Maternal Care-Providing Cichlid Neolamprologus furcifer Selectively Focuses on High-Threat Carnivorous Intruders, Limiting Attention to Other Threats

Animals adjust their behaviors based on information from multiple sources; however, the brain can effectively process limited amounts of information. Therefore, attention is restricted to a small portion of environmental stimuli. When animals process multiple information inputs, focusing on information that is deemed important improves detection probability. However, selective focus limits attention to other stimuli and associated behavioral responses. In this study, we examined how Tanganyikan cichlid, Neolamprologus furcifer, mothers selectively attack intruder fishes depending on the threat level and presence or absence of offspring. Species composition is complicated in Lake Tanganyika, and fish density is exceedingly high. Thus, parents must focus on high-threat-level intruders according to their parental care stage. Compared to females without offspring, mothers preferentially attacked carnivorous fishes farther from the nest over closer scale-eating fishes. Moreover, the percentage of females with injuries from scale-eating fish was significantly higher in those caring for offspring than those without offspring, demonstrating the cost of limited attention. Our results show that females focus on the early detection of carnivorous fishes because these predators dart in from long distances to forage eggs, fry, and juveniles, but this selective focus limits the attention placed on low-level threats. This study is the first to document the cost of limited attention in parents guarding offspring.

Parental care and neuropeptide dynamics in a cichlid fish Neolamprologus caudopunctatus

The hypothalamic neuropeptides arginine vasopressin (AVP) and oxytocin (OT) modulate social behavior across a wide variety of species. However, the role of arginine vasotocin (AVT) and isotocin (IT, the teleost homologs of AVP and OT) in regulating biparental care especially in the context of monogamy is not well studied. Here, using high-performance liquid chromatography (HPLC), we investigated how bioactive whole brain AVT and IT neuropeptide levels vary in relation to the phase of the breeding cycle and sex, in a monogamous biparental cichlid fish, Neolamprologus caudopunctatus. Since non-caring individuals of this species readily cannibalize eggs, but caring parents never do, we further investigated whether there might be changes in AVT/IT whole brain levels that correspond to the transition from a non-breeding, egg cannibal to an egg caring parent. We found that AVT levels were higher in females than in males and that AVT levels were highest when the need to defend the young was greatest. Breeding pairs that had a strong pair-bond and a higher frequency of nest care had the highest levels of AVT, whereas individuals that spent little time close to their breeding partner, displayed aggression towards their partner and neglected their nest duties (signs of a weak pair bond), had lower whole brain AVT levels. Isotocin (IT) levels did not differ between sexes and we did not detect any variation across the breeding cycle, with pair-bonding scores or with parental behavior. Our results show that whole brain AVT levels are linked to the breeding cycle, nest maintenance and pair-bonding score in this species. Furthermore, our study highlights species and sex-specific nonapeptides patterns in bi-parental caring fish and contributes to the increasing knowledge on neuroendocrinological mechanisms underlying parental care.