Smaller rival males do not affect male mate choice or cortisol but do affect 11-ketotestosterone in a unisexual-bisexual mating complex of fish

• Published in: Behavioural processes 2019-10, Vol.167, p.103916-103916, Article 103916
• Main Authors: Kim, Diana, Aspbury, Andrea S., Zúñiga-Vega, J. Jaime, Gabor, Caitlin R.
• Format: Article
• Language: English
• Subjects: Androgens; Animals; Female; Glucocorticoid; Gynogenetic; Hydrocortisone - analysis; Male; Mate choice; Mating Preference, Animal - physiology; Poecilia - physiology; Poeciliidae; Reproduction; Spermatozoa - physiology; Testosterone - analogs & derivatives; Testosterone - analysis; Water - chemistry
• ISSN: 0376-6357; 1872-8308
• DOI: 10.1016/j.beproc.2019.103916

•Social environment did not affect male mate choice for conspecific females.•Presence of a smaller rival did not affect cortisol levels of males or females.•Effect of rival on male 11-ketotestosterone was dependent on treatment order.•Focal male 11-ketotesterone was positively correlated with rival male body size.•Females increased 11-ketotestosterone in presence of a rival male. Male mate discrimination may be affected by the social environment (presence or absence of rival males or mates), which can also affect stress and sex hormones (e.g., cortisol and 11-ketotestosterone (11-KT)). The Amazon molly, Poecilia formosa, is an all-female fish species dependent on sperm from mating with male P. latipinna. We investigated male mate choice in P. latipinna between conspecific females and P. formosa with a rival male present and no rival male present. We measured cortisol and 11-KT release rates from all fish. The presence of a rival male had no effect on male mate choice for conspecific females nor overall mating effort. Male 11-KT decreased on the second day after exposure to a rival male on the first day. Focal male 11-KT is positively correlated with the size of the rival male. Both conspecific and heterospecific females released more 11-KT when in the rival male treatment than when not. Neither male nor female cortisol was affected by the presence or absence of the rival male. We did not find an effect of rival males on male mate choice in contrast to our prediction. Instead, our findings may indicate a hormonal response to social competition.