Biology Reference
In-Depth Information
(a)
(b)
(c)
(d)
Fig. 7.19
Two sperm displacement mechanisms in Odonata.
Crocethemis erythraea
:
(a) uninflated penis; (b) inflated penis. The horn-like structure repositions sperm of
previous males in the spermatheca.
Orthetrum cancellatum
: (c) the whip-like flagellum
is everted during copula; (d) it carries barbs which remove sperm from the narrow
ducts of the spermatheca. Siva-Jothy (1984). Photos by Michael Siva-Jothy.
does not originate from the female herself, but is deposited by the male at the end of
mating. The scent discourages other males from mating with the female, perhaps
because it resembles a scent used by males to repel one another in other contexts.
Sterile sperm
. In some invertebrates, males produce two types of sperm: 'eusperm',
which have the potential to fertilize the female's ova, and 'parasperm' which are sterile
(and may or may not contain a nucleus). In butterflies and moths, parasperm act as
'cheap fillers' of the female sperm storage organs, leading to a delay in female remating
(Cook & Wedell, 1999). In
Drosophila pseudoobscura
, parasperm help protect their
fertilizing brother eusperm from spermicide inside the female tract (Holman & Snook,
2008).
Accessory gland proteins (Acps)
. In many insects the male's ejaculate contains not only
sperm but also a cocktail of proteins that influence female behaviour and physiology. In
Drosophila melanogaster
no fewer than 80 Acps have been identified and their functions
Sterile sperm as
'cheap fillers'
Chemical
manipulation of
females
