details
Published in:The American naturalist 2007-12, Vol.170 (6), p.E162-E164
Main Authors: Johnston, S. D., Smith, B., Pyne, M., Stenzel, D., Holt, W. V.
Format: Article
Language:English
Subjects:
Animal reproduction
Animals
Body fluids
Echidna
Echidna - physiology
Echidnas
Ejaculation
Ejaculation - physiology
Female animals
Male
Male animals
Mammals
Mating behavior
Monotremata
Natural History Note
Penile Erection - physiology
Penis
Penis - anatomy & histology
Penis - physiology
Reproductive system
Reproductive tract infections
Semen
Sperm competition
Spermatozoa
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Summary:We report for the first time an unusual ejaculatory mechanism in the short‐beaked echidna in which each side of the bilaterally symmetrical, rosettelike glans penis is used alternately, with the other being shut down. This is unparalleled in mammals but is reminiscent of the use of hemipenes in squamate reptiles, providing further reproductive evidence of a sauropsidian lineage in the Monotremata. Further, we describe the occurrence of motile sperm bundles in ejaculated echidna semen and provide scanning electron micrographs of their morphology. Sperm bundling appears to confer increased sperm motility, which may provide the potential for sperm competition between males.
ISSN:0003-0147
1537-5323
DOI:10.1086/522847