Under laboratory conditions, we investigated the presence of chemical alarm signals in the threespine stickleback (Gasterosteus aculeatus). We exposed individual threespine sticklebacks to skin extract of conspecifics originating from either the same or a different population, fourspine sticklebacks (Apeltes quadracus; a member of the same prey guild as the threespine stickleback) or swordtails (Xiphophorus helleri), a species not known to possess alarm pheromones and which is phylogenetically distant and allopatric from the threespine stickleback. Threespine sticklebacks exhibited significant increases in anti-predator behaviour patterns when presented with skin extract from both populations of conspecifics and from fourspine sticklebacks, but not to swordtail skin extract. These results suggest, contrary to previous reports, that threespine sticklebacks possess chemical alarm signals, which appear to be similar to those of Ostariophysan fishes.
Parental convict cichlids, Cichlasoma nigrofasciatum, responded to the presence of a potential brood predator by decreasing net energy gains (food intake decreased and energy expenditure increased) while increasing parental effort (large allocation of time to brood defense). These behaviours are important factors in the life-history trade-off between current and future reproductive investments. The allocation of energy into defense behaviours and elevated activity levels, combined with a voluntary reduction of food consumption, represent an investment in the current brood which could (in nature) reduce future reproduction. Contrary to parental investment theory predictions, consistent increases in parental effort with brood age were not evident.
The cues associated with social familiarity and genetic relatedness and how they interact to influence the formation of social associations among individuals, and thus group composition and dynamics, is poorly understood. Here, we investigated the concurrent effects of social familiarity and kinship on social affiliations in free-swimming convict cichlid fish young or ‘fry’ (Amatitlania siquia) by pitting the cues of social familiarity and kinship against each other in a four-way choice apparatus. Individual focal fish were given a simultaneous choice to associate (‘shoal’) with conspecifics that were either socially familiar and kin (full sibs), socially unfamiliar and kin, socially familiar and not kin, or socially unfamiliar and not kin. Stimulus shoal preference differed depending on the body length of the focal fish; smaller fry exhibited no preference, whereas larger (more mobile) fry significantly preferred to associate with familiar kin. In the convict cichlid system, where brood mixing occurs in the wild, a preference to associate with familiar kin may confer fitness benefits to individuals, especially when fry become more mobile as they grow and encounter predators more often. Our results contribute to further our understanding of the roles of familiarity and kinship in the formation of social associations in the convict cichlid in particular and in animals in general.
Although male courtship displays have evolved primarily to sexually attract females, they also generate inadvertent public information that potentially reveals the courter’s relative sexual attractiveness and the perceived quality and sexual receptivity of the female being courted to nearby eavesdropping male competitors, who in turn may use this information to bias their social partner choices. We tested this hypothesis by first presenting individual eavesdropping male guppies (Poecilia reticulata) the opportunity to simultaneously observe two demonstrator males whose courtship behaviour was manipulated experimentally to differ, following which we tested them for their preference to associate socially with either demonstrator males. Test males preferentially associated with the demonstrator male who they had previously observed courting a female over the other (non-courting) demonstrator. This social association preference was not expressed in the absence of a female to court. Our findings highlight the potential for sexual behaviour influencing male-male social associations in nature.
Mobile young under parental care have a high potential for intermixing with other broods, which potentially increases the costs to the foster parents. Here, we examined for the first time the genetic composition of wild-caught broods of the convict cichlid (Amatitlania siquia), a socially monogamous biparental fish, for evidence of brood mixing and adoption. Our microsatellite genotyping data revealed that 79% of broods contained adopted young. Moreover, 25% of broods contained adopted sibsets likely arising from extra-pair matings, a phenomenon hitherto not documented for this species. Overall, adopted foreign fry and host fry in mixed broods were generally different in body length, as would be expected if they have different parents. However, fry from possible extra-pair matings were similar in body length to host fry, suggesting that they are of similar age. Our results are important because they reveal a very high prevalence and degree of brood mixing, and indicate that social monogamy does not necessarily lead to genetic monogamy in the convict cichlid in nature. These findings raise questions about potential brood-mixing mechanisms and the reproductive ecology (especially opportunities for polygamy in nature) of this important model species in the study of animal behaviour.