Researchers from Uppsala University in Sweden have found that brain size in female cichlids increases with more complex parental care.
The results of the study by Alejandro Gonzalez-Voyer, Svante Winberg and Niclas Kolm are to be published in the Proceedings of the Royal Society B: Biological Sciences.
The authors first carried out a phylogenetic analysis of 39 Lake Tanganyikan cichlid species using three mitochondrial genes (NADH 2, cytochrome b and the more variable control region).
They then carried out a comparative analysis to investigate the influence of ecology, sexual selection and parental care patterns on whole brain size, as well as to analyse sex-specific effects.
The authors found that there was a significant negative correlation between brain weight and diet, which suggests that species that feed on sessile food items (e.g. aufwuchs or fixed algae) have larger brains than species that feed on motile prey (e.g. fishes).
Furthermore, brain weight was significantly positively correlated with care type; species with female-only care have larger brains than species with biparental care.
In the sex-specific analyses (where males and females were analysed separately), the authors found that diet selects for brain size equally in both sexes, while the larger brains in species with uniparental care are a result of larger brains in females that provide sole care for offspring when compared with females that share parental care with their partner.
From the results of previous studies on cichlid ecology, the authors hypothesize that the prevalent, complex interspecific interactions and the fine-scale niche differentiation observed in algal and benthic feeders may result in increased cognitive demands that have selected for increased brain size.
The authors also surmise that emales providing sole parental care possibly face a higher investment in reproduction than females from biparental species, and thus may face stronger selection to control the choice of partner, which could select for increased cognitive abilities ....
For more information, see the paper: Gonzalez-Voyer, A, S Winberg and N Kolm (2008) Social fishes and single mothers: brain evolution in African cichlids. Proceedings of the Royal Society B: Biological Sciences doi:10.1098/rspb.2008.0979.