TheARTof mating: alternative reproductive tactics and mating success in a nest‐guarding fish

Abstract

Behavioural observations in the field of male Mediterranean damselfish Chromis chromis were combined with molecular analyses, using bi-parentally and maternally inherited markers, to investigate reproductive success patterns of alternative reproductive tactics (ARTs) in terms of number of eggs sired and number of females contributing to each nest. Cuckoldry was observed in every nest sampled, with at least two and up to seven sneaker males per nest. The nesting male, however, always significantly fertilized the greater number of eggs (on average 49%) in each clutch, whereas each sneaker fertilized around 7% of the clutch. The average number of females whose eggs were fertilized by nesting males was 6·76 (range 2-13), while each sneaker on average fertilized the eggs of 1·74 (range 1-8) females. Using this sibship reconstruction, some of the factors involved in the regulation of the dynamic equilibrium of reproductive success were investigated between the two ARTs shown by C. chromis males. Results show that the sneakers' reproductive success was positively linked to egg clutch size; the density of individuals in the nesting area negatively affected the size of egg clutches; the rate of defence behaviours performed by nesting males negatively influenced the number of females contributing to each nest.

Nest guarding behaviour of a temperate wrasse differs between sites off Mediterranean CO2 seeps

“…Previous observations for the same species suggest that when the risk of sperm competition is high under natural conditions, behavioural adjustments like increased guarding activity may occur to avoid further sneaker males approaching the nest (Alonzo & Warner, 2000). A similar response was observed in the nesting damselfish Chromis chromis, whose males switch from courting to parental care activities when the perceived risk of cuckoldry is high in the wild (Mascolino et al, 2016).…”

A Genetic Assessment of Parentage in the Blackspot Sergeant Damselfish, Abudefduf sordidus (Pisces: Pomacentridae)

“…These parasite-intruders might gain access to the nest through streaking (rapidly releasing gametes while rushing the spawning pair). In the damselfish Chromis chromis this occurs as many as 2.8 times per ten minutes during spawning [17], and cuckoldry was observed in every nest sampled [33]. Other tactics the parasite might employ to gain access to fertilizations include stealth in the form of drab coloration that is similar to female coloration [31].…”

Behavioural responses in a congested sea: an observational study on a coastal nest-guarding fish

“…The high number of individuals in one colony seemed to play a role in the investment in visual displays. High abundance of conspecific means high presence of females (thus possibly reduced effort to attract them to the nest) as well as higher presence of sneakers (Picciulin et al 2004;Mascolino et al 2016), conspecific males who can "sneak" in another male's nest to release sperm while the female is spawning, parasitically fertilising eggs at the expenses of the nesting male. The visual display is a signal that both females (the intended target) and sneakers (the opportunistic receiver) can detect.…”