Nuptial colouration and breeding behaviour in the white threespine stickleback (Gasterosteus aculeatus)

Abstract

The white Threespine Stickleback (Gasterosteus aculeatus) is an ecotype endemic to brackish environments in mainland Nova Scotia and the Bras d’Or Lake. During the breeding season, ‘white’ males are bright white and provide little parental care. By contrast, ‘common’ males have blue/brown dorsal nuptial colouration and show extensive parental care. My main goal was to quantify breeding behaviour and nuptial colouration in the two ecotypes and compare the mainland and Bras d’Or populations. To address this goal, I conducted field observations of behaviour and colouration, and investigated the cellular basis for colour differences. My findings indicate that: quantitative behavioural traits match earlier observations that white males court at a higher intensity than common males; the cellular basis for male brightness is associated with a reduced number or size of melanophores in both mainland and Bras d’Or white stickleback males; and white colouration becomes brighter in association with increased courtship.