title: Phenotypic engineering of sperm-production rate confirms evolutionary predictions of sperm competition theory.
abstract: Sperm production is a key male reproductive trait and an important parameter in sperm competition theory. Under sperm competition, paternity success is predicted to depend strongly on male allocation to sperm production. Furthermore, because sperm production is inherently costly, individuals should economize in sperm expenditure, and conditional adjustment of the copulation frequency according to their sperm availability may be expected. However, experimental studies showing effects of sperm production on mating behaviour and paternity success have so far been scarce, mainly because sperm production is difficult to manipulate directly in animals. Here, we used phenotypic engineering to manipulate sperm-production rate, by employing dose-dependent RNA interference (RNAi) of a spermatogenesis-specific gene, macbol1, in the free-living flatworm Macrostomum lignano. We demonstrate (i) that our novel dose-dependent RNAi approach allows us to induce high variability in sperm-production rate; (ii) that a reduced sperm-production rate is associated with a decreased copulation frequency, suggesting conditional adjustment of mating behaviour; and (iii) that both sperm production and copulation frequency are important determinants of paternity success in a competitive situation, as predicted by sperm competition theory. Our study clearly documents the potential of phenotypic engineering via dose-dependent RNAi to test quantitative predictions of evolutionary theory.
authors: Evolutionary Biology, Zoological Institute, University of Basel, , Basel, Switzerland, Department of Zoology, University of Oxford, Oxford, UK. kiyono.sekii@zoo.ox.ac.uk
authors: Kiyono
authors: K
authors: Sekii
authors: Dita B
authors: DB
authors: Vizoso
authors: Georg
authors: G
authors: Kuales
authors: Katrien
authors: K
authors: De Mulder
authors: Peter
authors: P
authors: Ladurner
authors: Lukas
authors: L
authors: Schärer
mesh_terms: D000818:Animals; D005075:Biological Evolution; D015801:Helminth Proteins / Q000235:genetics*; D008297:Male; D008954:Models, Biological; D010641:Phenotype; D010986:Platyhelminths / Q000235:genetics / Q000502:physiology*; D034622:RNA Interference; D012726:Sexual Behavior, Animal; D013091:Spermatogenesis / Q000235:genetics*
chemical_list: D015801:Helminth Proteins