Ontogeny of Parent-Contacting in Young Cichlasoma Citrinellum (Pisces, Cichlidae)

Abstract
Adult Cichlasoma citrinellum are polychromatic. About 92% of the adults of the population studied have a species-typical gray and black color pattern. The other 8%o are partially or completely xanthic. During the parental phase young nibble at the parents' bodies, apparently eating material from the surface. Such contacting behavior was also observed in nature as a regular phenomenon. Field observations suggested that the young were contacting the male parent more than the female, and that the amount of contacting was inversely related to the availability of food for the young. Contacting is not essential for survival in aquaria. Young raised in isolation from parents have survival and growth not significantly different from those raised with parents. The amount of contacting by young in aquaria is inversely related to their feeding: Hunger increases the amount of contacting. There is no apparent diurnal rhythm of contacting. Variations are related to the time of feeding. Contacting is shown by all young in aquaria. Initially young contact male and female parents about equally, regardless of color. At this stage contacting appears to be in proportion to the surface area available on each parent. Contacting changes with the age of the young. With increasing age, they contact a gray parent progressively more than a xanthic one. Also, they contact the male parent increasingly more than the female. These two preferences are apparently independent. Young, isolated from their parents in all respects but visually, did not develop preferences in contacting: When first exposed to parents, young fish, regardless of age, contacted each parent relatively the same amount. The continuous sight of their parents and of their siblings developing the contacting preferences was not sufficient for these semi-isolated young to develop the preferences. Hence, this development is not due just to changes in the young and/or the parents, but must involve direct experience. The experience of contacting a particular set of parents has an effect, of relatively short duration, on subsequent contacting preferences of the young. They learn the color and sex correlated factor of each parent. When tested against other parents, both sex and color play a role, but the natural banded color pattern appears to be more important than maleness. Parents, in pairs or individually, will accept other young of their species that are the same age or younger than their own. Older young are chased and eaten. Young can be raised in isolation and successfully re-introduced to their parents. And parents can be exchanged between families. In both such situations, both parents and young soon settle down and behave in typical fashion toward each other. The discussion centers on the possible bases for these preferences of the young and their development. Also considered are the origin of contacting as an alternate source of nutriment for the young, and its evolution within the Cichlidae.