Adult and fetal hemoglobins in the oviparous swell shark, Cephaloscyllium ventriosum

Abstract

Cephaloscyllium ventriosum is an oviparous, bottom-dwelling shark inhabiting shallow waters from central California to Chile. Hemoglobin oxygen affinities for adult, juvenile (5 and 8 months old), and pre- and posthatch (fetal up to 10 days posthatching) individuals were determined using thin-layer spectrophotometry of hemoglobin solutions stripped of organic phosphates. Adult hemogiobin had a P₅₀ of 4.72± 0.30 mm Hg (N = 4, mean ± SE), juvenìle hemoglobin had a P₅₀ of 3.77 ± 0.65 mmHg (N = 3), and pre- and posthatch hemoglobin had a P₅₀ of 2.51 ± 0.19 mmHg (N = 6)—significantly (P < 0.05) higher than adult hemoglobin oxygen affinity. Adult blood was slightly alkaline (7.60–8.04; N = 4), had low venous P_O2 values (0.5–14.5 mmHg; N = 4), and hematocrit and hemoglobin concentration increased with age. SDS-polyacrylamide gel electrophoresis revealed slight structural differences between the hemoglobin of adult and prehatch individuals. A hemoglobin with a higher intrinsic oxygen affinity may enable fetuses of C. ventriosum to more efficiently extract oxygen from the relatively stagnant environment within the egg case.