DEVELOPMENT OF HEMOGLOBIN, HEMATOCRIT, AND ERYTHROCYTE VALUES IN GALAPAGOS FUR SEALS

We studied the ontogeny of hemoglobin concentration, hematocrit and er ythrocyte counts in the Galapagos fur seal (Arctocephalus galapagoensi s, Heller 1904 ). Two hundred and fifty-three animals were sampled bet ween the ages of 22 d and greater than or equal to 8 yr, of which 46 w ere adult females. Body mass increased steadily with age from 6.1 +/- 1.2 kg in 1-mo-old pups (n = 27 ) to 28.5 +/- 3.3 kg in adult females. Even adult females increased in mass with age. Hemoglobin (Hb), hemat ocrit (Hct), and red blood cell (RBC) values all increased in a logari thmic fashion with age up to 2 yr. Blood values for pups were Hct: 35. 5 +/- 4.1%; Hb: 12.9 +/- 1.3 g/dl; RBC: 4.1 +/- 0.3 . 10(6)/mu l. Half -year-old fur seals (Hct: 42.1 +/- 3.2%; Hb: 15.7 +/- 1.3 g/dl; RBC: 4 .9 +/- 0.5 . 10(6)/mu l; n = 50) were the oldest age group to show sig nificantly lower blood values than adult females (P < 0.001 for all th ree parameters ). Yearling blood values (Hct: 47.2 +/- 3.6%; Hb: 17.3 +/- 1.6 g/dl; RBC: 5.6 +/- 0.4 . 10(6)/mu l; n = 56) did not differ si gnificantly from those of adult females (P < 0.32; P < 0.26; P < 0.23, respectively). Blood values of adult females were lower than those of 2-yr-olds (Hct: 49.6 +/- 2.4%; Hb: 18.5 +/- 1.2 g/dl; RBC: 5.7 +/- 0. 3 . 10(6)/mu l; n = 31). These differences were significant only for R BCs (P < 0.003). Up to the age of 1 yr, age was the best predictor for blood values, thereafter mass needed to be a better predictor. Female juveniles between the ages of 150 and 600 d had higher blood values t han same-age males. The relationship of blood value development to div ing activity is briefly described and the results are compared to valu es of other marine mammals. Ontogeny is discussed in relation to the d evelopment of these blood values in terrestrial mammals.