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In the peacock blenny (Salaria pavo) the reproductive behaviour is described to vary between two populations that differ in nest availability. At the Gulf of Trieste (GT), Italy, where nest availability is high, conventional sex roles are present and males adopting an alternative parasitic reproductive tactic are rare. Conversely, at Ria Formosa (RF), Portugal, where nest site availability is low, females are the courting sex and a high percentage of parasitic males occur. Laboratory experiments were used to study the degree of plasticity of the reproductive behaviours used by females and by the two male morphs in both populations. Nesting males were sequentially presented with a female and a female-like parasitic male and the reproductive behaviours of all fish were quantified. Under similar laboratory conditions, nesting males from both populations did not differ in sexual or agonistic displays towards females or parasitic males, showing that males from the sex-reversed population are also able to express significant levels of courtship. In contrast, females followed the typical population pattern, with females from RF courting nesting males more and more readily than females from GT. We hypothesised that apparent differences in behavioural plasticity between nesting males and females were a consequence of the perception of the presence of eggs in the nest. Nesting males from both populations received an empty nest during test trials and, thus, had to court females in order to receive a first spawn. On the other hand, females were probably unaware of the presence or absence of eggs when presented to the nesting male and assumed the population typical courtship profile. Interestingly, the parasitic males' behaviour towards the nesting male closely followed the displays of females from their own population; parasitic males from RF courted the nesting male with a high frequency of female-like displays while parasitic males from GT failed to exhibit female-like courtship behaviour. Taken together, the results suggest that S. pavo presents high levels of plasticity in reproductive behaviours and that these may underlie the interpopulation differences in behaviour reported for the species. Additionally, the results also suggest that the parasitic male reproductive tactic at GT is not based on female-mimicry. [ABSTRACT FROM AUTHOR]

We previously investigated the androgen responsiveness of males to simulated partner and territory intrusions in five African cichlid species (Neolamprologus pulcher, Lamprologus callipterus, Tropheus moorii, Pseudosimochromis curvifrons, Oreochromis mossambicus; Hirschenhauser et al., 2004). Here we re-analysed data on 11-ketotestosterone (11-KT) levels in holding water to compare the free (presumably from the gills) and conjugated (presumably from urine and faeces) 11-KT fractions. We sampled (i) pre-test baseline control levels from individual males in social isolation and (ii) response levels released after social interactions, either with an ovulating female or a male territory intruder. In four out of five species, conjugated metabolites contributed to the observed total 11-KT responses in water during social context, which was particularly apparent in peak responsive individuals exposed to male intruders. Thus, in water from males sampled in isolation immunoreactive 11-KT seemed to derive both from gills and urine, whereas the urinary 11-KT component apparently increased in the social context, particularly when a male was challenged by a same-sex intruder. These results suggest that (i) the social context may affect urine release patterns of males and (ii) 11-KT data acquired by using fish-holding water may not simply reflect the passive transmission of steroid hormones via the gills. [ABSTRACT FROM AUTHOR]

This study reveals the correlation between operational sex ratio (OSR), body characteristics and pairing in one-year-old reproductively active St. Peter's fish, Sarotherodon galilaeus, a mouth brooding tilapia that shows a wide variety in mating strategies including uni- vs biparental brood care, and monogamy vs polygamy. In this study individually marked fish were exposed to different OSR regimes: male-biased, balanced, and female-biased. Larger individuals formed a pair more rapidly than smaller ones. A bias in the OSR caused a longer delay in pairing for individuals of the more abundant sex. The same patterns were found in males and females, supporting the theory that assortative mating patterns emerge due to both male and female choice. Furthermore, we found that pairs that spawned during the experiment were more closely matched in body size than pairs that were not successful in spawning, suggesting that size assortative mating has benefits for reproductive success in S. galilaeus. [ABSTRACT FROM AUTHOR]

Male and female Uca tangeri (the only fiddler crab species to inhabit Europe) construct mudballs from mud excavated from within their burrows. Individual males placed similar patterns of mudballs each low tide, suggesting that there is some degree of stereotypy. When mudballs were experimentally moved further from the burrow or closer to it, males only repositioned those that were moved closer, placing them further away again. However, males did not replace mudballs that had been experimentally destroyed at the end of the mudballing phase when they had started to court females. In binary presentation tests, females showed no significant differences in response to mudballs made from different types of mud, or different numbers of mudballs. These results are consistent with earlier findings that male mudballs function as territory boundaries. However, we provide evidence that male mudballs have no function in female attraction, contrasting with previous studies. [ABSTRACT FROM AUTHOR]