Lateralization of ventral fins use during object exploration in the blue gourami (Trichogaster trichopterus).

Blue gourami fish have a pair of modified ventral fins that are used to obtain tactile information about surrounding objects. Use of ventral fins by blue gourami was investigated during initial exploration of novel objects. When exposed to a sequence of novel plastic objects, varying in shape and colour, the blue gourami showed preferential use of the left fin during initial contacts. Laterality apparently depends on the nature of the stimulus: Fish exposed to a randomized series of natural objects showed preferential use of the left fin for inanimate mineral objects, but no asymmetry was apparent for investigating animate objects. This would suggest that some form of 'handedness' may have been present prior to the appearance of tetrapods. On the other hand, measurements of fish monocular viewing revealed that the fin use was strongly associated with preferential use of the ipsilateral eye before the touching of the stimulus took place, thus, suggesting that the asymmetry in fin use may also be related to lateralization of the visual system.