Sperm competition risk drives plasticity in seminal fluid composition

Table 1 Mean sperm production parameters under contrasting cues of sperm competition risk and mating opportunities

Sperm competition (SC)	Mating rate (MR)	Paired testes mass (g)	Epididymal sperm count (x10⁶)	Daily sperm production (x10⁶)	Seminal vesicles mass (g)
High	Low	0.196 ± 0.007	6.72 ± 0.32	3.04 ± 0.24	0.151 ± 0.015
High	High	0.188 ± 0.009	6.69 ± 0.47	3.50 ± 0.33	0.139 ± 0.013
Low	Low	0.169 ± 0.006	5.36 ± 0.27	2.82 ± 0.14	0.117 ± 0.012
Low	High	0.174 ± 0.012	5.78 ± 0.46	2.60 ± 0.16	0.115 ± 0.012

Mean (± s.e.m.) sperm production parameters of male house mice exposed to different social cues of sperm competition risk and potential mating rate. Sperm competition risk (SC) was manipulated by altering the number of male competitors regularly encountered (one = low; three = high) and potential mating rate (MR) was manipulated by altering the number of females regularly encountered (two = low; four = high). Testes mass is the mass of both testes (in g); epididymal sperm count is the number of sperm recovered from the caput of the right epididymis (x 10⁶) and daily sperm production rate is the number of sperm produced per testis per day, based on spermatid head counts from testicular homogenates (x 10⁶). (n = 8 in each group, except for daily sperm production rate in the low SC, high MR treatment group where n = 7)

ISSN: 1741-7007