Reproductive behavior, egg trading, and correlates of male mating success in the simultaneous hermaphrodite, Serranus tabacarius

Abstract

SynopsisSerranus tabacarius (Serranidae), the tobaccofish, is a simultaneous hermaphrodite which belongs to a group of seabasses that exhibit a wide variety of social and mating systems . The reproductive behavior of tobaccofish is similar to other hermaphroditic seabasses, with individuals assuming sex-specific spawning behaviors that allow for the assignment of male and female roles in a mating sequence . Virtually all matings involved pairs of individuals, although streaking, an alternative male mating tactic, was observed once . Pairs engage in egg trading, where individuals divide their daily clutch into a series of sequentially released parcels and take turns releasing eggs for their partner to fertilize . Individuals mate over a late afternoon spawning period with a number of partners sequentially. Larger individuals have both more total matings and more spawning partners . Egg trading is not symmetrical, the number of male and female matings for an individual in a spawning sequence is often unequal . Overall, the ratio of male to female matings increases with individual size . Large individuals are socially dominant, chase conspecifics during the reproductive period, and are more likely to end a spawning bout with a partner immediately after mating in the male role . In addition, larger individuals are less likely to reciprocate female matings by a partner, either by only mating once (as a male) in a spawning bout or by mating consecutively as a male within a series of matings . Although larger individuals show this relative specialization in the male role, they maintain their simultaneous hermaphroditism and obtain a substantial percentage of their mating success through female function . Egg trading appears to reduce the opportunity for large individuals to specialize as pure males, and thus interacts with the environmental potential for polygamy in shaping the mating system and sex allocation pattern in this species .

Reproductive output traits of the simultaneous hermaphrodite <I>Serranus scriba</I> in the western Mediterranean

“…The S. scriba spawning season lasts approximately 4 months, with a high spawning fraction inferred from the prevalence of hydrated follicles in the ovaries (Alonso-Fernández et al 2011), as also seen in the present study. These findings indicate daily spawning behaviour, which is characteristic of other simultaneous hermaphrodites (Petersen 1995). However, species from the same genus, such as Serranus atricauda, have lower spawning fractions, around 25% (García-Díaz et al 2006).…”

Sexual Conflict in Hermaphrodites

“…Egg trading involves the parceling of the clutch into small subunits, which are then conditionally exchanged by alternating between adopting the preferred sex role, sperm donation, and the nonpreferred sex role, egg donation (or sperm receipt) (Fig. 2C) (Fischer 1980(Fischer , 1984(Fischer , 1987Pressley 1981;Petersen 1995Petersen , 2006. Early approaches modeled this as a two-player game with no option to desert and mate with another individual (Axelrod and Hamilton 1981;Fischer 1988;Leonard 1990).…”

Evolutionary Perspectives on Hermaphroditism in Fishes

“…With respect to egg-trading behavior in the serially monogamous seabasses, a 'tit-for-tat' model has been applied [Fischer and Petersen, 1987;Petersen, 1995]. The basic idea is that by releasing a clutch gradually and waiting for a partner to reciprocate, a pair-mating fish can better evaluate the mating situation and cut its losses if its partner deserts.…”