Ardea
Official journal of the Netherlands Ornithologists' Union

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Kempenaers B., Plompen W. & Briskie J.V. (1994) Patterns of sperm storage in two species of tits. ARDEA 82 (1): 185-191
The morphology of the sperm-storage tubules (SSTs) and the patterns of sperm storage within the SSTs was studied in two related species, the Great Tit Parus major and the Blue Tit Parus caeruleus. Sperm competition is important in both species, but Blue Tits have a much higher copulation rate than Great Tits and therefore differences in the sperm-storage organs could be expected. The female reproductive organs of three Blue Tits and three Great Tits were examined during laying. Controlling for female body mass, no differences were found between the two species in the number of sperm-storage tubules (SSTs), the form and size of the SSTs, or the proportion of SSTs filled with sperm. The total sperm load was somewhat higher in Great than in Blue Tits but the significance of this difference is not clear. The structure of the SSTs and the sperm storage capacity of both tit species are similar to those of other passerines.


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