Hemoglobins of reptiles. Expression of alpha-D-genes in the turtles, Chrysemys picta bellii and Phrynops hilarii (Testudines)

The hemoglobins of two turtles (Testudines)--Chrysemys picta bellii (suborder Cryptodira) and Phrynops hilarii (suborder Pleurodira)--were investigated. In both specimens we found two hemoglobin components with two distinct alpha-chains. The alpha-chains of the component HbD of Chrysemys picta bellii and of the component CII of Phyrynops hilarii belong to the alpha D-type, which has so far been reported to occur only in birds. The complete amino-acid sequences of both alpha D-chains are presented. Our further investigations on hemoglobins of other reptiles (Crocodilia, Lacertilia, Serpentes) did not give any evidence for the expression of alpha D-globin genes in the species examined. These findings are discussed with especial reference to the physiology of respiration. It is supposed that alpha D-genes were of certain significance in earlier times. There are findings suggesting that alpha D-genes are embryonic genes with persistent expression in many adult birds and turtles.