Seminal fluid proteins (SFPs) or accessory gland proteins (Acps) are one of the non-
sperm components of
semen. In many animals with
internal fertilization, males transfer a complex cocktail of
proteins in their semen to females during copulation. These seminal fluid proteins often have diverse, potent effects on female post-mating
phenotypes.[2] SFPs are produced by the
male accessory glands.
SFPs are best studied in
mammals and
insects,[3] especially in the common fruit fly, Drosophila melanogaster. Most species produce a wide variety of proteins that are transferred to females. For example, approximately 150 SFPs have been identified in D. melanogaster,[4][5] 46 in the mosquito Anopheles gambae,[6] and around 160 in humans.[7]
Additionally, SFPs show high rates of gene turnover compared to non-reproductive genes.[9]
Function
The function of SFPs is best understood in D. melanogaster. SFPs play a role in male–male
sperm competition. One study that manipulated the amount of SFPs male D. melanogaster produced found that when males were in competition, males that produced more SFPs sired a larger proportion of offspring.[14]
In many insect species, significant changes occur in female behavior and
physiology following mating; the isolated receipt of SFPs has been shown to be responsible for many of these changes. In D. melanogaster females, over 160 genes show either
up or down-regulation following isolated SFP receipt.[15] These
transcriptomic changes are not limited to the female's
reproductive tract.[16] SFPs lengthen the
refractory period (when the female is disinterested in mating) and stimulate
ovulation; additionally they can affect processes such as
sperm storage,
metabolism, and activity levels.[3]
Though SFPs seem to play a role in coordinating male and female reproductive efforts (e.g. in timing of ovulation), SFPs may also be a source of
sexual conflict. Studies of D. melanogaster have revealed that females who received SFPs suffered decreased
lifespan and
fitness.[17] Frequent mating in D. melanogaster is associated with a reduction in female lifespan,[18] and this cost of mating in females has been shown to be primarily mediated by receipt of SFPs.[19]
As SFPs play an important role in reproductive processes in disease-carrying species of mosquito and additionally tend to be highly species-specific, manipulation of SFPs may hold potential for highly targeted
control of these mosquito populations.[20]
^Chapman, Tracey; Liddle, Lindsay F.; Kalb, John M.; Wolfner, Mariana F.; Partridge, Linda (January 1995). "Cost of mating in Drosophila melanogaster females is mediated by male accessory gland products". Nature. 373 (6511): 241–244.
Bibcode:
1995Natur.373..241C.
doi:
10.1038/373241a0.
ISSN0028-0836.
PMID7816137.
S2CID4336339.