Maturation of the goldfish (Carassius auratus) erythrocyte.

1. Cohorts of [3H]thymidine-labelled erythrocytes were examined over a 42-day period in goldfish (Carassius auratus L.) recovering from phenylhydrazine HCl-induced anemia under normoxic conditions at 20 +/- 1 degree C and maintained with minimal disturbance on a high nutritional plane. 2. As judged by changes in primary and derived hematological variables, maturation required 16-20 days. 3. Similar estimates were obtained using cytomorphic variables obtained by image analysing methods. 4. These suggest that juvenile red cells in this species can be identified on the basis of the following characteristics: major axis less than 9.2 microM; one-sided surface area not greater than approximately 50 microns2; axis ratio greater than 0.774; form factor greater than 0.938. 5. Corresponding values for mature cells are: major axis greater than 11.2 microns; area greater than 68.5 microns2; axis ratio less than 0.716; form factor less than 0.912. 6. These criteria, with values for dividing and karyorrhectic cell numbers, offer a basis for more detailed and dynamic characterization of the erythron during response to environmental variation than has previously been possible.