The effect of dietary pigments on the coloration and behaviour of flame-red dwarf gourami, Colisa lalia

Colour patterns play an integral role in the signalling processes of many fish species. In particular, carotenoid-based pigments influence nuptial coloration patterns in ornamental fish. Less is known about the role of other dietary pigments in behavioural processes. We studied the effect of dietary pigments on skin pigmentation, growth and behaviour of male flame-red dwarf gourami. Groups of these fish were fed either a control diet or one of three different diets, Lucantin Pink, beetroot juice powder or Overseal Carantho powder, daily for 12 weeks. Mass and colour measurements were taken for each fish every 2 weeks. The addition of synthetic astaxanthin (Lucantin Pink) significantly increased red coloration, whereas betalain-based (beetroot juice powder) and anthocyanin-based (Overseal Carantho powder) pigments did not affect skin colour. Fish mass increased across all diets and the addition of these dietary pigments did not significantly affect growth. At the end of the 12-week trial, fish from each diet treatment were used to determine female preference to male colour intensity and male social interaction. Females preferred to associate with males fed Lucantin Pink and, although clear social hierarchies were observed among groups of male fish, no significant effects of diet on social interaction were found. Fish fed the control, Lucantin Pink and Overseal Carantho powder diets showed a lightening in skin coloration following group activity and social interaction. However, skin colour and skin lightness of fish fed the beetroot juice powder diet were unaffected by periods of social interaction, suggesting a possible colour maintenance property of betalain-based pigments.