Sex-peptides: seminal peptides of the Drosophila male

Abstract

Mating affects the reproductive behaviour of insect females: the egg-laying rate increases and courting males are rejected. These post-mating responses are induced mainly by seminal fluid. In Drosophila melanogaster, males transfer two peptides (sex-peptides, = Sps) that reduce receptivity and elicit increased egg laying in their mating partners. Similarities in the open reading frames of the genes suggest that they have arisen by gene duplication. In females, Sps bind to specific sites in the central and peripheral nervous system, and to the genital tract. The binding proteins of the nervous system and genital tract are membrane proteins, but they differ molecularly. The former protein is proposed to be a receptor located at the top of a signalling cascade leading to the two post-mating responses, whereas the latter is a carrier protein moving Sps from the genital tract into the haemolymph. Sps bind to sperm. Together with sperm they are responsible for the persistence of the two post-mating responses. But Sps are the molecular basis of the sperm effect; sperm is merely the carrier.

Oviposition preference for and positional avoidance of acetic acid provide a model for competing behavioral drives in Drosophila

“…However, mated and virgin females showed equivalently high OI values in response to AA-containing food (Fig. 1B); attraction to AA as an oviposition substrate is therefore an innate preference not affected by post-mating behavioral modifications (13).…”

Most sleep does not serve a vital function. Evidence from Drosophila melanogaster

“…Could this be a peculiarity of some virgin flies, hence an ethological laboratory artefact? In Drosophila, mating status is known to be acting as a major behavioural switch (38) that modifies, among other behaviours, the animals dietary preference (36,39) and their preference for feeding time (40). However, reaching sexual maturity only few hours after ecdysis, virgin female flies are likely to be a rare occurrence in the wild (41,42).…”

Love hangover

“…In rodents, exposure to dominant-male pheromones induces a female preference for dominant versus subordinate males that may involve introduction of new neurons into neural circuits 7 . Similarly, female jewel wasps change their response to male sex pheromones from attraction to aversion after mating 8 , and in D. melanogaster mated females will actively reject courtship, kicking and running away from a new male 9 . This type of 'mate guarding' does not require the continued presence of the successful male, maximizing his ability to mate with other females while still protecting his DNA investment.…”

“…The best-understood example of a behaviourally active seminal-fluid component is sex peptide in D. melanogaster 9 . It is produced in the male accessory gland, a prostate-like structure, and is absorbed into the female circulation from the vaginal tract.…”

“…Behaviours resulting from sexpeptide absorption include increased egg-laying and reduced receptivity to male courtship. Previous studies indicated that there are binding sites for sex peptide in the brain 9 , but the nature of the receptor or receptors was unknown.…”