Alternative reproductive tactics (ARTs) driven by environmental factors are common 28 among fish. However, the flexibility of fish to adopt distinct tactics in response to the 29 characteristics of their environment has received little attention. The aim of this study 30 was to study phenotypic plasticity in the adoption of dominant behaviour ("bourgeois 31 tactic") by the male of the river blenny Salaria fluviatilis (Asso, 1801). For this purpose, 32 two simultaneous experiments in aquaria were performed to examine the effect of 33 social cues and nest abundance on the acquisition of secondary sexual characteristics 34 (SSCs). Experiments were conducted with small (individuals without SSCs), medium-35 sized (one year old individuals), and large older dominant males (more than two years 36 old), all collected in the wild. In Experiment 1 the three sizes of males were combined 37 to compare their SSCs development depending on intrasexual context. In Experiment 2 38 the effect of nest abundance (two nests vs. six nests) was tested for each size of male. 39 Medium-sized males showed phenotypic plasticity in response to the environmental 40 conditions simulated in the two experiments. The absence of larger dominant males 41 was found to be the main factor enhancing SSCs and the onset of parental behaviour. 42Nest shortage also influenced the degree of cephalic crest development among 43 medium-sized males. This knowledge helps to understand how the population of 44 S.fluviatilis still persists when it is reduced to young individuals during the summer 45 droughts in Mediterranean streams. 46 3
Boldness is defined as the tendency of an individual to take risks when exposed to novel objects or situations. The main aim of this work was to dilucidate if boldness was related to the development of the secondary sexual traits (SSTs) in the male of the river blenny Salaria fluviatilis, a freshwater fish which takes care of eggs. As a second objective SSTs effect on parental status adoption was also be explored. Wild young fish were caught in the Segre River (Ebro basin) in November 2010. Fish were kept in five aquaria in groups of eight males and eight females with artificial nests. Boldness (boldness score and hesitancy) of males (initially with little SSTs development) was tested as the time required to exit a refuge when exposed to a new environment. Fish were mantained in the same aquaria for several months, and males’ SSTs development and reproductive behaviour were monitored. Boldness score was negatively associated to cephalic crest development. Hesitancy was negatively related to male length and was also influenced by the interaction between male length and cephalic crest. Parental status acquisition was positively related to the male’s length, marginally related to anal gland development, and non-related to cephalic crest. These results suggest an intrasexual role of the crest as an informative trait of boldness (honest signal) which might not necessarily be chosen by the females. It is also discussed that correlational selection could be responsible for linking boldness and growth rate in this species. Sexual selection, in addition to having directed the evolution of secondary sexual traits, might have favored certain personality traits (e.g. boldness) associated with the achievement of a larger body length.
In fishes, the parents’ presence generally improves embryos’ survival through parental care, but it is also associated with some disadvantages such as clutch cannibalism and loss of male physical condition. Captive breeding of the river blenny Salaria fluviatilis might improve if these disadvantages were avoided by artificially replacing parental care benefits in the lab. Before accepting this procedure, it should be studied whether embryo development is dependent or not on any other unknown effect related to the parents’ presence. In this study, the ontogenetic sequence and several morphological structures – standard length, head height, jaw length and yolk-sac volume – from embryos reared both in the presence and in the absence of the parents were compared. At day 11 after oviposition, in the parents’ absence treatment, well-developed embryos were obtained, but a smaller size of the yolk-sac, a greater head height and a tendency to have a greater jaw length than in the parents’ presence treatment were found. These results suggest that the parents’ presence might affect embryo development and perhaps offspring sexual determination. Given these differences, the practise of depriving clutches from their parents in captivity breeding programmes should be questioned.
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