Adjustment of brood size and androgen levels in a teleost species with exclusive male parental care

Abstract

Blenniidae brood size manipulation intersexual selection male quality peacock blenny Salaria pavo testosterone In maximizing reproductive success, individuals face a trade-off between parental care for their current offspring and investing in androgen-dependent sexual traits to produce further offspring. It has thus been proposed that parental effort would suppress androgen levels. Here, we studied parental effort by manipulating brood size in the peacock blenny, Salaria pavo, a littoral fish species in which males show long periods of paternal care. We focused on the effects of brood size on female spawning rate (measured as number of eggs received in the nest by focal males) and androgen levels. We found a positive linear relationship between brood size and the number of eggs received subsequently. Accordingly, spawning rate increased for males with experimentally enlarged broods while it decreased for males in which brood size was reduced. However, over a longer time interval, brood sizes of both treatments returned to the nonmanipulated brood size, suggesting an effect of additional factors such as male quality. Brood size did not show the expected negative relationship with levels of testosterone and 11-ketotestosterone. On the contrary, testosterone levels were positively correlated with brood size. However, in agreement with the prediction, changes in the level of parental care by manipulation of brood size showed an inverse relationship with testosterone levels. As with brood size, given time, testosterone levels tended to return to nonmanipulated levels. Such changes suggest that males adjust their brood size to an individual value through androgen modulation of courtship or other traits influencing female spawning rate. Ó

Context-dependent evaluation of prospective mates in a fish

“…Moreover, it seems to convey information on different time scales since its general development reflects genetic and/or condition at the time of formation and growth, whilst the colour intensity of its yellow patch signals current health status (Locatello et al 2012). Male mating success, in term of eggs received, appears to be influenced by specific male traits (Oliveira et al 1999; Gonçalves et al 2002a; Fagundes et al 2007; Ros et al 2010) as well as by his general attractiveness (Pizzolon et al 2012). In choosing prospective males, females assess male body size (Fagundes et al 2007), head crest size (these latter both positively related to male body size) (Gonçalves et al 2002a; Gonçalves and Oliveira 2003) and coloured ornamentation (Locatello et al 2012).…”

“…The peacock blenny, S. pavo , is a medium-size fish (up to 14 cm total length) that inhabits the rocky shores of the Mediterranean Sea and adjacent Atlantic coast (Zander 1986 ). The mating system is promiscuous: males continuously receive eggs in their nest from different females and care for overlapping clutches (Patzner et al 1986 ; Pizzolon 2010 ; Ros et al 2010 ; Pizzolon et al 2012 ), and females spawn with several males during the breeding season (Patzner et al 1986 ). Nesting males are larger than females and exhibit a pronounced head crest that during the breeding season shows a yellow patch on both sides (Oliveira et al 1999 ).…”

Reduction in Predator Defense in the Presence of Neighbors in a Colonial Fish

“…Proposed ways to reduce the costs is to breed in close proximity to multiple neighbors, which allows breeders to benefit from earlier detection, dilution of predation and by group defense [5] , [6] . At a theoretical level, cost/benefit models have long been applied to identify optimal investment in nest defense [7] – [14] . Empirically, a number of field studies have examined group defense by placing predators or models near breeding sites and observing the relative predator attack rates of neighbors.…”

Do reproduction and parenting influence personality traits? Insights from threespine stickleback

“…It is unlikely that this was due to a ‘ceiling’ effect in control males, as there was still variation in whether the control group experienced an increase or decrease in 11-kT release rate, albeit not as extreme as in the experimental group. In other fish species, males with high levels of androgens have greater paternity (Neff & Knapp, 2009), and higher 11-kT levels are associated with larger brood sizes (Ros et al, 2009). Therefore, males with higher 11-kT levels after parenting may be more likely to resume breeding, and may therefore be more willing to take risks.…”