In outcrossing hermaphrodites with unilateral mating, where for each mating interaction one individual assumes the female role and the other the male role, each individual must take a sexual role opposite to that of its partner. In the polychaete worm Ophryotrocha diadema, the decision on sexual role is likely at stake during the day-long courtship. Here we describe, for the first time, courtship and pseudocopulation in this species, quantify their pre-copulatory behavior, and search for behavioral traits predicting the prospective sexual role (i.e., behavioral sexual dimorphism), by analyzing the courtship behavior of pairs of worms during the day preceding a mating event. We did not find any behavioral cue predicting the sexual role worms were to play; partners’ pre-copulatory behaviors were qualitatively and quantitatively symmetrical. We interpret this as the outcome of a war of attrition where partners share the preference for the same sexual role, and both hide their ‘willingness’ to play the less preferred one, until one individual reaches its cost threshold and accepts the less preferred sexual role.
AlvarezB. (2017) Biological function of classical conditioning in Cornu aspersum and Lymnaea stagnalis: effects on food finding nutrition and mating. Doctoral thesis. Oviedo University Oviedo Spain. Retrieved from http://digibuo.uniovi.es/dspace/bitstream/10651/45081/1/TD_BeatrizAlvarezDiaz.pdf.
AnderssonM. (1994) Sexual Selection. Princeton University PressPrinceton, NJ, USA.
AnthesN.PutzA. & MichielsN.K. (2006) Hermaphrodite sex role preferences: the role of partner body size, mating history and female fitness in the sea slug Chelidonura sandrana. Behav. Ecol. Sociobiol.60359-367.
Bartels-HardegeH.D.HardegeJ.D.ZeeckE.MüllerC.WuB.L. & ZhuM.Y. (1996) Sex pheromones in marine polychaetes V: a biologically active volatile compound from the coelomic fluid of female Nereis (Neanthes) japonica (Annelida Polychaeta). J. Exp. Mar. Biol. Ecol.201275-284.
LorenziM.C.SchleicherováD. & SellaG. (2006) Life history and sex allocation in the simultaneously hermaphroditic polychaete worm Ophryotrocha diadema: the role of sperm competition. Integr. Comp. Biol.46381-389.
MichielsN.K. (1998) Mating conflicts and sperm competition in simultaneous hermaphrodites. In: T.R.Birkhead & A.P.Møller (Eds) Sperm Competition and Sexual Selection pp. 219-254. Academic PressSan Diego, CA, USA and London, U.K.
SchärerL. & PenI. (2013) Sex allocation and investment into pre- and post-copulatory traits in simultaneous hermaphrodites: the role of polyandry and local sperm competition. Philos. Trans. R. Soc. Lond. B Biol. Sci.36820120052. DOI:10.1098/rstb.2012.0052.
SchärerL.JanickeT. & RammS.A. (2014) Sexual conflict in hermaphrodites. In: W.R.Rice & S.Gravilets (Eds) The Genetics and Biology of Sexual Conflict pp. 265-290. Cold Spring Harbor PressNew York, NY, USAT.
SchleicherováD.LorenziM.C.SellaG. & MichielsN.K. (2010) Gender expression and group size: a test in a hermaphroditic and a gonochoric congeneric species of Ophryotrocha (Polychaeta). J. Exp. Biol.2131586-1590.
WestheideW. (1984) The concept of reproduction in polychaetes with small body size: adaptations in interstitial species. In: A.Fischer & H.D.Pfannenstiel (Eds) Polychaete Reproduction pp. 265-287. Fischer VerlagStuttgart, Germany.