Studies of Esterase 6 in Drosophila melanogaster. V. Progeny Production and Sperm Use in Females Inseminated by Males having Active or Null Alleles

Abstract

Despite more than a decade ofresearch, Aronshtam and Kuzin (1974) have shown the evolutionary significance of molecular that the anterior ejaculatory duct (a secrevariants of enzymes in Drosophila and tory organ connecting the testes and acother organisms is far from clear. Recently cessory glands to the ejaculatory bulb) several workers have stressed that a new contains EST 6 in concentrations nearly research strategy is needed which will in-as great as found in whole fly homogetegrate findings on the biochemistry and nates. Current studies indicate that this psysiology of enzyme variants with ob-enzyme is depleted in males and transserved changes in allele frequencies in nat-ferred to females during copulation (Richural or artificial populations (Clarke, mond et al., 1980(Clarke, mond et al., ). 1973Koehn, 1978). Our laboratory is en-Does this polymorphic enzyme, transgaged in a study of the extent and adap-ferred to females in significant amounts at tive significance of molecular variants at copulation, have a clear adaptive role in the autosomal, esterase 6 (Est 6) locus in Drosophila male and/or female reproduc-D. melanogaster (Cochrane, 1976; Coch-tive fitness? The availability of D. metarane and Richmond, 1979aRichmond, , 1979b. Re-nogaster stocks homozygous for null varicent work (Sheehan et al., 1979) has ants of Est 6 provides an excellent tool for shown that the specific activity of esterase examining this question. Many compo-6 (EST 6) reaches its maximum in adult nents of the male reproductive phenotype males. (The notation Est 6 will be used are potentially affected by a reproductive throughout to denote the genetic locus; the enzyme. These include aspects of courtnotation EST 6 refers to the esterase 6 en-ship, copulation, sperm transfer and storzyme.) Activity shows a gradual increase age, sperm viability and use by the fethrough larval until early pupal stages, male, as well as remating and sperm then remains constant until 12 h post eclo-displacement among males. sion. At this young adult stage, near the The absence of an enzyme which conbeginning of reproductive fertility, males tributes to reproductive fitness could be have about twice the EST 6 activity of expected to lower the productivity of matfemales. EST 6 activity remains at a con-ings, through an effect on one of these stant low level throughout female adult-components. Comparisons of the single hood, but rises to five times this level in mating productivity (progeny per female) males by three days post eclosion, and is of females inseminated by males homomaintained at these high levels in virgin zygous for an active Est 6 allele and males males.homozygous for a null allele were under-The increase in esterase activity in adult taken to test this expectation. Females males corresponds to the period when fer-having a genetic background similar to the tility and the frequency of mating is rising two male types, but homozygous for the in males (Stromnaes and Kvelland, 1962; sex-linked mutation forked, were used to Fowler, 1973). Furth...

The role of sperm numbers in sperm competition and female remating in Drosophila melanogaster

“…Initial use of stored sperm is high and inefficient, such that by 48 h after mating one half of peak storage is lost from the storage organs (Gilbert, 1981). As sperm are utilized and the number in storage is reduced, efficiency of sperm use increases (Kaufmann & Demerec, 1942;Gilbert et al, 1981). Remating is triggered by some small number of sperm remaining in storage (threshold Fig.…”

Mechanisms Underlying the Sperm Quality Advantage in Drosophila Melanogaster

“…and then frozen to the surface of media at Ϫ20ЊC until dissection. The SR of females was later dissected out, fixed, and stained with 2% orcein in 60% acetic acid (Gilbert 1981;Gilbert et al 1981). The absolute number of stained sperm heads residing within each consecutive 0.10-mm long section of the SR were counted across the entire organ at 400ϫ using differential interference contrast microscopy (Fig.…”

Molecular Social Interactions

“…Thus, getting sperm into storage is of vital importance to males, and male contributions appear to play an active role in making sure this happens. Time is also of the essence: sperm that remain unstored in the female’s uterus when she lays her first egg post-mating may be expelled from the female (Fowler 1973; Gilbert 1981), creating a potential tradeoff between the timing of sperm storage and egg output.…”

“…1) fail to elicit most post- mating responses in females (Kalb et al 1993, Xue & Noll 2000). It is known that the ejaculatory duct and ejaculatory bulb also produce secreted proteins that constitute part of seminal fluid, and that some of these proteins are necessary for post-mating responses (e.g., Gilbert et al 1981; Meikle et al 1990; Ludwig et al 1991; Samakovlis et al 1991; Lung & Wolfner 2001; Lung et al 2001; Iida & Cavener 2004; Bretman et al submitted). These results together demonstrate that sperm and Sfps are both required to induce long-term post mating responses in females (Manning 1962, 1967; Kalb et al 1993; Heifetz et al 2001; Kubli 2003).…”

“…Mutant or transgenic males in which Sfps are increased, decreased, or eliminated can be used to dissect the effect(s) of particular Sfps on female post-mating responses (e.g., Gilbert et al 1981; Herndon et al 1995; Neubaum & Wolfner 1999; Chapman et al 2003; Liu & Kubli 2003; Iida & Cavener 2004; Ravi Ram et al 2006; Ravi Ram & Wolfner 2007b; Mueller et al 2008; Wong et al 2008a, Bretman et al , submitted). A large collection of freely available genomic databases (e.g., FlyBase; Fly atlas, Chintapalli et al 2007) facilitate rapid progress as well.…”