Comparative analysis of brain cytoarchitecture of labroid fishes with different degree of cognitive abilities

Labroides dimidiatus (Labridae) is a model fish in research concerning cleaner fish mutualism. Recent studies shows that cleaners possess the ability to establish complicated relationships (Bshary and Würth 2001). This well-developed network is one of the most complex interspecies communication systems known in fishes and require complex cognitive abilities (Marshall et al. 2003). It makes the cleaners particularly interesting object of comparative analysis of morphology and cytoarchitecture of brain and brain centers in telencephalon, optic tectum and cerebellum, parts of the brain potentially involved in cognitive functions related to behaviors in complex social system (Demski and Beaver 2001). Similar conclusion were drawn in primates, Carniforous and bats, where strong correlations between development of neocortex and size of social group (as measurement of the complexity of social behavior) were found (Dunbar 1992, Joffe and Dunbar 1997, Bshary and Würth 2001). According to the basic theoretical assumption, centers located in the telencephalon, optic tectum and cerebellum involved in skills associated with complex social behavior, learning and memory, differ qualitatively and quantitatively between cleaners and species with less complicated behavior.