The Maturation and Regulation of Glancing Off the Parents By Young Orange Chromides (Etroplus Maculatus: Pisces - Cichlidae)

Abstract

I. During the parental period (3 to 4 weeks) young Etroplus maculatus skim or bounce against the body wall of the parent, a response termed glancing. 2. The glancing rate for the individual does not change during the first week of free-swimming but thereafter it increases; the increase, however, is only apparent in fry that have been fed. The glancing rate for the school decreases during the first week but this is due to mortality. 3. The individual glancing rate is independent of the number of individuals within a school (25-125 individuals) regardless of age. 4. Hour-to-hour changes in glancing rate also occur and are related to the time of feeding. 5. The orientation of glancing when characterized by 3 divisions, a ventral, a medial, and a dorso-anterior division, remains unchanged during development. 6. The orientation of glancing, when characterized by an anterior and a posterior division, shows definite ontogenetic changes. The anterio-posterior changes in orientation are reinacted each day, but steadily less so as the fry become older. 7. Feeding does not change the glancing rate for individuals about 7 days old or less, but it increases the amount of glancing 1.6-fold for fry 12 days old and 2.2-fold for fry 18 days old. The hour-to-hour changes in glancing rate can also be predicted from pre-feeding performance. 8. Feeding affects the school organization. After feeding the school becomes more uniform, moves closer to the parent, and as it does the young glance more. 9. Fry with normal parental care undergo progressive morphological changes. Fry deprived of parental care have a high mortality rate, while growth and morphological differentiation are severely retarded. After 9 days of parental care, fry have completed the major morphological changes and can survive independently of the parent. 10. During the early free-swimming days of the fry, the number of mucus glands in the epidermis of the parent increases by 34%. 11. When parents were coated with carbon powder it was shown that young actually eat from the parents' side when glancing, and presumedly eat mucus. 12. The changes in behavior during development are discussed with regard to the possible mechanisms by which feeding influences glancing rate, causal factors that might affect orientation of glancing, and the possible functional and ecological significance of this behavior.